Role of the Hippocampus in Decision Making Under Uncertainty

Abstract

The role of the hippocampus in decision making is poorly understood. Because it represents future state values, we hypothesized that it might be required specifically when decisions involve evaluation of uncertain rewards. Here, we investigated how a rare group of nineteen individuals with focal hippocampal damage valued reward against uncertainty compared to evaluation of reward against another key attribute -- physical effort. Hippocampal damage was associated with reduced sensitivity to reward when making uncertain decisions, but crucially not when decisions required evaluating reward against the effort required to obtain it. Further, reduced reward sensitivity against uncertainty correlated with severity of hippocampal damage. A similar effect was also observed in an active information gathering task, where participants acquired information to reduce uncertainty, but had to pay a cost to do so. Together, these findings provide evidence for a context-sensitive role of the hippocampus in value-based decision making, apparent under conditions of uncertainty but not for allocation of effort.