Cross-correlogram between rat hippocampal and prefrontal neuronal activities.

We recorded spontaneous multiple unit activities (MUAs) of the hippocampus and prefrontal cortex in urethane-anesthetized rats and analyzed cross-correlograms between these MUAs to investigate the functional connectivity of neuronal activities. Results of these analyses reveal a significant correlation between MUAs in these regions, in which the firing initiated from either hippocampus (type H-P) or prefrontal cortex (type P-H) according to the significant peak of cross-correlograms. Furthermore, the MUA bursts were counted: a significant correlation was found between the peak height of cross-correlograms and MUA burst counts in type H-P, but not type P-H. These results suggest that the correlation between the hippocampus and prefrontal cortex MUAs that are related to the burst firing might reflect functional connectivity.