Branched projections of cat sensorimotor cortex: multiple retrograde labeling via commissural corticocortical, decussated corticostriatal and undecussated corticostriatal axons.

The common origins and interrelationships of commissural corticocortical and descending corticostriatal projections were assessed by multiple retrograde labeling of neurons in the precruciate sensorimotor cortex of the cat. The major finding was that some of these neurons had axons that branched at least twice to send collaterals to contralateral cortical sites and bilateral subcortical sites in the caudate nucleus. Regardless of their collateralization, these axons originated mainly from pyramidal neurons of small-medium size located in cortical laminae III-V. A considerable component of the corticocortical and corticostriatal inputs derived from the same neurons. These fibers subserve both intra- and interhemispheric linkages of the sensorimotor cortex with itself and the basal ganglia.