Neural coordination mechanisms for associative memory recall and decision making in the hippocampal-prefrontal network

Associative memory recall involves brain-wide networks comprising sensory and cognitive regions, with key roles for the hippocampus and prefrontal cortex (PFC). To investigate underlying network coordination mechanisms, we monitored activity in olfactory, hippocampal, and prefrontal regions in rats performing an associative memory task in which they recalled odor-place associations to obtain reward. During recall, the beta rhythm (15-30 Hz) was prominent and coherent across the three regions for correct decisions. Furthermore, single neurons and ensembles in both hippocampus and PFC encoded recalled associations. Ensemble dynamics predicted animals’ upcoming decisions and were linked specifically with beta rhythm coordination. Despite this relationship, we found that beta rhythms did not directly phase-modulate all association-coding neurons. Our findings suggest that beta rhythms coordinate ensemble activity within the hippocampal-prefrontal network to support associative memory recall and decision making, and play a permissive rather than instructive role in this process.