Dr. David Eagleman

So let me back up to answer the question about my new theory about why we dream, because this has everything to do with brain plasticity.

So here's where this got started.

By about 2013, some of our colleagues at Harvard did this experiment where they put people in the scanner and they blindfolded them tightly and they were looking at what was going on in the brain and, you know, with touch and with sounds.

And it turns out that if you're blindfolded after about an hour, you start seeing a little bit of activity in the visual cortex when you are touched or when you hear something.

Now, this was crazy because we know that if somebody goes blind, hearing and touch will take over that territory.

But we thought that was on the scale of years.

And here what they were demonstrating is that within 60 to 90 minutes, you start seeing little blips of activity.

Why?

It's because you've got all this cross-modal wiring.

In other words, you've got neurons, let's say, in the auditory cortex that actually reach all the way over to the visual cortex.

And same with touch neurons and so on.

These are normally silent.

They don't normally do anything.

but they are ready.

They're like silent sentinels that say, hey, just in case this territory stops getting used, I'm taking over.

Okay, so here's what my student and I realized is that

Because we live on a planet that rotates into darkness every night, the visual system is at a unique disadvantage.

Because when it's dark, you can still hear and smell and touch and taste, but you can't see.

And obviously I'm talking about evolutionary time before the invention of lights, which is the last nanosecond of evolutionary history.

It was really dark at night and you can't see.