• J Douglas Bremner, Eric Vermetten, Christian Schmahl, Viola Vaccarino, Meena Vythilingam, Nadeem Afzal, Christian Grillon, and Dennis S Charney.
• Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA 30306, USA. jdbremn@emory.edu
• Psychol Med. 2005 Jun 1; 35 (6): 791-806.

BackgroundIn the conditioned fear paradigm, repeated pairing of an aversive unconditioned stimulus (US) (e.g. electric shock) with a neutral conditioned stimulus (CS) (e.g. bright light) results in a conditioned fear response to the light alone. Animal studies have shown that the amygdala plays a critical role in acquisition of conditioned fear responses, while the medial prefrontal cortex (including anterior cingulate), through inhibition of amygdala responsiveness, has been hypothesized to play a role in extinction of fear responses. No studies have examined neural correlates of fear conditioning and extinction in patients with post-traumatic stress disorder (PTSD).MethodWomen with early childhood sexual-abuse-related PTSD (n = 8) and women without abuse or PTSD (n = 11) underwent measurement of psychophysiological (skin conductance) responding as well as positron emission tomographic (PET) measurement of cerebral blood flow during habituation, acquisition and extinction conditions. During habituation subjects were repeatedly exposed to a blue square on a screen. During acquisition, exposure to the blue square (CS) was paired with an electric shock to the forearm (US). With extinction, subjects were again exposed to the blue squares without shock. On a different day subjects went through the same procedure with electric shocks administered randomly in the absence of the blue square.ResultsSkin conductance responding to the CS was consistent with the development of conditioned responses with this paradigm. PTSD patients had increased left amygdala activation with fear acquisition, and decreased anterior cingulate function during extinction, relative to controls.ConclusionsThese findings implicate amygdala and anterior cingulate in the acquisition and extinction of fear responses, respectively, in PTSD.

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