The inability to suppress inappropriate fear responses is the hallmark of anxiety disorders, such as post-traumatic stress (PTSD), panic, and phobic disorders (Rauch et al., 2006; Rosen and Schulkin, 1998). A common, empirically-validated approach to treat these disorders is Cognitive Behavioral Therapy (CBT) (Norton and Price, 2007), one component of which involves repeated exposure to fear-linked cues to produce “extinction” (clinically referred to as exposure therapy leading to desensitization) of fear and avoidance responses to these cues (Hofmann, 2008). After repeated presentations, the patient learns that the previously feared stimulus does not actually predict a negative outcome and anxiety is reduced. This exposure-based learning can be modeled in the laboratory, in both animals and humans, using Pavlovian fear conditioning models in which fear is first linked to a previously innocuous cue (conditioned stimulus; CS) and then decreased by presenting the CS alone (producing extinction).
