We’re jostling to buy gifts, standing in lines, fighting after-work traffic to pick up goodies for holiday parties. But we’ve been unwittingly prepared for these moments of competition and cooperation — by our dreams.
Those little movies projected on the backs of our eyelids are more than head-scratching nonsense. Their content is filled with either friendly or aggressive interactions, depending on what part of the sleep cycle we are in, says Patrick McNamara, director of the Evolutionary Neurobehavior Laboratory at the School of Medicine and an associate professor of psychiatry.
“Dreaming has social effects,” says McNamara (CAS’86, GRS’91), who recently cowrote an article for the Journal of Affective Disorders on the impact of REM sleep on distortions of self-concept, mood, and memory in depressed and anxious participants and is editing an encyclopedia of sleep and dreams. His most recent book, Nightmares: The Science and Solution of Those Frightening Visions During Sleep (Praeger), was published in 2008.
BU Today: What’s the difference between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep cycles?
McNamara: REM is an odd physiological state. The bulk of it occurs in the latter half of the night’s sleep, toward morning. The brain is hyper-activated, more activated than during the daytime. Yet the body is paralyzed. All the antigravity muscles aren’t working, so you can’t move, and the eyes dart back and forth as if watching some scene. There is sexual activation. The autonomic nervous system is going through what we call periodic storms, or discharges. It’s a strange biological conglomerate.
Every night when you go into REM, men get erections, and if you’re a female the clitoris gets engorged. We engage in pelvic thrusting movements. Every 90 minutes human beings go into this sexual activation.
Great, now I’m going to be too self-conscious to fall asleep. Is there an evolutionary reason for this?
There must be. The first thing that suggests itself is that it somehow increases reproductive fitness. For men who complain of impotence, one way to determine if it’s psychological or physiological is to observe them during sleep.
Does the content of our dreams change between sleep cycles?
In non-REM, you have different activation patterns in the brain and totally different types of dreams; in one analysis, we could not find a single instance of the dreamer inflicting aggression on another character. That’s ubiquitous in REM dreams, when there’s a lot of emotion, a lot of characters engaging in social interactions, a lot of memories that pop up. And a lot of male strangers, malicious men meaning to do us harm.
What’s the explanation for the male stranger? Do you turn to Freud here?
Freud made a lot of contributions, but I don’t get into interpretations. It’s a can of worms. From an evolutionary point of view, it would make sense. In primordial conditions, the biggest source of mortality was attack by a neighboring tribe. The biggest threat to a child or adult during the 50,000 years we were hunter-gatherers was a male stranger.
So dreams are a practicing ground?
Dreams certainly reflect our evolutionary history. Are they helping us to practice against threats? Perhaps. But there are many more types of REM dreams that go way beyond practice against evolutionary threats like male strangers or spiders or snakes. REM dreams are as diverse as waking cognition.
Dreams simulate what human beings have to worry about. We have to learn to cooperate with others so dreams simulate friendly interactions, which the non-REM system does. We also have to be aggressive in social interactions at times, so the REM system simulates that.
How do you conduct your dream studies?
You put electrodes on people’s brains. You wake them up, and they report whatever they remember thinking or dreaming. Those reports are analyzed with computerized programs so there’s no bias.
I never have a sense of time passing in my dreams. Can an epic dream be compressed into a minute?
Studies suggest that if telling the story takes 45 minutes, it will take you 45 minutes to dream it. As the night goes along, you have REM episode number one and episode number two, and the memories that occur in episode number one are recent and the memories from episode number four are from the remote past. That’s one of the clues that REM has something to do with memory, among other functions.
Something irrelevant occurs during the day that I don’t give a second thought to, then it appears in a dream that night. Why?
Some say that one of the things dreams do is take all the irrelevant stuff and strip it from the memory system. So it appears transiently in dreams and then disappears forever.
What is the role of nightmares?
A nightmare is a failure of the REM system to diffuse the intensity of a painful emotional experience. Let’s say you’re a combat veteran and saw your friends go up in smoke before your eyes. How do you integrate that without destroying your self-construct or your view of the world? You need a way to move forward and forget. Dreams, in part, strip emotional memory of its context, making it easier to integrate into the memory system. Nightmares happen when that stripping process isn’t successful.
That accounts for one set of nightmares, but there’s a whole other set of nightmares where we have no idea what’s going on.
When I was using the nicotine patch to quit smoking, I experienced some vivid dreams.
I hear this over and over. Very likely the reason is because the nicotine patch is a shot of cholinergic activity into the brain. The cells that are involved in generating REM sleep are cholinergic. So you’re going to get a surge in REM sleep physiology.
Caleb Daniloff can be reached at email@example.com.