Projections of the ascending somesthetic pathways to the cat superior colliculus visualized by the horseradish peroxidase technique.

Projections of the somesthetic ascending pathways to the superior colliculus (SC) of the cat have been demonstrated by means of the horseradish peroxidase (HRP) tracing technique. Following HRP injection in one SC, marked neurons were found in the contralateral dorsal horn and in the contralateral dorsal column nuclei, mainly the cuneate nucleus. Moreover, in the contralateral trigeminal complex, the sub-nucleus caudalis of the spinal nucleus of the Vth nerve, and the subnucleus oralis plus the main sensory trigeminal nucleus were labeled. Thus, the anterolateral system and the lemniscal system subserving face and forelimb sensation send afferent fibers to the contralateral SC.