MS. REBECCA SHEIR
To start things off, WAMU environmental reporter Sabri Ben-Achour takes a walk on the wild side.
MR. SABRI BEN-ACHOUR
At the National Zoo, some naked mole-rats are scrambling around through tubes.
MR. DAVID KESSLER
You guys want to say hello?
David Kessler, small mammal biologist at the zoo, holds up one of the fleshy, pink, wrinkly and nearly-blind rodents. He says when they sleep, they do something kind of funny.
They grind their incisors, their front teeth and you'll see them lying on their back twitching a little bit with those front teeth going back and forth and back and forth.
Could they be dreaming, dreaming of burrowing and gnawing?
I have no idea. You know, I can barely get into the mind of my wife or my son. I can barely get in the mind of myself so I don't presume to get into the mind of blessed, naked mole-rat.
No one can really, but we can measure REM sleep.
MR. DON MOORE
Rapid eye movement or REM sleep.
Don Moore is associate director of Animal Care Science at the zoo.
When we're in a deep sleep, our muscles don't move, but our eyes are moving, moving, moving.
In humans, it's when we dream.
We've shown REM sleep in a lot of different animals, cats, monkeys, shrews, possums, armadillos and my dogs.
The question is what's going on in their brains?
We can't interview a cat and ask what it dreamt about, but we can sort of see what it's seeing when it dreams, really. Patrick McNamara is an associate professor of neurology at the Boston University School of Medicine.
DR. PATRICK MCNAMARA
When you knock out the cells that normally inhibit movement when you're asleep...
So let me just explain real quick here. Normally, when you go into REM sleep and dream, your brain paralyzes your body so you don't actually get up and run around while you're dreaming. So as McNamara was saying, when you turn off that paralysis in animals...
If you knock those cells out and the animal goes into REM sleep, they start to exhibit these behaviors that strongly suggest that they're seeing things and they're reacting to what they're seeing. If it's -- for example, if it's a cat, it will -- it appears to be chasing a mouse or some sort of prey animal and playing with it and slapping it around and doing what cats do to trapped mice.
Scientists at MIT analyzed rat brain waves while they ran through a maze and then while they slept afterwards. The brain patterns were so similar, the researchers could say this rat right now is dreaming about being at this place in the maze.
And those, to me, should be called dreams.
Okay, so a lot of animals dream, but why? Why do animals dream? Why do we dream?
There's the question, isn't it? I mean, that's one of the fundamental mysteries of biology. Why is there REM sleep?
To realize just how much of a mystery it is, you need to realize that REM sleep, dreaming, is kind of insane, like, really.
Your brain gets very highly activated, even more activated than it is during the daytime. But your body is paralyzed. You can't move and your sexual system is activated during REM sleep. And the autonomic nervous system goes through these -- what we call autonomic nervous system storms that are very injurious to the organism. So your brain is highly activated. You're sexually activated. You're paralyzed and then you're forced to watch these things we call dreams. So why would Mother Nature do something like this? Nobody knows.
But there are some clues written into evolutionary history. The most ancient animals, the fish, the amphibians, the reptiles don't appear to dream. Birds do, but just for a few seconds at a time. But even the most primitive mammals seem to dream.
Well, it seems to have something to do with the advent of mammals. So mammals, in particular, needed this form of sleep.
It could be a product of advanced networked brains. It could be a way to sort through memories or reinforce learning. It could just be an evolutionary byproduct that we and most other species of mammal are stuck with. We do it every night, but we don't know why. I'm Sabri Ben-Achour.
Transcripts of WAMU programs are available for personal use. Transcripts are provided "As Is" without warranties of any kind, either express or implied. WAMU does not warrant that the transcript is error-free. For all WAMU programs, the broadcast audio should be considered the authoritative version. Transcripts are owned by WAMU 88.5 FM American University Radio and are protected by laws in both the United States and international law. You may not sell or modify transcripts or reproduce, display, distribute, or otherwise use the transcript, in whole or in part, in any way for any public or commercial purpose without the express written permission of WAMU. All requests for uses beyond personal and noncommercial use should be referred to (202) 885-1200.