Essentials: How Your Brain Functions & Interprets the World | Dr. David Berson

Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. And now for my discussion with Dr. David Berson. For more than 20 years, you've been my go-to source for all things nervous system, how it works, how it's structured, so today I want to ask you some questions about that. I think people would gain a lot of insight into this machine that makes them think, and feel, and see, et cetera. If you would, could you tell us how we see? You know, a photon of light enters the eye. What happens?

Right.

I mean, w- how is it that I look outside, I see a truck drive by, or I look on the wall, I see a photo of my dog, how does that work?

Right. So this is an old question obviously, and clearly, in the end, the reason you have a visual experience is that your brain has got some pattern of activity that it associates with the input from the periphery. But you can have a visual experience with no input from the periphery as well. When you're dreaming-

Mm-hmm.

... you're seeing things that aren't coming through your eyes.

Are those memories?

Uh, I would say in a sense they may reflect your visual experience. They are not necessarily specific visual memories, but of course they can be. But the point is that the experience of seeing is actually a brain phenomenon, but of course under normal circumstances we see the world because we're looking at it and we're using our eyes to look at it, and fundamentally, when we're looking at the exterior world, it's what the retina is telling the brain that matters. So there are cells called ganglion cells, these are neurons that are the key cells for communicating between eye and brain. The eye is like the camera. It's detecting the initial image, doing some initial processing, and then that signal gets sent back to the brain proper, and of course it's there at the level of the cortex that we have this conscious visual experience. There are many other places in the brain that get visual input as well doing other things with that kind of information.

So I- I get a lot of questions about color vision. If you would, could you explain how is it that we can perceive reds and greens and blues and things of that sort?

Right. So the first thing to understand about light is that it's just a form of electromagnetic radiation. Uh, it's vibrating. It's oscillating. But light is-

When you say it's vibrating, it's oscillating, you mean that photons are actually moving?

Well, in a sense, photons are, they're certainly moving through space. We think about photons as particles, and that's one way of thinking about light, but we can also think of it as a wave, like a radio wave. Either way is acceptable. And the radio waves have frequencies like the frequencies on the, your radio dial, and certain frequencies in the electromagnetic spectrum can be detected by neurons in the retina. Those are the things we see. But there are still different wavelengths within the light that can be seen by the eye, and those different wavelengths are unpacked in a sense, or decoded by the nervous system to lead to our experience of color. Um, essentially different wavelengths give us the sensation of different colors through the auspices of different neurons that are tuned to different wavelengths of light.