Minimizing threat via heuristic and optimal policies recruits hippocampus and medial prefrontal cortex

Abstract

Jointly minimizing multiple threats over extended time horizons enhances survival. Consequently, many tests of approach–avoidance conflicts incorporate multiple threats for probing corollaries of animal and human anxiety. To facilitate computations necessary for threat minimization, the human brain may concurrently harness multiple decision policies and associated neural controllers, but it is unclear which. We combine a task that mimics foraging under predation with behavioural modelling and functional neuroimaging. Human choices rely on immediate predator probability—a myopic heuristic policy—and on the optimal policy, which integrates all relevant variables. Predator probability relates positively and the associated choice uncertainty relates negatively to activations in the anterior hippocampus, amygdala and dorsolateral prefrontal cortex. The optimal policy is positively associated with dorsomedial prefrontal cortex activity. We thus provide a decision-theoretic outlook on the role of the human hippocampus, amygdala and prefrontal cortex in resolving approach–avoidance conflicts relevant for anxiety and integral for survival.Korn and Bach show that when humans have to trade off the opportunity to forage with the necessity of avoiding threat, they use a mix of optimal decision-making and heuristics. Hippocampal and medial prefrontal activity reflects these computations.