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Posts Tagged ‘sleep’

1 sleepless night increases dopamine in the human brain

Just one night without sleep can increase the amount of the chemical dopamine in the human brain, according to new imaging research in the August 20 issue of The Journal of Neuroscience. Because drugs that increase dopamine, like amphetamines, promote wakefulness, the findings offer a potential mechanism explaining how the brain helps people stay awake despite the urge to sleep. However, the study also shows that the increase in dopamine cannot compensate for the cognitive deficits caused by sleep deprivation.

“This is the first time that a study provides evidence that in the human brain, dopamine is involved in the adaptations that result from sleep deprivation,” said Nora Volkow, MD, director of the National Institute on Drug Abuse, who led the study.

Volkow and colleagues found that in healthy participants, sleep deprivation increased dopamine in two brain structures: the striatum, which is involved in motivation and reward, and the thalamus, which is involved in alertness. The researchers also found that the amount of dopamine in the brain correlated with feelings of fatigue and impaired performance on cognitive tasks.

“These findings suggest dopamine may increase after sleep deprivation as a compensatory response to the effects of increased sleep drive in the brain,” said David Dinges, PhD, at the University of Pennsylvania School of Medicine, an expert unaffiliated with the study. “The extent to which this occurs may differentiate how vulnerable people are to the neurobehavioral effects of sleep loss,” Dinges said.

The researchers studied 15 healthy participants who were either kept awake all night or allowed a good night’s sleep. Researchers tested the same participants in both conditions. On the morning of the study, participants rated how tired they were and did cognitive tasks testing visual attention and working memory.

The researchers used the imaging technique positron emission tomography to study the changes in the dopamine system that occur with sleep deprivation. Compared to well-rested participants, sleep-deprived participants showed reduced binding of a radiolabeled compound ([11C]raclopride) that binds to dopamine receptors in the striatum and thalamus. Because raclopride competes with dopamine for the same receptors, decreased raclopride binding indicates increased levels of dopamine, according to the study authors.

Although decreases in raclopride binding could also indicate a reduction in the number of dopamine receptors, these findings are consistent with prior research implicating increased dopamine levels in wakefulness. For example, some stimulants that prevent sleep, like amphetamines, increase dopamine in the brain, and sleepiness is common in people with Parkinson’s disease, which kills dopamine neurons.

The rise in dopamine following sleep deprivation may promote wakefulness to compensate for sleep loss. “However, the concurrent decline in cognitive performance, which is associated with the dopamine increases, suggests that the adaptation is not sufficient to overcome the cognitive deterioration induced by sleep deprivation and may even contribute to it,” said study author Volkow.

Future research will examine the long-term effects of chronic sleep disturbances on dopamine brain circuits.

Source: Society for Neuroscience

Sleep-deprived brains alternate between normal activity and ‘power failure’

New imaging research shows that brain activity differs in sleep-deprived and well-rested people. The study, in the May 21 issue of The Journal of Neuroscience, shows that individuals who are sleep-deprived experience periods of near-normal brain function, but these periods are interspersed with severe drops in attention and visual processing.

This study shows what happens in the sleep-deprived brain and may explain why sleep-deprived people fail to stay alert. “The main finding is that the brain of the sleep-deprived individual is working normally sometimes, but intermittently suffers from something akin to power failure,” said Clifford Saper, MD, PhD, of Harvard University, an expert unaffiliated with the study. STL-B

The research team, led by Michael Chee, MBBS, at the Duke–National University of Singapore Graduate Medical School in Singapore (Duke-NUS), used functional magnetic resonance imaging (fMRI) to measure brain blood flow in people who were either kept awake all night or allowed a good night’s sleep. Researchers tested the same participants in both conditions.

During imaging, participants did a task that required visual attention. Researchers showed them large letters composed of many smaller letters. Participants were asked to identify either the large or small letters and to indicate their responses by pushing a button.

Well-rested and sleep-deprived volunteers showed a range of reaction times. Those participants with the fastest responses, both in sleep-deprived and well-rested conditions, showed similar patterns of brain activity. However, well-rested and sleep-deprived participants with the slowest responses—also called attentional lapses—showed different patterns of brain activity.

Previous research showed that attentional lapses normally induce activity in frontal and parietal regions of the brain, “command centers” that may compensate for lost focus by increasing attention. However, during attentional lapses, Chee and colleagues found reduced activity in these brain command centers in sleep-deprived compared to well-rested volunteers. This finding suggests that sleep deprivation reduces the brain’s ability to compensate for lost focus.

Sleep-deprived people also showed reduced activity in brain regions involved in visual processing during attentional lapses. Because the brain becomes less responsive to sensory stimuli during sleep, reduced activity in these regions suggests that, during attentional lapses, the sleep-deprived brain enters a sleep-like state.

“To my knowledge, this is one of the first studies to look carefully at brain imaging during lapses of consciousness after sleep deprivation, the equivalent of ‘blanking out,’” said Emmanuel Mignot, MD, PhD, at Stanford University, who was not involved in the study. Although attentional lapses result in the same behaviors, “lapses due to sleep deprivation are clearly different neurobiologically than lapses in well-rested people,” Mignot said.

Saper says the study highlights the importance of preventing sleep deprivation in people who are doing critical tasks, like night driving. Although sleep deprivation harms decision making and may increase on-the-job errors, sleep-deprived workers may not know they are impaired. “The periods of apparently normal functioning could give a false sense of competency and security when, in fact, the brain’s inconsistency could have dire consequences,” study author Chee said.

Source: Society for Neuroscience

Andrew says:


This seems to be true in my experience… especially when programming. It’s the morning-after thousand-yard stare. So after an all-nighter, while trying to work the next morning, 6am to 1pm seem to fly by with little productivity. Tens of minutes will pass before my brain “wakes itself up.” However, if there is some emergency demanding my all my focus, like a morning exam, my brain never has an opportunity to “fail to compensate” and I perform fine.

Type of anesthetic will improve sleeping medication, probe mysteries of the snooze

Researchers at the University of Alberta have discovered sleep patterns in a type of anesthesia that are the closest ever to a natural, non-groggy snooze.

The anesthetic used in the study, known as ethyl carbamate or urethane, provides researchers with a tool to more thoroughly investigate ways of treating sleep disorders and improving existing sleep medications, says Clayton Dickson, one of the study’s co-authors and an associate professor of psychology, physiology and neuroscience at the University of Alberta in Canada. … Continue Reading »