Experience-dependent maturation of somatosensory parvalbumin interneurons during social development in prairie voles.

Social touch facilitates our attachment to others, especially early in life, which may be linked to the maturation of parvalbumin interneurons (PVI) in the somatosensory cortex (S1). These neurons respond to social touch, mature in a sensory experience-dependent manner, and influence both somatosensory processing and social behavior in models of Autism Spectrum Disorder. Prairie voles (Microtus ochrogaster) are an ideal rodent model for studying these concepts since they engage in a species-typical social touch called "huddling." In this study, we first found that over development from juvenile to adult, same-sex siblings showed a reduction in huddling and an increase in time investigating one another or behaving apart. Next, we tracked two markers of plasticity indicative of PVI maturation, extracellular perineuronal nets (PNNs) and nuclear transcription factor Myocyte enhancing factor 2C (Mef2c)-across seven developmental timepoints. We found that, while PV expression in S1 was stable by P21, PNNs, and Mef2c continued to shift afterwards, indicating a protracted development. Finally, to determine environmental factors affecting these processes, environmental enrichment between P21 to P28 advanced PVI maturation, and increased conspecific investigation consistent with adult behavior. This developmental mapping provides a particularly salient model to investigate the molecular underpinnings of cortical and social development.