Amygdala Hyperfunction in phobic fear normalizes after exposure

Background: The amygdala is implicated as a key brain structure in fear processing. Studies exploring this process using the paradigm of fear conditioning have implicated the amygdala in fear acquisition and in generating behavioral fear responses. As such, fear extinction could be expected to induce a reduction in amygdala activity. However, exposure in specific phobia has never been shown persistently to reduce amygdala activity. Methods: By means of event-related functional magnetic resonance imaging, responses to phobia-related, general threat, and neutral pictures were measured before and 2 weeks after an intensive exposure session in 20 subjects with specific phobia for spiders and compared with healthy control subjects. Results: Phobic subjects showed increased amygdala activity at baseline. This hyperactivity was significantly reduced 2 weeks after exposure therapy. Furthermore, a significant reduction of hyperactivity in anterior cingulate cortex and insula was found postexposure. Conclusions: To our knowledge, this is the first study demonstrating the effect of exposure on the amygdala in specific phobia. Our findings suggest that exposure therapy can have an effect on subcortical structures.