Coronal somatosensory unit responses in cats with dorsal column lesions.

In the preceding study a, we found that the effects of cervical dorsal column (DC) lesions were revealed by neurological and roughness-discrimination tests if the lesions destroyed at least 90 ~o of the total DC cross-sectional area. Since the dorsal columns form the major spinal input to the coronal somatosensory cortex12,13,18, unit recordings from this area should reflect the effects of DC lesions. In particular, we wished to determine the changes in cortical neuron response accompanying DC lesions which produce behavioral deficits. Accordingly, we recorded unit activity from the forepaw focus of coronal cortex 12, using most of the animals that had been behaviorally tested in the previous experiment. We found that only the DC lesions producing behavioral deficits (over 90 ~ of the dorsal columns destroyed) significantly reduced the proportion of both responding and short latency (10 msec or less) units, reduced the proportion of units with receptive fields having sharp, well-defined borders, and increased the average area of receptive fields. Such lesions were estimated to involve approximately 90~o of the DC fibers from the forepaw contralateral to the recording electrode; ineffective lesions spared a greater proportion of these fibers.