Rat hippocampal CA1 region represents learning-related action and reward events with shorter latency than the lateral entorhinal cortex

Electrophysiological recordings in rats reveal that the hippocampal CA1 region represents learning-related action and reward events faster than the lateral entorhinal cortex. The hippocampus and entorhinal cortex are deeply involved in learning and memory. However, little is known how ongoing events are processed in the hippocampal-entorhinal circuit. By recording from head-fixed rats during action-reward learning, here we show that the action and reward events are represented differently in the hippocampal CA1 region and lateral entorhinal cortex (LEC). Although diverse task-related activities developed after learning in both CA1 and LEC, phasic activities related to action and reward events differed in the timing of behavioral event representation. CA1 represented action and reward events almost instantaneously, whereas the superficial and deep layers of the LEC showed a delayed representation of the same events. Interestingly, we also found that ramping activity towards spontaneous action was correlated with waiting time in both regions and exceeded that in the motor cortex. Such functional activities observed in the entorhinal-hippocampal circuits may play a crucial role for animals in utilizing ongoing information to dynamically optimize their behaviors.

Automated summary

Electrophysiological recordings in rats show that the hippocampal CA1 region represents learning-related action and reward events faster than the lateral entorhinal cortex. The timing of representation of action and reward events differs between the two regions. Additionally, ramping activity towards spontaneous action is correlated with waiting time in both regions, suggesting the involvement of the entorhinal-hippocampal circuits in optimizing behaviors.