Some observations on the central pathway for cutaneous impulses in the cat.

Abstract

1. The responses of single neural units in the cat's thalamus to electrical stimulation of the saphenous nerve, and to mechanical stimulation of the saphenous skin area, have been studied after chronic lesions had been made in various parts of the spinal pathway.2. Thalamic responses to stimulating hairs, mediated by saphenous fibres of the aβγ group, were found after the whole spinal cord had been cut except for the dorsal columns. These were both ipsilateral and contralateral to the peripheral stimulus.3. Thalamic responses to a variety of cutaneous stimuli were found after cutting the dorsal columns, one or both ventrolateral columns having been left intact. These included responses to stimulating hairs, mediated by saphenous fibres of the aβγ group, and responses to stronger stimuli, mediated by the saphenous δ group.4. In experiments in which the spinal cord was cut across except for the ventrolateral column of one or other side, it was found that impulses can activate the ipsilateral thalamus by crossing the midline below the lesion and crossing back at some point above it. Impulses activating the contralateral thalamus can cross the midline at some point above the lesion. These are probably only examples of a variety of possible paths for such impulses.5. These results do not support any simple diagrammatic representation of the afferent cutaneous pathway.