Information interactions between prefrontal cortex and hippocampus during performance of a spatial working memory task

Abstract

Spatial working memory (SWM) refers to a short-term system for temporary manipulation of spatial information and requires the cooperation of multiple brain regions. Despite evidence that hippocampus (HPC) and prefrontal cortex (PFC) are involved in SWM, how PFC and HPC coordinate the neural information during SWM remains puzzling. In this study, local field potentials (LFPs) were recorded simultaneously from rat ventral HPC and medial PFC during SWM tasks. Then cross-frequency coupling algorithm was used as functional connectivity for construction of undirected networks; Grange causality algorithm was used as effective connectivity for construction of directed networks. Finally, information interactions across two brain regions were analyzed based on undirected and directed networks. Experimental results show that LFPs power in PFC and HPC both decreased over learning days and peaked before the reference point during SWM, moreover, LFPs mainly distributed in theta and gamma. From the undirected aspect, undirected PFC subnetwork and HPC subnetwork have the same effect on information transmission for SWM; the PAC between PFC-gamma and HPC-theta in undirected PFC-HPC network is related to SWM formation and contributes to information interactions between PFC and HPC. From the directed aspect, the effect of information transmission in directed HPC subnetwork is greater than PFC subnetwork; the enhancement of coordination between directed PFC and HPC subnetworks contributes to correct execution of SWM tasks; directed HPC→PFC network plays a predominant role in information interaction; with the increasing of learning days, PFC and HPC tend to be the causal sink and causal source of information flow.