Reward-associated configural cues elicit theta oscillations of rat retrosplenial neurons phase-locked to LFP theta cycle

Previous behavioral studies implicated the retrosplenial cortex (RSC) in stimulus-stimulus associations, and also in retrieval of remote associative memory based on EEG theta oscillations. To investigate the neural mechanisms underlying these processes, RSC neurons and local field potentials (LFPs) were simultaneously recorded from well-trained rats performing a cue-reward association task. In the task, simultaneous presentation of two multimodal conditioned stimuli (configural CSs) predicted a reward outcome opposite to that associated with individual presentation of each elemental CS. Here, we show neurophysiological evidence that the RSC is involved in stimulus-stimulus association where configural CSs are discriminated from each elementary CS that is a constituent of the configural CSs, and that memory retrieval of rewarding CSs is associated with theta oscillation of RSC neurons during CS presentation, which is phase-locked to LFP theta cycles.