David Eagleman

And in fact, right now I'm working with a couple of young engineers in Ukraine to implement this for their defense.

So this is a hypothesis that my student and I came up with some years ago.

Which is the following.

If you go blind, as we mentioned earlier, if you go blind, that territory, your visual cortex gets taken over by neighboring kingdoms of data, like hearing and touch.

But the surprise in neuroscience is how fast this can happen.

So some colleagues of mine at Harvard did this experiment where they took normally sighted people and they blindfolded them and they put them in the brain scanner.

And what they found to their surprise is that after about an hour, they could start seeing activity in the visual cortex.

When you touch somebody or when you play a sound for them, you're actually seeing the visual cortex start responding to that.

And what that means is that this takeover process can start happening really fast because essentially everything in the brain is wired up to everything else.

You know, there's these very long distance connections such that everything has, you know, roadways to get wherever it needs to get.

And so somehow this takeover starts after about an hour.

So what we realized was, given the rotation of the planet...

you know, this causes a real problem for the visual system because you end up in the dark for half the cycle.

And obviously the thing of interest here is evolutionary time before we had lights, which is just the last, you know, nanosecond of evolutionary time where we had lights or even fire.

Most of our history, it's been extremely dark at nighttime, and that means your visual system is disadvantaged during the night.

You can still hear and smell and taste and touch during the night, but you can't see.

And so we realized the problem is the visual system needs some way of defending itself against takeover, and that is what dreams are about.

So every 90 minutes, you've got these –

very ancient circuits in your midbrain that just blast random activity just into your visual cortex.

That's the only place it's hitting is just primary visual cortex.