Recharge, reboot, rewire: sleep optimizes information processing in neural circuits

Of the many proposed functions of sleep, its role in cognitive processing has received the most experimental support. Across animal phyla, sleep disruption interferes with sustained attention, sensory processing, and memory encoding, consolidation, and recall. However, identifying sleep dependent mechanisms underlying these processes has posed a challenge. This is due in part to the complexity of sleep states, which simultaneously alter brain circuit and neuronal activity patterns, neuromodulation, transcription, translation, and other neurophysiological parameters. In addition, the cognitive processes affected by sleep or sleep loss are complex, occur within the most complex biological system known to man (i.e., the brain) and in many cases involve cellular mechanisms that are not fully resolved. This review provides a simplified framework for considering sleep's roles in cognition-drawing an analogy to information processing in a simple computational circuit. The contributions of sleep to the energy supply (i.e., the battery), the activity (the current), and the connectivity (the wires) of this simplified circuit are considered, with the aim of understanding how these aspects of sleep function interact within the brain.