Orienting reactions to light tactile stimuli after single and repeated partial spinal cord lesions in the cat

Cats which had been trained to remain quietly standing were tested for orienting responses to light tactile stimulation (ORLT) of either hindlimb before and after different single, and subsequently increased, low thoracic spinal cord lesions. The individual lesions covered one dorsal column, and/or the dorsal part of one lateral funiculus, and/or the ventral part of the lateral funiculus, and/or one entire lateral funiculus and/or one or both ventral quadrants. Normal ORLTs were produced from the first post-operative test after each of the above lesions alone, or in combination with one of the others. Acute and chronic disappearances and/or disturbances of the ORLTs were observed for one hindlimb only after lesions involving at least the dorsal column and the dorsal part of the lateral funiculus of the ipsilateral side, as well as the contralateral lateral funiculus. The amount of disturbance varied with the technique in such a way that the number of operations which had been carried out to cause the actual lesion was inversely correlated to the degree of post-operative defect. The findings showed that the severity of the tactile symptoms after spinal cord lesions may depend on the speed with which they had developed. The types of lesions causing defects indicated that cats, under normal conditions, may utilize one of the three ascending spinal pathways for orienting reactions to light tactile stimulation. In relation to the peripheral receptive fields, these pathways are the ipsilateral dorsal column and spinocervical pathways, and a pathway of the contralateral lateral funiculus. The possible spinothalamic character of the crossed pathway has yet to be established.