Figure 1.

Schematic representation of the possible alteration of sleep-dependent consolidation of declarative memories in older adults. (A) During wakefulness, information is encoded in neocortical and hippocampal networks (black arrow). During SWS, recently acquired information is repeatedly reactivated within hippocampal networks. Reactivations are associated with sharp waves-ripples and are driven by slow oscillations which also synchronize hippocampal memory reactivations with the occurrence of sleep spindles. These reactivations stimulate the transfer of memory traces toward neocortical sites for long term storage (red arrow). This transfer is allowed by low levels of acetylcholine and cortisol during early sleep. (B) With age, the decrease in SWS and slow oscillations combined with anatomical and functional changes in memory-related brain areas and neurochemical changes (acetylcholine, cortisol) are likely to explain that sleep-dependent memory consolidation is impaired in older adults. Adapted from Born et al. (2006).