Cognitive consequences of sleep and sleep loss.

Although we still lack any consensus function(s) for sleep, accumulating evidence suggests it plays an important role in homeostatic restoration, thermoregulation, tissue repair, immune control and memory processing. In the last decade an increasing number of reports continue to support a bidirectional and symbiotic relationship between sleep and memory. Studies using procedural and declarative learning tasks have demonstrated the need for sleep after learning in the offline consolidation of new memories. Furthermore, these consolidation benefits appear to be mediated by an overnight neural reorganization of memory that may result in a more efficient storage of information, affording improved next-day recall. Sleep before learning also appears to be critical for brain functioning. Specifically, one night of sleep deprivation markedly impairs hippocampal function, imposing a deficit in the ability to commit new experiences to memory. Taken together, these observations are of particular ecologic importance from a professional and education perspective when considering that sleep time continues to decrease across all age ranges throughout industrialized nations.