BEHAVIORAL SCIENCES WORKSHOP
Abstract: Human and non-human primates tend to live in large social groups. These groups typically have dominant and subordinate members. The status of primates within an hierarchical structure - their hierarchical status - profoundly impacts their ability to thrive by influencing fluid and food access, mating priority, and defensive behavior. Indeed, appropriate social interactions in a variety of settings, such as interviewing for a job or attending a family reunion, depend upon an assessment of the hierarchical status – or value - of other people. Candidate brain areas for providing a neural representation of hierarchical status include three densely interconnected areas: the amygdala and two parts of the pre-frontal cortex (PFC), the orbitofrontal and anterior cingulate cortices (OFC and ACC). All three brain structures contain neurons that represent the value of non-social stimuli, but it is unknown whether the same neuronal ensembles process information about the value of social stimuli, such as hierarchical information. Here we provide evidence that the primate amygdala encodes the hierarchical status of individuals in the same neuronal ensembles that also encode the rewards associated with non-social stimuli. By contrast, despite representing the value of non-social stimuli, orbitofrontal and anterior cingulate cortices lack strong representations of hierarchical status. These results challenge the traditional view that the processing of social stimuli occurs in dedicated neural systems, a proposal referred to as the “social brain” hypothesis. Our results instead indicate that neuronal ensembles in the amygdala that learn the value of non-social stimuli may also be engaged to learn the hierarchical status, or value, of individuals, a process critical for social behavior.
C. Daniel Salzman specializes in the neural basis of cognitive and emotional behavior.