Dissociable roles for the hippocampus and the amygdala in human cued versus context fear conditioning.
Lesion studies in animals have identified a critical role of the hippocampus in context fear conditioning. To extend these findings to human volunteers, we used functional magnetic resonance imaging to investigate neural responses associated with context fear conditioning in humans. Our novel conditioning paradigm consisted of aversive electrical shocks (unconditioned stimulus) that were delivered either cue or context related. Differential evoked responses, related to the conditioned stimulus (CS), were found in the anterior cingulate cortex and the bilateral insular cortices, regions that have been implicated in anticipatory anxiety. In case of context conditioning, a similar pattern was observed during the presentation of the entire context. In line with previous conditioning studies, differential responses in the amygdala showed a time by stimulus interaction, suggesting rapid adaptation of CS-specific responses. More importantly, a similar differential decay of activation was observed during context conditioning in the hippocampus, in agreement with a role of the hippocampus in the acquisition phase of human context fear conditioning.