Human amygdala responses to fearful eyes

Fearful facial expressions evoke increased neural responses in human amygdala. We used event-related fMRI to investigate whether eye or mouth components of a fearful face are critical in evoking this increased amygdala activity. In addition to prototypical fearful (FF) and neutral (NN) faces, subjects viewed two types of chimerical face: fearful eyes combined with a neutral mouth (FN), and neutral eyes combined with a fearful mouth (NF). FE faces evoked specific responses in left anterior amygdala. FN faces evoked responses in bilateral posterior amygdala and superior colliculus. Responses in right amygdala, superior colliculus, and pulvinar exhibited significant time x condition interactions with respect to faces with fearful eyes (FF, FN) vs neutral eyes (NF, NN). These data indicate that fearful eyes alone are sufficient to evoke increased amygdala activity. In addition, however, left amygdala displayed discriminatory responses to fearful eyes in different configural contexts (i.e., in FF and FN faces). These results suggest, therefore, that human amygdala responds to both feature-specific and configural aspects of fearful facial expressions.