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Thursday, October 15, 2015

Half Asleep

Lasers Help Prove Parts of the Brain 'Sleep' While You're Awake

Steve Dent | October 14, 2015

Have you ever spaced out in the middle of a conversation without dozing off completely? MIT scientists now have a better idea why: only part of your brain is sleeping while the rest stays awake. Neuroscientists always suspected that, but the MIT team proved it in mice by using "optogenetics" to stimulate a part of the brain associated with sleep. They showed that the "thalamic reticular nucleus" (TRN) not only triggers slow sleep waves across the brain, but controls individual regions as well. The research could lead to safer anesthetic techniques and improved drugs for insomniacs.


<more at; related links: (How the brain controls sleep. Brain structure generates pockets of sleep within the brain. October 13, 2015) and (Thalamic reticular nucleus induces fast and local modulation of arousal state. Laura D. Lewis, Jakob Voigts, Francisco J.Flores, Lukas I. Schmitt, Matthew A. Wilson, Michael M. Halassa, and Emery N. Brown. DOI: Published October 13, 2015. [Abstract: During low arousal states such as drowsiness and sleep, cortical neurons exhibit rhythmic slow wave activity associated with periods of neuronal silence. Slow waves are locally regulated, and local slow wave dynamics are important for memory, cognition, and behaviour. While several brainstem structures for controlling global sleep states have now been well characterized, a mechanism underlying fast and local modulation of cortical slow waves has not been identified. Here, using optogenetics and whole cortex electrophysiology, we show that local tonic activation of thalamic reticular nucleus (TRN) rapidly induces slow wave activity in a spatially restricted region of cortex. These slow waves resemble those seen in sleep, as cortical units undergo periods of silence phase-locked to the slow wave. Furthermore, animals exhibit behavioural changes consistent with a decrease in arousal state during TRN stimulation. We conclude that TRN can induce rapid modulation of local cortical state.]>

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