Developmental divergence of sensory stimulus representation in cortical interneurons

Vasocative-intestinal-peptide (VIP + ) and somatostatin (SST + ) interneurons are involved in modulating barrel cortex activity and perception during active whisking. Here we identify a developmental transition point of structural and functional rearrangements onto these interneurons around the start of active sensation at P14. Using in vivo two-photon Ca 2+ imaging, we find that before P14, both interneuron types respond stronger to a multi-whisker stimulus, whereas after P14 their responses diverge, with VIP + cells losing their multi-whisker preference and SST + neurons enhancing theirs. Additionally, we find that Ca 2+ signaling dynamics increase in precision as the cells and network mature. Rabies virus tracings followed by tissue clearing, as well as photostimulation-coupled electrophysiology reveal that SST + cells receive higher cross-barrel inputs compared to VIP + neurons at both time points. In addition, whereas prior to P14 both cell types receive direct input from the sensory thalamus, after P14 VIP + cells show reduced inputs and SST + cells largely shift to motor-related thalamic nuclei. Sensory neuronal circuits adapt during maturation when animals start to actively interact with the external world. The authors reveal structural and functional rearrangements of the input cortical interneurons receive around the time the animals start active sensation.