On the possible functional role of afferent pathways in skin sensation

Single unit activity was recorded from postcentral gyrus (SI) neurons in chronically prepared macaque monkeys. Lesions of the dorsal funiculi (especially cuneatus), or the lateral lemniscus (at the mesencephalic level) failed to significantly modify the properties of the cortical responses to peripheral stimuli, while combined lesions of both pathways were quite effective in this regard. An additional finding was that combined “deafferentation” of a hemisphere caused a significant proportion of cells in it to respond to ipsilateral stimuli. We conclude that both the medial lemniscal and spinothalamic pathways carry information—in parallel—to the cortex, that this information is conveyed in two modes by each pathway (“elemental” and “convergent”) and that ipsilateral inputs relayed to SI are revealed by partial deafferentation of its contralateral inputs.