The role of the medial lemniscal and spinocervicothalamic pathways on tactile reactions in cats.

The role of dorsal column (DC)-medial lemniscus and spinocervicothalamic systems on tactile reactions, placing and tactile localization (turning to localize a point touched on the body) was studied in cats with spinal and bulbar lesions. The cats with vision occluded were trained preoperately on horizontal bars for tactile localization. The bulbar lesions of cervicothalamic tract (CTT), which anatomically overlaps with gracile nuclear efferent projection, resulted in permanent loss of tactile placing and localization in contralateral hindlimb. Section of dorsal half of lateral funiculus at C3, which interrupts afferents to lateral cervical nucleus but also involves descending motor pathways, gave loss of tactile placing without impairment of tactile localization. However, combined lesions of both systems abolished tactile placing and localization permanently. Results suggest that tactile placing and localization persists after CTT lesion alone; temporarily loss after DC section but permanently abolished after destruction of both systems. It. is also noted that cats after lesions of both systems without involving motor pathways could walk on bars without vision. The deficits following combined lesions are suggested to be primarily sensory in nature.