Animal studies implicate the amygdala and its connections in the recognition of aversive stimuli. A recent PET study demonstrated that the human amygdala and left orbitofrontal cortex show substantial increases in regional cerebral blood flow (rCBF) during exposure to aversive odourants. To examine if aversive gustatory stimuli similarly activate these regions, nine healthy women tasted an aversive saline solution, pure water and chocolate while rCBF was measured with PET. The aversive saline condition, when contrasted with the water condition, increased activity in the right amygdala, left anterior orbitofrontal cortex, medial thalamus, pregenual and dorsal anterior cingulate, and the right hippocampus. The right amygdala, left orbitofrontal cortex and pregenual cingulate remained significantly activated when saline was compared with chocolate. The present results indicate that the amygdala and orbitofrontal cortex respond to aversive stimuli in both the olfactory and gustatory modalities, and highlight the role of the pregenual cingulate in negative emotional processing.
- Medial thalamus