RESPONSE AND HABITUATION OF THE HUMAN AMYGDALA DURING VISUAL PROCESSING OF FACIAL EXPRESSION

We measured amygdala activity in human volunteers during rapid visual presentations of fearful, happy, and neutral faces using functional ma gnetic resonance imaging (fMRI). The first experiment involved a fixed order of conditions both within and across runs, while the second one used a fully counterbalanced order in addition to a low level baselin e of simple visual stimuli. In both experiments, the amygdala was pref erentially activated in response to fearful versus neutral faces. In t he counterbalanced experiment, the amygdala also responded preferentia lly to happy versus neutral faces, suggesting a possible generalized r esponse to emotionally valenced stimuli. Rapid habituation effects wer e prominent in both experiments. Thus, the human amygdala responds pre ferentially to emotionally valenced faces and rapidly habituates to th em.