Developmental dynamics of marmoset prefrontal cortical SST and PV interneuron networks highlight primate-specific features.

The primate prefrontal cortex (PFC) undergoes protracted postnatal development, crucial for the emergence of cognitive control and executive function. Central to this maturation are inhibitory interneurons (INs), particularly parvalbumin-expressing (PV+) and somatostatin-expressing (SST+) subtypes, which regulate cortical circuit timing and plasticity. While rodent models have provided foundational insights into IN development, the trajectory of postmigratory maturation in primates remains largely uncharted. In this study, we characterized the expression of PV, SST, the chloride transporter KCC2, and the ion channels Kv3.1b and Nav1.1 across six PFC regions (areas 8aD, 8aV, 9, 46, 11 and 47L) in the postnatal marmoset. We report a prolonged maturation of PV+ INs into adolescence, accompanied by progressive upregulation of ion channels that support high-frequency firing. In contrast, SST+ INs show a postnatal decline in density, diverging from rodent developmental patterns. These findings reveal distinct, cell type-specific maturation dynamics in the primate PFC and offer a developmental framework for understanding how inhibitory circuit refinement may underlie vulnerability to neurodevelopmental disorders.