Fear learning is the process of gathering information about the internal and external environment in situations that evoke fear. Fear learning is the first step toward creating memories for fearful events (fear memories), which are robust and represent a long-lasting record of the acquired information that is capable of modifying behavior when retrieved. Like other forms of learning, fear learning (fear memory acquisition) is followed first by memory consolidation, a period of time when memories are still labile and can be modulated (enhanced or impaired), and then by memory storage (McGaugh, 2000).

Because memories cannot be directly observed and assayed, their existence is, by necessity, inferred from changes in behavior following an experience (Cahill, McGaugh, and Weinberger, 2001). Thus, to study learning and memory, subjects are interrogated by observing their performance in carefully designed behavioral tasks. In the study of fear learning...