Behavior-dependent states of the hippocampal network affect functional clustering of neurons

Local versus distant coherence of hippocampal CA1 pyramidal cells was investigated in the behaving rat. Temporal cross-correlation of pyramidal cells revealed a significantly stronger relationship among local (<140 microm) pyramidal neurons compared with distant (>300 microm) neurons during non-theta-associated immobility and sleep but not during theta-associated running and walking. In contrast, cross-correlation between local pyramidal cell-interneuron pairs was significantly stronger than between distant pairs during theta oscillations but were similar during non-theta-associated behaviors. We suggest that network state-dependent functional clustering of neuronal activity emerges because of the differential contribution of the main excitatory inputs, the perforant path, and Schaffer collaterals during theta and non-theta behaviors.