Spacing out after staying up late? Here’s why
Ever sleep poorly and then walk out of
the house without your keys? Or space out while driving to work and
nearly hit a stalled car?
A new study led by UCLA’s Dr. Itzhak Fried
is the first to reveal how sleep deprivation disrupts brain cells’
ability to communicate with each other. Fried and his colleagues believe
that disruption leads to temporary mental lapses that affect memory and
visual perception. Their findings are published online by Nature
Medicine.
“We discovered that starving the body of sleep also robs neurons of
the ability to function properly,” said Fried, the study’s senior
author, a professor of neurosurgery at the David Geffen School of Medicine at UCLA and Tel Aviv University. “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 at UCLA for epilepsy. 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 study 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, their brain cells did, too.
“We were fascinated to observe how sleep deprivation dampened brain
cell activity,” said lead author Yuval Nir of Tel Aviv University.
“Unlike the usual rapid reaction, the neurons responded slowly and fired
more weakly, and their transmissions dragged on longer than usual.”
Lack of sleep 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 car.
“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.”
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,” 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.”
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,” Fried said. “Yet no legal or medical standards exist for
identifying overtired drivers on the road the same way we target drunk
drivers.”
In future research, 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.