The human amygdala drives reflexive orienting towards facial features

The human amygdala is reliably activated by facial expressions [1], but the precise functional relevance of such activity change is not well understood, because most previous studies did not allow for separating effects of the emotional expression from the distribution of specific facial features and neglected corresponding attentional processes. Findings on rare patients with bilateral amygdala damage indicate that the amygdala might be involved in triggering shifts of overt attention towards specific facial features such as the eyes [2]. Moreover, it was reported that healthy individuals show a preference for attending to the eye region across different emotional expressions [3]. This early attentional bias was linked to amygdala activity [4], and was found to be most pronounced for fearful faces and less pronounced for happy facial expressions [3,5]. These findings indicate that healthy individuals show a tendency to automatically attend to facial features that are diagnostic of the current emotional state of conspecifics [6]. Here, we examined an otherwise healthy, male adult individual (MW) with unilateral right-sided amygdala loss in a novel, eye-tracking-based face perception task in order to clarify the functional role of the amygdala complex in driving attentional orienting. Compared to a sample of matched controls, MW showed an isolated deficit in reflexive gaze shifts towards diagnostic emotional facial features during brief stimulus presentations as compared to normal performance during longer viewing periods. These results suggest that the amygdala is implicated in quickly detecting diagnostic facial features in the visual periphery and driving reflexive saccades towards these locations.