Social Approach Dynamics in Freely-Moving Rat Dyads are Not Impacted by Lesions to the Retrosplenial Cortex

Abstract

Social interaction in rodents can involve a dynamic interplay of approach and withdrawal movements, requiring the brain to rapidly update information about where others are and where they may intend to go. In mammals, the posterior parietal cortex (PPC) and adjacent, reciprocally-connected retrosplenial cortex (RSC) are high-level hubs for spatial information processing. To test the role of these regions in dynamic social approach, we evaluated rats' relative orientation, movement, and position (ROMP) with a freely-moving social-stimulus rat following bilateral lesions to the PPC or anterior RSC. RSC animals showed overall more and faster movements, and greater attention to environment boundaries across multiple behavioral conditions (open field, social, object, static social, and dynamic object) compared with sham-lesioned controls. Increased attention to boundaries was correlated with reduced orienting to a social stimulus; however, this appeared to have little observable impact on the social interactions themselves. Rear-sniffing was lower in RSC rats, but only during the latter half of the 10 minute social exposures, and there were no detected differences in the dynamics of their social approach compared with sham controls. PPC lesion spread was more limited, and social behavior was mostly indistinguishable from sham controls, though this group was more likely to chase the dynamic object. Results suggest that social approach within short (peripersonal) distances is largely accomplished through sensorimotor adjustments that do not require higher-level, spatial-predictive processing taking place in the RSC.