To investigate whether and how the hippocampus contributes to value-based decision making, we compared value-related neural activity in CA3 vs. CA1 regions of the hippocampus in rats performing a dynamic foraging task in a modified T-maze. Neural signals necessary to update the value of chosen action, namely chosen value and choice outcome signals, converged in both CA3 and CA1 when a trial outcome was revealed at the reward sites. However, choice outcome signals were stronger in CA1 than CA3. Also, whereas chosen value signals subsided rapidly in CA3, they persisted in CA1 while the animal stayed at the reward sites. Moreover, reward prediction error and updated chosen value signals were stronger in CA1 than CA3. Together with our previous finding that CA1 conveys stronger value signals than the subiculum, these results raise the possibility that CA1 may play a particularly important role among hippocampal subregions in evaluating values of experienced events. It remains to be determined whether and how these value-related signals contribute to hippocampal neural processes underlying evaluation of experienced events.
