The Science of Hearing, Balance & Accelerated Learning

00:00:00.000 | - Welcome to the Huberman Lab Podcast,

00:00:02.280 | where we discuss science and science-based tools

00:00:04.900 | for everyday life.

00:00:05.900 | I'm Andrew Huberman,

00:00:10.120 | and I'm a professor of neurobiology and ophthalmology

00:00:12.960 | at Stanford School of Medicine.

00:00:15.080 | Today, we're going to talk all about hearing and balance

00:00:18.700 | and how you can use your ability to hear specific things

00:00:22.200 | and your balance system in order to learn anything faster.

00:00:27.000 | The auditory system, meaning the hearing system,

00:00:29.520 | and your balance system,

00:00:30.680 | which is called the vestibular system,

00:00:32.520 | interact with all the other systems of the brain and body

00:00:37.000 | and used properly can allow you

00:00:39.240 | to learn information more quickly,

00:00:41.020 | remember that information longer and with more ease,

00:00:45.040 | and you can also improve the way you can hear.

00:00:47.800 | You can improve your balance.

00:00:49.440 | We're going to talk about tools for all of that.

00:00:51.840 | This is one area of science where we understand a lot

00:00:56.260 | about the cells and the mechanisms in the ear

00:00:59.240 | and in the brain and so forth,

00:01:00.840 | so we're going to talk about that a little bit,

00:01:02.480 | and then we're going to get directly into protocols,

00:01:05.660 | meaning tools.

00:01:06.800 | We're also going to talk about ways

00:01:09.380 | in which the auditory and balance systems suffer.

00:01:11.920 | We're going to talk about tinnitus,

00:01:13.120 | which is this ringing of the ears that,

00:01:15.920 | unfortunately for people that suffer from it,

00:01:18.420 | they really suffer.

00:01:19.840 | It's very intrusive for them.

00:01:21.540 | We're going to talk about some treatments that can work

00:01:24.400 | in some circumstances and some of the more recent

00:01:27.720 | emerging treatments that I think many people

00:01:30.140 | aren't aware of.

00:01:31.640 | We're also going to talk about this,

00:01:33.180 | what seems like kind of a weird fact,

00:01:34.840 | which is that 70% of people, all people,

00:01:38.800 | make what are called autoacoustic emissions.

00:01:41.980 | Their ears actually make noises.

00:01:43.520 | Chances are your ears are making noises right now,

00:01:46.780 | but you can't perceive them,

00:01:48.440 | and yet those can have an influence on other people

00:01:51.560 | and animals in your environment.

00:01:53.800 | It's a fascinating aspect to your biology.

00:01:56.240 | You're going to learn a lot about how your biology

00:01:59.080 | and brain and ears and the so-called inner ear

00:02:01.940 | that's associated with balance,

00:02:03.080 | you're going to learn a lot about how all those work.

00:02:05.480 | You're going to learn a lot of neuroscience.

00:02:07.420 | I'll even tell you what type of music to listen to,

00:02:10.000 | and if you listen to me,

00:02:10.960 | you can leverage that in order to learn faster.

00:02:13.660 | Before we begin talking about the science

00:02:15.580 | of hearing and balance and tools that leverage hearing

00:02:18.380 | and balance for learning faster,

00:02:20.360 | I want to provide some information about another way

00:02:23.340 | to learn much faster.

00:02:25.740 | There's a paper that was published recently.

00:02:27.800 | This is a paper that was published in Cell Reports,

00:02:30.620 | an excellent journal.

00:02:32.400 | It's a peer-reviewed paper from a really excellent group

00:02:36.500 | looking at skill learning.

00:02:38.900 | Now, previously, I've talked about how

00:02:42.840 | in the attempt to learn skills,

00:02:45.300 | the vital thing to do is to get lots of repetitions.

00:02:50.300 | You've heard of the 10,000 hours thing.

00:02:52.540 | You've heard of lots of different strategies

00:02:55.180 | for learning faster, 80/20 rule and all that.

00:02:57.980 | The bottom line is you need to generate

00:03:00.960 | many, many repetitions of something

00:03:03.500 | that you're trying to learn,

00:03:04.660 | and the errors that you generate

00:03:06.500 | are also very important for learning.

00:03:08.340 | It also turns out that taking rest

00:03:13.020 | within the learning episode is very important.

00:03:16.520 | I want to be really clear what I'm referring to here.

00:03:19.380 | In earlier episodes, I've discussed how

00:03:21.860 | when you're trying to learn something, it's beneficial,

00:03:24.180 | it's been shown in scientific studies,

00:03:26.660 | that if you take a 20-minute shallow nap

00:03:30.100 | or you simply do nothing after a period of learning,

00:03:33.820 | that it enhances the rates of learning

00:03:35.880 | and the depth of learning,

00:03:37.060 | your ability to learn and remember that information.

00:03:40.820 | What I'm about to describe are new data

00:03:43.120 | that say that you actually should be injecting rest

00:03:46.620 | within the learning episode.

00:03:48.540 | Now, I'm not talking about going to sleep while learning.

00:03:51.900 | This is the way that the study was done.

00:03:54.340 | The study involved having people learn sequences of numbers

00:03:58.940 | or keys on a piano.

00:04:00.300 | So let's use the keys on a piano example.

00:04:03.180 | I'm not a musician, but I think I'll get this correct.

00:04:06.500 | They asked people to practice a sequence of keys,

00:04:12.220 | G-D-F-E-G, G-D-F-E-G, G-D-F-E-G,

00:04:17.000 | and they would practice that either continually

00:04:19.260 | for a given amount of time,

00:04:21.020 | or they would just do that for 10 seconds.

00:04:23.300 | They would play G-D-F-E-G, G-D-F-E-G, G-D-F-E-G,

00:04:26.820 | G-D-F-E-G for 10 seconds,

00:04:28.420 | and then they would take a 10-second pause, a rest.

00:04:31.780 | They would just take a space or a period of time

00:04:35.460 | where they do nothing for 10 seconds.

00:04:37.080 | Then they would go back to G-D-F-E-G, G-D-F-E-G.

00:04:40.420 | So the two conditions essentially

00:04:43.840 | were to have people practice continually,

00:04:46.740 | lots of repetitions,

00:04:48.300 | or to inject or insert these periods of 10 seconds idle time

00:04:53.300 | where they're not doing anything,

00:04:54.520 | they're not looking at their phone,

00:04:55.860 | they're not focusing on anything,

00:04:57.060 | they're just letting their mind drift

00:04:59.020 | wherever it wants to go,

00:05:00.620 | and they are not touching the keys on the keyboard.

00:05:04.260 | What they found was that the rates of learning,

00:05:07.460 | the skill acquisition and the retention of the skills

00:05:10.300 | was significantly faster

00:05:11.980 | when they injected these short periods of rest,

00:05:14.400 | these 10-second rest periods.

00:05:16.260 | And the rates of learning were,

00:05:19.380 | when I say significantly faster, were much, much faster.

00:05:22.780 | I'll reveal what that was in just a moment.

00:05:25.120 | But you might ask, why would this work?

00:05:28.460 | Why would it be that injecting these 10-second rest periods

00:05:31.020 | would enhance rates of learning?

00:05:32.740 | What they called them was micro-offline gains

00:05:35.300 | because they're sort of taking their brain offline

00:05:37.180 | from the learning task for a moment.

00:05:38.420 | Well, it turns out the brain isn't going offline at all.

00:05:42.060 | You've probably heard of the hippocampus,

00:05:43.460 | the area of the brain involved in memory,

00:05:45.520 | and the neocortex, the area of the brain

00:05:47.220 | that's involved in processing sensory information.

00:05:50.340 | Well, it turns out that during these brief periods of rest,

00:05:53.500 | these 10-second rest periods,

00:05:55.600 | the hippocampus and the cortex are active in ways

00:05:59.940 | such that you get a 20-times repeat of the GDFEG.

00:06:05.780 | It's a temporal compression, as they say.

00:06:08.200 | So basically, the rehearsal continues while you rest,

00:06:12.460 | but at 20 times the speed.

00:06:14.700 | So if you were normally getting just, let's just say,

00:06:17.620 | five repetitions of GDFEG, GDFEG, GDFEG per 10 seconds,

00:06:22.620 | now you multiply that times 20.

00:06:25.080 | In the rest periods, you've practiced it 100 times.

00:06:27.720 | Your brain has practiced it.

00:06:29.100 | We know this because they were doing brain imaging,

00:06:31.100 | functional imaging of these people with brain scanners

00:06:33.780 | while they were doing this.

00:06:35.360 | This is an absolutely staggering effect.

00:06:38.920 | And it's one that, believe it or not,

00:06:41.140 | has been hypothesized or thought to exist

00:06:43.480 | for a very long time.

00:06:45.580 | This effect is called the spacing effect,

00:06:50.920 | and it was actually first proposed by Ebington in 1885.

00:06:55.920 | And since then, it's been demonstrated

00:06:58.820 | for a huge number of different what they call domains,

00:07:01.340 | in the cognitive domain, so for learning languages,

00:07:04.160 | in the physical domain, so for learning skills

00:07:06.240 | that involve a motor sequence.

00:07:08.520 | It's been demonstrated for a huge number

00:07:10.720 | of different categories of learning.

00:07:13.660 | If you want to learn all about the spacing effect

00:07:17.040 | and the categories of learning that it can impact,

00:07:19.480 | there's a wonderful review article.

00:07:21.360 | I'll provide a link to it.

00:07:23.160 | The title of the review article is

00:07:25.420 | Parallels Between Spacing Effects

00:07:27.160 | During Behavioral and Cellular Learning.

00:07:29.100 | What that review really does is it ties

00:07:31.040 | the behavioral learning and the improvement of skill

00:07:33.680 | to the underlying changes in neurons

00:07:37.540 | that can explain that learning.

00:07:39.480 | I should mention that the paper that I'm referring to,

00:07:41.960 | the more recent paper that injects these 10-second

00:07:45.040 | little micro offline gains rest periods,

00:07:49.160 | is the work of the laboratory of Leonard Cohen,

00:07:52.360 | not the musician Leonard Cohen.

00:07:54.280 | He passed away, he was not a neuroscientist,

00:07:56.320 | a wonderful poet and musician, but not a neuroscientist.

00:07:59.760 | Again, the paper was published in Cell Reports,

00:08:01.420 | and we will provide a link to the full paper as well.

00:08:04.320 | So the takeaway is if you're trying to learn something,

00:08:08.200 | you need to get those reps in,

00:08:09.640 | but one way that you can get 20 times the number of reps in

00:08:12.960 | is by injecting these little 10-second periods

00:08:16.040 | of doing nothing.

00:08:17.080 | Again, during those rest periods,

00:08:19.580 | you really don't want to attend to anything else

00:08:21.880 | as much as possible.

00:08:22.800 | You could close your eyes if you want,

00:08:24.280 | or you can just simply wait

00:08:25.600 | and then get right back into generating repetitions.

00:08:28.720 | I find these papers that Cell Reports

00:08:31.400 | and other journals have been publishing recently

00:08:32.960 | to be fascinating because they're really helping us

00:08:35.320 | understand what are the best protocols

00:08:37.400 | for learning anything,

00:08:39.080 | and they really leverage the fact

00:08:41.760 | that the brain is willing to generate repetitions for us,

00:08:44.400 | provided that we give it the rest that it needs.

00:08:47.680 | So inject rest throughout the learning period,

00:08:49.760 | and if you can, based on the scientific data,

00:08:52.680 | you would also want to take a 20-minute nap

00:08:54.840 | or a 20-minute decompressed period

00:08:56.820 | where you're not doing anything after a period of learning.

00:09:00.080 | I think those could both synergize

00:09:02.960 | in order to enhance learning even further,

00:09:05.160 | although that hasn't been looked at yet.

00:09:07.000 | Before we begin talking about hearing and balance,

00:09:09.540 | I just want to mention that this podcast is separate

00:09:11.740 | from my teaching and research roles at Stanford.

00:09:14.240 | It is, however, part of my desire and effort

00:09:16.500 | to bring zero cost to consumer information about science

00:09:19.360 | and science-related tools to the general public.

00:09:22.540 | In keeping with that theme,

00:09:24.040 | I want to thank the sponsors of today's podcast

00:09:27.080 | and make it clear that we only work with sponsors

00:09:29.400 | whose products we absolutely love

00:09:31.320 | and that we think you will benefit from as well.

00:09:34.780 | Our first sponsor is Roca.

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00:13:52.840 | Can you hear me?

00:13:54.580 | Can you hear me?

00:13:55.980 | Okay, well, if you can hear me, that's amazing,

00:13:58.380 | because what it means is that my voice

00:14:01.980 | is causing little tiny changes in the airwaves

00:14:04.940 | wherever you happen to be,

00:14:06.700 | and that your ears and whatever's contained in those ears

00:14:10.480 | and in your brain can take those sound waves

00:14:13.700 | and make sense of them.

00:14:14.860 | And that is an absolutely fantastic

00:14:17.500 | and staggering feat of biology,

00:14:20.140 | and yet we understand a lot about how that process works.

00:14:23.700 | So I'm going to teach it to you now in simple terms

00:14:26.140 | over the next few minutes.

00:14:28.100 | So what we call ears have a technical name.

00:14:30.880 | That technical name is oracles,

00:14:34.660 | but more often they're called pinna, the pinna, P-I-N-N-A,

00:14:39.180 | pinna.

00:14:40.360 | And the pinna of your ears,

00:14:42.980 | this outer part that is made of cartilage and stuff,

00:14:45.880 | is a range such that it can capture sound

00:14:50.120 | in the best way for your head size.

00:14:53.340 | We're going to talk about ear size also,

00:14:54.980 | 'cause it turns out that your ears change size

00:14:57.160 | across the lifespan and that how big your ears are,

00:15:01.020 | or rather how fast your ears are changing size

00:15:05.120 | is a pretty good indication of how fast you're aging.

00:15:08.140 | So we'll get to that in a few minutes,

00:15:09.460 | but I want to talk about these things that we call ears

00:15:12.820 | and some of the stuff contained within them

00:15:14.940 | that allow us to hear.

00:15:16.640 | So the shape of these ears that we have

00:15:19.540 | is such that it amplifies high-frequency sounds,

00:15:23.320 | high-frequency sounds as the name suggests

00:15:25.120 | are the squeakier stuff, right?

00:15:27.020 | So low-frequency sound.

00:15:28.780 | Costello snoring in the background,

00:15:30.080 | that's a low-frequency sound or high-frequency sound, okay?

00:15:34.760 | So we have low-frequency sounds and high-frequency sounds

00:15:37.200 | and everything in between.

00:15:38.860 | Now those sound waves get captured by our ears

00:15:41.860 | and those sound waves,

00:15:43.700 | for those of you that don't

00:15:45.060 | maybe fully conceptualize sound waves,

00:15:47.580 | are literally just fluctuations or shifts

00:15:51.960 | in the way that air is moving toward your ear

00:15:56.580 | and through space.

00:15:57.420 | In the same way that water can have waves,

00:15:59.940 | air can have waves, okay?

00:16:01.820 | So it's reverberation of air.

00:16:04.060 | Those come in through your ears

00:16:08.260 | and you have what's called your eardrum.

00:16:10.800 | And on the inside of your eardrum,

00:16:13.280 | there's a little bony thing

00:16:14.880 | that's shaped like a little hammer.

00:16:16.440 | So attached to that eardrum,

00:16:18.520 | which can move back and forth like a drum,

00:16:20.680 | it's like a little membrane,

00:16:22.480 | you've got this hammer attached to it.

00:16:24.400 | And that hammer has three parts.

00:16:26.320 | For those of you that want to know,

00:16:27.300 | those three parts are called malleus, incus, and stapes.

00:16:30.980 | It's like, but basically you can just think about it

00:16:32.880 | as a hammer.

00:16:33.720 | So you've got this eardrum and then a hammer.

00:16:36.280 | And then that hammer has to hammer on something.

00:16:39.040 | And what it does is it hammers

00:16:41.000 | on a little coiled piece of tissue

00:16:44.280 | that we call the cochlea,

00:16:45.720 | sometimes called the cochlea,

00:16:47.040 | depending on where somebody lives in the country.

00:16:50.020 | So typically in the Midwest, on the East Coast,

00:16:51.900 | they call them cochlea.

00:16:52.960 | And on the West Coast, we call them cochlea.

00:16:54.720 | Same thing, okay?

00:16:57.280 | So this snail-shaped structure in your inner ear

00:17:00.220 | is where sound gets converted into electrical signals

00:17:05.020 | that the brain can understand.

00:17:06.880 | But I want to just bring your attention

00:17:08.540 | to that little hammer

00:17:10.000 | because that little hammer is really, really cool.

00:17:12.200 | What it means is that sound waves come in through your ears.

00:17:14.400 | That's what's happening right now.

00:17:16.280 | That eardrum that you have is like a,

00:17:18.880 | it's like the top of a drum.

00:17:20.080 | It's like a membrane, or it can move back and forth.

00:17:22.980 | It's not super rigid.

00:17:24.380 | And it moves that little hammer.

00:17:25.800 | And then the hammer goes,

00:17:26.960 | doon, doon, doon, doon, doon,

00:17:28.100 | and hits this coil-shaped thing

00:17:31.060 | that we're calling the cochlea, okay?

00:17:34.000 | Now, the cochlea at one end is more rigid than the other.

00:17:39.000 | So one part can move really easily,

00:17:41.440 | and the other part doesn't move very easily.

00:17:44.300 | And that turns out to be very important for decoding

00:17:48.660 | or separating sounds that are low frequency,

00:17:51.900 | like Costello's snoring,

00:17:53.680 | and sounds that are of high frequency,

00:17:56.280 | like a shriek or a shrill.

00:17:59.000 | And that's because within that little coiled thing

00:18:03.840 | we call the cochlea,

00:18:05.460 | you have all these tiny little, what are called hair cells.

00:18:09.740 | Now, they look like hairs,

00:18:11.120 | but they're not at all related to the hairs on your head

00:18:13.560 | or elsewhere on your body.

00:18:15.180 | They're just shaped like hairs.

00:18:16.360 | We call them hair cells.

00:18:18.660 | Those hair cells, if they move,

00:18:22.080 | send signals into the brain

00:18:23.980 | that a particular sound is in our environment.

00:18:26.740 | And if those hair cells don't move,

00:18:28.620 | it means that particular sound is not in our environment.

00:18:32.320 | Okay?

00:18:33.160 | So just to give you the mental picture of this,

00:18:35.600 | sound waves are coming in

00:18:36.860 | because there's stuff out there making noises,

00:18:39.980 | like my voice.

00:18:40.920 | It's changing the patterns of air around you

00:18:43.980 | in very, very subtle ways.

00:18:45.940 | That information is getting funneled into your ears

00:18:48.940 | because your pinna's are shaped in a particular way.

00:18:51.620 | The eardrum then moves this little hammer

00:18:54.140 | and the hammer bangs on this little snail-shaped thing.

00:18:57.740 | And because that snail-shaped thing at one end

00:19:00.980 | is very rigid, it doesn't want to move.

00:19:02.780 | And at the other end, it's very flexible.

00:19:05.140 | It can separate out high-frequency and low-frequency sounds.

00:19:09.660 | And the fact that this thing in your inner ear

00:19:12.260 | that we call the cochlea is coiled

00:19:14.440 | is actually really important to understand

00:19:17.560 | because along its length,

00:19:19.660 | it varies in how rigid or flexible it is.

00:19:22.260 | I already mentioned that before.

00:19:24.020 | And at the base, it's very rigid.

00:19:28.000 | And that's where the hair cells, if they move,

00:19:31.420 | will make high-frequency sounds.

00:19:33.880 | And at the top, what's called the apex,

00:19:35.940 | it's very flexible and it's more like a bass drum.

00:19:38.980 | So basically what happens is sound waves come into your ears

00:19:42.420 | and then at one end of this thing that we call the cochlea,

00:19:46.680 | at the top, it's essentially encoding

00:19:50.480 | or only responding to sounds that are like

00:19:52.920 | doom, doom, doom, doom.

00:19:55.060 | Whereas at the bottom,

00:19:56.760 | it responds to high-frequency sounds

00:19:59.040 | like a cymbal, tss, tss, tss, tss, tss, tss, tss.

00:20:02.740 | Okay, and everywhere in between,

00:20:05.060 | we have other frequencies, medium frequencies.

00:20:08.640 | Now, this should stagger your mind.

00:20:11.660 | If it doesn't already, it should.

00:20:13.720 | Because what this means is that

00:20:16.400 | everything that's happening around us,

00:20:18.100 | whether or not it's music or voices or crying or screaming

00:20:21.460 | or screaming of delight from small children

00:20:24.700 | who are excited 'cause they're playing

00:20:26.160 | or 'cause they get cake,

00:20:28.020 | all of that is being broken down into its component parts.

00:20:32.340 | And then your brain is making sense of what it means.

00:20:34.960 | These things that I've been talking about,

00:20:37.940 | like the pinna of your ears and this little hammer

00:20:40.700 | and the cochlea, that's all purely mechanical.

00:20:43.740 | It has no mind of its own.

00:20:45.440 | It's just breaking things down into high frequencies,

00:20:48.060 | medium frequencies, and low frequencies.

00:20:50.060 | And if you don't understand sound frequency,

00:20:51.840 | it's really simple to understand.

00:20:54.060 | Just imagine ripples on a pond.

00:20:56.180 | And if those ripples are very close together,

00:20:58.780 | that's high frequency.

00:20:59.960 | They occur at high frequency.

00:21:01.940 | If those ripples are further apart, it's low frequency.

00:21:05.380 | And obviously, medium frequency is in between.

00:21:07.380 | So just like you can have waves in water,

00:21:08.820 | you can have waves in air.

00:21:10.140 | So that's really how it works.

00:21:12.300 | Now, we are all familiar with light

00:21:16.660 | and how if you take a prism and put it in front of light,

00:21:20.240 | it will split that light into its different wavelengths,

00:21:22.980 | its different colors, red, green, blue, et cetera, right?

00:21:26.260 | So like the Pink Floyd, "Dark Side of the Moon" album,

00:21:29.780 | I think has a prism and it's converting white light

00:21:32.820 | into all the colors,

00:21:34.900 | all the wavelengths that are contained in white light.

00:21:37.580 | Your cochlea essentially acts as a prism.

00:21:40.740 | It takes all the sound in your environment

00:21:42.980 | and it splits up those sounds into different frequencies.

00:21:46.740 | So you can think of the cochlea of your ear

00:21:48.920 | sort of like a prism.

00:21:50.340 | And then the brain takes that information

00:21:52.620 | and puts it back together and makes sense of it.

00:21:55.100 | So those hair cells in each of your two cochlea,

00:21:58.160 | 'cause you have two ears, you also have two cochlea,

00:22:01.340 | send little wires, what we call axons,

00:22:04.860 | that convey their patterns of activity into the brain.

00:22:09.580 | And there are a number of different stations

00:22:12.180 | within the brain that information arrives at

00:22:14.780 | before it gets up to the parts of your brain

00:22:17.100 | where you are consciously aware.

00:22:19.100 | And because some of you have asked for more names

00:22:21.220 | and nomenclature, I'll give that to you.

00:22:22.600 | If you don't want a lot of detailed names,

00:22:25.140 | you can just ignore what I'm about to say.

00:22:26.740 | But basically the cochlea send information

00:22:29.940 | to what's called the spiral ganglion.

00:22:32.300 | The spiral ganglion, a ganglion, by the way,

00:22:34.260 | if you're going to learn any neuroscience,

00:22:35.820 | just know that anytime you hear ganglion,

00:22:37.980 | a ganglion is just a clump.

00:22:40.100 | So it means a bunch of neurons, so a clump of cells.

00:22:43.580 | So the spiral ganglion is a bunch of neurons

00:22:46.140 | that the information then goes off to

00:22:48.540 | what are called the cochlear nuclei in the brainstem.

00:22:51.740 | Brainstem is kind of down near your neck.

00:22:53.980 | Then up to a structure that has a really cool name

00:22:55.860 | called the superior olive,

00:22:57.220 | because you have one on each side of your brain.

00:22:59.780 | And if I were to bring you to my lab

00:23:01.900 | and show you the superior olives in your brain

00:23:04.340 | or anyone else's brain, they look like little olives.

00:23:07.180 | They even have a little divot in them

00:23:08.400 | that to me looks like a pimento,

00:23:10.620 | but they just call them the superior olive.

00:23:13.300 | And then the neurons in the superior olive,

00:23:15.540 | then they send information up

00:23:16.940 | to what's called the inferior colliculus,

00:23:18.660 | only called inferior because it sits below

00:23:20.820 | a structure called the superior colliculus.

00:23:22.700 | And then the information goes up

00:23:24.540 | to what's called the medial geniculate nucleus,

00:23:27.340 | and then up to your neocortex

00:23:28.880 | where you make sense of it all.

00:23:31.460 | Now, you don't have to remember all that,

00:23:32.900 | but you should know that there are a lot of stations

00:23:36.620 | in which auditory information is processed

00:23:39.100 | before it gets up to our conscious detection.

00:23:42.460 | And there is a good reason for that,

00:23:45.880 | which is that more important than knowing what you're hearing

00:23:50.660 | you need to know where it's coming from.

00:23:52.900 | It's vital to our survival that if something, for instance,

00:23:57.700 | is falling toward us,

00:23:59.080 | that we know if it's coming to our right side,

00:24:01.120 | if it's going to hit us from behind,

00:24:03.220 | we have to know, for instance,

00:24:04.260 | if a car is coming at us from our left or from our right,

00:24:07.620 | and our visual system can help with that,

00:24:10.460 | but our auditory and our visual system collaborate

00:24:13.020 | to help us find and locate the position of things in space.

00:24:17.820 | That should come as no surprise.

00:24:19.500 | If you hear somebody talking off to your right,

00:24:22.380 | you tend to turn to your right, not to your left.

00:24:24.780 | If you see somebody's mouth moving in front of you,

00:24:28.220 | you tend to assume that the sound

00:24:29.440 | is going to come from right in front of you.

00:24:32.220 | Disruptions in this auditory hearing and visual matching

00:24:37.220 | are actually the basis of what's called

00:24:39.660 | the ventriloquism effect,

00:24:41.260 | which we'll talk about in a few minutes in more depth.

00:24:44.100 | But the ventriloquism effect

00:24:45.940 | can basically be described in simple terms

00:24:48.360 | as when you essentially think that a sound

00:24:52.460 | is coming from a location

00:24:54.100 | that it's not actually coming from.

00:24:56.300 | We'll talk about that in a moment,

00:24:58.420 | but what I'd like you to realize

00:25:01.060 | is that one of these stations deep in your brainstem

00:25:05.020 | is responsible for helping you identify

00:25:07.320 | where sounds are coming from

00:25:09.480 | through a process that's called interaural time differences.

00:25:12.880 | And that sounds fancy,

00:25:13.980 | but really the way you know where things are coming from,

00:25:17.980 | what direction a car or a bus or a person is coming from

00:25:21.280 | is because the sound lands in one ear before the other.

00:25:25.060 | And you have stations in your brain,

00:25:27.660 | meaning you have neurons in your brain

00:25:29.180 | that calculate the difference in time of arrival

00:25:31.860 | for those sound waves in your right versus your left ear.

00:25:35.340 | And if they arrive at the same time,

00:25:37.240 | you assume that thing is making noise right in front of you.

00:25:40.980 | If it's off to your right,

00:25:42.220 | you assume it's over on your right.

00:25:43.740 | And if the sound arrives first to your left ear,

00:25:45.980 | you assume quite correctly

00:25:47.820 | that the thing is coming toward your left ear.

00:25:50.940 | So it's a very simple and kind of a mechanical system

00:25:53.740 | at the level of sound localization.

00:25:57.900 | But what about up and down?

00:25:59.260 | If you think about it,

00:26:00.240 | a sound coming from above is going to land on your right ear

00:26:02.860 | and your left ear at the same time.

00:26:04.660 | A sound from below is going to land on your right ear

00:26:07.740 | and your left ear at the same time.

00:26:09.520 | So the way that we know where things are

00:26:12.700 | in terms of what's called elevation,

00:26:15.220 | where they are in the up and down plane

00:26:17.700 | is by the frequencies.

00:26:21.300 | The shape of your ears actually modifies the sound

00:26:25.460 | depending on whether or not it's coming straight at you

00:26:27.780 | from the floor or from high above.

00:26:30.740 | And so already at the level of your ears,

00:26:34.340 | you are taking information about the outside world

00:26:37.140 | and determining where that information is coming from.

00:26:40.740 | Now, this all happens very, very fast in a subconscious,

00:26:44.100 | but now you know why.

00:26:46.220 | If people really want to hear something,

00:26:48.680 | they make a cup around their ear.

00:26:51.620 | They essentially make their ear

00:26:53.280 | into more of a fennec fox type ear.

00:26:55.720 | If you've ever seen those cute little fennec fox things,

00:26:58.360 | they have these big spiky ears.

00:26:59.800 | They kind of look like a French bulldog,

00:27:01.440 | although they're kind of the fox version

00:27:03.400 | of the French bulldog.

00:27:04.440 | These big, tall ears,

00:27:06.080 | and they have excellent sound localization.

00:27:08.200 | And so when people lean in with their hand like this,

00:27:12.200 | if you're listening to this,

00:27:13.040 | I'm just cupping my hand at my ear,

00:27:15.220 | I'm giving myself a bigger pinna.

00:27:17.840 | Oh yeah, and if I do it on the left side, I can do this side.

00:27:20.280 | And if I really want to hear something,

00:27:21.760 | I do it on both sides, okay?

00:27:23.640 | So this isn't just gesturing.

00:27:25.320 | This actually serves a mechanical role.

00:27:27.400 | And actually, if you want to hear

00:27:28.980 | where things are coming from

00:27:30.360 | with a much greater degree of accuracy,

00:27:33.700 | this can actually help

00:27:35.240 | because you're capturing sound waves

00:27:36.940 | and funneling them better.

00:27:39.160 | It's really remarkable, this whole system.

00:27:41.600 | So you've got these two ears,

00:27:43.660 | and because of the differences in the timing

00:27:45.820 | of when things arrive in those two ears,

00:27:47.560 | as well as these differences in the frequencies

00:27:50.520 | that certain things sound,

00:27:52.880 | or I should say the differences in the frequencies

00:27:56.060 | that arrive at your ears,

00:27:57.280 | depending on whether or not the thing is above you

00:27:59.920 | or right in front of you or below you,

00:28:01.600 | you're able to make out

00:28:02.440 | where things are in space pretty well.

00:28:04.320 | So now you're probably starting to realize

00:28:06.120 | that these two things on the side of our head

00:28:07.600 | that we call ears are there for a lot more

00:28:10.720 | than hanging earrings on or for other aesthetic purposes

00:28:14.840 | or for putting sunglasses on top of.

00:28:17.620 | They are very powerful devices

00:28:21.260 | for allowing us to capture sound waves from our environment.

00:28:25.140 | Now I have a question for you,

00:28:28.620 | which is, can you move your ears?

00:28:31.960 | Turns out that unlike other animals,

00:28:35.520 | humans are not terrifically good at moving their ears.

00:28:38.900 | Other animals can move their ears even independently.

00:28:42.240 | So Costello is pretty good at raising his ears,

00:28:44.880 | the two of them together.

00:28:45.760 | He can't really move his ears separately.

00:28:48.280 | Some dogs can do that really well.

00:28:50.480 | In fact, sighthounds and some scent hounds

00:28:53.740 | do that exquisitely well.

00:28:55.480 | Some animals like deer and other animals

00:28:58.440 | that really have a very acute hearing

00:29:02.080 | will put one ear down to a very particular angle

00:29:05.960 | and will tilt the other one

00:29:07.180 | and they will actually capture information

00:29:10.520 | about two distant sound-making organisms.

00:29:15.040 | Those could be hunters coming after them

00:29:16.940 | or other animals coming after them.

00:29:18.600 | They are very good at doing this.

00:29:20.220 | We're not so good at it,

00:29:21.440 | but about 60% of people it's thought

00:29:24.960 | can move their ears consciously

00:29:27.520 | without having to touch their ears.

00:29:29.240 | So can you do that?

00:29:30.680 | Maybe you should try it.

00:29:31.520 | Ask someone to look at you

00:29:32.920 | and see whether or not you can do it.

00:29:34.440 | The typical distances that people can move it

00:29:37.680 | is usually no more than two or three millimeters.

00:29:40.300 | It's subtle, but can you flap your pinna

00:29:42.940 | with just using mental control?

00:29:45.720 | If you can, or if you can't,

00:29:48.460 | try looking all the way to your right

00:29:52.180 | or all the way to your left.

00:29:53.560 | Obviously, if you're driving a car

00:29:54.920 | or doing something or exercising,

00:29:56.480 | don't put yourself in danger right now,

00:29:57.780 | but if you move your eyes all the way to your left,

00:30:01.380 | which I'm doing now, or all the way to my right,

00:30:04.020 | you might feel a little bit of a contraction of the muscles.

00:30:07.000 | It's that control ear movement, all right?

00:30:11.800 | Now I want to ask you this.

00:30:12.780 | Can you raise one eyebrow?

00:30:14.560 | I'm not very good at it.

00:30:15.640 | I can do a little bit,

00:30:16.580 | but it's mostly by like cramping down my face on one side,

00:30:20.040 | and I certainly can't raise my right eyebrow.

00:30:22.280 | I can only do my left eyebrow.

00:30:24.620 | I'm trying to talk while I'm doing this,

00:30:25.460 | so this is why it looks strange.

00:30:27.040 | People who can raise one eyebrow very easily

00:30:30.120 | almost always can move their ears

00:30:33.840 | without having to touch them.

00:30:35.480 | It's controlled by the same motor pathway,

00:30:39.520 | and there does seem to be a small

00:30:41.440 | but statistically significant sex difference

00:30:44.200 | in the ability to move one's ears.

00:30:47.180 | Typically, men can do this more than women can,

00:30:50.480 | although plenty of women can move their ears as well.

00:30:53.080 | Now, if you think that is all a little strange

00:30:56.960 | or off topic, it's not,

00:30:58.540 | because what we're really talking about here

00:31:01.400 | is a system of the brain, but also of the body,

00:31:05.480 | of the musculature for localizing things in space,

00:31:08.400 | and so you might find it interesting to note

00:31:11.220 | that one of the things that we share very closely

00:31:14.640 | with other primates, with non-human primates,

00:31:17.960 | like macaque monkeys and chimpanzees,

00:31:20.480 | if you look at their ears,

00:31:22.520 | their ears are remarkably similar to our ears,

00:31:25.780 | or rather our ears are remarkably similar to their ears.

00:31:29.900 | The eyes of certain monkeys, like macaque monkeys,

00:31:33.620 | are remarkably similar to human eyes.

00:31:36.920 | This is one of the reasons

00:31:37.920 | why if you look at a baby macaque monkey,

00:31:40.080 | it has this unbelievably human element to it,

00:31:44.300 | but the ears of these primates is very similar to our ears,

00:31:49.020 | our ears similar to their ears.

00:31:51.620 | If you're interested in ear movements

00:31:54.180 | and what they could mean,

00:31:56.440 | and some of the things that ear movements correlate with

00:31:59.240 | in other aspects of our biology,

00:32:01.540 | there's a nice paper, actually, a scientific paper.

00:32:04.700 | The author's last name is Code, C-O-D-E.

00:32:07.940 | It was published in 1995.

00:32:09.600 | I'll give a reference to that.

00:32:11.020 | It's a review article that discusses

00:32:13.480 | some of the sex differences in ear movement control,

00:32:16.920 | as well as the relationship

00:32:17.980 | between ear movements and eye movements,

00:32:20.160 | and it's a pretty accessible paper.

00:32:21.840 | It's one that I think any of you

00:32:23.380 | who are interested in this topic could parse fairly easily,

00:32:27.020 | and there's some very interesting underlying biology

00:32:29.860 | and some theories as to why humans

00:32:32.200 | would have this so-called vestigial

00:32:34.320 | or ancient carryover of a system for moving our ears.

00:32:37.920 | Now, if ear movement seems strange,

00:32:43.000 | next I want to talk about a different feature

00:32:45.780 | of your hearing and ears that's even stranger,

00:32:49.900 | but that has some really interesting implications

00:32:53.220 | for your biology,

00:32:55.660 | and I'm guessing that you've not heard of this.

00:32:59.120 | What I'm about to describe are called

00:33:02.820 | autoacoustic emissions,

00:33:05.160 | and autoacoustic emissions, as the name suggests,

00:33:08.180 | are sounds that your ears make.

00:33:10.880 | Believe it or not,

00:33:13.220 | 70% of people make noises with their ears,

00:33:18.220 | but they don't actually detect them.

00:33:20.380 | Like I said, you've never heard of this.

00:33:21.820 | Okay, that's not what I mean,

00:33:24.580 | but what I do mean is that 70% of people's ears

00:33:28.700 | are making noise that's cast out of the ear,

00:33:32.060 | and these autoacoustic emissions

00:33:33.560 | actually can be detected by microphones.

00:33:35.380 | Sometimes they can be detected by other people in the room

00:33:38.420 | if they have very good hearing.

00:33:40.480 | Now, it turns out that women,

00:33:43.580 | or I should be technical here,

00:33:45.140 | females who report themselves as heterosexual

00:33:48.620 | have a higher frequency, not frequency of sound,

00:33:52.660 | but a higher frequency of autoacoustic emissions

00:33:56.840 | than do men who report themselves as heterosexual.

00:34:00.420 | Women who report themselves as homosexual or bisexual

00:34:04.220 | make fewer autoacoustic emissions than heterosexual women.

00:34:09.540 | These are data that come from Dennis McFadden's lab

00:34:13.620 | at the University of Texas, Austin.

00:34:15.700 | He actually discovered these,

00:34:17.460 | what are called sexual dimorphisms

00:34:19.380 | and differences based on sexual orientation

00:34:22.480 | without looking for them.

00:34:23.540 | He was studying hearing, he's a auditory scientist,

00:34:27.180 | and people were coming into his laboratory

00:34:29.060 | and they were detecting these autoacoustic emissions,

00:34:31.380 | and they started to notice the group differences

00:34:35.060 | in autoacoustic emissions.

00:34:36.260 | So they started asking people about their sex

00:34:39.300 | and about their sexual orientation,

00:34:41.300 | and these differences fell out of the data, as we say.

00:34:45.580 | And it's interesting because autoacoustic emissions

00:34:48.440 | are not something that we associate with sex

00:34:50.900 | or sexual dimorphism,

00:34:52.360 | but what these data really underscore is,

00:34:54.860 | first of all, a lot of us are making noises with our ears,

00:34:57.740 | some of us more than others,

00:34:59.420 | and that exposure to certain combinations of hormones

00:35:04.220 | during development are very likely shaping

00:35:07.100 | the way that our hearing apparati,

00:35:09.700 | meaning the cochlea and the pinna and all sorts of things,

00:35:12.540 | how those develop and how those function

00:35:14.340 | throughout the lifespan.

00:35:15.620 | We did do an episode on hormones and sexual development,

00:35:19.160 | which gets much deeper into the other effects

00:35:21.940 | that hormones have on the developing brain and body.

00:35:24.380 | If you want to check out that episode,

00:35:26.660 | we will put a link to it in the captions.

00:35:29.820 | So now I want to shift to talking about

00:35:31.920 | ways to leverage your hearing system, your auditory system,

00:35:36.340 | so that you can learn anything,

00:35:37.860 | not just auditory information, but anything faster.

00:35:41.900 | I get a lot of questions about so-called binaural beats.

00:35:45.920 | Binaural beats, as their name suggests,

00:35:48.220 | involve playing one frequency of sound to one ear

00:35:52.480 | and a different frequency of sound to the other ear.

00:35:55.180 | So it might be doon, doon, doon, doon to your right ear,

00:35:59.200 | and it might be doon, doon, doon, doon, doon, doon,

00:36:01.620 | to the left ear.

00:36:03.060 | And the idea is that the brain

00:36:05.820 | will take those two frequencies of sound,

00:36:09.300 | and because the pathways that bring information

00:36:12.260 | from the ears into the brain eventually cross over,

00:36:14.860 | they actually share that information

00:36:16.940 | with both sides of the brain,

00:36:18.640 | that the brain will average that information

00:36:21.500 | and come up with a sort of intermediate frequency.

00:36:25.020 | And the rationale is that those intermediate frequencies

00:36:28.340 | place the brain into a state that is better for learning.

00:36:32.340 | And when I say better for learning,

00:36:34.660 | I want to be precise about what I mean.

00:36:36.620 | That could mean more focus for encoding

00:36:39.400 | or bringing the information in.

00:36:42.820 | As you may have heard me say before,

00:36:44.720 | we have to be alert and focused in order to learn.

00:36:47.240 | There is no passive learning

00:36:48.440 | unless we're little tiny infants.

00:36:50.140 | So can binaural beats make us more focused?

00:36:54.760 | Can binaural beats allow us to relax more if we're anxious?

00:36:58.760 | I know some people, they go to the dentist

00:37:00.300 | and the dentist offers binaural beats

00:37:02.360 | as they drill into your teeth and give root canals

00:37:04.640 | and things of that sort,

00:37:05.580 | probably causing some anxiety

00:37:06.820 | just describing those things right now.

00:37:09.720 | But those are available in several dentists,

00:37:12.440 | many dental practices.

00:37:14.840 | Their binaural beats have been thought

00:37:16.460 | to increase creativity,

00:37:18.500 | or at least have been proposed to increase creativity.

00:37:20.620 | So what are the scientific data say about binaural beats?

00:37:23.320 | There are a number of different apps out there

00:37:25.640 | that offer binaural beats.

00:37:26.980 | There are a number of different programs.

00:37:28.500 | I think you can also even just find these on YouTube

00:37:31.420 | and on the internet, but typically it's an app

00:37:33.380 | and you'll program in a particular outcome that you want,

00:37:36.120 | more focused, more creative, fall asleep,

00:37:38.400 | less anxious, et cetera.

00:37:40.500 | So what are the scientific data say?

00:37:42.420 | So believe it or not, the science on binaural beats

00:37:45.040 | is actually quite extensive and very precise.

00:37:48.500 | So sound waves are measured typically in hertz or kilohertz.

00:37:53.500 | I know many of you aren't familiar

00:37:54.780 | with thinking about things in hertz or kilohertz,

00:37:56.900 | but again, just remember those waves on a pond,

00:37:59.700 | those ripples on a pond.

00:38:01.780 | If they're close together,

00:38:03.660 | then they are of high frequency.

00:38:06.420 | And if they're far apart, then they are low frequency.

00:38:08.700 | So when you hear more hertz,

00:38:10.840 | what you're essentially hearing is higher frequency, right?

00:38:14.660 | And so if it's many more kilohertz,

00:38:16.320 | then it's much higher frequency

00:38:17.540 | than if it's fewer hertz or kilohertz.

00:38:19.500 | And so you may have heard of these things as delta waves

00:38:23.220 | or theta waves or alpha waves or beta waves, et cetera.

00:38:26.680 | Delta waves would be big slow waves, so low frequency.

00:38:30.320 | And indeed there's quality evidence

00:38:33.660 | from peer-reviewed studies that are not sponsored

00:38:36.060 | by companies that make binaural beat apps

00:38:38.800 | that tell us that delta waves like one to four hertz,

00:38:42.780 | so very low frequency sounds, think Costello's snoring,

00:38:46.300 | can help in the transition to sleep and for staying asleep.

00:38:51.300 | And that theta rhythms, which are more like four to eight hertz

00:38:55.020 | can bring the brain into a state of subtle sleep

00:39:00.020 | or meditation, so deeply relaxed, but not fully asleep.

00:39:04.340 | And then you can sort of ascend the staircase of findings

00:39:07.020 | here, so to speak, and you'll find evidence

00:39:08.980 | that alpha waves, eight to 13 hertz,

00:39:10.760 | can increase alertness to a moderate level.

00:39:14.300 | That's a great state for the brain to be in

00:39:16.340 | for recall of existing information, okay?

00:39:20.620 | And that beta waves, 15 to 20 hertz,

00:39:23.420 | are great for bringing the brain into focus states

00:39:27.300 | for sustained thought or for incorporating new information

00:39:31.660 | and especially gamma waves, the highest frequency,

00:39:34.100 | the most frequent ripples of sound, so to speak,

00:39:37.680 | 32 to 100 hertz for learning and problem solving.

00:39:41.600 | Now, all of this matches, or I should say maps onto

00:39:45.920 | what I've said before about learning really nicely,

00:39:48.540 | which is that you need to be in a highly alert state

00:39:50.860 | in order to bring new information in,

00:39:52.840 | in order to access a state of mind

00:39:55.440 | in which you can tell your brain,

00:39:57.600 | or the brain is telling itself, okay, I need to learn this.

00:39:59.860 | This is why stress and unfortunate circumstances

00:40:02.440 | are so memorable is because our brain gets

00:40:04.440 | into a really high alert system.

00:40:06.080 | Here, we're talking about the use of binaural beats

00:40:08.380 | in order to increase our level of alertness

00:40:11.200 | or our level of calmness.

00:40:14.140 | Now, that's important to underscore

00:40:16.260 | because it's not that there's something

00:40:17.720 | fundamentally important about the binaural beats.

00:40:20.780 | They are yet another way of bringing the brain

00:40:23.380 | into states of deep relaxation through low-frequency sound

00:40:27.480 | or highly alert states for focused learning

00:40:31.380 | with more high-frequency sound.

00:40:33.460 | So they are effective,

00:40:35.780 | and I'll review a little bit of the data in detail.

00:40:39.020 | They're effective, but it's not

00:40:40.860 | that they're uniquely special for learning.

00:40:44.920 | It's just that they can help some people

00:40:46.900 | bring their brain into the state

00:40:48.460 | that allows them to learn better.

00:40:50.820 | So there are a lot of studies that allowed us to arrive,

00:40:55.020 | or I should say allowed the field to arrive

00:40:57.740 | on these parameters of slow, low-frequency waves

00:41:02.660 | are going to bring you into relaxed states,

00:41:03.900 | high-frequency waves into more alert states.

00:41:06.840 | There's very good evidence for anxiety reduction

00:41:11.620 | from the use of binaural beats.

00:41:14.260 | And what's interesting is the anxiety reduction

00:41:18.300 | seems to be most effective when the binaural beats

00:41:22.980 | are bringing the brain into delta,

00:41:25.280 | so those slow, big waves like sleep, theta, and alpha states.

00:41:30.240 | And I'll link to a couple of these studies,

00:41:32.300 | although I will probably link more to the list

00:41:36.020 | that really segregates them out one by one

00:41:38.020 | so you can see them all next to one another.

00:41:40.120 | There's good evidence that binaural beats

00:41:41.580 | can be used to treat pain, chronic pain.

00:41:43.860 | There's three studies in peer-reviewed journals

00:41:47.620 | which I took a look at,

00:41:48.560 | and they seem to be of good quality,

00:41:51.580 | not sponsored research, as we say,

00:41:53.280 | not paid for by any specific company.

00:41:55.940 | Binaural beats have been shown

00:41:57.140 | to modestly improve cognition, attention,

00:42:00.740 | working memory, and even creativity.

00:42:03.700 | But the real boost from binaural beats appears to be

00:42:07.420 | for anxiety reduction and pain reduction.

00:42:10.980 | Some people might find these beneficial

00:42:12.700 | for these oral surgeries, right?

00:42:16.100 | Believe it or not, there are people who would rather

00:42:18.800 | have the entire root canal or cavity drilled

00:42:22.680 | without Novocain, and that's because they sometimes

00:42:25.420 | have a syringe phobia or something of that sort,

00:42:28.340 | or they just don't like being numb from the Novocain,

00:42:30.120 | or maybe there's an underlying medical reason.

00:42:32.100 | But I think most people don't enjoy

00:42:34.340 | getting their teeth drilled,

00:42:35.300 | even if they have Novocain in there or a root canal.

00:42:37.700 | And so it seems that binaural beats can be effective

00:42:40.500 | in that environment, and you don't have to go

00:42:42.620 | into that sort of extreme environment

00:42:43.980 | to benefit from binaural beats.

00:42:45.260 | Binaural beats are a either relatively inexpensive thing

00:42:51.380 | to access, most of the apps are pretty inexpensive.

00:42:53.720 | I don't have a favorite binaural beats app

00:42:56.480 | to recommend to you.

00:42:57.880 | I confess I did use binaural beats a few years ago.

00:43:00.140 | I kind of shifted over to other what I call NSDR,

00:43:04.020 | non-sleep deep breath protocols in favor of those.

00:43:06.520 | But many people like binaural beats

00:43:08.580 | and say that they benefit from them,

00:43:10.720 | especially while studying or learning.

00:43:13.440 | I think part of the reason for that relates to the ability

00:43:17.580 | to channel our focus when we have some background noise.

00:43:21.380 | And this is something I also get asked about a lot.

00:43:24.140 | Is it better to listen to music and have background noise

00:43:27.140 | when studying, or is it better to have complete silence?

00:43:29.820 | Well, there's actually a quite good literature

00:43:32.380 | on this as well, but not so much as it relates

00:43:35.200 | to binaural beats, but rather whether or not people

00:43:37.900 | are listening to music, so-called white noise,

00:43:41.500 | brown noise, believe it or not, there's white noise

00:43:43.580 | and there's brown noise, there's even pink noise,

00:43:46.080 | and how that impacts brain states that allow us

00:43:49.700 | to learn information better or not.

00:43:52.340 | So now I'd like to talk about white noise.

00:43:55.100 | And I want to be very clear that white noise has been shown

00:43:58.940 | to really enhance brain states for learning

00:44:02.480 | in certain individuals, in particular in adults.

00:44:06.460 | But white noise actually can have a detrimental effect

00:44:09.460 | on auditory learning and maybe even the development

00:44:12.040 | of the auditory system in very young children,

00:44:14.900 | in particular in infants.

00:44:16.940 | So first I'd like to talk about the beneficial effects

00:44:19.880 | of white noise on learning.

00:44:22.280 | There are some really excellent studies on this.

00:44:25.460 | The first one that I'd like to just highlight is one

00:44:29.340 | that's entitled Low-Intensity White Noise Improves

00:44:32.200 | Performance in Auditory Working Memory Task, an FMRI study.

00:44:35.980 | This is a study that explored whether or not learning

00:44:41.180 | could be enhanced by playing white noise in the background.

00:44:45.100 | But the strength of the study is that they looked

00:44:48.860 | at some of the underlying neural circuitry

00:44:50.620 | and the activation of the neural circuitry in these people

00:44:52.820 | as they did the learning task.

00:44:54.380 | And what it essentially illustrates is that white noise,

00:44:58.220 | provided that white noise is of low enough intensity,

00:45:01.980 | meaning not super loud, right?

00:45:04.880 | Not imperceptible, so not so quiet that you can't hear it,

00:45:09.100 | but not super loud either.

00:45:10.740 | It actually could enhance learning to a significant degree.

00:45:13.740 | And this has been shown now for a huge number

00:45:16.540 | of different types of learning.

00:45:18.280 | There's a terrific article as well,

00:45:21.940 | as in a somewhat obscure journal, at least obscure to me,

00:45:24.540 | which is the effects of noise exposure

00:45:26.240 | on cognitive performance and brain activity patterns.

00:45:29.260 | That's a study involving 54 subjects.

00:45:32.660 | They basically were evaluated for mental workload

00:45:36.400 | and attention under different levels of noise exposure,

00:45:39.700 | background noise, and different,

00:45:42.020 | essentially loudness of noise.

00:45:43.480 | And the reason I like this study is that they looked

00:45:45.740 | at different levels of noise and types of noise,

00:45:47.940 | and they varied a number of different things,

00:45:50.440 | as opposed to just doing a kind of two-condition,

00:45:52.780 | either white noise or no white noise type thing.

00:45:55.260 | And what they found, again, is that provided

00:45:57.620 | the white noise is not extremely loud,

00:46:00.680 | it could really enhance brain function

00:46:02.920 | for sake of learning any number

00:46:04.500 | of different kinds of information.

00:46:07.380 | Now, that's all great, but it really doesn't get

00:46:10.420 | to the kind of deeper guts of mechanism.

00:46:12.900 | And as a neuroscientist, what I really want to see is not

00:46:15.380 | just that something has an effect, that's always nice.

00:46:17.660 | It's always nice to see in a nice peer-reviewed study

00:46:20.320 | without any kind of commercial biases that there's an effect.

00:46:23.220 | Okay, binaural beats can enhance learning,

00:46:25.260 | or listening to white noise not too loud

00:46:27.460 | can enhance learning.

00:46:28.940 | But you really want to understand mechanism,

00:46:31.580 | because once you understand mechanism,

00:46:34.780 | not only does it start to make sense,

00:46:36.300 | but you can also imagine ways

00:46:37.660 | in which you could develop better tools and protocols.

00:46:40.660 | So I was very relieved to find, or I should say excited

00:46:44.500 | to find this study published

00:46:46.180 | in the Journal of Cognitive Neuroscience.

00:46:48.460 | This is a 2014 paper.

00:46:50.620 | White noise improves learning by modulating activity

00:46:54.700 | in dopaminergic midbrain regions

00:46:57.380 | and the right superior temporal sulcus, okay?

00:46:59.620 | Now, I don't expect you to know

00:47:00.500 | what the right superior temporal sulcus is.

00:47:02.460 | I don't expect you to know

00:47:03.500 | what the dopamine midbrain region is,

00:47:05.260 | but if you're like me,

00:47:07.260 | you probably took highlighted notice

00:47:09.740 | of the word dopaminergic.

00:47:11.220 | Dopamine is a neuromodulator,

00:47:13.660 | meaning it's a chemical that's released in our brain

00:47:15.840 | and body, but mostly in our brain,

00:47:18.020 | that modulates, meaning controls the likelihood

00:47:23.020 | that certain brain areas will be active

00:47:24.780 | and other brain areas won't be active.

00:47:26.480 | And dopamine is associated with motivation.

00:47:28.740 | Dopamine is associated with craving.

00:47:30.500 | Motivation is associated with all sorts of different things,

00:47:32.800 | including movement.

00:47:34.220 | But what this study so nicely shows

00:47:37.220 | is that white noise can really enhance the activity

00:47:42.900 | of neurons in what's called the substantia nigra VTA.

00:47:45.720 | The substantia nigra VTA is a very rich source of dopamine,

00:47:50.220 | and that's because it's very chock-a-block full

00:47:53.620 | of dopamine neurons.

00:47:55.500 | It's an area of the brain that is perhaps

00:47:58.140 | the richest source of dopamine neurons.

00:48:01.260 | And you actually can see this brain region

00:48:03.740 | under the microscope, if you take a slice of brain

00:48:06.100 | or you look at a brain without even staining it

00:48:08.200 | for any proteins or dopamine or anything,

00:48:10.460 | it's two very dark regions at the kind of bottom

00:48:13.980 | of the brain, and the reason it's called substantia nigra,

00:48:17.500 | nigra meaning dark, is because the dopamine neurons

00:48:21.220 | actually make something that makes those neurons dark.

00:48:25.740 | And so you've got these two regions down there

00:48:28.300 | that contain dopamine and can release dopamine

00:48:30.560 | and essentially activate other brain regions

00:48:32.960 | and activate our sense of motivation

00:48:34.680 | and activate our sense of desire

00:48:36.700 | to continue focusing and learning.

00:48:39.020 | But you can't just snap your fingers

00:48:41.460 | and make them release dopamine.

00:48:42.500 | You actually have to trigger dopamine release from them.

00:48:44.940 | Now, that trigger can be caused

00:48:46.520 | by being very excited about something

00:48:49.080 | or the fact that that thing gave you a lot of pleasure

00:48:51.540 | in the past, or you're highly motivated by fear or desire.

00:48:55.160 | But what's so interesting to me is that it appears

00:48:58.600 | that white noise itself can raise

00:49:02.020 | the what we call the basal, the baseline levels of dopamine

00:49:05.280 | that are being released from this area,

00:49:07.440 | the substantia nigra.

00:49:09.280 | So now we're starting to get a more full picture

00:49:13.000 | of how particular sounds in our environment

00:49:15.660 | can increase learning, and that's in part, I believe,

00:49:20.420 | through the release of dopamine from substantia nigra.

00:49:24.700 | So I'm not trying to shift you away from binaural beats,

00:49:28.220 | if that's your thing, but it does appear

00:49:30.820 | that turning on white noise at a low level, not too loud,

00:49:33.860 | you may say, "Well, how loud?"

00:49:35.100 | And I'll tell you in a moment,

00:49:36.140 | but not too loud can allow you to learn better

00:49:39.360 | because of the ways that it's modulating

00:49:41.280 | your brain chemistry.

00:49:42.660 | So how loud or how soft should that white noise be

00:49:47.040 | while you learn?

00:49:48.020 | Well, in these studies, it seemed that white noise

00:49:52.460 | that could be heard by the person,

00:49:54.300 | so it wasn't imperceptible to them,

00:49:55.820 | so it was loud enough that they could hear,

00:49:58.740 | but not so loud that they felt it was intrusive

00:50:03.740 | or irritating to them, okay?

00:50:05.740 | So that's going to differ from person to person

00:50:07.640 | because people have different levels of auditory sensitivity.

00:50:10.860 | It's going to depend on age,

00:50:11.820 | going to depend on a number of different factors.

00:50:13.800 | So I can't tell you turn to level two

00:50:16.600 | on your volume controller.

00:50:17.900 | That's just not going to work.

00:50:18.740 | Also, I don't know how far you are

00:50:20.080 | from a given speaker in the room,

00:50:21.580 | or if you've got earphones in your head,

00:50:23.440 | or you've got speakers in the room,

00:50:26.060 | or if it's coming out of your computer.

00:50:27.760 | I don't know those things.

00:50:28.960 | So what you're going to have to do is adjust that white noise

00:50:31.420 | to a place where it's not interfering

00:50:33.860 | with your ability to focus,

00:50:35.080 | but rather it's enhancing your ability to focus.

00:50:37.800 | I think a good rule of thumb is going to be

00:50:41.200 | to put it probably on the lower third

00:50:43.860 | of any kind of volume dial,

00:50:46.080 | as opposed to in the upper third

00:50:49.160 | where it would really be blasting.

00:50:51.480 | And really blasting any noise, frankly, is not good,

00:50:55.840 | but that's especially not good,

00:50:58.200 | meaning it's especially bad, if you have headphones in.

00:51:01.440 | I do want to mention something about headphones

00:51:03.460 | before I talk about white noise in the developmental context

00:51:07.000 | and why it can be dangerous there.

00:51:08.640 | When you put headphones in your ears,

00:51:12.460 | it has this incredible effect of making the sounds

00:51:17.720 | like they come from inside your head,

00:51:19.680 | not from out in the room.

00:51:21.640 | And now that might seem like kind of a duh,

00:51:23.720 | but that's actually really amazing, right?

00:51:25.880 | Your brain assumes that the sounds

00:51:27.720 | are coming from inside your head,

00:51:30.120 | as opposed from the environment that you're in

00:51:32.020 | the moment you put headphones in.

00:51:33.600 | So if you're listening to an audio book,

00:51:34.940 | or maybe you're listening to this podcast with headphones,

00:51:37.240 | that's very different than when you're listening

00:51:39.100 | to something out in the room and there are other sounds,

00:51:41.640 | other sound waves,

00:51:42.600 | especially if you use these noise cancellation headphones.

00:51:45.200 | So if you're going to use white noise

00:51:48.100 | to enhance studying or learning of any kind,

00:51:50.560 | or this also could be for skill learning,

00:51:52.000 | motor skill learning while you're exercising,

00:51:54.620 | my suggestion would be that if you're using headphones

00:51:58.200 | to keep it quite low, right?

00:52:00.280 | This is an effect on the midbrain dopamine neurons.

00:52:03.380 | That's a background effect of raising the baseline

00:52:05.840 | of dopamine release.

00:52:06.680 | The way that dopamine neurons fires, they're always firing.

00:52:08.880 | Yours are firing right now, so are mine.

00:52:10.680 | When something exciting happens, they fire a lot.

00:52:12.960 | And when something disappointing happens,

00:52:14.360 | that firing, the release of dopamine

00:52:16.280 | goes down below baseline.

00:52:17.960 | What you're talking about here is raising

00:52:19.560 | your overall levels of attention and motivation,

00:52:21.620 | which translate to better learning,

00:52:23.440 | by just tickling those neurons a little bit,

00:52:26.280 | raising the baseline firing, okay?

00:52:28.100 | So you're not turning up the white noise

00:52:30.280 | to the point where you're feeling amazing.

00:52:32.060 | This isn't like turning on your favorite song.

00:52:34.060 | This is actually the opposite.

00:52:35.800 | This is about getting that baseline up just a bit, okay?

00:52:39.820 | So I recommend turning the volume up just a bit

00:52:43.420 | so that you can focus entirely on the tasks

00:52:46.720 | that you're trying to do.

00:52:47.560 | And of course, you've turned on white noise,

00:52:49.240 | so your attention might drift to that for a moment.

00:52:50.860 | Is it too loud? Is it too soft?

00:52:52.840 | If you can disappear into the work, so to speak,

00:52:55.280 | if your attention can disappear into the work,

00:52:57.140 | then that's probably sufficiently quiet.

00:53:00.280 | And for those of you that say,

00:53:01.200 | "Well, I like really loud music,

00:53:02.560 | and if I just blast the music,

00:53:04.400 | then I forget about the music,"

00:53:06.820 | I don't suggest blasting music.

00:53:08.520 | And this is coming from somebody who really likes loud music.

00:53:12.200 | I grew up with kind of a loud, fast rules mentality.

00:53:14.640 | And if you don't know what loud, fast rules means,

00:53:17.400 | then I can't help you.

00:53:18.740 | But there's a time and a place, perhaps,

00:53:22.460 | to listen to music loud, but especially with headphones,

00:53:25.500 | you can trigger, excuse me, hearing loss quite rapidly.

00:53:30.000 | And unfortunately, because these hair cells

00:53:33.180 | that we talked about earlier,

00:53:34.120 | our central nervous system neurons, they do not regenerate.

00:53:37.120 | They do not come back.

00:53:39.000 | Now, along the lines of hearing loss,

00:53:41.940 | I should just say that the best way

00:53:45.200 | to blow out your hearing for good, to eliminate your hearing,

00:53:49.000 | is to have very loud sounds

00:53:51.860 | superimposed on a loud environment, okay?

00:53:54.860 | So loud environments can cause hearing loss over time.

00:53:57.380 | So if you work at a construction site clanging really loud,

00:54:00.300 | or if you work the soundboard in a club or something,

00:54:03.700 | you are headed towards hearing loss

00:54:05.740 | unless you protect your hearing

00:54:07.600 | with earplugs and headphones.

00:54:09.980 | Nowadays, some of the earplugs are very low profile,

00:54:12.780 | meaning you can't see them.

00:54:13.840 | So that's kind of nice, so you're not like the,

00:54:15.940 | like when I was younger, you didn't want to be the dork

00:54:17.940 | to go to the concert with the earplugs,

00:54:19.360 | but turns out those dorks were smarter than everybody else

00:54:21.780 | because they're not the ones who are craning their neck

00:54:24.700 | to try and hear trivial things

00:54:26.420 | at the age of 30 or so because they blew out their hearing.

00:54:32.440 | So if you are working in a loud environment

00:54:35.340 | or you expose yourselves to a loud environment,

00:54:38.660 | you really want to avoid big inflections

00:54:41.980 | in sound above that.

00:54:43.360 | So loud environment plus fireworks,

00:54:47.180 | loud environment plus gunshot,

00:54:49.140 | loud environments plus very high-frequency intense sound,

00:54:53.580 | that's what we call the two-hip model.

00:54:55.580 | When you, this is also true for concussion,

00:54:57.800 | that you can take a kind of a stimulus

00:54:59.860 | that normally would be below the threshold of injury,

00:55:02.020 | you add another stimulus at the same time

00:55:05.140 | that would be below the threshold of injury,

00:55:06.820 | and then suddenly you killed the neurons.

00:55:08.800 | So I don't want to make people paranoid,

00:55:10.580 | but you do want to protect your hearing.

00:55:11.860 | It's no fun to lose your hearing.

00:55:13.600 | If you're going to use headphones

00:55:15.160 | and you feel like you want to crank it up all the way,

00:55:17.040 | just remember that the more that you can get

00:55:20.740 | out of a lower volume,

00:55:22.060 | meaning the longer that you can go listening

00:55:23.820 | to things at lower volume,

00:55:25.640 | the longer you'll be able to hear that music or that thing.

00:55:30.120 | So again, I'm not the hearing cop, that's not my job,

00:55:35.120 | but as somebody who's lost

00:55:36.740 | some of his high-frequency hearing,

00:55:38.660 | I can tell you it's not a pleasure.

00:55:41.860 | The old argument that it helps you not have to hear

00:55:45.480 | or listen to people that you don't want to listen to,

00:55:47.260 | that it doesn't really work,

00:55:48.340 | they just send you text messages instead.

00:55:50.380 | So what about white noise and hearing loss in development?

00:55:53.980 | You know, a lot of people with children

00:55:55.340 | have these kind of noise machines,

00:55:57.580 | like sound waves and things like that,

00:55:59.240 | that help the kids sleep.

00:56:00.980 | And look, I think kids getting good sleep

00:56:03.620 | and parents getting good sleep is vital

00:56:05.500 | to physical and mental health and family health.

00:56:08.940 | So I certainly sympathize with those needs.

00:56:13.860 | However, there are data that indicate

00:56:17.020 | that white noise during development

00:56:19.780 | can be detrimental to the auditory system.

00:56:22.400 | I don't want to frighten any parents,

00:56:23.700 | if you played white noise to your kids,

00:56:25.460 | this doesn't mean that their auditory system

00:56:27.060 | or their speech patterns are going to be disrupted

00:56:29.740 | or that their interpretation of speech

00:56:31.100 | is going to be disrupted forever,

00:56:32.900 | but there are data published in the journal Science,

00:56:37.140 | in Science being one of the three apex journals,

00:56:39.580 | Science, Nature, Cell, the most stringent journals,

00:56:42.360 | data published in the journal Science some years ago,

00:56:46.180 | actually by a scientist who I know quite well,

00:56:48.300 | his name is Edward Chang, he's a medical doctor now,

00:56:50.820 | he's a neurosurgeon,

00:56:51.900 | he's actually the chair of neurosurgery at UCSF,

00:56:55.100 | and he runs a laboratory where they study auditory learning,

00:56:58.840 | neuroplasticity, et cetera.

00:57:00.440 | He and his mentor at the time, Mike Mursinek,

00:57:04.740 | published a paper showing that if young animals,

00:57:08.580 | and this wasn't animal models,

00:57:10.460 | were exposed to white noise,

00:57:13.100 | so shh, the very type of noise that I'm saying

00:57:17.140 | as a older person, and when I say older,

00:57:19.760 | I mean somebody who's in their late teens,

00:57:21.940 | early 20s and older, could benefit from listening to that

00:57:25.060 | at a low level in the background for sake of learning,

00:57:28.500 | well, they exposed very young animals to this white noise,

00:57:32.040 | it actually disrupted the maps of the auditory world

00:57:36.600 | within the brain.

00:57:37.680 | And we haven't talked about these maps yet,

00:57:39.240 | but I want to take a moment and talk about them

00:57:40.640 | and explain this effect and what it might mean for you

00:57:44.000 | if you have kids or if you were exposed

00:57:45.560 | to a lot of white noise early on.

00:57:47.620 | So auditory information goes up into our cortex,

00:57:52.280 | into essentially the outside portion of our brain

00:57:55.740 | that's responsible for all of our higher level cognition,

00:57:59.520 | our planning, our decision-making, et cetera,

00:58:01.800 | creativity, and up there,

00:58:04.680 | we have what are called tonotopic maps.

00:58:06.920 | What's a tonotopic map?

00:58:08.400 | Well, remember the cochlea, how it's coiled,

00:58:10.720 | and at one end, it responds to high frequencies,

00:58:12.680 | and the other end, it responds to low frequencies?

00:58:15.520 | Sort of like a piano, the keys sound different

00:58:17.720 | as you extend down and up the piano keys,

00:58:20.960 | and it's organized in a very systematic way, right?

00:58:23.680 | It's not all intermixed high frequencies and low frequencies,

00:58:26.280 | it's organized in a very systematic way

00:58:29.040 | from one end to the other.

00:58:30.700 | Your visual system is in what's called a retinotopic map,

00:58:33.640 | so neighboring points in space off to my right,

00:58:36.860 | like my two fingers off to my right,

00:58:38.900 | are mapped to neighboring points in space in my brain,

00:58:43.000 | and the space right in front of me

00:58:45.420 | is mapped to a different location in my brain,

00:58:47.160 | but it's systematic, it's regular, it's not random,

00:58:49.800 | it's not salt and pepper, it goes from high to low

00:58:52.440 | or from right to center to left.

00:58:54.960 | In the auditory system,

00:58:56.080 | we have what are called tonotopic maps,

00:58:58.460 | where frequency, high frequency to low frequency,

00:59:02.320 | and everything in between is organized

00:59:04.240 | in a very systematic way.

00:59:06.340 | Now, our experience of life from the time we're a baby

00:59:09.520 | until the time that we die is not systematic,

00:59:12.640 | we don't hear low frequencies at one part of the room

00:59:15.160 | or at one part of the day,

00:59:16.040 | and high frequencies at another part of the room

00:59:17.660 | and another part of the day, they're all intermixed,

00:59:20.400 | but if you remember, the cochlea separates them out

00:59:23.480 | just like a prism of light separates out

00:59:25.560 | the different wavelengths of light,

00:59:26.740 | the cochlea separates out the different frequencies,

00:59:29.980 | and the developing brain takes those separated out

00:59:33.880 | frequencies and learns this relationship

00:59:37.000 | between itself, meaning the child, and the outside world.

00:59:41.860 | White noise essentially contains no tonotopic information,

00:59:48.440 | the frequencies are all intermixed, it's just noise,

00:59:52.840 | whereas when I speak, my voice has,

00:59:55.400 | now I'm getting technical, but it has what's called

00:59:57.380 | a certain envelope, meaning it has some low frequencies

01:00:00.100 | and some slightly high frequencies,

01:00:01.440 | I can make my voice higher, although I'm not very good

01:00:03.820 | at that, my voice starts to crack,

01:00:05.820 | and I can make my voice lower,

01:00:07.180 | although not as low as Costello's snore,

01:00:08.860 | so it has an envelope, it has a container,

01:00:11.420 | white noise has no container,

01:00:14.020 | it's like all the colors of the rainbow spread out together,

01:00:17.400 | which is actually what you get when you get white light,

01:00:19.860 | white noise is analogous to white light.

01:00:23.400 | So one of the reasons why hearing a lot of white noise

01:00:28.400 | during development for long periods of time

01:00:31.600 | can be detrimental to the development of the auditory system

01:00:34.360 | is that these tonotopic maps don't form normally,

01:00:37.120 | at least they don't in experimental animals.

01:00:39.040 | Now, the reason I'm raising this is that many people I know,

01:00:43.400 | in particular friends who have small children,

01:00:45.800 | they say, I want to use a white noise machine while I sleep,

01:00:51.980 | but is it okay for my baby to use a white noise machine?

01:00:56.160 | And I consulted with various people, scientists about this,

01:00:59.740 | and they said, well, you know,

01:01:02.080 | the baby is also hearing the parents' voices

01:01:04.360 | and is hearing music and is hearing the dog bark,

01:01:06.500 | so it's not the only thing they're hearing.

01:01:08.320 | However, every single person that I consulted with said,

01:01:12.780 | but you know, there's neuroplasticity during sleep,

01:01:15.800 | that's when the kid is sleeping,

01:01:17.640 | and I don't know that you'd want to expose a child

01:01:20.460 | to white noise the entire night,

01:01:22.560 | because it might degrade that tonotopic map.

01:01:26.320 | It might not destroy it, it might not eliminate it,

01:01:28.880 | but it could make it a little less clear,

01:01:32.000 | like sort of taking the keys on the piano

01:01:34.960 | and taping a few of them together, right?

01:01:37.360 | So you've still got the highs and lows

01:01:38.720 | in the appropriate order and everything in between,

01:01:41.080 | but when you tape the keys together,

01:01:42.720 | you don't get the same fidelity,

01:01:44.320 | you don't get the same precision

01:01:46.360 | of the noise that comes out of that piano.

01:01:49.760 | So again, I don't want to scare anybody,

01:01:52.920 | but I would say if you are in a position

01:01:54.600 | to make the choice of either using white noise

01:01:57.600 | or something similar,

01:01:58.600 | pink noise is just a kind of variation,

01:02:00.260 | it's got a little bit more of a certain frequency,

01:02:02.260 | just like pink light has a little bit more

01:02:04.200 | of a certain wavelength than white light,

01:02:06.000 | kind of if you are in a position to make choices

01:02:11.000 | about things to put in a young,

01:02:13.860 | especially very young child's sleeping environment,

01:02:16.400 | white noise might be something to consider avoiding,

01:02:19.680 | again, I'm not telling you what to do,

01:02:21.200 | but it's something to perhaps consider avoiding.

01:02:23.720 | I don't think most pediatricians

01:02:25.380 | are going to be aware of these data,

01:02:27.300 | but if you talk to any auditory physiologists

01:02:30.200 | or an audiologist or somebody

01:02:31.940 | who studies auditory development,

01:02:34.280 | I'm fairly certain that they would have opinions about that.

01:02:37.200 | Now, whether or not their opinions agree with mine

01:02:39.440 | and these folks that I consulted with or not

01:02:41.840 | is a separate matter, I don't know 'cause I don't know them,

01:02:44.960 | but it's something that I felt was important enough

01:02:47.280 | to cue you to, especially since I've highlighted,

01:02:51.440 | excuse me, the opposite effect is true in adulthood.

01:02:54.060 | Once your auditory system has formed,

01:02:56.460 | once it's established these tonotopic maps,

01:02:58.640 | then the presence of background white noise

01:03:01.120 | should not be a problem at all.

01:03:02.720 | In fact, it shouldn't be a problem at all

01:03:05.240 | because you're also not attending to it.

01:03:07.300 | The idea is that it's playing at a low enough volume

01:03:09.460 | that you kind of forget it in the background

01:03:11.080 | and that it's supporting learning by bringing your brain

01:03:13.960 | into a heightened state of alertness

01:03:15.200 | and especially this heightened state of dopamine,

01:03:17.640 | dopaminergic activation of the brain,

01:03:19.800 | which will make it easier to learn faster

01:03:22.360 | and easier to learn the information.

01:03:24.680 | So now I want to talk about auditory learning

01:03:27.340 | and actually how you can get better

01:03:29.000 | at learning information that you hear,

01:03:30.960 | not just information that you see on a page

01:03:33.860 | or motor skill learning.

01:03:35.920 | There are a lot of reasons to want to do this.

01:03:37.560 | A lot of classroom teaching,

01:03:39.000 | whether or not it's by Zoom or in person

01:03:41.520 | is auditory in nature.

01:03:42.960 | Not everything is necessarily written down for us.

01:03:47.080 | It's also good to get better at listening or so I'm told.

01:03:52.080 | So there's a phenomenon called the cocktail party effect.

01:03:55.960 | Now, even if you've never been to a cocktail party,

01:03:58.040 | you've experienced and participated

01:04:00.780 | in what's called the cocktail party effect.

01:04:02.900 | The cocktail party effect is where you are in an environment

01:04:05.780 | that's rich with sound, many sound waves

01:04:08.200 | coming from many different sources, many different things.

01:04:10.520 | So in a city, in a classroom, in a car

01:04:14.060 | that contains people having various conversations,

01:04:16.520 | you somehow need to be able to attend

01:04:20.560 | to specific components of those sound waves,

01:04:22.880 | meaning you need to hear certain people and not others.

01:04:25.640 | The reason it's called the cocktail party effect

01:04:27.920 | is that you and meaning your brain are exquisitely good

01:04:32.920 | at creating a cone of auditory attention,

01:04:37.640 | a narrow band of attention with which you can extract

01:04:40.960 | the information you care about

01:04:42.760 | and wipe away or erase all the rest.

01:04:46.100 | Now, this takes work, it takes attention.

01:04:50.360 | One of the reasons why you might come home

01:04:52.380 | from a loud gathering, maybe a stadium, a sports event,

01:04:55.960 | or a cocktail party for that matter and feel just exhausted

01:04:59.200 | is because if you were listening to conversations there

01:05:01.720 | or trying to listen to those conversations

01:05:03.400 | while watching the game and people moving past you

01:05:05.720 | and hearing all this noise, clinking of glasses, et cetera,

01:05:10.520 | it takes attentional effort

01:05:12.360 | and the brain uses up a lot of energy just at rest,

01:05:17.360 | but it uses up even more energy

01:05:19.940 | when you are paying strong attention to something,

01:05:22.160 | literally caloric energy,

01:05:23.660 | burning up things like glucose, et cetera.

01:05:25.480 | Even if you're ketogenic, it's burning up energy.

01:05:28.640 | So the cocktail party effect has been studied extensively

01:05:32.660 | in the field of neuroscience.

01:05:33.840 | And we now know at a mechanistic level

01:05:36.580 | how one accomplishes this feat of attending to certain sounds

01:05:40.740 | despite the fact that we are being bombarded

01:05:43.480 | with all sorts of other sounds.

01:05:45.380 | So there are a couple of ways that we do this.

01:05:46.880 | First of all, much as with our visual system,

01:05:51.880 | we can expand or contract our visual field of view.

01:05:56.980 | So we can go from panoramic vision,

01:05:59.560 | see the entire scene that we are in by dilating our gaze,

01:06:03.320 | talked a lot about this on this podcast and elsewhere.

01:06:05.840 | We can, for instance, keep our head and eyes stationary

01:06:08.520 | or mostly stationary.

01:06:09.560 | You don't have to be rigid about it.

01:06:10.560 | And you can expand your field of view

01:06:11.920 | so you can see the walls and ceiling and floor,

01:06:14.200 | can see yourself in the environment.

01:06:15.360 | That's panoramic view.

01:06:16.720 | It's what you would accomplish without having to try at all

01:06:18.880 | if you went to a horizon, for instance.

01:06:21.880 | Or we can contract our field of view.

01:06:23.520 | I can bring my focus to a particular location,

01:06:26.720 | what we call a vergence point, directly in front of me.

01:06:28.560 | Now I'm pointing at the camera directly in front of me.

01:06:31.480 | Okay, we can do that.

01:06:32.320 | We can expand and contract our visual field of view.

01:06:34.220 | Well, we can expand and contract

01:06:37.200 | our auditory field of view, so to speak,

01:06:40.840 | or our auditory window.

01:06:43.080 | You can try this next time you are in an environment

01:06:46.400 | that's rich with noise, meaning lots of different sounds.

01:06:49.440 | You can just tune out all the noise to a background chatter.

01:06:54.440 | You kind of just, you try not focus

01:06:56.900 | on any one particular sound

01:06:59.280 | and you get the background kind of chatter of noise.

01:07:02.840 | And you'll find that it's actually very relaxing

01:07:05.040 | in comparison to trying to listen to somebody

01:07:06.840 | at a cocktail party and you're shouting back and forth.

01:07:08.560 | Now, if you're very, very interested in that person

01:07:10.560 | or getting to know them better, or what they're telling you,

01:07:13.940 | or some combination of those things,

01:07:15.440 | then you'll be very motivated to do it,

01:07:17.420 | but nonetheless it requires energy and effort and attention.

01:07:21.220 | How do we do this?

01:07:23.280 | Well, it's actually quite simple,

01:07:27.280 | or at least it's simple in essence,

01:07:29.600 | although the underlying mechanisms are complex.

01:07:32.720 | Here I have to credit the laboratory

01:07:35.900 | of a guy named Mike Wehr, W-E-H-R,

01:07:39.560 | up at the University of Oregon,

01:07:41.160 | who essentially figured out that we are able

01:07:45.220 | to accomplish this extraction of particular sounds.

01:07:48.040 | We can really hear one person or a small number of people

01:07:52.160 | amidst a huge background of chatter

01:07:54.840 | because we pay attention to the onset of words,

01:07:59.840 | but also to the offset of words.

01:08:03.000 | Now, the way to visualize this is if the background noise

01:08:07.040 | is just like a bunch of waves of noise,

01:08:08.920 | it's literally just sound waves coming every frequency,

01:08:11.320 | low frequency, high frequency, glasses clinking together.

01:08:13.720 | If you're at a game, people are shouting,

01:08:15.200 | people are talking on their phone.

01:08:17.080 | There's the crack of the ball if somebody actually manages

01:08:20.280 | to hit the ball, the announcer, et cetera.

01:08:24.420 | But whatever we're paying attention to,

01:08:27.300 | we set up a cone of auditory attention,

01:08:29.620 | a kind of a tunnel of auditory attention

01:08:32.280 | where we are listening, although we don't realize it,

01:08:34.400 | we are listening for the onset and the offset of those words.

01:08:39.060 | Now, this is powerful for a couple of reasons.

01:08:41.660 | First of all, it's a call to arms, so to speak,

01:08:46.660 | to disengage your auditory system

01:08:50.520 | when you don't need to focus your attention

01:08:52.420 | on something particular.

01:08:53.840 | So if you are somebody, you're coming home from work,

01:08:56.020 | you've had a very long day and you're trying to make out

01:09:00.180 | a particular conversation on background noise,

01:09:03.420 | you might consider just not having that conversation,

01:09:06.380 | just letting your auditory landscape be very broad,

01:09:10.420 | almost like panoramic vision.

01:09:11.880 | If you're trying to learn how to extract sound information,

01:09:17.040 | it could be notes of music, it could be scales of music,

01:09:22.340 | it could be words spoken by somebody else.

01:09:24.780 | Maybe somebody is telling you what you need to say

01:09:27.500 | for a particular speech or the information

01:09:30.260 | that you need to learn for a particular topic

01:09:32.560 | and they're telling it to you.

01:09:34.060 | Deliberately paying attention both to the onset

01:09:37.740 | and to the offset of those words can be beneficial

01:09:41.320 | because it is exactly the way that the auditory system

01:09:44.860 | likes to bring in information.

01:09:47.220 | So one of the more common phenomenon

01:09:50.460 | that I think we all experience is you go to a party

01:09:53.460 | and/or you meet somebody new and you say,

01:09:55.780 | "Hi," I would say, "Hi, I'm Andrew,"

01:09:57.360 | and they'd say, "Hi, I'm Jeff," for instance.

01:09:59.820 | Great, great to meet you.

01:10:00.660 | And then a minute later, I can't remember the guy's name.

01:10:03.920 | Now, is it because I don't care what his name is?

01:10:05.660 | No, somehow the presence

01:10:08.100 | of other auditory information interfered.

01:10:10.260 | It's not that my mind was necessarily someplace else,

01:10:12.740 | it's that the signal to noise, as we say, wasn't high enough.

01:10:17.500 | Somehow the way he said it or the way it landed on my ears,

01:10:22.460 | which is really all that matters, right,

01:10:24.660 | when it comes down to learning,

01:10:26.440 | is such that it just didn't achieve

01:10:29.820 | high enough signal to noise.

01:10:31.620 | The noise was too high or the signal was too low

01:10:33.940 | or some combination of those.

01:10:35.820 | So the next time you ask somebody's name,

01:10:37.460 | remember, listen to the onset of what they say

01:10:40.060 | and the offset.

01:10:40.900 | So it would be paying attention to the j in Jeff

01:10:43.940 | and it would be paying attention to the th in F, in Jeff.

01:10:47.500 | Excuse me, all right?

01:10:49.540 | And chances are you'll be able to remember that name.

01:10:53.140 | Now, I don't know if people who are super learners of names

01:10:58.020 | do this naturally or not.

01:10:59.360 | I don't have access to their brains.

01:11:01.020 | I don't think they're going to give me access

01:11:02.180 | to their brains either.

01:11:03.500 | But it's a very interesting way to take the natural biology

01:11:07.060 | of auditory attention and learning

01:11:08.820 | and apply it to scenarios where you're trying to remember

01:11:11.700 | either people's names or specific information.

01:11:14.540 | Now, I do acknowledge that trying to learn every word

01:11:17.580 | in a sentence by paying attention to its onset and offset

01:11:21.560 | could actually be kind of disruptive

01:11:23.020 | to the learning process.

01:11:24.780 | So this would be more for specific attention.

01:11:27.340 | Like you're asking directions in a city and somebody says,

01:11:29.520 | okay, you say you're lost and they say, okay,

01:11:32.220 | you're going to go two blocks down,

01:11:34.540 | you're going to turn left,

01:11:35.860 | and then you're going to see a landmark on your right

01:11:37.820 | and then you're going to go in the third door on your left.

01:11:42.820 | That's a lot of information, at least for me, okay?

01:11:45.420 | So the way you would want to listen to that is

01:11:48.180 | you're going to go down the road.

01:11:50.260 | See, I already forgot.

01:11:51.240 | You're going to go left and you're just going to program.

01:11:54.720 | And instead of just hearing the word left,

01:11:56.220 | you're going to think the L at the front of left and the T.

01:11:59.900 | You're going to left, okay?

01:12:02.140 | And then, so you're coding in specific words.

01:12:05.060 | And what this does is this kind of hijacks

01:12:07.780 | these naturally occurring attention mechanisms

01:12:09.980 | that the auditory system likes to use.

01:12:12.500 | It's a little bit of data that for auditory encoding,

01:12:15.460 | this kind of thing can be beneficial.

01:12:17.640 | There are a lot of data that attention

01:12:20.580 | for auditory coding is beneficial.

01:12:23.660 | There are a little bit of data showing

01:12:26.660 | that deliberately encoding auditory information this way,

01:12:29.980 | meaning trying to learn auditory information this way,

01:12:32.740 | can be beneficial or can accelerate learning.

01:12:35.580 | And some of these features of what I'm describing here

01:12:39.000 | map onto some of the work of Mike Merzenich and others

01:12:43.580 | that have been designed to try and overcome things

01:12:46.500 | like stutter and to treat various forms

01:12:49.780 | of auditory learning disorders.

01:12:52.180 | But more importantly, and perhaps more powerful,

01:12:56.620 | is the work of Mike Merzenich

01:12:59.020 | that was done with his then graduate student,

01:13:01.260 | Greg Recanzone, that showed that

01:13:04.660 | using the attentional system,

01:13:06.700 | we can actually learn much faster

01:13:09.380 | and we can actually activate neuroplasticity

01:13:12.660 | in the adult brain, something that's very challenging to do,

01:13:15.980 | and that the auditory system is one of the main ways

01:13:19.460 | in which we can access neuroplasticity more broadly.

01:13:22.580 | So I just want to take a couple of minutes

01:13:24.120 | and describe the work of Recanzone and Merzenich

01:13:26.340 | because it's absolutely fantastic and fascinating.

01:13:30.500 | What they did is they had subjects

01:13:33.980 | try to learn auditory information,

01:13:36.940 | except that they told them to pay attention

01:13:40.020 | to particular frequencies.

01:13:42.400 | So now you know what frequencies are,

01:13:43.760 | so essentially high-pitched sounds or low-pitched sounds.

01:13:47.420 | What they found was just passively listening

01:13:52.300 | to a bunch of stuff does not allow the brain to change

01:13:56.180 | and for that stuff to be remembered at all.

01:13:58.920 | That's not a surprise.

01:13:59.940 | We've all experienced the phenomenon of having someone talk

01:14:03.540 | and we see their mouth moving and we're like,

01:14:04.900 | yeah, this is really important, this is really important,

01:14:06.620 | we're listening, we're trying to listen,

01:14:07.980 | and then they walk away and we think,

01:14:09.260 | I didn't get any of that.

01:14:11.340 | And you wonder whether or not it was them.

01:14:13.340 | Maybe this is happening to you right now.

01:14:15.020 | You wonder whether or not it was you.

01:14:17.720 | You wonder whether or not you have trouble with learning

01:14:19.740 | or you have attention deficit.

01:14:21.220 | It could be any number of different things,

01:14:23.180 | but what Recanzone and Merzenich discovered

01:14:25.260 | was that if you instruct subjects to listen

01:14:28.480 | for particular cues within speech or within sounds,

01:14:32.780 | that not only can you learn those things more quickly,

01:14:35.740 | but that you can remap these tonotopic maps in the cortex

01:14:40.740 | that I referred to earlier.

01:14:43.140 | You actually get changes in the neural architecture,

01:14:45.420 | the neural circuitry in the brain,

01:14:46.980 | and this can occur not only very rapidly,

01:14:50.640 | but they can occur in the adult brain,

01:14:53.100 | which prior to their work

01:14:54.860 | was not thought to be amenable to change.

01:14:57.340 | It was long thought that neuroplasticity

01:14:59.420 | could only occur in the developing brain,

01:15:01.220 | but the work of Recanzone and Merzenich

01:15:03.180 | in the auditory system actually was some of the first

01:15:06.780 | that really opened up everybody's eyes and ears

01:15:10.700 | to the idea that the brain can change in adulthood.

01:15:14.060 | So here's how this sort of process would work

01:15:16.340 | and how you might apply it.

01:15:18.340 | If you are trying to learn music

01:15:20.540 | or you're trying to learn information

01:15:23.520 | that you're going to then recite,

01:15:25.180 | you can decide to highlight certain words

01:15:30.100 | or certain frequencies of sound

01:15:33.620 | or certain scales or certain keys on the piano

01:15:36.380 | and to only focus on those for certain learning bouts.

01:15:40.220 | So I'll give an example that's sort of real time for me,

01:15:44.320 | meaning it's happening right now.

01:15:45.980 | I know generally what I want to say when I arrive here.

01:15:51.340 | I even know specifically certain things

01:15:53.280 | that I want to make sure get across to you,

01:15:55.500 | but I don't think about every single word

01:15:58.900 | that I'm going to say and the precise order

01:16:01.460 | in which I'm going to say those things.

01:16:03.300 | That would be actually very disruptive

01:16:05.200 | because it wouldn't match my normal patterns of speech

01:16:07.500 | and you'd probably think I was sounding rather robotic

01:16:10.540 | if I were to do that.

01:16:11.840 | So one way that we can remember information is

01:16:15.780 | as we write out, for instance, something that we want to say,

01:16:19.140 | we can highlight particular words.

01:16:20.900 | We can underline those.

01:16:22.280 | If we're listening to somebody

01:16:24.660 | and they are telling us information,

01:16:28.780 | we can decide just to highlight particular words

01:16:31.740 | that they said to us and write those down.

01:16:34.380 | Now, of course, we're listening to all the information,

01:16:36.980 | but the work of Reconzone and Merzenich

01:16:38.900 | and the work of others, in addition to them,

01:16:42.500 | his former student or former postdoc, I don't know which,

01:16:46.620 | Michael Kilgard, who's now got his own lab down in Texas,

01:16:49.540 | or others, have shown that the queuing of attention

01:16:52.440 | to particular features of speech,

01:16:54.700 | particular components of speech,

01:16:57.020 | the way in which it increases our level of attention overall

01:17:00.420 | allows us to capture more of the information overall.

01:17:04.100 | And so I don't want this to be abstract at all.

01:17:05.980 | What this means is when you're listening,

01:17:07.880 | you don't have to listen to every word.

01:17:10.380 | You're already listening to every word.

01:17:12.080 | All the information's coming in through your ears.

01:17:14.380 | What you're trying to extract is particular things

01:17:18.740 | or themes within the content.

01:17:20.740 | So maybe you decide, if you're listening to me,

01:17:22.580 | that you're only going to listen to the word tools

01:17:26.180 | or you're only going to listen

01:17:27.220 | to when my voice kind of goes above background.

01:17:29.820 | You get to decide what you decide to listen to or not.

01:17:32.700 | And what you decide to focus on

01:17:34.940 | isn't necessarily as important

01:17:37.360 | as the fact that you're focusing.

01:17:39.240 | So I hope that's clear.

01:17:40.540 | The auditory system does this all the time

01:17:42.780 | with the cocktail party effect.

01:17:44.020 | What I'm talking about is exporting certain elements

01:17:46.720 | of the mechanisms of the cocktail party effect,

01:17:49.360 | paying attention to the onset and offset of words

01:17:51.820 | or particular notes within music or particular scales,

01:17:55.500 | or you can make it even broader

01:17:58.020 | and particular motifs of music

01:18:00.200 | or particular sentences of words or particular phrases.

01:18:03.500 | And in doing that,

01:18:04.480 | you extract more of the information overall,

01:18:08.280 | even though you're not paying attention

01:18:09.500 | to all the information at once.

01:18:11.780 | Now I'd like to talk about a phenomenon

01:18:13.420 | that you've all experienced before, which is called Doppler.

01:18:17.900 | So the Doppler effect is the way that we experience sound

01:18:24.300 | when the thing that's making that sound is moving.

01:18:27.840 | The simplest way to explain this

01:18:30.540 | is to translate the sound into the visual world once again.

01:18:35.380 | So if you've ever seen a duck or a goose

01:18:39.080 | sitting in a pond or a lake,

01:18:41.820 | and it's kind of bobbing up and down,

01:18:44.420 | what you'll notice is that the ripples of water

01:18:46.580 | that extend out from that duck or goose

01:18:49.360 | are fairly regularly spaced in all directions.

01:18:52.060 | And that's because that duck or goose is stationary.

01:18:54.700 | It's moving up and down,

01:18:55.540 | but it's not moving forward or backward or to the side.

01:18:58.960 | Now, if that duck or goose were to swim forward

01:19:02.100 | by paddling its little webbed feet under the surface,

01:19:05.900 | you would immediately notice that the ripples of water

01:19:09.080 | that are close to and in front of that duck or goose

01:19:12.460 | would be closer together than the ones that trailed it,

01:19:15.480 | that were behind.

01:19:16.780 | And that is essentially what happens with sound as well.

01:19:21.160 | With the Doppler effect,

01:19:23.300 | we experience sounds that are closer to us

01:19:25.740 | at higher frequency, the ripples are closer together,

01:19:29.440 | and sounds that are further away at lower frequency,

01:19:32.700 | especially when they're moving past us.

01:19:35.000 | So if you've ever, for instance,

01:19:37.060 | heard a siren in the distance,

01:19:39.360 | [hums]

01:19:41.360 | that's essentially my rendition of a siren.

01:19:50.400 | I don't know what ambulance or police or what,

01:19:52.860 | passing you on a street.

01:19:54.900 | That is the Doppler effect.

01:19:57.260 | The Doppler effect is one of the main ways

01:19:59.920 | that we make out the direction that things are arriving from

01:20:04.920 | and their speeds and trajectories.

01:20:08.020 | And we get very good from a very young age

01:20:11.680 | at discerning what direction things are arriving from

01:20:15.280 | and the direction that they are going to pass us in.

01:20:19.300 | And the Doppler effect has probably saved your life

01:20:21.240 | many, many times.

01:20:22.980 | In this way, you just don't realize it

01:20:24.520 | because you'll step off the curb

01:20:25.940 | or you're driving your car and you pull to the side

01:20:29.260 | so that the ambulance or fire truck can go by

01:20:32.120 | because you heard that siren off in the distance.

01:20:37.060 | And then you pull away from the curb

01:20:38.500 | and you get back on the road,

01:20:39.960 | in part because you don't see it any longer,

01:20:41.840 | but also you don't hear any other sirens in the distance.

01:20:44.940 | Now, some animals such as bats are exquisitely good

01:20:49.000 | at navigating their environments according to sound.

01:20:51.920 | Now, we've all heard that bats don't see.

01:20:55.320 | That's actually not true.

01:20:56.360 | They actually have vision,

01:20:57.680 | but they just rely more heavily on their auditory system.

01:21:00.280 | And the way that bats navigate in the dark

01:21:03.520 | and the way that bats navigate using sound

01:21:06.280 | is through Doppler.

01:21:07.880 | Now, they don't simply listen to whether or not

01:21:11.120 | things are coming at them or moving away from them

01:21:14.640 | and pay attention to Doppler

01:21:15.760 | like the siren example I gave for you

01:21:18.920 | what they do is they generate their own sounds.

01:21:22.600 | So a bat, as it flies around is sending out clicks.

01:21:27.600 | I think that's my best bat sound

01:21:30.400 | or maybe it's, and they're clicking.

01:21:33.180 | They're actually propelling sound out

01:21:35.080 | at a particular frequency that they know.

01:21:38.320 | Now, whether or not they're conscious of it, I don't know.

01:21:40.180 | I've never asked them.

01:21:41.020 | And if I did ask them, I don't think they could answer.

01:21:42.500 | And if they could answer,

01:21:43.340 | they couldn't answer in a language that I could understand.

01:21:45.820 | But the bat is essentially flying around,

01:21:48.120 | sending out sound waves,

01:21:49.760 | pinging its environment with sound waves

01:21:52.040 | of a particular frequency.

01:21:53.360 | And then depending on the frequency of sound waves

01:21:55.800 | that come back,

01:21:57.200 | they know if they're getting closer to an object

01:21:59.940 | or further away from it.

01:22:01.120 | So if they send out sounds at a frequency of,

01:22:03.860 | this was much slower than it would actually occur,

01:22:06.660 | but let's say one every half second [mumbles]

01:22:10.720 | and it's coming back even faster [mumbles]

01:22:13.760 | then they know they're getting closer, right?

01:22:15.720 | Because of the Doppler effect.

01:22:18.000 | And if it comes back more slowly,

01:22:20.240 | they know that there's nothing in front of them.

01:22:22.280 | So the bat is essentially navigating its world

01:22:25.840 | by creating these auras of sound

01:22:29.380 | that bounce back onto them from the various objects,

01:22:32.960 | trees, et cetera, buildings, and people.

01:22:35.520 | It's kind of eerie to think about,

01:22:36.360 | but yes, they see you with the,

01:22:38.200 | experience you with their sound.

01:22:39.880 | They sense you.

01:22:40.800 | And they're using Doppler to accomplish it.

01:22:44.440 | Now I'd like to talk about ringing in the ears.

01:22:48.000 | This is something that I get asked about a lot.

01:22:51.000 | And speaking of signal to noise,

01:22:53.360 | I don't know if I get asked about it a lot

01:22:55.540 | because many people suffer from ringing in their ears

01:22:58.920 | or because the people who suffer

01:23:00.400 | from ringing in their ears suffer so much

01:23:03.120 | that they are more prone to ask.

01:23:05.460 | So it could be a sampling bias, I don't know,

01:23:08.280 | but I've been asked enough times

01:23:10.400 | and some of the experiences of discomfort

01:23:12.780 | that people have expressed about having

01:23:15.040 | this ringing of the ears really motivated me

01:23:18.100 | to go deep into this literature.

01:23:20.640 | So the ringing of the ears that one experiences

01:23:24.120 | is called tinnitus, not tinnitus, but tinnitus.

01:23:29.120 | And tinnitus can vary in intensity,

01:23:32.700 | and it can vary according to stress levels.

01:23:36.200 | It can vary across the lifespan or even time of day.

01:23:40.520 | So it's very subject to kind of background effects

01:23:43.360 | and contextual effects.

01:23:45.800 | So I think we all know that we should do our best

01:23:48.820 | to maximize healthy sleep.

01:23:50.160 | We did a number of episodes on that.

01:23:51.960 | Essentially the first four episodes

01:23:53.760 | of the Huberman Lab Podcast were all about sleep

01:23:55.620 | and how to get better sleep.

01:23:57.020 | We all know that we should try and limit our stress,

01:24:00.120 | and we had an episode about stress

01:24:02.200 | and ways to mitigate stress as well.

01:24:04.400 | However, there are people, it seems,

01:24:08.440 | that are suffering from tinnitus

01:24:09.840 | for which stress or lack of sleep

01:24:12.400 | just can't explain the presence of the tinnitus.

01:24:15.000 | Tinnitus can be caused by disruption to these hair cells

01:24:20.560 | that we talked about earlier or damage to the hair cells.

01:24:23.640 | So that's another reason why,

01:24:25.200 | even if you have good hearing now,

01:24:28.400 | that you want to protect that hearing

01:24:30.040 | and really avoid putting yourself

01:24:32.560 | into these kind of two-hit environments,

01:24:34.680 | environments where there's a lot of background noise,

01:24:36.920 | and then you add another really loud auditory stimulus.

01:24:40.960 | This also can happen at different times, I should mention.

01:24:43.560 | If you go to a concert

01:24:45.280 | or you listen to loud music with your headphones,

01:24:48.000 | and then you go to a concert

01:24:49.620 | or you go into a very loud work environment,

01:24:52.120 | the hair cells can still be vulnerable.

01:24:53.920 | And once those hair cells are knocked out,

01:24:56.560 | currently we don't have the technology to put them back,

01:24:58.780 | although many groups,

01:24:59.920 | including some excellent groups at Stanford and elsewhere too,

01:25:03.440 | of course, are working on ways

01:25:05.360 | to replenish those hair cells and restore hearing.

01:25:08.720 | There are treatments for tinnitus

01:25:11.520 | that involve taking certain substances.

01:25:16.400 | There are medications for tinnitus.

01:25:19.880 | In the non-prescription landscape,

01:25:21.800 | which is typically what we discuss on this podcast

01:25:24.280 | when we discuss taking anything,

01:25:26.020 | there are essentially four compounds

01:25:29.620 | for which there are quality peer-reviewed data

01:25:32.560 | where there does not appear to be any overt commercial bias,

01:25:36.880 | meaning that nothing's reported in the papers

01:25:39.040 | as funding from a particular company.

01:25:41.120 | And those are melatonin, ginkgo bilboa, zinc, and magnesium.

01:25:46.120 | Now, I've talked about melatonin before.

01:25:49.080 | I'm personally not a fan of melatonin as a sleep aid,

01:25:53.080 | but there are four studies.

01:25:55.440 | First one entitled "The Effects of Melatonin on Tinnitus"

01:26:01.560 | and "Sleep."

01:26:02.680 | Second one, "Treatment of Sensual and Sensory Neural Tinnitus

01:26:05.780 | with Orally Administered Melatonin,"

01:26:07.640 | and then the title goes on much longer,

01:26:09.600 | but it's a randomized study.

01:26:11.560 | I'm not going to read out all of these.

01:26:12.600 | "Melatonin, Can it Stop the Ringing?"

01:26:14.660 | which is an interesting article, double-blinded study,

01:26:17.720 | and "The Effects of Melatonin on Tinnitus."

01:26:20.060 | Each one of these studies has anywhere from 30

01:26:23.840 | to more than 100 subjects,

01:26:26.960 | in one case, 102 subjects, both genders,

01:26:29.240 | as they list them out.

01:26:30.960 | Typically, it's listed as sex, not gender in studies,

01:26:34.040 | so it should say both sexes, but nonetheless.

01:26:37.400 | An age range anywhere from 30 years old

01:26:42.560 | all the way up to 65 plus.

01:26:44.400 | I didn't see any studies of people younger than 30.

01:26:47.780 | All three focused on melatonin,

01:26:51.980 | not surprisingly because of the titles.

01:26:54.600 | Looking at a range of dosages,

01:26:56.080 | anywhere from three milligrams per day,

01:26:58.600 | which is sort of typical of many supplements for melatonin,

01:27:02.280 | still much higher than one would manufacture endogenously

01:27:06.440 | through your own pineal gland,

01:27:08.320 | but three milligrams in these studies

01:27:12.280 | for a duration of anywhere from 30 days

01:27:15.340 | to much longer, in some cases, six months.

01:27:19.260 | And all four of these studies found modest

01:27:22.680 | yet still statistically significant effects

01:27:26.040 | of taking melatonin by mouth,

01:27:28.200 | so it's orally administered melatonin,

01:27:30.460 | in reducing the severity of tinnitus.

01:27:36.280 | So that's compelling, at least to me.

01:27:39.040 | It doesn't sound like a cure.

01:27:40.920 | And of course, as always, I'm not a physician.

01:27:44.420 | I'm a scientist, so I don't prescribe anything.

01:27:46.480 | I only profess things.

01:27:47.480 | I report to you the science.

01:27:48.640 | You have to decide if melatonin is right for you,

01:27:51.040 | if you have tinnitus.

01:27:53.100 | And certainly, I say that both to protect myself

01:27:56.260 | but also protect you, you're responsible

01:27:58.360 | for your health and wellbeing.

01:28:00.000 | And I'm not telling anyone to run out

01:28:02.360 | and start taking melatonin for tinnitus,

01:28:05.240 | but it does seem that it can have some effects

01:28:07.300 | in reducing its symptoms.

01:28:09.480 | Ginkgo boa boa is an interesting compound.

01:28:13.120 | It's been prescribed for or recommended for many,

01:28:17.160 | many things, but there are a few studies,

01:28:21.840 | again, double-blinded studies lasting one to six months,

01:28:24.920 | any one that has an impressive number of subjects,

01:28:27.940 | 978 subjects ranging from age 18 all the way up to 65,

01:28:32.940 | so on and so forth, that show not huge effects of ginkgo,

01:28:38.080 | but as they quote, "Limited evidence suggests

01:28:43.220 | that if tinnitus is a side effect of something else,

01:28:47.160 | in particular cognitive decline,"

01:28:49.440 | so age-related tinnitus might be helped by ginkgo boa boa.

01:28:54.440 | I won't go through all the details of the zinc studies,

01:28:58.960 | but it seems that zinc supplementation at higher levels

01:29:01.440 | than are typical of most people's intake,

01:29:03.280 | so 50 milligrams per day,

01:29:05.280 | do appear to be able to reduce subjective symptoms

01:29:07.460 | of tinnitus in most of the people

01:29:09.960 | that took the supplemented zinc.

01:29:11.720 | There aren't a lot of studies on that,

01:29:13.860 | so I could only find one double-blinded study.

01:29:16.800 | It lasted anywhere from one to six months, 41 subjects,

01:29:19.560 | both genders listed out again here, 45 to 64,

01:29:23.400 | and they saw a decrease in the severity of tinnitus symptoms

01:29:27.280 | with 50 milligrams of elemental zinc supplementation.

01:29:31.280 | And then last but not least is the magnesium study.

01:29:34.320 | Again, only a single study.

01:29:36.360 | It's a phase two study looking

01:29:38.720 | at a fairly limited number of subjects,

01:29:41.000 | so only 19 subjects,

01:29:42.920 | taking 532 milligrams of elemental magnesium.

01:29:46.460 | For those of you that take magnesium,

01:29:47.720 | there's magnesium and elemental magnesium,

01:29:49.560 | and it's always translated on the bottle,

01:29:52.280 | but it was associated with a lessening of symptoms

01:29:54.760 | related to tinnitus.

01:29:56.060 | So for you tinnitus sufferers out there,

01:29:59.740 | you may already be aware of this.

01:30:01.200 | You may already be taking these things

01:30:03.680 | and had no positive effects,

01:30:06.280 | meaning they didn't help, maybe not.

01:30:08.440 | I hope that you'll at least consider these,

01:30:11.520 | talk to your doctor about them.

01:30:13.120 | I do realize that tinnitus is extremely disruptive.

01:30:16.240 | I can't say I empathize

01:30:18.880 | because I don't from a place of experience, that is,

01:30:21.520 | because I don't have tinnitus,

01:30:22.660 | but for those of you that don't, including myself,

01:30:24.640 | you can imagine that hearing sounds

01:30:27.120 | of things that aren't there

01:30:28.320 | and the ringing in one's ears can be very disruptive

01:30:30.400 | and I think would be very disruptive

01:30:33.000 | and explains why people with tinnitus reach out so often

01:30:36.300 | with questions about how to alleviate that,

01:30:38.360 | and I hope this information was useful to you.

01:30:40.840 | I'd like to now talk about balance and our sense of balance,

01:30:44.800 | which is controlled by, believe it or not,

01:30:48.040 | our ears and things in our ears,

01:30:50.960 | as well as by our brain and elements of our spinal cord.

01:30:55.540 | But before I do that, I want to ask you another question,

01:30:58.160 | or I would rather, I'd like to ask you

01:31:00.720 | to ask yourself a question and answer it,

01:31:03.360 | which is how big are your ears?

01:31:07.240 | It turns out that the ears grow our entire life.

01:31:10.520 | In the early stage of our life, they grow more slowly,

01:31:15.400 | and then as we age, they grow more quickly.

01:31:19.120 | You may have noticed, if you have family members

01:31:22.120 | who are well into their 70s and 80s,

01:31:25.000 | and if you're fortunate, into their 90s

01:31:28.840 | and maybe even hundreds,

01:31:30.760 | is that the ears of some of these individuals

01:31:33.460 | get very, very big relative to their previous ear sizes.

01:31:38.400 | It turns out that biological age

01:31:41.440 | can actually be measured according to ear size.

01:31:46.180 | Now, you have to take a few measurements,

01:31:47.500 | but believe it or not,

01:31:49.140 | there is a formula in the scientific literature.

01:31:51.880 | If you know your ear circumference,

01:31:56.560 | so the distance around your ear, ears, plural,

01:32:01.320 | presumably you have two, most people do, in millimeters,

01:32:05.300 | so you're going to take the circumference

01:32:07.460 | of your ears in millimeters, how would you do this?

01:32:10.140 | How would you do this?

01:32:11.040 | Maybe you take a string and you put it around your ear,

01:32:14.360 | and then you measure the string.

01:32:15.420 | That's probably going to be easier than marching around

01:32:18.080 | your ear or somebody else's ear with a ruler

01:32:20.400 | and measuring in millimeters.

01:32:21.560 | So what's your ear circumference?

01:32:23.520 | On the outside, don't go in on the divot or anything.

01:32:26.380 | You're just going around as if you were going to trace

01:32:28.020 | the closest fitting oval, assuming your ears are oval,

01:32:32.320 | closest fitting oval that matches your ear circumference.

01:32:36.000 | Take that number in millimeters, subtract from it.

01:32:40.920 | Oh, excuse me, I should do this correctly.

01:32:43.240 | Do that for both ears, add them together,

01:32:46.060 | add those numbers together, divide by two,

01:32:47.840 | get the average for your two ears,

01:32:50.120 | get your average ear circumference

01:32:51.820 | from across your two ears.

01:32:53.520 | Then take that number in millimeters, subtract 88.1,

01:32:58.180 | and then whatever value that is, multiply it times 1.96,

01:33:04.360 | and that will tell you your biological age.

01:33:07.360 | Now, why in the world would this be accurate?

01:33:10.700 | Well, as we age, there are changes in a number

01:33:14.100 | of different biological pathways.

01:33:15.760 | One of those pathways is the pathways related

01:33:19.700 | to collagen synthesis.

01:33:21.760 | So not only are our ears growing,

01:33:24.520 | but our noses are growing too.

01:33:27.000 | My nose seems to be growing a lot, but then again,

01:33:29.380 | I did sports where I would get my nose broken,

01:33:31.200 | something I don't recommend.

01:33:32.460 | So I always point out, you don't get a nose like mine

01:33:34.180 | doing yoga, but nonetheless, my nose is still growing

01:33:38.380 | and my ears are still growing,

01:33:39.500 | and I suspect as I get older, if I have the good fortune

01:33:42.100 | of living into my 80s and 90s,

01:33:44.980 | my ears are going to continue to grow.

01:33:47.300 | A comparison between chronological age and biological age

01:33:50.180 | is something that's of really deep interest these days,

01:33:52.340 | and the work of David Sinclair at Harvard Medical School

01:33:56.440 | and others, so-called Horvath clocks

01:33:59.220 | that people have developed, have tapped into

01:34:01.980 | how the epigenome and the genome can give us some insight

01:34:05.580 | into our biological age and how that compares

01:34:08.520 | to our chronological age.

01:34:09.800 | Most of us know our chronological age

01:34:11.980 | because we know when we were born,

01:34:13.840 | and we know where we are relative to that now.

01:34:16.920 | But you can start to make a little chart, if you like,

01:34:21.920 | about your rates of ear growth.

01:34:23.860 | Your rates of ear growth actually correlate pretty well

01:34:26.320 | with your rates of biological progression

01:34:29.640 | through this thing that we call life.

01:34:32.440 | So it's not something that we think about too often,

01:34:34.680 | but just like our DNA and our epigenome

01:34:38.780 | and some other markers of metabolic health

01:34:41.460 | and hormone health relate to our age,

01:34:43.920 | so does our collagen synthesis.

01:34:45.980 | And one of the places that shows up the most

01:34:48.020 | is in these two little goodies on the sides of our heads,

01:34:50.260 | which are our ears.

01:34:51.740 | So even though it's a little bit of a bizarre metric,

01:34:54.860 | it makes perfect sense in the biological context.

01:34:57.660 | So let's talk about balance

01:34:59.180 | and how to get better at balancing.

01:35:01.660 | The reason why we're talking about balance

01:35:03.300 | and how to get better at balancing

01:35:04.960 | in the episode about hearing is that all the goodies

01:35:08.880 | that are going to allow you to do that are in your ears.

01:35:12.540 | They're also in your brain,

01:35:15.300 | but they're mostly in your ears.

01:35:17.680 | So as you recall from the beginning of this episode,

01:35:19.940 | you have two cochleas that are one on each side of your head

01:35:24.940 | and that's a little spiral snail-shaped thing

01:35:27.780 | that converts sound waves into electrical signals

01:35:30.640 | that the rest of your brain can understand.

01:35:33.340 | Right next to those,

01:35:34.680 | you have what are called semicircular canals.

01:35:37.420 | The semicircular canals can be best visualized

01:35:41.420 | as thinking about three hula hoops with marbles in them.

01:35:45.340 | So imagine that you have a hula hoop

01:35:48.320 | and it's not filled with marbles all the way around,

01:35:51.380 | it's just got some marbles down there at the base, okay?

01:35:54.740 | So if you were to move that hula hoop around,

01:35:57.280 | the marbles will move around, [whooshing]

01:35:59.860 | okay?

01:36:00.860 | You've got three of those

01:36:01.960 | and each one of those hula hoops has these marbles

01:36:04.760 | that can move around.

01:36:05.820 | One of those hula hoops is positioned vertically

01:36:10.320 | with respect to gravity.

01:36:12.760 | So it's basically parallel to your nose.

01:36:15.520 | It's like this if you're watching on a video,

01:36:17.520 | but basically it's upright.

01:36:19.160 | Another one of those hula hoops is basically

01:36:23.320 | at a 90-degree angle to your nose.

01:36:27.340 | It's basically parallel to the floor

01:36:29.740 | if you're standing upright now, if you're seated, okay?

01:36:33.640 | And the other one is kind of tilted

01:36:37.200 | about 45 degrees in between those.

01:36:40.140 | Now, why is the system there?

01:36:42.860 | Well, those marbles within each one of those hula hoops

01:36:45.260 | can move around, but they'll only move around

01:36:49.720 | if your head moves in a particular way.

01:36:51.660 | And there are three planes or three ways

01:36:54.520 | that your head can move.

01:36:56.300 | Your head can move up and down like I'm nodding right now.

01:37:00.080 | So that's called pitch.

01:37:01.620 | It's pitching forward or pitching back, okay?

01:37:05.700 | So it's a nod, up and down.

01:37:08.480 | Or I can shake my head no, side to side.

01:37:11.540 | That's called yaw.

01:37:12.920 | You pilots will be very familiar with this, yaw.

01:37:16.000 | Not yawn, yaw.

01:37:18.260 | And then there's roll, tilting the head from side to side

01:37:22.220 | the way that a cute puppy might look at you

01:37:24.780 | from side to side, okay?

01:37:26.600 | Where if somebody doesn't really understand

01:37:29.500 | or believe what you're saying,

01:37:30.660 | they might tilt their head.

01:37:32.820 | Very common phenomenon.

01:37:34.220 | I mean, nobody does that to me,

01:37:35.500 | but they do that to each other.

01:37:37.640 | So pitch, yaw, and roll are the movements of the head

01:37:41.920 | in each of the three major planes of motion, as we say.

01:37:45.300 | And each one of those causes those marbles to move

01:37:49.700 | in one or two of the various hula hoops, okay?

01:37:54.460 | So if I move my head up and down, when I nod,

01:37:57.220 | one of those hula hoops, literally right now,

01:38:00.040 | the marbles are moving back and forth.

01:38:01.380 | They aren't actually marbles, by the way.

01:38:03.180 | These are little, kind of like little stones, basically,

01:38:08.180 | little calcium-like deposits.

01:38:10.980 | And when they roll back and forth,

01:38:13.780 | they deflect little hairs, little hair cells

01:38:17.740 | that aren't like the hair cells

01:38:18.900 | that we use for measuring sound waves.

01:38:21.000 | They're not too different,

01:38:22.200 | but they are different from them,

01:38:24.560 | not like the hairs on our heads,

01:38:27.020 | but they're basically rolling past these little hair cells

01:38:30.880 | and causing them to deflect.

01:38:32.560 | And when they deflect downward, the neurons,

01:38:36.140 | because hair cells are neurons,

01:38:37.300 | send information up to the brain.

01:38:40.680 | So if I move my head like this,

01:38:42.480 | there's a physical movement of these little stones

01:38:45.540 | in this hula hoop, as I'm referring to it,

01:38:48.400 | but they deflect these hairs,

01:38:49.840 | send those hairs, which are neurons,

01:38:52.720 | those hair cells, send information off to the brain.

01:38:54.900 | If I move my head from side to side,

01:38:56.620 | different little stones move.

01:38:58.580 | If I roll my head, different stones move.

01:39:00.860 | This is an exquisite system that exists

01:39:03.860 | in all animals that have a jaw.

01:39:07.500 | So any fish that has a jaw has this system.

01:39:10.580 | A puppy has this system.

01:39:12.260 | Any animal that has a jaw has this so-called balance system,

01:39:16.080 | which we call the vestibular system.

01:39:18.240 | One of the more important things to know

01:39:20.080 | about the vestibular, the balance system,

01:39:22.460 | is that it works together with the visual system.

01:39:26.440 | Let's say I hear something off to my left

01:39:30.000 | and I swing my head over to the left to see what it is.

01:39:32.760 | There are two sources of information

01:39:35.700 | about where my head is relative to my body,

01:39:38.060 | and I need to know that.

01:39:39.940 | First of all, when I quickly move my head to the side,

01:39:43.900 | those little stones, as I'm referring to them,

01:39:46.380 | I realize they're not actually stones,

01:39:47.740 | but as I'm referring to them,

01:39:49.420 | they quickly activate those hair cells

01:39:52.380 | in that one semicircular canal

01:39:54.880 | and send a signal off to my brain

01:39:56.880 | that my head just moved to the side like this.

01:39:58.720 | Not that it went like this and pitched back

01:40:00.640 | or not that it tilted, but it just moved to the side.

01:40:03.940 | But also visual information slid past my field of view.

01:40:08.700 | I didn't have to think about it,

01:40:09.720 | but just slid past my field of view.

01:40:11.660 | And when those two signals combine,

01:40:15.680 | my eyes then lock to a particular location.

01:40:18.600 | Now, if this is at all complicated,

01:40:21.240 | you can actually uncouple these things.

01:40:23.780 | It's very easy to do.

01:40:25.080 | You can do this right now.

01:40:26.180 | In fact, I'd like you to do this experiment

01:40:27.860 | if you're not already doing something else

01:40:29.560 | that requires your attention,

01:40:30.820 | and certainly don't do this if you're driving.

01:40:33.660 | You're going to sit down,

01:40:35.460 | and you're going to move your head to the left very slowly,

01:40:39.400 | with your eyes open.

01:40:42.060 | So you're going to move it very, very slowly.

01:40:45.360 | The whole thing should take about five, six,

01:40:47.420 | maybe even 10 seconds to complete.

01:40:49.320 | Okay, I just did it.

01:40:53.680 | Now I'm going to do it very quickly.

01:40:54.940 | I'd like you to do it very quickly as well.

01:40:57.100 | Now do it slowly again.

01:40:59.600 | Okay, what you probably noticed

01:41:05.740 | is that it's very uncomfortable to do it slowly,

01:41:08.560 | but you can do it very quickly

01:41:12.020 | without much discomfort at all.

01:41:13.340 | You just move your head to the side.

01:41:14.940 | The reason is when you move your head very slowly,

01:41:18.780 | those little stones at the base of that hula hoop,

01:41:21.980 | they don't get enough momentum to move.

01:41:24.000 | So you're actually not generating this signal to the brain

01:41:28.180 | that your head is moving.

01:41:29.200 | And what you'll notice is that your eyes have to go boom,

01:41:32.500 | boom, boom, jumping over step by step.

01:41:35.300 | Whereas if you move your head really quickly,

01:41:37.260 | the signal gets off to your brain,

01:41:38.440 | and your eyes just go boom,

01:41:39.620 | right to the location you want to look at.

01:41:41.860 | So moving your body slowly is actually very disruptive

01:41:46.280 | to the vestibular system.

01:41:48.940 | And it's very disruptive to your visual system.

01:41:52.280 | Now, if you've ever had the misfortune of being on a boat

01:41:54.580 | and you're going through big oscillations on the boat,

01:41:57.040 | for those of you folks that get seasick,

01:41:59.660 | this can actually make certain people seasick

01:42:01.460 | just to hear about it.

01:42:02.760 | That was big oscillations going up and down

01:42:05.680 | and up and down.

01:42:07.000 | Those are very disruptive.

01:42:08.740 | We'll talk about nausea in a minute

01:42:09.980 | and how to offset that kind of nausea.

01:42:12.060 | I get pretty seasick,

01:42:12.980 | but there are ways that you can deal with this.

01:42:16.140 | But this is incredible,

01:42:17.460 | because what it means is it's a purely physical system

01:42:19.460 | of these little stones rolling around in there

01:42:22.020 | and directing where your eyes should go.

01:42:24.680 | Okay, so you can do this also just by looking up.

01:42:27.140 | So let's just say you're sitting in a chair.

01:42:29.200 | You're going to look up towards the ceiling

01:42:30.980 | and your eyes will just go there.

01:42:32.300 | You're doing this eyes open and you look down.

01:42:34.180 | Now try doing it really, really slowly.

01:42:39.900 | Some people even get motion sick doing this,

01:42:44.240 | which if you do, then just stop, okay?

01:42:46.900 | So you can do this also to the side,

01:42:49.080 | although it works best if you're moving your head

01:42:50.480 | from side to side or nodding up and down.

01:42:55.320 | So what we're doing here

01:42:56.440 | is we're uncoupling these two mechanisms.

01:42:58.280 | We're pulling them apart,

01:42:59.160 | the visual part and the vestibular part,

01:43:00.920 | just to illustrate to you that normally these mechanisms

01:43:05.000 | in your inner ear tell your eyes where to go,

01:43:09.000 | but as well, your eyes tell your balance system,

01:43:12.540 | your vestibular system, how to function.

01:43:15.420 | So I'd like you to do a different experiment.

01:43:18.000 | I'm not going to do it right now, but basically stand up.

01:43:21.520 | If you get the opportunity,

01:43:22.360 | you can do this safely wherever you are.

01:43:23.780 | You're going to stand up

01:43:25.080 | and you're going to look forward about 10, 12 feet.

01:43:28.000 | Pick a point on a wall or you can, anywhere that you like.

01:43:31.500 | If you're out in public, just do it anyway.

01:43:33.680 | Just tell them you're listening to "Cuberman Lab Podcast"

01:43:36.720 | and someone's telling you to do it.

01:43:38.900 | Anyway, if you don't want to do it, don't do it,

01:43:40.280 | but basically do it.

01:43:41.480 | Stand on one leg and lift up the other leg.

01:43:45.120 | You can bend your knee if you like,

01:43:46.640 | and just look off into the distance about 10, 12 feet.

01:43:50.340 | If you can do that, if you can stand on one leg,

01:43:53.560 | now close your eyes.

01:43:54.740 | Chances are you're going to suddenly feel

01:43:58.200 | what scientists call postural sway.

01:44:00.360 | You're going to start swaying around a lot.

01:44:02.480 | It is very hard to balance with your eyes closed.

01:44:06.480 | You might think, well, and if you think about that,

01:44:07.840 | it's like, why is that?

01:44:09.080 | That's crazy.

01:44:10.080 | Why would it be that it's hard to balance

01:44:11.920 | with your eyes closed?

01:44:12.740 | Well, information about the visual world

01:44:15.800 | also feeds back onto this vestibular system.

01:44:18.720 | So the vestibular system informs your vision

01:44:20.720 | and tells you where to move your eyes,

01:44:22.120 | and your eyes and their positioning

01:44:24.080 | tell your balance system, your vestibular system,

01:44:27.000 | how it should function.

01:44:28.660 | So there's a really cool way

01:44:31.020 | that you can learn to optimize balance.

01:44:33.680 | You're not going to try and do this

01:44:34.800 | by learning to balance with your eyes closed.

01:44:37.300 | What you can do is you can raise one leg,

01:44:41.040 | and you can look at a short distance,

01:44:43.000 | maybe off to just the distance that your thumb would be

01:44:45.240 | if you were to reach your arm out in front of you,

01:44:46.700 | although you don't necessarily have to put your thumb

01:44:48.560 | in front of you.

01:44:49.400 | So maybe just about two feet in front of you.

01:44:51.540 | Then while still balancing,

01:44:52.680 | you're going to step your vision out a further distance,

01:44:56.240 | and then a further distance,

01:44:57.420 | and as far as you can possibly see

01:44:58.840 | in the environment that you're in.

01:45:00.560 | And then you're going to march it back to you.

01:45:03.200 | Now, what the literature shows

01:45:05.540 | is that this kind of balance training

01:45:07.560 | where you incorporate the visual system

01:45:10.580 | and extending out and then marching back in,

01:45:14.140 | the point at which you direct your visual focus,

01:45:16.880 | sends robust information about the relationship

01:45:20.480 | between your visual world and your balance system.

01:45:24.100 | And of course, the balance system includes

01:45:25.460 | not just these hula hoops, these semicircular canals,

01:45:28.540 | but they communicate with the cerebellum,

01:45:30.420 | this little so-called mini brain,

01:45:31.640 | it actually means mini brain in the back of your brain,

01:45:33.900 | combines that with visual information

01:45:35.420 | and your map of the body surface.

01:45:37.520 | That pattern of training is very beneficial

01:45:44.100 | for enhancing your ability to balance

01:45:47.300 | because the ability to balance is in part

01:45:50.100 | the activation of particular postural muscles,

01:45:53.300 | but just as much, perhaps even more so,

01:45:57.220 | it's about being able to adjust those postural muscles,

01:46:02.220 | excuse me, it's about the ability

01:46:03.700 | to adjust those postural muscles

01:46:05.620 | as you experience changes in your visual world.

01:46:08.900 | And one of the most robust ways that you can engage changes

01:46:12.180 | in your visual world is through your own movement.

01:46:15.180 | And so most people are not trying to balance in place.

01:46:19.280 | They're not just trying to stand there

01:46:20.540 | like a statue on one leg.

01:46:22.260 | Most of what we think about when we think about balance

01:46:24.180 | is for sake of sport or dynamic balance

01:46:26.760 | of being able to break ourselves

01:46:28.100 | and when we're lunging in one particular direction

01:46:30.820 | to stop ourselves, that is,

01:46:32.180 | and then to move in another direction

01:46:33.900 | or for skateboarding or surfing or cycling

01:46:36.700 | or any number of different things, gymnastics.

01:46:39.160 | So the visual system is the primary input

01:46:41.940 | by which you develop balance,

01:46:43.340 | but you can't do it just with the visual system.

01:46:46.460 | So what I'm recommending is if you're interested

01:46:49.300 | in cultivating a sense of balance,

01:46:50.700 | understand the relationship

01:46:52.000 | between these semicircular canals.

01:46:54.440 | Understand that they are both driving eye movements

01:46:58.820 | and they are driven by eye movements.

01:47:01.100 | It's a reciprocal relationship.

01:47:03.060 | And then even just two or three minutes a day

01:47:06.500 | or every once in a while, even three times a week,

01:47:10.020 | maybe five minutes, maybe 10 minutes, you pick.

01:47:13.500 | But if you want to enhance balance,

01:47:14.820 | you have to combine changes in your visual environment

01:47:18.860 | with a static posture, standing on one leg

01:47:21.180 | and shifting your visual environment,

01:47:23.600 | or static visual view, looking at one thing

01:47:28.600 | and changing your body posture, okay?

01:47:32.640 | So those two things we now know

01:47:34.160 | from the scientific literature combine

01:47:37.040 | in order to give an enhanced sense of balance.

01:47:39.020 | And there's a really nice paper that was published in 2015

01:47:42.620 | called "Effects of Balance Training on Balance Performance."

01:47:45.560 | This was in healthy adults.

01:47:47.940 | It's a systematic review and a meta-analysis.

01:47:50.980 | A meta-analysis is when you combine a lot of literature

01:47:53.500 | from a lot of different papers

01:47:54.660 | and extract the really robust

01:47:56.640 | and the less robust statistical effects.

01:47:59.300 | So it's a really nice paper as well.

01:48:02.080 | There are some papers out there, for instance,

01:48:04.740 | a comparison of static balance

01:48:06.760 | and the role of vision in the elite athletes.

01:48:09.360 | This is essentially the paper that I've extracted

01:48:11.540 | most of the information that I just gave you from.

01:48:14.540 | And that paper, and there are some others as well,

01:48:18.220 | but basically I distilled them down

01:48:19.840 | into their core components.

01:48:20.820 | The core components are move your vision around

01:48:23.900 | while staying static still, but in a balanced position,

01:48:28.080 | like standing on one leg.

01:48:29.340 | Could be something more complicated

01:48:30.620 | if you're somebody who can do more complicated movements.

01:48:33.420 | Unilateral movements seem to be important.

01:48:37.160 | So standing on one leg as opposed to both, right?

01:48:40.400 | Or trying to generate some tilt

01:48:43.420 | is another way to go about it, or imbalance,

01:48:45.420 | meaning one limb asymmetrically being activated

01:48:48.100 | compared to the other limb.

01:48:49.780 | And then the other way to encourage or to cultivate

01:48:54.420 | and build up this vestibular system

01:48:56.700 | and your sense of balance

01:48:57.960 | actually involves movement itself, acceleration.

01:49:01.420 | So that's what we're going to talk about now.

01:49:03.420 | So up until now, I've been talking about balance

01:49:05.320 | only in the static sense,

01:49:06.700 | like standing on one leg, for instance,

01:49:08.440 | but that's a very artificial situation.

01:49:11.060 | Even though you can train balance that way,

01:49:13.160 | most people who want to enhance their sense of balance

01:49:15.820 | for sport or dance or some other endeavor

01:49:18.780 | want to engage balance in a dynamic way,

01:49:21.520 | meaning moving through lots of different planes of movement,

01:49:24.180 | maybe even sometimes while squatting down low

01:49:26.860 | or jumping and landing

01:49:28.140 | or making trajectories that are different angles.

01:49:31.360 | For that, we need to consider that the vestibular system

01:49:35.980 | also cares about acceleration.

01:49:39.540 | So it cares about head position.

01:49:40.960 | It cares about eye position

01:49:42.620 | and where the eyes are and where you're looking,

01:49:44.700 | but it also cares about what direction you're moving

01:49:47.840 | and how fast.

01:49:49.380 | And one of the best things that you can do

01:49:52.420 | to enhance your sense of balance

01:49:54.860 | is to start to bring together your visual system,

01:49:59.400 | the semicircular canals of the inner ear,

01:50:02.300 | and what we call linear acceleration.

01:50:05.060 | So if I move forward in space rigidly upright,

01:50:08.880 | it's a vastly different situation

01:50:11.000 | than if I'm leaning to the side.

01:50:14.600 | One of the best ways to cultivate a better sense of balance,

01:50:19.160 | literally within the sense organs and the neurons

01:50:23.000 | and the biology of the brain is to get into modes

01:50:27.960 | where we are accelerating forward, typically it's forward,

01:50:31.940 | while also tilted with respect to gravity.

01:50:35.640 | Now, this would be the carve on a skateboard

01:50:38.500 | or on a surfboard or a snowboard.

01:50:40.720 | This would be the taking a corner on a bike

01:50:44.260 | while being able to lean safely, of course,

01:50:46.780 | lean into the turn so that your head is actually tilted

01:50:50.480 | with respect to the earth.

01:50:52.840 | So anytime that we are rigidly upright,

01:50:55.740 | we aren't really exercising the vestibular system

01:50:59.140 | and balance.

01:51:00.420 | This is why, you know, you see people in the gym on these,

01:51:03.120 | what are those Bonshi balls?

01:51:04.660 | Bonshi balls, the one that the guys roll in the park, right?

01:51:07.460 | Bonshi balls where they're balancing back and forth,

01:51:09.480 | that will work the small stabilizing muscles.

01:51:11.900 | But what I'm talking about is getting into modes

01:51:13.820 | where you actually tilt the body and the head

01:51:17.240 | with respect to earth.

01:51:19.420 | What I mean is with respect to earth's gravitational pull.

01:51:24.060 | Now, the cerebellum is a very interesting structure

01:51:27.320 | because not only is it involved in balance,

01:51:29.800 | but it's also involved in skill learning

01:51:33.020 | and in generating timing of movements.

01:51:35.940 | It's a fascinating structure deserving of an entire episode

01:51:39.020 | or several episodes all on its own.

01:51:41.760 | But some of the outputs of the cerebellum,

01:51:44.960 | meaning the neurons in the cell cerebellum get inputs,

01:51:47.800 | but they also send information out.

01:51:50.480 | The outputs of the cerebellum are strongly linked

01:51:53.400 | to areas of the brain that release neuromodulators

01:51:56.520 | that make us feel really good,

01:51:58.880 | in particular, serotonin and dopamine.

01:52:01.320 | And this is an early emerging subfield within neuroscience,

01:52:05.020 | but a lot of what are called the non-motor outputs

01:52:07.880 | of the cerebellum have a profound influence,

01:52:11.200 | not just on our ability to learn how to balance better,

01:52:15.640 | but also how we feel overall.

01:52:18.420 | So for you exercisers out there,

01:52:20.740 | I do hope people are getting regular,

01:52:22.680 | healthy amounts of exercise.

01:52:23.900 | We've talked about what that means in previous episodes.

01:52:26.560 | So at least 150 minutes a week of endurance work,

01:52:29.080 | some strength training,

01:52:29.920 | a minimum of five sets per body part

01:52:31.800 | to maintain musculature.

01:52:33.340 | Even if you don't want to grow muscles,

01:52:34.880 | you want to do that in order to maintain healthy strength

01:52:37.320 | and bones, et cetera.

01:52:39.440 | If you're doing that, but you're only doing things

01:52:42.540 | like curls in the gym, squats in the gym,

01:52:44.720 | riding the Peloton, or even if you're outside running

01:52:47.440 | and you're getting forward acceleration,

01:52:49.440 | but you're never actually getting tilted, right?

01:52:51.240 | You're never actually getting tilted

01:52:52.800 | with respect to Earth's gravitational pull.

01:52:56.400 | You're not really exercising

01:52:58.560 | and getting the most out of your nervous system.

01:53:03.200 | Activation of the cerebellum in this way of being tilted

01:53:07.840 | or the head being tilted and the body being tilted

01:53:09.880 | while in acceleration, typically forward acceleration,

01:53:12.960 | but sometimes side to side,

01:53:14.920 | has a profound and positive effect

01:53:18.280 | on our sense of mood and wellbeing.

01:53:20.240 | And as I talked about in a previous episode,

01:53:22.840 | it can also enhance our ability to learn information

01:53:26.180 | in the period after generating those tilts

01:53:29.600 | and the acceleration.

01:53:31.360 | And that's because the cerebellum has these outputs

01:53:33.800 | to these areas of the brain

01:53:34.840 | that release these neuromodulators like serotonin

01:53:37.560 | and dopamine, and they make us feel really good.

01:53:41.440 | I think this is one of the reasons why growing up,

01:53:44.160 | I had some friends, some of whom might've been

01:53:47.560 | the world heavyweight champions of laziness

01:53:50.240 | for essentially everything except they would wake up

01:53:53.800 | at 4.30 in the morning to go surf.

01:53:56.320 | They would drive, they would get up so early to go surf.

01:54:00.080 | It's not just surfers, and some surfers, by the way,

01:54:02.400 | I should point out, are not lazy humans.

01:54:04.680 | They do a lot of other things.

01:54:06.040 | But I knew people that couldn't be motivated to do anything,

01:54:08.940 | but they were highly driven to get into these experiences

01:54:13.120 | of forward acceleration while tilted

01:54:15.200 | with respect to gravity.

01:54:16.580 | Likewise with snowboarding or skiing or cycling.

01:54:21.120 | Those modes of exercise seem to have an outsized effect

01:54:25.800 | both on our wellbeing and our ability to translate

01:54:30.200 | the vestibular balance that we achieve in those endeavors

01:54:33.640 | to our ability to balance while doing other things.

01:54:37.100 | So, and I don't mean psychological balance necessarily,

01:54:39.680 | I mean physical balance.

01:54:41.540 | So for those of you that don't think of yourselves

01:54:43.440 | as very coordinated or with very good balance,

01:54:46.960 | getting into these modes of acceleration,

01:54:49.000 | forward movement or lateral movement while getting tilted,

01:54:51.720 | even if you have to do it slowly, could be beneficial.

01:54:54.220 | I do believe, and the scientific literature points

01:54:56.540 | to the fact that it will be beneficial

01:54:58.720 | for cultivating better sense of physical balance.

01:55:02.500 | It can really build up the circuits

01:55:04.440 | of this vestibular system.

01:55:06.280 | And then of course the feel-good components

01:55:08.800 | of acceleration while tilted or while getting the head

01:55:12.340 | into different orientations relative to gravity.

01:55:16.200 | Well, that's the explanation for roller coasters.

01:55:18.740 | Some people hate roller coasters.

01:55:20.040 | They make them feel nauseous.

01:55:21.960 | Many people love roller coasters.

01:55:24.840 | And one of the reasons they love roller coasters

01:55:26.720 | is because of the way that when you get the body,

01:55:30.260 | even if you're not generating the movement,

01:55:31.880 | you get the body into forward acceleration

01:55:33.980 | and you're going upside down and tilted to the side

01:55:36.480 | as the tracks go from side to side and tilt, et cetera,

01:55:39.220 | you're getting activation of these deeper brain nuclei

01:55:42.800 | that trigger the release of neuromodulators

01:55:45.280 | that just make us feel really, really good.

01:55:47.200 | In fact, some people get a long arc, a long duration

01:55:50.360 | kind of buzz from having gone through those experiences.

01:55:53.080 | Some people who hate roller coasters

01:55:54.760 | are probably getting nauseous just hearing about that.

01:55:57.960 | So I encourage people to get into modes of acceleration

01:56:01.740 | while tilted every once in a while,

01:56:03.280 | provided you can do it safely.

01:56:04.660 | It's an immensely powerful way to build up your skills

01:56:08.560 | in the realm of balance.

01:56:10.120 | And it's also, for most people, very, very pleasing.

01:56:14.040 | It feels really good because of the chemical relationship

01:56:16.620 | between forward acceleration and head tilt and body tilt.

01:56:21.200 | Now, speaking of feeling nauseous,

01:56:23.520 | some people suffer from vertigo.

01:56:27.240 | Some people feel dizzy.

01:56:28.840 | Some people get lightheaded.

01:56:31.360 | An important question to ask yourself always

01:56:33.900 | if you're feeling quote unquote dizzy or lightheaded is,

01:56:36.940 | are you dizzy or are you lightheaded?

01:56:39.620 | Now, we're not going to diagnose anything here

01:56:41.700 | because there's just no way we can do that.

01:56:43.420 | This is essentially me shouting into a tunnel

01:56:45.300 | so we don't know what's going on

01:56:46.800 | with each and every one of you.

01:56:48.240 | But if ever you feel that your world is spinning

01:56:51.860 | but that you can focus on your thumb, for instance,

01:56:56.520 | but the rest of the world is spinning

01:56:58.580 | and your thumb is stationary,

01:57:00.460 | that's called being dizzy.

01:57:01.920 | Now, if you feel like you're falling

01:57:05.140 | or that you feel like you need to get down onto the ground

01:57:07.960 | because you feel lightheaded, that's being lightheaded.

01:57:12.060 | And oftentimes with language, we don't distinguish

01:57:14.340 | between being dizzy and being lightheaded.

01:57:16.580 | Now, there are a lot of ways that dizziness

01:57:19.160 | and lightheadedness can occur.

01:57:21.000 | And I don't even want to begin to guess

01:57:22.440 | at the number of different things and ways

01:57:24.820 | that it could happen for those of you that suffer from it

01:57:26.740 | because it could be any number of them.

01:57:28.920 | But oftentimes if people are lightheaded,

01:57:31.920 | yes, it could be low blood sugar.

01:57:33.200 | It could also be that you're dehydrated.

01:57:35.820 | It could also be that you are low in electrolytes.

01:57:38.720 | We talked about this in a previous episode,

01:57:40.680 | but we will talk about it more in a future episode.

01:57:43.280 | Many people have too little sodium in their system, salt,

01:57:46.920 | and that's why they feel lightheaded.

01:57:49.360 | I have family members who for years

01:57:51.220 | thought they had disrupted blood sugar.

01:57:53.780 | They would get shaky, jittery, lightheaded,

01:57:56.960 | feel like they were nauseous, et cetera.

01:57:59.160 | And simply the addition of a little sea salt

01:58:02.160 | to their water remedied the problem entirely.

01:58:04.320 | I don't think it's going to remedy every issue

01:58:06.680 | of lightheadedness out there by any stretch,

01:58:08.940 | but just the addition of salt in this particular case

01:58:12.020 | helped the person and they are not alone.

01:58:14.600 | Many people who think that they have low blood sugar

01:58:16.440 | actually are lightheaded because of low electrolytes.

01:58:19.640 | And because of the way that salt carries water

01:58:22.920 | into the system and creates changes in blood volume, et cetera

01:58:26.800 | low sodium can often be a source of lightheadedness

01:58:30.480 | as can low blood sugar and of course other things as well.

01:58:33.440 | Now for dizziness or seasickness,

01:58:36.020 | we were all taught that you need to pick a point

01:58:38.880 | on the horizon and focus on it,

01:58:41.700 | but actually that's not correct.

01:58:44.280 | It is true that if you are down in the cabin of a boat

01:58:49.460 | or you're on the lower deck

01:58:51.140 | and all you can see are things up close to you

01:58:54.760 | that getting sloshed around like so

01:58:57.360 | or the boat going up and down like so,

01:58:59.840 | I think I'm getting a little seasick

01:59:00.860 | even as I do this and I describe it.

01:59:02.660 | Focusing on things close to you can be problematic.

01:59:09.120 | And in that case, the advice to go up on deck

01:59:12.380 | and get fresh air and to look off into the horizon,

01:59:15.900 | that part is correct.

01:59:17.600 | But focusing your eyes on a particular location

01:59:20.000 | on the horizon is effectively like trying

01:59:23.080 | to move very slowly as I had you do before

01:59:26.260 | where you're trying to move your head very slowly

01:59:28.240 | while fixating on one location.

01:59:30.480 | Your eyes and your balance system

01:59:31.920 | were designed to move together.

01:59:33.920 | So really what you want to do is allow your visual system

01:59:36.800 | to track with your vestibular system.

01:59:40.220 | This is why sitting in the back of an Uber or a taxi

01:59:43.440 | and being on your phone

01:59:45.300 | can make you suddenly feel very nauseous.

01:59:47.720 | Sometimes the cabs, particularly in New York City,

01:59:49.700 | they have a lot of occluders.

01:59:51.000 | They have a lot of stuff blocking your field of view.

01:59:53.160 | There's usually a little portal out there

01:59:55.000 | where you can see out to the front windshield,

01:59:59.240 | but there's all this stuff now.

02:00:00.280 | Television's in the back seat

02:00:01.800 | and you're watching that television and the cab is moving.

02:00:04.120 | You're in linear acceleration

02:00:06.300 | and sometimes you're taking corners, you're braking,

02:00:09.000 | so then your vestibular system has to adjust to that.

02:00:11.680 | If you're looking at your phone or a book,

02:00:14.520 | or even if you're talking to somebody,

02:00:16.960 | actually, I'm starting to feel a little nauseous

02:00:18.360 | just talking about it.

02:00:19.200 | I promise I'm not going to finish this episode

02:00:20.880 | by vomiting at the end, at least not here.

02:00:23.860 | But what can happen is that you're uncoupling

02:00:28.120 | the visual information from your motion,

02:00:31.120 | from your vestibular information.

02:00:32.860 | You want those to be coupled.

02:00:34.160 | This is why a lot of people have to drive.

02:00:36.920 | They can't be in the passenger seat

02:00:38.400 | because when you drive,

02:00:39.240 | you also get what's called proprioceptive feedback.

02:00:41.480 | Your body is sending signals also to the vestibular system

02:00:44.920 | about where you are in space.

02:00:46.880 | When you're the passenger,

02:00:48.060 | you're just getting jolted around as the person is driving.

02:00:51.120 | And if you're looking at your phone, it's even worse.

02:00:53.340 | And if you're looking at the occluder

02:00:54.660 | between you and the two front seats, that's even worse.

02:00:58.660 | So this is why staring out the front windshield is great,

02:01:01.360 | but you don't want to fixate, okay?

02:01:03.300 | So hopefully I spared a few people

02:01:05.900 | and hopefully a few cab drivers

02:01:07.560 | of having people get sick in their cars or Ubers.

02:01:10.300 | Let your visual system

02:01:12.360 | and your vestibular system work together.

02:01:15.320 | If appropriate, get into linear acceleration

02:01:18.560 | and you'll improve your sense of balance.

02:01:20.820 | Once again, we've covered a tremendous amount of information.

02:01:24.300 | Now you know how you hear,

02:01:25.940 | how you make sense of the sounds in your environment,

02:01:29.560 | how those come into your ears

02:01:31.160 | and how your brain processes them.

02:01:33.420 | In addition, we talked about things

02:01:35.080 | like low-level white noise and even binaural beats,

02:01:38.100 | which can be used to enhance certain brain states,

02:01:40.740 | certain rhythms within the brain and even dopamine release

02:01:44.180 | in ways that allow you to learn better.

02:01:46.820 | And we talked about the balance system

02:01:48.500 | and this incredible relationship

02:01:50.300 | between your vestibular apparatus,

02:01:52.940 | meaning the portions of your inner ear

02:01:55.160 | that are responsible for balance

02:01:56.520 | and your visual system and gravity.

02:01:59.560 | And you can use those to enhance your learning as well,

02:02:02.780 | as well as just to enhance your sense of balance.

02:02:05.620 | If you're learning from this podcast,

02:02:07.340 | please subscribe on YouTube.

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02:02:10.100 | In addition, please leave us any comments or feedback

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02:02:29.720 | During this episode, I mentioned some supplements.

02:02:32.100 | We partnered with Thorne

02:02:33.220 | because Thorne has the very highest levels of stringency

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02:02:38.260 | and accuracy about the amounts of those ingredients

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02:02:45.480 | you can go to thorne.com/u/huberman.

02:02:50.480 | So that's thorne.com/u/huberman

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02:03:07.300 | It's patreon.com/andrewhuberman.

02:03:10.460 | And there you can support our podcast

02:03:12.140 | at any level that you like.

02:03:13.840 | In addition, if you'd like to support the podcast,

02:03:16.460 | please check out our sponsors

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02:03:19.380 | That is absolutely the best way to support us.

02:03:21.860 | Last but not least,

02:03:22.760 | I'd like to thank you for your time and attention

02:03:25.160 | and desire and willingness to learn

02:03:27.280 | about vision and balance.

02:03:29.120 | And of course, thank you for your interest in science.

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The Science of Hearing, Balance & Accelerated Learning

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