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Tactile sensation and vision are often both utilized for the exploration of objects that are within reach though it is not known whether or how these two distinct sensory systems might combine such information. Here in mice we find that stimulation of the contralateral whisker array suppresses visually evoked activity in a subarea of primary visual cortex (VISp) whose visual space covers the whisker search space. This is mediated by local fast spiking interneurons that receive a direct cortico-cortical input predominantly from layer 6 of the primary somatosensory barrel cortex (SSp-bfd). These data demonstrate functional convergence within and between two primary sensory cortical areas for multisensory object detection and recognition.

While it is known that Semaphorin 3C acts as a guidance cue for axons during brain development, their potential role during interneuron migration is largely unknown. One striking observation is that Sema3C demarcates the pallial/subpallial border and the intracortical pathway of cortical interneurons in the dorsal telencephalon. Moreover, migrating cortical interneurons express Neuropilin1 and Neuropilin2, described receptors for Semaphorin 3A, 3F and 3C. All these reasons prompt us to examine possible roles for Sema3C on cortical interneuron migration.Using several in vitro approaches, we showed that Nrp1-expressing MGE-derived interneurons from the deep migratory stream migrate towards the increasing Sema3C gradients. In contrast, inhibitory neurons from the superficial migratory stream that express Nrp2, do not respond to this guidance cue. In the present study, we proposed that diffusible Sema3C expressed in the Pallium provides a permissive corridor that attracts the Nrp1- expressing interneurons from the DMS into the dorsal telencephalon.