A role for the superior colliculus in the modulation of threat responsiveness in primates: toward the ontogenesis of the social brain

Defense and social mechanisms in primates seem to share, at least in infancy, common neural sub-strata. Among these, recent research has implicated the primate superior colliculus (SC) on tasks involving visual detection and recognition of threatening stimuli, such as snakes and faces with emotional expressions. There is also evidence that both kinds of stimuli share specific characteristics and command special attention in the primate visual system. The present review focuses on the role of the SC in these seemingly overlapping functions. We present social behavioral data from capuchin monkeys in which the bilateral lesion of the SC induced a transitory impairment of social behaviors. The findings presented here are compared with previous studies, our own and others, on social behaviors and threat detection. We argue that, although the SC may participate in both systems, its role is more prominent in the detection/recognition of threat. Social interactions more likely depend on larger and more complex neural systems, where the SC may play a key role in early infancy. The implications of these recent findings are discussed under an evolutionary perspective.