Maternal separation reshapes layer-specific PV-PNN architecture in the mouse barrel cortex

Early-life adversity alters inhibitory circuit maturation across developing brain systems, but most studies have focused on corticolimbic regions involved in emotional and cognitive regulation. Whether early adversity also reshapes inhibitory extracellular matrix architecture in primary sensory cortex remains less clear. Here, we examined the effects of maternal separation on parvalbumin-positive (PV+ ) interneurons and Wisteria floribunda agglutinin-labeled perineuronal nets (PNNs) in the mouse primary somatosensory barrel cortex (S1BF), a highly organized sensory region in which laminar position carries clear developmental and functional significance. Mice underwent daily maternal separation from postnatal day 1 to 14, and PV/PNN anatomical features were analyzed in young adulthood. PV density, PNN density, PV/PNN co-labeled cell density, and PNN-only density were quantified across layers 2/3, 4, and 5/6 of S1BF. Maternal separation did not alter PV+ interneuron density in any cortical layer. Instead, its effects were selective to PNN-related measures in layer 4, where both PNN density and PV/PNN co-labeled cell density were significantly increased. By contrast, PNN structures not associated with PV cells remained unchanged, indicating that the increase in PNN density was predominantly associated with PV-labeled interneurons. These findings show that maternal separation does not produce a generalized loss of PV-PNN architecture in barrel cortex. Rather, early adversity selectively enhances PV-associated PNN organization in the principal thalamorecipient layer of S1BF. This layer-specific pattern suggests that early-life stress may alter the timing or distribution of plasticity and stabilization within primary sensory circuits, with potential consequences for how tactile information is filtered and integrated during cortical maturation.