The amygdala and development of the social brain

The amygdala comprises part of an extended network of neural circuits that are critically involved in the processing of socially salient stimuli. Such stimuli may be explicitly social, such as facial expressions, or they may be only tangentially social, such as abstract shapes moving with apparent intention relative to one another. The coordinated interplay between neural activity in the amygdala and other brain regions, especially the medial prefrontal cortex, the occipitofrontal cortex, the fusiform gyrus, and the superior temporal sulcus, allows us to develop social responses and to engage in social behaviors appropriate to our species. The harmonious functioning of this integrated social cognitive network may be disrupted by congenital or acquired lesions, by genetic anomalies, and by exceptional early experiences. Each form of disruption is associated with a slightly different outcome, dependent on the timing of the experience, the location of the lesion, or the nature of the genetic anomaly. Studies in both humans and primates concur; the dysregulation of basic emotions, especially the processing of fear and anger, is an almost invariable consequence of such disruption. These, in turn, have direct or indirect consequences for social behavior.