The Japanese journal of neuropsychology

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ArticleTitle	Physiological understanding of social cognitive function using macaques
Language	J
AuthorList	Masaki Isoda
Affiliation	Department of Physiology, Kansai Medical University School of Medicine
Publication	Japanese Journal of Neuropsychology: 31 (1), 17-25, 2015
Received
Accepted
Abstract	There has been an increasing attention to the study of social brain functions. This field of research, called social neuroscience, aims to understand the neural basis for our effective and sensible social functioning. In social neuroscience, studies on human subjects are surely indispensable as they can tell us about our social mind most directly. Yet research using other animal species is also informative. Indeed, social neuroscience encompasses a wide range of methodologies and species, each of which has unique advantages. For example, insects are ideal for studying specific group behaviors and their genetic basis. Rodents offer great opportunities for utilizing optogenetic manipulation, thereby demonstrating a cause-and-effect relationship between neural activity and social behavior. Nonhuman primates serve as a more ecologically valid model owing to their social behaviors and environments being most similar to ours. In particular, human and other primates bear a striking resemblance in brain structures and networks that are dedicated to social functioning. The author recently developed a behavioral paradigm in which two monkeys actively monitored each other's actions for their own action selection. Using this model, single-unit activity was recorded from the medial frontal cortex (MFC), a critical node in the social brain networks, in order to clarify the neuronal mechanisms underlying social action monitoring. Results revealed that the MFC contained many neurons that specifically responded to other's actions ('other type'), in addition to those neurons that selectively responded to one's own actions ('self type') or to both other's actions and one's own actions ('mirror type'). The other-type neurons were significantly more frequent in the dorsomedial convexity region (mainly the mesial surface of Brodmann area 8) than in the cingulate sulcus region (mainly area 24c), whereas the self-type neurons were significantly more prevalent in the cingulate sulcus region. Furthermore, a sizable number of MFC neurons exhibited a phasic increase in activity in response to other's action errors. These 'other-error neurons' were distributed in two segregated populations: the dorsomedial convexity region, where other's errors were detected, and cingulate sulcus region, where one's correct behavior following other's errors was encoded. These findings suggest that the MFC plays a pivotal role in differentiating between self-actions and other's actions and in monitoring other's actions for adaptive social decisions. Continuing efforts in this research direction could uncover the neuronal basis whereby primates have become such successful social beings in the animal kingdom.
Keywords	social cognitive function, action, self, other, medial frontal cortex