Hippocampal-cortical interaction in decision making

Abstract

When making a decision it is often necessary to consider the available alternatives in order to choose the most appropriate option. This deliberative process, where the pros and cons of each option are considered, relies on memories of past actions and outcomes. The hippocampus and prefrontal cortex are required for memory encoding, memory retrieval and decision making, but it is unclear how these areas support deliberation. Here we examine the potential neural substrates of these processes in the rat. The rat is a powerful model to investigate the network mechanisms underlying deliberation in the mammalian brain given the anatomical and functional conservation of its hippocampus and prefrontal cortex to other mammalian systems. Importantly, it is amenable to large scale neural recording while performing laboratory tasks that exploit its natural decision-making behavior. Focusing on findings in the rat, we discuss how hippocampal-cortical interactions could provide a neural substrate for deliberative decision making.

Keywords: Decision making; Deliberation; Hippocampus; Memory; Prefrontal cortex; Sharp-wave ripples.

Figure 1

The W-track alternation task. To perform the task and continuously receive reward, the rat must visit the arms in an alternating pattern. An inbound trial starts on the outside arm and ends on the center arm. An outbound trial starts in the center arm and ends on the outside arm.

Figure 2

SWRs could provide choice options for deciding which outside arm to visit when making an outbound decision. Potential trajectories are reactivated during SWRs during the decision-making period. When SWRs are disrupted, the choice options may not be available at the time of deliberation, impairing the decision-making process.

Figure 3

A proposed mechanism for deliberation in the W-track alternation task. The hippocampus recalls alternative choice trajectories from memory and provides this serially to the PFC. The PFC compares the option against a rule for the task and a representation of the previous trajectory stored in working memory. If the comparison conforms to the rule, a decision is made to accept that option. In case it does not, this process is reiterated.