In our working model (Fig. 3), we propose that theta activity represents the successful reinstatement of the memory representation after cueing. Thus, increase in theta activity will occur when (a) the association between the memory cue and the to-bereactivated memory representation is strong enough and (b) when the cue is presented at an appropriate time and in an appropriate way (i.e. intensity, etc.) to successfully reinstate the associated
memory representation. We assume that increases in theta activity are in principle independent of the macro state of the brain (i.e. sleep vs. wakefulness, NREM vs. REM sleep, etc.). Thus, increases in theta activity after successful memory reactivation should occur during NREM sleep, waking and maybe even REM sleep. As described above, increases in theta activity have been consistently observed during successful retrieval and recognition during wakefulness as well as during successful reactivation during NREM sleep (Schreiner & Rasch, 2015a) and is assumed to coordinate replay activity during working memory maintenance