Repeated presentations of emotional facial expressions were used to assess habituation in the human brain using fMRI. Significant fMRI signal decrement was present in the left dorsolateral prefrontal and premotor cortex, and right amygdala. Within the left prefrontal cortex greater habituation to happy vs fearful stimuli was evident, suggesting devotion of sustained neural resources for processing of threat vs safety signals. In the amygdala, significantly greater habituation was observed on the right compared to the left. In contrast, the left amygdala was significantly more activated than the right to the contrast of fear vs happy. We speculate that the right amygdala is part of a dynamic emotional stimulus detection system, while the left is specialized for sustained stimulus evaluations.
1Psychiatric Neuroimaging Group and Nuclear Magnetic Resonance Center, Massachusetts General Hospital, Harvard Medical School, 13th St., Bldg 149, CNY-9, Charlestown, MA 02129; 2Brigham Behavioral Neurology Group, Department of Neurology, Brigham and Women's Hospital, Boston, MA 02115; 3Departments of Psychology and Psychiatry, University of Wisconsin, 6001 Research Park Blvd., Madison, WI 53719; 4Department of Psychology, Tufts University, Medford, MA 02155, USA
CA,1Corresponding Author and Address
Received 9 October 2000; accepted 23 November 2000