Dr. David Berson

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

Are those memories?

I would say in a sense, they may reflect your visual experience.

They're 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.

Right.

So the first thing to understand about light is that it's just a form of electromagnetic radiation.