Speaker: Vladyslav Vyazovskiy, UW Department of Psychiatry
Abstract: Sleep is usually thought of as a global behavior and a global brain state. However, recent evidence indicates that sleep intensity, measured as electroencephalogram (EEG) slow-wave activity, is not uniformly distributed across cortical areas. Some brain regions appear to need more sleep (or more "intense" sleep) than others, and such local sleep regulation occurs in a use-dependent manner. When the brain is awake, neurons in the cerebral cortex fire irregularly and the EEG displays low-amplitude, high-frequency oscillations. After falling asleep, neurons start oscillating between ON periods, when they fire as during wake, and OFF periods, when they stop firing altogether, and the EEG displays high amplitude slow waves. However, after sleep deprivation, cortical neurons can go briefly "OFF line" as they do in sleep, accompanied by slower waves in the local EEG. Strikingly, neurons often go OFF line in one cortical area and not in another. During these periods of "local sleep", whose incidence increases with wake duration, rats appear awake, active, and display a wake EEG. Thus, in sleep-deprived rats, though both the EEG and behavior indicate wakefulness, local populations of neurons in the cortex may be falling asleep.