That Euphoric Feeling
"For most people not sleeping well leads to being the person most likely to be avoided the next morning. A lesser known side effect of sleep deprivation is short-term euphoria, which can potentially lead to poor judgment and addictive behavior, according to new research from the University of California, Berkeley. Researchers at UC Berkeley and Harvard Medical School studied the brains of healthy young adults and found that their pleasure circuitry got a big boost after a missed night’s sleep. But that same neural pathway that stimulates feelings of euphoria, reward and motivation after a sleepless night may also lead to risky behavior, their study suggests.
Sleep deprivation is the condition of not having enough sleep; it can be either chronic or acute. A chronic sleep-restricted state can cause fatigue, daytime sleepiness, clumsiness and weight loss or weight gain. It adversely affects the brain and cognitive function. Few studies have compared the effects of acute total sleep deprivation and chronic partial sleep restriction. Complete absence of sleep over long periods is impossible for humans to achieve (unless they suffer from fatal familial insomnia); brief microsleeps cannot be avoided. Long-term total sleep deprivation has caused death in lab animals.
"When functioning correctly, the brain finds the sweet spot on the mood spectrum. But the sleep-deprived brain will swing to both extremes, neither of which is optimal for making wise decisions," said Matthew Walker, associate professor of psychology and neuroscience at UC Berkeley and lead author of the study.
The findings, published today, March 22, in the Journal of Neuroscience, underscore the need for people not to shortchange themselves on sleep, Walker said.
"We need to ensure that people making high-stakes decisions, from medical professionals to airline pilots to new parents, get enough sleep," Walker said. "Based on this evidence, I’d be concerned by an emergency room doctor who’s been up for 20 hours straight making rational decisions about my health."
Sleep deprivation can adversely affect the brain and cognitive function. A 2000 study, by the UCSD School of Medicine and the Veterans Affairs Healthcare System in San Diego, used functional magnetic resonance imaging (fMRI) technology to monitor activity in the brains of sleep-deprived subjects performing simple verbal learning tasks. The study showed that regions of the brain's prefrontal cortex displayed more activity in sleepier subjects. Depending on the task at hand, the brain would sometimes attempt to compensate for the adverse effects caused by lack of sleep.
The temporal lobe, which is a brain region involved in language processing, was activated during verbal learning in rested subjects but not in sleep-deprived subjects. The parietal lobe, not activated in rested subjects during the verbal exercise, was more active when the subjects were deprived of sleep. Although memory performance was less efficient with sleep deprivation, greater activity in the parietal region was associated with better memory.
The body alternates between two main phases of sleep during the night: Rapid Eye Movement (REM), when body and brain activity promote dreams, and Non-Rapid Eye Movement (NREM), when the muscles and brain rest. Previous brain studies indicate that these sleep patterns are disrupted in people with mood disorders.
Puzzled as to why so many people with clinical depression feel more positive after a sleepless night — at least temporarily — the researchers used functional Magnetic Resonance Imaging to study the brains of 27 young adults, half of whom got a good night’s rest and the other half of whom pulled an all-nighter.
Participants viewed numerous images, including pleasant scenes (for example, bunnies or ice cream sundaes), and were asked to rate the pictures as either neutral or positive. Across the board, those who had skipped a night’s sleep gave more positive ratings for all the images while the well-rested participants gave more moderate scores.
Moreover, brain scans of the participants who pulled all-nighters showed heightened activity in the mesolimbic pathway, a brain circuit driven by dopamine, a neurotransmitter that regulates positive feelings, motivation, sex drive, addiction, cravings and decision making.
The findings build upon previous research by Walker and his team that shows sleep deprivation shuts down the brain’s key planning and decision-making regions — namely the prefrontal cortex — while activating more primal neural functions such as the fight-or-flight reflex in the amygdala region of the brain.
The latest study shows a similar disconnect between the prefrontal cortex and the misolimbic pathway after a night of no sleep:
As for a therapy for people who are clinically depressed, sleep deprivation is not a viable solution, according to Walker.
For further information: http://newscenter.berkeley.edu/2011/03/22/pulling-an-all-nighter/