Dear Diedrich,
Like most cats, I enjoy curling up for a quick snooze by my sunny office window. But I know that some people don’t love sleeping. They want to go go go without a break.
I talked about that with my friend Greg Belenky. He runs the Sleep and Performance Research Center at Washington State University’s Spokane campus.
He told me that we need to sleep. Without it, we can’t do basic or complex things.
“All you have to do is look at behavior,” he said. “Somebody who’s sleep deprived for 84 hours can hardly do anything. They’re docile and easily led. They don’t think very fast. They tend to fall asleep.”
Belenky told me the upper limit for not sleeping is 84 hours.
But nobody know why that is. It’s possible sleep helps conserve energy and process memories. Or maybe we need sleep simply because we get sleepy.
It turns out all animals need sleep—but not always the same way.
Elephants only sleep two hours a day. Some marine animals like whales don’t sleep with their whole brains. They let one hemisphere sleep while the other stays active. Then they swap. That means they’re always partially awake.
Humans need about eight hours of sleep every day. Belenky told me about an experiment he did. Four different groups of people slept for different amounts of time—three hours, five hours, seven hours or nine hours.
“The people who got nine hours of sleep looked amazing,” he said. “The seven-hour group and the five-hour group didn’t perform as well. The performance of the three-hour group went off the cliff.”
This type of brain scan is called an fMRI, or functional magnetic resonance imaging. It detects changes in blood flow. Here, the colored areas have increased blood flow. That means those areas of the brain are active. Image: First Science/Wiki
Scientists can watch what happens in the brain. If you hook up a well-rested person to a brain scan and ask them a simple question, the whole brain becomes active. That happens because the brain is preparing itself for any difficulty of problem.
That means if someone is given a problem that begins with the number four, the brain comes up with everything associated with four. The problem may wind up being 4+4. Or it could be 4 times 58 or 7,000 divided by 4. The brain doesn’t know what’s coming.
When someone’s tired, the brain is much less active when that four is presented.
“Everything you’re thinking and feeling is just shallower,” Belenky said. “When you’re fatigued the bloom of brain activity on a scan shrinks. The glowing area becomes dimmer. You’re slower to get the answer. You may never get the answer.”
What about the people who say they’re fine with just a few hours of sleep?
Belenky told me that’s unlikely. They may think they’re doing ok, but they’re not performing as well as they could.
Sleeping might not be super exciting, but it helps you do your best when you’re awake. And that’s good s-nooze.
Sincerely,
Dr. Universe