Feedforward and disinhibitory circuits differentially control activity of cortical somatostatin-positive interneurons during behavioral state transitions

Local inhibitory neurons (INs), specifically those involved in disinhibitory circuits like somatostatin (SST) and vasoactive intestinal peptide (VIP)-positive INs, are essential for regulating cortical function during behavior. However, it is unclear the mechanisms by which these INs are recruited during active states and whether their activity is consistent across different sensory cortices. We now reveal that in mice, locomotor activity strongly recruits SST-INs in primary somatosensory (S1) but not visual (V1) cortex. This diverse engagement of SST-INs could not be explained by differences in VIP-IN function but was absent in the presence of visual sensory drive suggesting involvement of feedforward sensory pathways. In agreement, inactivating the somatosensory thalamus, but not decreasing VIP-INs activity, significantly reduces the recruitment of SST-INs in S1 by locomotion. Finally, model simulations suggest differences in SST-INs activity can be explained by varying ratios of VIP-driven inhibition and thalamus-driven cortical excitation. Our work suggests that by integrating feedforward activity with neuromodulation, SST-INs play a central role in adapting sensory processing to behavioral states.