EMOTION, OLFACTION, AND THE HUMAN AMYGDALA - AMYGDALA ACTIVATION DURING AVERSIVE OLFACTORY STIMULATION

Electrophysiologic and lesion studies of animals increasingly implicat e the amygdala in aspects of emotional processing. Yet, the functions of the human amygdala remain poorly understood. To examine the contrib utions of the amygdala and other limbic and paralimbic regions to emot ional processing, we exposed healthy subjects to aversive olfactory st imuli while measuring regional cerebral blood flow (rCBF) with positro n emission tomography. Exposure to a highly aversive odorant produced strong rCBF increases in both amygdalae and in the left orbitofrontal cortex. Exposure to less aversive odorants produced rCBF increases in the orbitofrontal cortex but not in the amygdala. Change of rCBF withi n the left amygdala and the left OFC was highly intercorrelated, indic ating a strong functional interaction between these brain regions. Fur thermore, the activity within the left amygdala was associated signifi cantly with subjective ratings of perceived aversiveness. These findin gs provide evidence that the human amygdala participates in the hedoni c or emotional processing of olfactory stimuli.