Role of the Anterior Cingulate Cortex ACC

Numerous studies that have used neuroimaging methods to probe patterns of brain activation during the arousal of emotion have reported that the ACC activates in response to emotion. Recent work (e.g., Bush et al., 2000; Whalen et al., 1998) has started to distinguish between cognitive and affective subdivisions of the ACC, based on the location of activation in response to cognitive versus emotional tasks. For example, dorsal ACC activation is consistently found in response to the classical Stroop task, compared to the more anterior activation to an emotional Stroop task.

Every activation study of PTSD subjects finds involvement of the cingulate. However, in some studies there is increased (Bremner, 1999b, 1999a; Shin et al., 2001; Lanius et al., 2001) and in others decreased (Sachinvala, 2000) activations. The very process of activating emotion in the unfamiliar context of a laboratory environment might activate the anterior cingulate, including exposure to the stressful laboratory environment itself. Carter et al. (1999) have suggested that ACC activation results in a call for further processing by other brain circuits to address the conflict that has been detected. In most people, automatic mechanisms of emotion regulation are likely invoked to dampen strong emotion that may be activated in the laboratory. The PTSD neuroimaging studies suggest that many traumatized subjects are less capable of activating the ACC in response to emotionally arousing stimuli. In our treatment outcome study of PTSD (Levin et al., 1999), we found increased ACC activation after effective treatment.

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