Neurophysiological Mechanisms of Sleep-Dependent Memory Consolidation and Its Facilitation by Prenatal Choline Supplementation

Understanding the role of sleep in memory consolidation is an important topic in cognitive neuroscience because it could help us understand the functions of sleep as well as how memory is being consolidated off-line during sleep. Here we review recent studies that focus on the neurophysiological changes that occur during sleep and how these sleep-dependent changes could benefit memory consolidation. In particular, rapid eye movement (REM) sleep provides a preferential time window for memory consolidation across molecular, cellular and synaptic levels while slow-wave sleep (SWS) provides a second time window for memory consolidation at the neural-network level. It is proposed that high-frequency oscillations in the hippocampus (e.g., ripple events) serve as an endogenous trigger for long-term potentiation that plays a critical role in connecting a variety of sleep-dependent neurophysiological processes. We further suggest that repeated alternation of SWS and REM are needed in order to get a good night's sleep. New findings from studies examining how prenatal choline supplementation produces organizational changes in hippocampal function, may provide a useful model for validating the importance of hippocampal ripple events in facilitating memory consolidation during both REM sleep and SWS. These data support our general conclusion that the types of neural plasticity supported by prenatal choline supplementation and sleep are vital for cognitive health, because they produce a host of neurophysiological changes, some of which are also important for memory consolidation.