Human Sleep Deprivation Studied In Zebrafish: Stanford

PALO ALTO, CA — Researchers at the Stanford University School of Medicine have found that neural signatures in sleeping zebrafish are similar to those of humans, suggesting that the brain activity evolved at least 450 million years ago.

Scientists have known for more than 100 years that fish enter a sleep-like state, but until now they didn’t know if their sleep resembled that of land animals, the Stanford News Service reported.

The researchers found that when zebrafish sleep, they can display two states that are similar to those found in mammals. The discovery marks the first time these brain patterns have been recorded in fish, the News Service indicated.

“This moves the evolution of neural signatures of sleep back quite a few years,” scholar Louis Leung said.

A paper describing the research was published July 10 in Nature. Philippe Mourrain, an associate professor of psychiatry and behavioral sciences, is the senior author. Leung is the lead author.

To study the zebrafish, scientists recorded brain activity while the fish slept and observed the heart rate, eye movement and muscle tone of the sleeping fish using a fluorescence-based polysomnography.

These researchers named the sleep states observed as “slow bursting sleep,” which is analogous to slow-wave sleep and “propagating wave sleep,” analogous to REM sleep. Though the fish don’t move their eyes during REM sleep, the brain and muscle signatures are similar, the News Service added. Note: fish also don’t close their eyes when they sleep, as they have no eyelids.

While scientists can’t say for certain that all animals sleep, it appears to be a universal need among vertebrates and invertebrates. Animals will die if they are deprived of sleep long enough, and people who fail to receive adequate sleep suffer from mental problems such as memory lapses and impaired judgment, along with a higher risk of disorders such as obesity and high blood pressure.

Still, the exact benefits of sleep are still a mystery.

“It’s an essential function, but we don’t know precisely what it does.” Mourrain said.

He added that sleep disorders are linked to most neurological disorders such as those linked to autism disorders, Alzheimer’s and Parkinson’s disease.

“Sleep disturbances are an aggravating factor of these disorders,” Mourrain said.

The discovery means sleep research can be conducted on zebrafish, which are easy and convenient to study.

“Because the fish neural signatures are in essence the same as ours, we can use information about them to generate new leads for drug trials,” Leung said.

Stanford’s Department of Psychiatry and Behavioral Sciences also supported the work.