Sleep Bolsters Emotional Control
> 10/23/2007 2:33:13 PM

Today's Science Times in the New York Times focuses on sleep. The centerpiece article "An Active, Purposeful Machine That Comes Out at Night to Play?," while interesting, focuses entirely on learning and memory tasks. It cannot be denied that students planning  an all-nighter before their final need to know about the learning impairments of sleep-deprivation, but many researchers suspect that there are additional impairments that have not yet been fully explored. In an article published yesterday in Current Biology, Dr. Matthew Walker confirmed these suspicions by finding that the ability to regulate emotion degrades if the brain misses sleep.

Dr. Walker divided 26 subjects up into two groups; subjects in the first group were allowed to sleep normally without interference, while subjects in the second group were kept awake for approximately a day and a half. Both groups were shown images that ranged from neutral (i.e, a forest) to disturbing (i.e. a growling bear charging out of the forest). Dr. Walker's team used fMRI scans to observe activation levels in the subjects' brains. Of course, both groups displayed elevated levels of activation in the emotional centers when exposed to disturbing imagery, but the sleep-deprived group was much more affected. Subjects in the sleep-deprived group displayed 60% greater activation in the amygdala, a difference that Dr. Walker attributed to an impaired medial-prefrontal cortex. Evolutionarily, the MPFC is a recent addition to the human brain, saddled with the tough responsibility of reining in overly strong emotional responses from the more primitive amygdala. If sleep-deprivation renders your MPFC less able to fulfill its regulatory duties, then you may be vulnerable to extreme swings into anger, fear, and sadness.

The idea that sleep helps the brain regulate emotions is not entirely short-changed by the New York Times. At the very end of an article on nightmares, the Times mentions "fear extinction memories," discussed by Dr. Levin and Dr. Nielsen in a recent Psychological Bulletin article. The idea of extinction memories is that they are more palatable mixtures of experiences that led to the formation of emotional reactions that are no longer adaptive. Fear of highchairs may have made sense in the years after you fell out of one as a baby, but after you have grown too large to fit in highchairs, such fear is no longer useful. By mixing images of highchairs with neutral images, the brain is able to dilute the emotional reaction.

Researchers have compiled convincing evidence that one of sleep's purposes is to help us control emotion. This insight may help doctors treat a variety of mental illnesses that are linked to sleep disturbances, such as depression, bipolar disorder, and PTSD. It is very possible that sleep disturbance is not just a random symptom of these disorders, but rather something that exacerbates or even causes the primary problem. For example, depressed patients may worsen as they lose sleep because their impaired MPFC leaves them unable to suppress extreme negative emotional reactions. If you have a negative reaction to this article, or you failed to learn anything from it, perhaps you should take a nap.


This interesting research adds further support to the dream theory first put forward in 1993 by the Irish psychologist and dream researcher, Joe Griffin. His ‘Expectation Fulfilment Theory of Dreaming’ fully explains how REM sleep dreaming dearouses the autonomic nervous system from unacted out expectations from the previous day, and why all dream content is metaphorical – and has to be. Griffin has also explained the connection between dreaming and the finding that depressed people always wake up tired and unmotivated. He and his colleagues have also developed a clear model that explains the link between dreaming and the symptoms of psychosis as well as suggesting an explanation for why we evolved to forget our dreams.Anyone interested in sleep research and dreaming should understand these developments. You can read about them on this site:
Posted by: Eleanor 10/26/2007 7:16:25 AM

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