Dr. Matt Walker

And that's what's producing these huge, big, powerful waves.

So the analogy in the football stadium would be at this point now, and I'll come across to your university, Stanford is winning and the crowd is buoyant.

And all of a sudden the Stanford crowd is singing, Berkeley sucks, Berkeley sucks.

And they're all united.

The whole stadium cries out at the same time.

and then goes silent at the same time.

It's an epic display of coordinated neural activity in a way that we don't see in any other brain state.

It's phenomenal.

So it turns out that all of these stages that we'll describe, different stages of sleep do different things for your brain and your body at different times of night.

And it's very understandable that people sort of in the public will come over to me and say, you know, how do I get more deep sleep or how do I get more REM sleep?

And my question back to them firstly is, why do you want more REM sleep?

And they'll say, well, isn't that the good stuff?

And I will say, well, it turns out that they're all important.

You need all of them.

We can come on to, I'll speak about non-REM sleep functions first, and then I can probably, I should unpack REM sleep and then explain its functions.

But as an overview, what we know is that during deep sleep, first you switch over in terms of your body's nervous system to what we call the parasympathetic nervous system that you've spoken about a lot before, which is this kind of very quiescent, calming state of your body's nervous system.

The sympathetic nervous system, which is very poorly named because it's anything but sympathetic.

It's very aggravating and activating.

And when we're awake, that seems to be somewhat more dominant depending on what state you're in.

But in sleep, especially in deep sleep, you shift over into this very strong parasympathetic, quiescent, calm state.