When first encountering a fear-eliciting stimulus, animals evince innate defensive behaviors, such as freezing. With time, most are able to overcome their automatic fear reactions and regain the capacity for organized, goal-directed action. Rodent research suggests that activity in the central nucleus of the amygdala drives stereotyped, automatic fear responses. Activity in the basal nucleus of the amygdala, conversely, appears to enable flexible and adaptive fear responses. Evidence suggests that the central and basal nuclei compete for dominance during fear, with the "winning" (more active) nucleus determining the behavior expressed.
Do similar patterns of neural activity subsume these behaviors in humans? In Kate Collins' dissertation, she is exploring the neural substrates of both automatic and goal-directed fear responses, and the transition between the two opposing states.