Amygdala activity in response to forward versus backward dynamic facial expressions.

Observations of dynamic facial expressions of emotion activate several brain regions, but the psychological functions of these regions remain unknown. To investigate this issue, we presented dynamic facial expressions of fear and happiness forwards or backwards, thus altering the emotional meaning of the facial expression while maintaining comparable visual properties. Thirteen subjects passively viewed the stimuli while being scanned using fMRI. After image acquisition, the subject's emotions while perceiving the stimuli were investigated using valence and intensity scales. The left amygdala showed higher activity in response to forward compared with backward presentations, for both fearful and happy expressions. Amygdala activity showed a positive relationship with the intensity of the emotion experienced. These results suggest that the amygdala is not involved in the visual but is involved in the emotional processing of dynamic facial expressions, including specifically the elicitation of subjective emotions.