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.