The serotonin 2A receptors are located in multiple brain regions, but they have a tremendous amount of expression in the so-called neocortex, the outside of the brain that includes things like our prefrontal cortex, which is involved in understanding context, right? Which behaviors, thoughts, and speech patterns are appropriate for certain circumstances, how to switch context and category switch when you go from, you know, playing sports to hang out with friends to being in a professional setting, you change your behavior and the way that you speak and perhaps even the way that you think.

You might think some things that are out of context, but you probably keep those to yourself, and your ability to keep those to yourself are dependent on a functional prefrontal cortex. There are a lot of 5HT2A, and by the way, 5HT is the abbreviation for serotonin, so there are a lot of serotonin 2A receptors in the prefrontal cortex.

Also in other areas of the cortex that are associated with sensation and perception, that is hearing of sounds, that is seeing of particular things, and in particular, there is a very, very, very high expression of serotonin 2A receptors in the visual cortex. And that is one of the reasons why psilocybin triggers visual hallucinations.

And provided psilocybin is present at sufficient enough concentration, that is taken at a sufficient dosage, one will experience profound visual hallucinations regardless of whether or not their eyes are open or their eyes are closed. Now, that's an important fact because it explains one of the major effects of psilocybin that people experience while they are on the drug.

Now, as I'll talk about a little bit later in terms of what constitutes a useful psilocybin session, useful meaning that it's leading to adaptive improvements in mood, adaptive improvements in creativity and cognition, et cetera, is that people not have their eyes open for at least the majority of the psilocybin session.

This is something I've discussed with several experts who are running clinical studies on psilocybin in their laboratories, some of whom are going to be guests on the "Huberman Lab" podcast in upcoming episodes. Again, I can't underscore this enough. Because your visual cortex contains so many of these serotonin 2A receptors, and because psilocybin binds so strongly to that serotonin 2A receptor, you're going to experience a lot of visual hallucinations when you are under the influence of psilocybin.

There's no surprise there. This has been known for hundreds, if not thousands of years. It's one of the main reasons why people take psilocybin. However, as I mentioned earlier, these hallucinations occur even when the eyes are closed. And it's now fairly well-established that if people are to take psilocybin and have their eyes open, much of their cognition, much of their thinking, much of the time spent in that psilocybin journey is focused on the altered perceptions of things in the outside environment.

Sometimes this looks like a sort of a fracturing of the outside world into kind of geometric shapes. Sometimes it appears as a kind of melting of things in the visual environment, including people's faces or a morphing of people's faces. All of that has a strong, let's just call it a draw for a lot of people who are looking for a highly unusual experience inside of the psilocybin journey.

But I think if one's goal is to derive the long-lasting benefit from the psilocybin experience, it's very clear that having an eye mask or some other eye covering or something that ensures that one's eyes are closed for the majority, if not the entire psilocybin session, is going to be very useful because it's going to limit the extent to which one is focused on those outside changes in visual perception, aka hallucinations, and rather will allow the person to go inward to combine whatever it is that they happen to be seeing in their mind's eye with the different thoughts and memories and changes in their emotions that are occurring.

And that going inward by staying in the eye mask, at least for the majority of the time, seems to be a very, if not the, critical feature of making the psilocybin journey effective in the therapeutic sense. (upbeat music) (upbeat music)