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New study reinforces the importance of sleep cycle

By Amabel Karoub, Daily Staff Reporter
Published April 1, 2014

Tired? Going to sleep is more important than you may think.

Many people may have heard of circadian rhythms — they’re the reason for your 4 p.m. exhaustion or your jetlag after returning from spring break in Paris. In simple terms, these rhythms tell your body when to sleep and when to wake up.

The rhythms usually work in 24-hour periods and are run by cells known as ‘clock neurons.’ In a recent study, University researchers discovered that these clock neurons are much more complex than they previously thought.

In the past, scientists believed a small group of neurons controlled the thousands of clock neurons in the human brain. Orie Shafer, assistant professor of molecular, cellular and developmental biology, found evidence showing that different groups of clock neurons actually play their own parts in keeping time for the body.

“We used to think there was one small set of neurons that were the conductors,” Shafer said. “Our work suggests that it’s more of a committee decision. There are several important groups of time neurons that interact with each other to produce a sense of time.”

The researchers studied fruit flies, organisms with circadian rhythms similar to those of humans. Rackham student Zepeng Yao said many of the 150 clock neurons in fruit flies responded to environmental cues rather than cues from “conductor” neurons.

“Some of them might respond to light information … some of them might be more sensitive to temperature changes,” Yao said. “These cues will either advance or delay the clock neurons.”

Clock neurons are highly sensitive in response to environmental factors, Shafer said. The clock can be prompted to reset by receiving a waking cue at a time when it wants to sleep. For example, in the modern world, the constant input of light when clock neurons want darkness can keep one’s body awake. In the same way, eating late at night can also reset the clock.

“In this very complicated modern world, we get all the natural cues — for example, the sun coming up and going down every day,” Shafer said. “People who stay up late, they’re getting conflicting information about what time it is.”

Failure to follow circadian rhythms is associated with stress, obesity, diabetes and cancer. Shafer said in light of his research displaying how complex clock neurons are, one should be wary ignoring them.

“Not being able to follow your own body clock is really bad for you,” Shafer said. “You shouldn’t continually ignore what time it is in your brain … These are intricate, highly evolved timepieces that are there for a reason.”

Although circadian rhythms are far from completely understood, Yao said this discovery could lead to new insights. In the long run, it could lead to a method of targeting specific neurons to reduce negative effects of deviating from the rhythms.

“We hope with our research we can pinpoint which neurons are responsible for which kinds of behavior,” Yao said. “We want to see whether we can change the properties with drugs or other processes to alleviate sleeping disorders and other syndromes.”


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