Interstitial axon collaterals of callosal neurons form association projections from the primary somatosensory to motor cortex in mice
Document Type
Article
Publication Date
11-1-2021
Abstract
Association projections from cortical pyramidal neurons connect disparate intrahemispheric cortical areas, which are implicated in higher cortical functions. The underlying developmental processes of these association projections, especially the initial phase before reaching the target areas, remain unknown. To visualize developing axons of individual neurons with association projections in the mouse neocortex, we devised a sparse labeling method that combined in utero electroporation and confocal imaging of flattened and optically cleared cortices. Using the promoter of an established callosal neuron marker gene that was expressed in over 80% of L2/3 neurons in the primary somatosensory cortex (S1) that project to the primary motor cortex (M1), we found that an association projection of a single neuron was the longest among the interstitial collaterals that branched out in L5 from the earlier-extended callosal projection. Collaterals to M1 elongated primarily within the cortical gray matter with little branching before reaching the target. Our results suggest that dual-projection neurons in S1 make a significant fraction of the association projections to M1, supporting the directed guidance mechanism in long-range corticocortical circuit formation over random projections followed by specific pruning.
Keywords
Barrel cortex, Corticocortical projection, Inter-areal connection, Optical tissue clearing, Sensorimotor integration
Divisions
InstituteofBiologicalSciences
Funders
Takeda Science Foundation (TSF),Naito Memorial Foundation,Japanese Society for Promoting Science (JPSP KAKENHI) [JP23800027]
Publication Title
Cerebral Cortex
Volume
31
Issue
11
Publisher
Oxford University Press
Publisher Location
JOURNALS DEPT, 2001 EVANS RD, CARY, NC 27513 USA