A new UCLA-led study is the first to reveal how sleep deprivation disrupts brain cells' ability to communicate with each other. Itzhak Fried, MD, PhD '81, professor of neurosurgery, and his colleagues believe that disruption leads to temporary mental lapses that affect memory and visual perception.
“We discovered that starving the body of sleep also robs neurons of the ability to function properly,” Dr. Fried says. “This leads to cognitive lapses in how we perceive and react to the world around us.”
The international team of scientists studied 12 people who were preparing to undergo surgery for epilepsy at UCLA. The patients had electrodes implanted in their brains in order to pinpoint the origin of their seizures prior to surgery. Because lack of sleep can provoke seizures, patients stay awake all night to speed the onset of an epileptic episode and shorten their hospital stay.
Researchers asked each participant to categorize a variety of images as quickly as possible. The electrodes recorded the firing of a total of nearly 1,500 brain cells (from all of the participants combined) as the patients responded, and the scientists paid particular attention to neurons in the temporal lobe, which regulates visual perception and memory. Performing the task grew more challenging as the patients grew sleepier. As the patients slowed down, so did their brain cells.
Lack of sleep also interfered with the neurons' ability to encode information and translate visual input into conscious thought. The same phenomenon can occur when a sleep-deprived driver notices a pedestrian stepping in front of his or her car. “The very act of seeing the pedestrian slows down in the driver's overtired brain,” Dr. Fried says. “It takes longer for the driver's brain to register what he or she is perceiving.”
The researchers also discovered that slower brain waves accompanied sluggish cellular activity in the temporal lobe and other parts of the brain. “Slow, sleep-like waves disrupted the patients' brain activity and performance of tasks,” Dr. Fried says. “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.”
The study's findings raise questions about how society views sleep deprivation. “Severe fatigue exerts a similar influence on the brain to drinking too much,” Dr. Fried says. “Yet no legal or medical standards exist for identifying overtired drivers on the road the same way we target drunk drivers.”
Dr. Fried and his colleagues plan to more deeply explore the benefits of sleep and to unravel the mechanism responsible for the cellular glitches that precede mental lapses. Previous studies have tied sleep deprivation to a heightened risk of depression, obesity, diabetes, heart attacks and stroke. Research has also shown that medical school residents who work long shifts without sleep are more prone to make errors in patient care.
“Selective Neuronal Lapses Precede Human Cognitive Lapses Following Sleep Deprivation,” Nature Medicine, November 6, 2017
