The Sleeping Brain

Abstract

The role of sleep has long baffled scientists, but the latest research is providing new indicators about what it does for both the brain and body. While scientists believe that sleep re-energizes the body's cells, clears waste from the brain, and supports learning and memory, much still needs to be learned about the part it plays in regulating mood, appetite and libido. Source/Shutterstock.

Figure 1

Top, Schematic diagram describing the main claim of SHY: net synaptic increase occurs during wake (during the day in humans and diurnal animals), when many circuits in the brain get potentiated (dark blue lines in the brain schematic), resulting in cellular and systems’ costs, followed by synaptic renormalization during sleep, when most, if not all circuits undergo synaptic down-selection (light blue lines). Bottom, Parameters used to test SHY. While structural and molecular measures more directly reflect synaptic strength, electrophysiological measures such as responses evoked by direct stimulation of the cerebral cortex can be strongly affected by other factors that modulate intrinsic neuronal excitability, including the levels of neuromodulators and the balance between excitation and inhibition, and thus cannot be used alone to infer synaptic strength. In the upper panel (structural), the red line indicates the axon to spine interface (ASI), and the yellow area outlines the head of the spine. In the middle panel (molecular), excitatory glutamatergic receptors (AMPARs) are shown as squared boxes.