Pyramidal cells in rat temporoauditory cortex project to both striatum and inferior colliculus.

A retrograde fluorescent double-labeling technique was employed to examine whether the cortico-striate fibers are collaterals of the corticofugal fibers directed to the inferior colliculus in the rat. Following injections of two different fluorescent tracers into the striatum and the inferior colliculus, double-labeled cells were found in layer V pyramidal cells of the temporal cortex. These double-labeled cells were located mostly in the area corresponding to the rat primary auditory cortex, and constituted 6.4% of the pyramidal cells projecting to the inferior colliculus. This study has revealed the existence of a common innervation of the basal ganglia and the auditory system by the pyramidal cell of the auditory cortex.