Oxytocin modulates fMRI responses to facial expression in macaques

Ning Liu, Fadila Hadj-Bouziane, Katherine B. Jones, Janita N. Turchi, Bruno B. Averbeck, Leslie G. Ungerleider
2015 Proceedings of the National Academy of Sciences of the United States of America  
Increasing evidence has shown that oxytocin (OT), a mammalian hormone, modifies the way social stimuli are perceived and the way they affect behavior. Thus, OT may serve as a treatment for psychiatric disorders, many of which are characterized by dysfunctional social behavior. To explore the neural mechanisms mediating the effects of OT in macaque monkeys, we investigated whether OT would modulate functional magnetic resonance imaging (fMRI) responses in face-responsive regions (faces vs. blank
more » ... screen) evoked by the perception of various facial expressions (neutral, fearful, aggressive, and appeasing). In the placebo condition, we found significantly increased activation for emotional (mainly fearful and appeasing) faces compared with neutral faces across the faceresponsive regions. OT selectively, and differentially, altered fMRI responses to emotional expressions, significantly reducing responses to both fearful and aggressive faces in face-responsive regions while leaving responses to appeasing as well as neutral faces unchanged. We also found that OT administration selectively reduced functional coupling between the amygdala and areas in the occipital and inferior temporal cortex during the viewing of fearful and aggressive faces, but not during the viewing of neutral or appeasing faces. Taken together, our results indicate homologies between monkeys and humans in the neural circuits mediating the effects of OT. Thus, the monkey may be an ideal animal model to explore the development of OT-based pharmacological strategies for treating patients with dysfunctional social behavior. oxytocin | neuroimaging | nonhuman primate | social stimuli I n the last decade, oxytocin (OT), a mammalian hormone, has become one of the most studied peptides of the neuroendocrine system. In humans, accumulating evidence has demonstrated that OT affects a wide range of social behavior and cognition, including perception, recognition and memory of social stimuli (1-5), socially reinforced learning (6) , and more complex sociocognitive behaviors [e.g., trust (7, 8), cooperation (9), generosity (10), and empathy (6, but see ref. 11)]. Therefore, it has been proposed that OT may serve as a treatment for various disorders with dysfunctional social behavior, such as autism spectrum disorders, antisocial personality disorder, and schizophrenia (for review, see ref. 12). A recent study found that OT enhances brain activity for socially meaningful stimuli but attenuates activity for nonsocially meaningful stimuli in children with autism spectrum disorders (13). Although these studies suggest very promising prospects of OT for clinical use, the neural mechanisms underlying OT's modulatory effects remain elusive. To understand these mechanisms, it is important to investigate the effect of OT on brain activity, especially in regions involved in social behavior and cognition. Functional magnetic resonance imaging (fMRI) has been the major approach to investigating altered brain activation patterns in response to OT in humans. OT may affect the perception of social stimuli, and thus mediate subsequent social information processing (e.g., learning and memory, etc.) (14). Many fMRI studies have examined the effects of OT on brain activity during the perception of social stimuli to probe the brain regions that underlie OT's modulatory effects. Emotional stimuli, which are crucial for social communication and interaction, have been mainly used. For example, Kirsch et al. showed that OT reduces activation in response to fear-inducing stimuli in the amygdala, a key brain region involved in emotional regulation (15). Subsequently, a series of studies examined the effects of OT on responses to facial expressions (3, 16), to conditioned facial expressions (17), and to threatening scenes (18). These studies showed that activity evoked by emotional stimuli, especially negative stimuli (e.g., fearful faces, but see refs. 3 and 16 for happy faces), is systematically altered within an interconnected network of brain regions after OT administration. Because of the limitation of experimental approaches with human subjects, animal models are essential not only for investigating the neural mechanisms underlying the effects of OT but also for exploring OT-based therapeutic strategies for individuals with dysfunctional social behavior. Given the similarities between monkeys and humans in the neural circuitry underlying social cognition (19), the rhesus macaque could be an ideal animal model to examine the effects of OT. To date, only a few studies have investigated the behavioral consequences of OT administration in monkeys (20) (21) (22) (23) (24) (25) . Consistent with the human literature, these studies have found that intranasal administration of OT affects social behavior and cognition in monkeys, Significance Oxytocin (OT), a mammalian hormone, may serve as a treatment for psychiatric disorders because of its beneficial effect on social behavior. Here, we found that in monkeys, OT selectively altered brain activity within multiple neural systems (visual perception, emotion, attention, and higher cognition function) and functional coupling between the amygdala and areas in the ventral visual pathway evoked by negative emotional expressions. Our findings provide key information for understanding the behavioral consequences of OT administration and indicate homologies between monkeys and humans in the neural circuits mediating the effects of OT. Thus, the monkey may be an ideal animal model to explore the development of OT-based pharmacologic strategies for treating patients with dysfunctional social behavior.
doi:10.1073/pnas.1508097112 pmid:26015576 pmcid:PMC4475931 fatcat:nhnufi7pibbn7eq5v4n5zxc3jy