A short review of slow phase synchronization and memory: evidence for control processes in different memory systems?

An integrative theoretical approach about memory related oscillations is presented. The basic assumptions are that memory related oscillations are probably confined to theta and upper alpha and that other frequencies particularly in the gamma range are important for memory primarily because they become coupled to lower frequencies and/or because they play a specific role for a high precision timing of neural events (including phenomena such as LTP or LTD). In contrast to previous studies, where we related theta and upper alpha to a variety of different memory processes, we suggest here that these oscillations are associated with top-down control processes in two large storage systems, working memory (WM) and long-term memory (LTM). These systems may have their own types of top-down processes that control access to and/or manipulation of stored information. The hypothesis, suggested here is that theta and upper alpha reflect these processes which can be best studied when analyzing phase.