One of the most interesting areas of current investigation into memory formation in general, and hippocampus-dependent memory formation specifically, are studies asking whether sleep is involved in memory formation (32-36). Specifically, current hypotheses from several groups posit that hippocampus-dependent memory consolidation requires sleep, or at least sleep-associated processes.
Sleep is, of course a mysterious process, so testing the role of sleep specifically is quite difficult (see reference 36). It is not sufficient to define sleep as a lack of consciousness, and indeed it is clear from monitoring CNS activity patterns that being unconscious is different from being asleep. In the modern era, sleep is specifically defined in the context of EEG patterns: several different specific stages of sleep have been defined including four progressive stages of "slow-wave" sleep and rapid eye movement (REM) sleep. I find it intriguing that REM sleep is associated with the same synchronized theta-frequency discharges in the hippocampus as are observed in exploring animals (see text). Thus, while "sleep" seems a fairly intuitive term, in fact the phenomenon is a very complex CNS circuit phenomenon, involving almost all areas of the brain, which is quite inconstant over the course of a single sleep episode. Thus, testing the hypothesis that sleep is required for memory is not straightforward. Moreover, sleep disruption
Was this article helpful?