Increased blood flow during sleep tied to critical brain function

January 18, 2021

Our brains experience significant changes in blood flow and neural activity during sleep, according to Penn State researchers. Such changes may help to clean out metabolic brain waste that builds up during the day.

"We studied the sleep patterns of mice during both rapid eye movement and non-rapid eye movement sleep stages, as well as in different alertness states," said Patrick Drew, Huck Distinguished Associate Professor of Engineering Science and Mechanics, Neurosurgery and Biomedical Engineering.

Mice were chosen for the study because of their brains' remarkable similarity with human brains, said the researchers.

In both mice and humans, non-REM sleep is the first stage of sleep that occurs when a person falls to sleep for about the first hour or two, according to Drew, while REM sleep is characterized by rapid eye movements and vivid dreams.

During the different sleep and alertness states, the researchers monitored the neural activity, blood vessel dilation, electromyography activity and whisker and body movements of the mice.

Mice move their whiskers during rapid eye movement (REM) sleep instead of moving their eyes, and also sleep with their eyelids open.

"The mice naturally fall asleep very quickly even while their heads were restrained to allow for neural imaging," Drew said. "We used machine learning algorithms to continually monitor the sleep stages the animals were in, and also when they were awake, as they greatly impact blood flow fluctuations."

Using optical imaging and two-photon microscopy, report in eLIfe that the researchers found that brain arterioles, or small branches of arteries, were more much more dilated when the mice were in non-REM sleep than when they were awake. During REM sleep, the dilation was even larger than during non-REM sleep.

Such blood flow changes indicate the brain is healthy, according to Drew.

"The dilated blood vessels and increased blood flow may help the brain move waste products out of the brain," he said.

This is why disrupted sleep is associated with diseases that afflict the brain, such as Alzheimer's and dementia.

"The working hypothesis is that with diseases affecting the brain, the body fails to clear the neural waste fluid due to lack of sleep," Drew said. "And decreases in cerebral blood flow?often proceed degenerative brain illnesses."

Further, insomnia could negatively contribute to mental health conditions like anxiety and depression, as the brain is unable to clear out the waste fluid when sleep is disrupted for an extended period of time.

"The knowledge of brain processes gained through this study is basic, but it could be applied to a number of clinical studies in the future," Drew said.
In addition to Drew, Penn State researchers include Elizabeth Proctor, assistant professor of neurosurgery, pharmacology, biomedical engineering and engineering science and mechanics; Kevin Turner, doctoral candidate in bioengineering; and Kyle Gheres, doctoral candidate in molecular, cellular and integrative biosciences.

The National Institutes of Health supported this study.

Penn State

Related Sleep Articles from Brightsurf:

Size and sleep: New research reveals why little things sleep longer
Using data from humans and other mammals, a team of scientists including researchers from the Santa Fe Institute has developed one of the first quantitative models that explains why sleep times across species and during development decrease as brains get bigger.

Wind turbine noise affects dream sleep and perceived sleep restoration
Wind turbine noise (WTN) influences people's perception of the restorative effects of sleep, and also has a small but significant effect on dream sleep, otherwise known as REM (rapid eye movement) sleep, a study at the University of Gothenburg, Sweden, shows.

To sleep deeply: The brainstem neurons that regulate non-REM sleep
University of Tsukuba researchers identified neurons that promote non-REM sleep in the brainstem in mice.

Chronic opioid therapy can disrupt sleep, increase risk of sleep disorders
Patients and medical providers should be aware that chronic opioid use can interfere with sleep by reducing sleep efficiency and increasing the risk of sleep-disordered breathing, according to a position statement from the American Academy of Sleep Medicine.

'Short sleep' gene prevents memory deficits associated with sleep deprivation
The UCSF scientists who identified the two known human genes that promote 'natural short sleep' -- nightly sleep that lasts just four to six hours but leaves people feeling well-rested -- have now discovered a third, and it's also the first gene that's ever been shown to prevent the memory deficits that normally accompany sleep deprivation.

Short sleep duration and sleep variability blunt weight loss
High sleep variability and short sleep duration are associated with difficulties in losing weight and body fat.

Nurses have an increased risk of sleep disorders and sleep deprivation
According to preliminary results of a new study, there is a high prevalence of insufficient sleep and symptoms of common sleep disorders among medical center nurses.

Common sleep myths compromise good sleep and health
People often say they can get by on five or fewer hours of sleep, that snoring is harmless, and that having a drink helps you to fall asleep.

Sleep tight! Researchers identify the beneficial role of sleep
Why do animals sleep? Why do humans 'waste' a third of their lives sleeping?

Does extra sleep on the weekends repay your sleep debt? No, researchers say
Insufficient sleep and untreated sleep disorders put people at increased risk for metabolic problems, including obesity and diabetes.

Read More: Sleep News and Sleep Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to