Fig. 7.

Schematic of present findings. The left column depicts infraslow and δ LFP lags between the hippocampus and most of cortex, highlighting the DMN, VIS, and AUD. The temporal delays found between the hippocampus and these cortical systems agrees with the directions predicted by the two-stage reciprocal dialogue model (Fig. 1), if infraslow activity is taken to represent the low-frequency component of the model and δ LFPs represent the higher frequency component. However, the right column demonstrates that precisely the opposite lags are found when considering the putamen and the SMN with respect to the hippocampus. Dotted red lines designate temporal lags implied, but not directly observed, by mirrored dissociation between systems. We hypothesize that the temporal lags depicted in the left and right columns may represent the parallel functions of the declarative and procedural memory systems, respectively. As depicted in the right column, our results suggest that the hippocampus is in an ongoing dialogue with the procedural memory system.