Transient callosal projections of L4 neurons are eliminated for the acquisition of local connectivity

Abstract

It is traditionally believed that callosal and non-callosal fates are determined early after a neuron’s birth, and that cortical layer (L) 4 excitatory neurons of the primary somatosensory (S1) barrel cortex project only ipsilaterally. However, here authors demonstrate, using a novel axonal retrotracing strategy, that L4 neurons develop transient interhemispheric axons that are refined in an area- and layer-specific manner during postnatal development.