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October 30, 2007

Sleep Tight and Memories Will be Forever

lady sleeping on bedA recent study done by Dr. Mathew Walker (director of the University of California, Berkeley's Sleep and Neuroimaging Laboratory) and colleagues, published in October 22 issue of Current Biology, has found an association between sleep deprivation and emotional instability.

In their study, they divided 26 undergraduates into two groups. While subjects in the test group were kept awake for about 35 hours at a stretch; those in the control group, were allowed to sleep during nighttime during the study. At the end (of 35 hours since the starting of the study), both the groups were shown drawings and figures capable of evoking emotions. The subjects' brains were scanned by fMRI (a real time scan that portrays neural activities on the basis of enhanced metabolism) while they were shown the images. In the sleep deprived, it was found out, that amygdala, a portion of their brain was much more active in comparison to their well slept counterparts. Amygdala, is concerned with the physiological "fight or flight response" (our body's primitive, automatic, inborn response which prepares us for imminent danger) and thus its activation in the sleep starved, made them more emotionally driven and they showed stronger response to the images. The fMRI pattern was more like that of depression and PTSD (post traumatic stress disorder) in the sleep deprived.

Normally, the prefrontal cortex is in charge. This part of the brain is rather new, evolutionarily. This part thinks logically. Amygdala, on the other hand, is primitive and is less logical and more impulse driven. In the sleep deprived state, the amygdala is overdriven and takes the 'steering wheel'. As in the heart, where the SA Node (the normal pacemaker) is taken over by faster pacemakers (ectopic/ abnormal pacemakers which fire at a higher rate than the SA Node); here also the prefrontal cortex is usurped by the amygdala. Amygdala, in turn activates locus coeruleus, a part of the brain that produces Nor-adrenaline, the fight or flight chemical.

The inference: sleep deprivation may lead to psychiatric problems even in healthy subjects, or exacerbate them, in those already suffering from a psychiatric disorder. The study suggests that the brain is re-wired during sleep deprivation. From another angle, it may be construed that while we sleep, the brain goes into a state akin to the computers' restart procedure, where the brain organizes it's own circuitry, when the running programs are cut down to the minimum.

Thus it is necessary to sleep, not only to dream but also to remain sane. The actions of noradrenaline has been beautifully illustrated by Metallica, in their song 'Whiplash' (I don't think he did it for this purpose though!)

"Adrenaline starts to flow
You're thrashing all around
Acting like a maniac
Whiplash"

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