Encoding of social exploration by neural ensembles in the insular cortex

The insular cortex participates in diverse complex brain functions including sociality, yet little is known about their cellular bases. Using microendoscopic calcium imaging of the agranular insular cortex (AI) in mice interacting with freely-moving and restrained social targets, we identified two subsets of AI neurons -a larger fraction of Social-ON cells and a smaller fraction of Social-OFF cells- that change their activity in opposite directions during social exploration. Social-ON cells included those that represented social investigation independent of location and consisted of multiple subsets, each of which were preferentially active during exploration under particular behavioral state or with a particular target of physical contact. These results uncover a previously unknown function of AI neurons in encoding conjunctive information on social behavior and suggest that AI may act to monitor the ongoing status of social exploration while an animal interacts with unfamiliar conspecifics.