Assemblies of Perisomatic GABAergic Neurons in the Developing Barrel Cortex

The developmental journey of cortical interneurons encounters several activity-dependent milestones. During the early postnatal period in developing mice, GABAergic neurons are transient preferential recipients of thalamic inputs and undergo activity-dependent migration arrest, wiring, and programmed cell-death. Despite their importance for the emergence of sensory experience and the role of activity in their integration into cortical networks, the collective dynamics of GABAergic neurons during that neonatal period remain unknown. Here, we study coordinated activity in GABAergic cells of the mouse barrel cortex using in vivo calcium imaging. We uncover a transient structure in GABAergic population dynamics that disappears in a sensory-dependent process. Its building blocks are anatomically clustered GABAergic assemblies mostly composed by prospective parvalbumin-expressing cells. These progressively widen their territories until forming a uniform perisomatic GABAergic network. Such transient patterning of GABAergic activity is a functional scaffold that links the cortex to the external world prior to active exploration. [Display omitted] •In the developing barrel cortex, GABAergic neurons form functional assemblies•Prospective parvalbumin interneurons segregate into spatially clustered assemblies•Somatostatin interneurons display broadly correlated firing•GABA assemblies are regulated by sensory inputs Using in vivo imaging in the barrel cortex, Modol et al. show that prospective parvalbumin interneurons form patches of correlated activity that merge during postnatal development. These assemblies are regulated by whisker inputs and altered by sensory deprivation.