PT - JOURNAL ARTICLE AU - F. Scala AU - D. Kobak AU - S. Shan AU - Y. Bernaerts AU - S. Laturnus AU - C.R. Cadwell AU - L. Hartmanis AU - E. Froudarakis AU - J. Castro AU - Z.H. Tan AU - S. Papadopoulos AU - S. Patel AU - R. Sandberg AU - P. Berens AU - X. Jiang AU - A.S. Tolias TI - Neocortical layer 4 in adult mouse differs in major cell types and circuit organization between primary sensory areas AID - 10.1101/507293 DP - 2019 Jan 01 TA - bioRxiv PG - 507293 4099 - http://biorxiv.org/content/early/2019/04/11/507293.short 4100 - http://biorxiv.org/content/early/2019/04/11/507293.full AB - Layer 4 (L4) of mammalian neocortex plays a crucial role in cortical information processing, yet a complete census of its cell types and connectivity remains elusive. Using whole-cell recordings with morphological recovery, we identified one major excitatory and seven inhibitory types of neurons in L4 of adult mouse visual cortex (V1). Nearly all excitatory neurons were pyramidal and all somatostatin-positive (SOM+) non-fast-spiking neurons were Martinotti cells. In contrast, in somatosensory cortex (S1), excitatory neurons were mostly stellate and SOM+ neurons were non-Martinotti. These morphologically distinct SOM+ interneurons corresponded to different transcriptomic cell types and were differentially integrated into the local circuit with only S1 neurons receiving local excitatory input. We propose that cell-type specific circuit motifs, such as the Martinotti/pyramidal and non-Martinotti/stellate pairs, are optionally used across the cortex as building blocks to assemble cortical circuits.