Dr. Matt Walker

And as you'll remember, we described that in the first two or three hours of sleep is when you get most of your deep sleep.

And they were targeting those deep, slow brain waves that we spoke about, those big, slow, powerful waves that define deep sleep.

And what they did in one of those groups, the other group was the placebo group, they still had the electrodes applied, they still went to sleep.

In the stimulation group, they waited until those individuals went into deep sleep.

And I told you in the first episode that those deep sleep brainwaves were going up and down very, very slowly, maybe just once or twice a second.

So they started to stimulate the brain, inputting these stimulation pulses at a very slow rhythm.

trying to match the rhythm of the brain.

In fact, they were less than one hertz, less than one cycle per second in terms of a pulse.

It's almost as though we're trying to act like a choir to a flagging lead vocalist.

And as these brainwaves are going up and down, you're trying to sing in time with those deep sleep brainwaves.

And in doing so, you're trying to boost and amplify the size of those deep sleep brainwaves.

Now, to begin with, they just waited until they went into deep sleep and they started to stimulate at that frequency.

And I'll come back to why that's important in a second.

But sure enough, what they demonstrated, they were able to boost the electrical quality of that deep sleep by about 60%.

And they were also able to almost double the amount of memory benefit that sleep provided, which is very impressive.

Now, I should note that there was more recently a replication attempt of that paper, and they did a very good job.

They really did it to the letter, and they weren't able to replicate the effects as powerfully.

However...

Subsequent studies have now taken a more nuanced approach and it's the one that we've taken too.

And it's called closed loop stimulation.