Layer 1 NDNF+ interneurons control bilateral sensory processing in an age- and layer-dependent manner

Bilateral sensory information is indispensable for navigating the world. In most mammals, signals sensed by either side of the midline will ultimately reach the cortex where they will be integrated for perception and appropriate action selection. Even though information transferred across the hemispheres is routed through the corpus callosum, how and which microcircuits are key in integrating it across development is not well understood. Here we identify an essential role for layer 1 NDNF+ inhibitory cells of mice in controlling the bilaterally evoked whisker stimulation in layer (L)4 before, and L2/3 and L5 after postnatal day (P)14. Specifically, removal of the NR1 subunit of NMDA receptors from NDNF+ cells diminishes their bilateral integration of whisker information and leads to an increase in the late spiking activity at the somatosensory barrel cortex. Our results identify a feed-forward regulatory pathway for bilateral cortical processing regulated via layer 1 NDNF+ interneurons in a distinct manner before versus after the start of bilateral active whisking in mice at P14.