What is the purpose of sleep? This question is more complex than it may initially seem, given that sleep isn’t merely a form of rest. A lack of sleep can severely damage our health, even putting our lives at risk–something simple rest can’t remedy.
A new study. A recent study published in Cell explores the neurological role of sleep and reveals new insights into what occurs in our brains while we sleep. One of the most striking findings concerns the effectiveness of certain sleeping pills. Researchers conclude that they may not be as beneficial in combating the detrimental effects of sleep deprivation as many believed.
Cleaning the brain. One key function of sleep is “cleaning” the brain. This goes beyond memory processing and involves biological clearance. Each night, the brain eliminates around four grams of waste, which amounts to the average weight of the brain itself over the course of a year.
The glymphatic system, which was discovered in 2013, is responsible for this clearance. It uses cerebrospinal fluid to remove unwanted substances. These include beta-amyloid plaques, which are associated with the onset of neurological disorders like Alzheimer’s disease.
“It’s like turning on the dishwasher before you go to bed and waking up with a clean brain,” study author Maiken Nedergaard explained in a press release. Nedergaard was also part of the research team that discovered the glymphatic system.
The role of norepinephrine. The recent paper also uncovers a crucial mechanism in the functioning of the brain’s waste clearance system: norepinephrine. In an experiment conducted on mice, researchers found that this molecule, which acts both as a hormone and a neurotransmitter, plays a vital role in the brain’s clearance processes.
The team examined what occurs in the mouse brain while it sleeps, focusing on the relationship between norepinephrine and blood flow during the deepest phases of sleep.
Tiny waves. Researchers observed that the mice’s brain flow exhibited tiny waves of norepinephrine, with pulses repeating around every 50 seconds. Norepinephrine causes blood vessels to contract. The result is “slow pulsations” that operate independently of the conventional heartbeat and are responsible for pumping waste out of the brain.
Author Natalie Hauglund likened the role of norepinephrine to that of a conductor in an orchestra. “There’s a harmony in the constriction and dilation of the arteries, which then drives the cerebrospinal fluid through the brain to remove the waste products,” she said.
Sleep and Alzheimer’s disease. Interestingly, the research team encountered an issue with certain sleeping pills affecting this mechanism. Scientists administered zolpidem to some mice and then re-examined the brain activity.
The results showed that while the mice that received the sleeping pill fell asleep more quickly, the activity of norepinephrine waves was reduced by half, and fluid transport in the brain decreased by 30%. This suggests that some sleeping pills may not provide all the benefits associated with restful sleep.
Image | Kinga Howard
Related | In Their Relentless Fight Against Alzheimer’s, Scientists Have Discovered an Unexpected Ally: Coffee
View 0 comments