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

Local versus distant coherence of hippocampal CA1 pyramidal cells was inves tigated in the behaving rat. Temporal cross-correlation of pyramidal cells revealed a significantly stronger relationship among local (<140 <mu>m) pyr amidal neurons compared with distant (>300 mum) neurons during non-theta-as sociated immobility and sleep but not during theta-associated running and w alking. In contrast, cross-correlation between local pyramidal cell-interne uron pairs was significantly stronger than between distant pairs during the ta oscillations but were similar during non-theta-associated behaviors. We suggest that network state-dependent functional clustering of neuronal acti vity emerges because of the differential contribution of the main excitator y inputs, the perforant path, and Schaffer collaterals during theta and non -theta behaviors.