Abstract
Although the neuropeptide oxytocin (OT) is thought to regulate prosocial behavior in mammals, there is considerable debate as to how intranasal OT influences primate behavior. The aim of this study was to determine whether intranasal OT has a general anxiolytic effect on the performance of rhesus monkeys tasked with matching face stimuli, or a more selective effect on their behavior towards aversive facial expressions. To this end, we developed an innovative delayed match-to-sample task where the exact same trials could be used to assess either a monkey’s ability to match facial expressions or facial identities. If OT has a general affect on behavior, then performance in both tasks should be altered by the administration of OT. We tested four male rhesus monkeys (Macaca mulatta) in both the expression and identity task after the intranasal administration of either OT or saline in a within-subjects design. We found that OT inhalation selectively reduced a selection bias against negatively valenced expressions. Based on the same visual input, performance in the identity task was also unaffected by OT. This dissociation provides evidence that intranasal OT affects primate behavior under very particular circumstances, rather than acting as a general anxiolytic, in a highly translatable nonhuman model, the rhesus monkey.
Highlights
The neuropeptide oxytocin (OT) is thought to regulate prosocial behavior in mammals, there is considerable debate as to how intranasal OT influences primate behavior
Its effect on primate social cognition is of general interest because there is an argument that intranasal OT could be used as a possible pharmacotherapy for humans[4,5]
We developed a behavioral task to test identity and expression matching performance in rhesus monkeys without changing the visual input
Summary
The neuropeptide oxytocin (OT) is thought to regulate prosocial behavior in mammals, there is considerable debate as to how intranasal OT influences primate behavior. The studies that have demonstrated that OT administration selectively modulates attention towards faces conveying fearful expressions has been used to argue that OT effects are stimulus-driven and social in nature[32,33] and, the OT signaling pathway promotes specific operations involved in processing social stimuli[7,8,20,34] These studies suffer from the common criticism; that it would be easier to explain these findings in terms of general changes in the internal state of the subjects, such as reduced anxiety, increased motivation, or improved attention[12,13,35,36]. If intranasal OT interacts with a discrete neural circuit responsible for evaluating social salience or emotional valence, the impact of OT administration should be limited to the expression matching task
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