Many competing theories have been advanced to discover the links between sleep and learning. One theory of sleep is that consolidates and optimizes the layout of memories. Studies have shown that sleep deprivation leads to impaired consolidation of both declarative and procedural memories. As a result, we do not improve on learned tasks and do not consolidate the learned material. In consecutive NREM and REM phases, memories are played back to and from the hippocampus so that their representations in the neocortex can be optimized. This, among others, serves generalization and minimization of memory interference.
Popular sayings such as "sleep on it" or "consult the pillow" reflect the theory that remolded memories produce new creative associations in the morning. According to some sleep clinic research, the negative effects of sleep deprivation are particularly dramatic in procedural learning. Many studies demonstrate that a healthy sleep produces a significant learning performance boost. Healthy sleep must include the appropriate sequence and proportion of NREM and REM phases, which play a different role in memory consolidation-optimization process.
Other researchers' theories on additional functions of sleep differ significantly. One older idea is the energy conservation theory. Others claim that REM sleep is needed to "refresh" the brain after NREM phase, or that REM is needed to prevent stasis of fluids in the eye. These theories have dwindling support in the sleep research community.
For popular scientific articles on the sleep-learning connection:
- http://www.sciam.com/explorations/2000/101600tetris/index.html ("Scientific American")
- http://www.nature.com/nsu/010426/010426-15.html ("Nature")
- http://www.sciencemag.org/cgi/content/full/282/5397/2163 ("Science Magazine")
- http://europe.cnn.com/2000/HEALTH/11/22/sleep.memory.ap/ ("CNN.com")
See also papers from:
- http://osiris.rutgers.edu/Buzsaki/ (Buzsaki Lab - one of the best sleep-hippocampus research centers)