Sleep deprivation has long been known to affect our physical and mental well-being, and has been linked to a host of diseases including high blood pressure and diabetes, but a new study by Israeli and American neuroscientists now says lack of sleep directly impacts our brain cells too, disrupting their ability to communicate and even causing parts of our brain to doze.
The study, by Dr. Yuval Nir of Tel Aviv University, Professor Yitzhak Fried of UCLA and Tel Aviv Medical Center and sleep experts Profs. Chiara Cirelli and Giulio Tononi at the University of Wisconsin-Madison, found that sleep deprivation causes brain cells to slow down, affecting memory, reactive behavior and visual perception.
“When we’re sleep-deprived, a local intrusion of sleep-like waves disrupts normal brain activity while we’re performing tasks,” said Dr. Nir in a Tel Aviv University press statement.
Fried, a professor of neurosurgery at the David Geffen School of Medicine at UCLA and Tel Aviv University, said starving the body of sleep also robs neurons — nerve cells that transmit and receive signals from the brain — “of the ability to function properly.”
“This leads to cognitive lapses in how we perceive and react to the world around us,” he says.
Not only does sleep deprivation cause irritation, mental fog, malaise and forgetfulness, and affects mood and physical appearance, it can also lead to serious or potentially fatal road and work accidents.
The scientists have likened being sleep-deprived to being drunk and argue that the dangers are similar.
“Severe fatigue exerts a similar influence on the brain to drinking too much,” Fried says. “Yet no legal or medical standards exist for identifying overtired drivers on the road the same way we target drunk drivers.”
In their study, the team of scientists recorded the brain activity of 12 patients with epilepsy who were preparing to undergo surgery to treat the neurological disorder. The patients had electrodes implanted to identify the origins of their seizures. Because lack of sleep can bring on seizures, the patients were deprived of sleep to accelerate the onset of an episode and thus speed up their medical diagnosis.
The scientists then presented the patients with images of celebrities and famous places and asked them to quickly identify them.
“Performing this task is difficult when we’re tired and especially after pulling an all-nighter,” says Dr. Nir. “The data gleaned from the experiment afforded us a unique glimpse into the inner workings of the human brain. It revealed that sleepiness slows down the responses of individual neurons, leading to behavioral lapses.”
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The researchers, whose findings were published in Nature Medicine this week, observed responses to over 30 images and recorded the activity of a total of 1,500 neurons, paying particular attention to those in the temporal lobe, which regulates memory and visual perception.
“Unlike the usual rapid reaction, the neurons responded slowly and fired more weakly, and their transmissions dragged on longer than usual,” says Nir.
Fried says that “during such behavioral lapses, the neurons gave way to neuronal lapses — slow, weak and sluggish responses. These lapses were occurring when the patients were staring at the images before them, and while neurons in other regions of the brain were functioning as usual.”
These lapses were also accompanied by slower brain waves, according to the findings, indicating that parts of the brain were actually slumbering.
“Slow, sleep-like waves disrupted the patients’ brain activity and performance of tasks,” Fried said. “This phenomenon suggests that select regions of the patients’ brains were dozing, causing mental lapses, while the rest of the brain was awake and running as usual.”
It’s the reason an overtired driver is slow to react as lack the brain’s ability to compute information and translate visual input is compromised
“The very act of seeing the pedestrian slows down in the driver’s overtired brain,” Fried said. “It takes longer for his brain to register what he’s perceiving.”
Sleep deprivation has long been associated with parents of young children, medical residents working long, rigorous shifts with little sleep, university students cramming for finals, truck and delivery drivers making long hauls and other workers laboring through irregular hours that disrupt the circadian rhythms.
But, increasingly, studies are showing that our way of life in general is not conducive to sleep. One neuroscientist, Michael Rosbash of Brandeis University who last month won the Nobel Prize for Medicine, said sleep deprivation in Western society was becoming a “real public health problem.”
“All of Western society is a little bit sleep deprived and, when I say a little bit, I mean chronically,” he told the Guardian in October after winning the prize.
Nir said he, Fried and their colleagues hoped to translate the results of their study “into a practical way of measuring drowsiness in tired individuals before they pose a threat to anyone or anything.”