Progressive engagement of SST+ interneurons via Elfn1 regulates the barrel-septa response identity in the somatosensory cortex of mice

Abstract

AbstractThe vibrissae system of rodents, akin to human hands and fingers, provides somatosensory information coming from individual whiskers for object exploration and recognition. Just as separated digits enhance somatosensation in humans, the ability of mice to sense objects through multiple whiskers in segregated streams is crucial. The segregation begins at the level of the whiskers and is maintained through their precise somatotopic organization in the Brainstem→ Thalamus→ Cortex axis, culminating in the so-called barrels and the in-between “spaces” called septa. Here, by performingin-vivosilicon probe recordings simultaneously in the barrel and septa domains in mice upon repeated 10Hz single and multi-whisker stimulation, we identify and characterize a temporal divergence in the spiking activity between these domains. Further, through genetic fate-mapping, we reveal that cortical SST+ and VIP+ inhibitory neurons show a layer-dependent differential preference in septa versus barrel domains. Utilizing a genetic manipulation that affects the temporal facilitation dynamics onto only these two inhibitory cell classes, we largely abolish the temporal response divergence between the two cortical domains. Finally, usingin-vivoviral tracing, whole-brain clearing and imaging, we show a differential barrel and septa projection pattern to cortical regions S2 and M1. We hence reveal that local temporally engaging cortical inhibition provided by SST+ neurons contribute to the functional segregation of barrel and septa domains and potentially their downstream targets.