Dr. Matthew Walker

They are not faithful to the dream because if I were to gently wake you as you're sleep talking and say what was going through your head, you'll say nothing at all and you don't report a dream.

So what we know is that Matt Wilson's data during non-rapid eye movement sleep, the brain was replaying those memories 10 to 20 times faster.

So...

But when you go into REM sleep, it's down to 0.5 times.

So listening to this podcast now and you hit that speed button and you drop it down to 0.5, that seems to be the replay speed during REM sleep.

We've not yet been able to confirm that in human beings, but if we did, does that mean we can explain the time differences that seem to happen in the dream state, that time is longer in the dream world than it is in the waking world?

I think that's fascinating.

But you're right, it does point us more towards the question, though, of what are the functions of this state called dreaming.

And we can get on to whether or not dreaming is a very faithful recapitulation of our waking experiences.

And I'll give you a spoiler now.

No, but I'll give you the data in a second.

But the functions of dreaming come back to some of the functions of REM sleep that we described in an earlier episode.

Those two related functions in the episode on learning and memory was that one function of REM sleep seems to be creativity.

associating memories together so that you can come up with these wonderfully divine solutions to problems you couldn't answer when you're awake.

The second came in our last episode about emotional and mental wellness.

And we spoke about this theory that we put forward that REM sleep is a form of overnight therapy.

And we described the evidence supporting that therapy.

So I would say that those are the two leading theories of REM sleep and associated dreaming.

But I perhaps didn't give you the full story there.

There is a twist in both of those stories.