Somatosensory function and cortical unit activity in cats with only dorsal column fibers

Abstract

Cats received lesions that transected the entire thoracic cord except for partial sparing of the dorsal columns. The cats were required to discriminate the side on which they were touched, the size of simultaneously presented discs, or the direction their fur was stroked to obtain food reward. All cats found by anatomical and/or electrophysiological criteria to have any functional continuity in the dorsal columns were able to master the first of these tasks; some responded above chance on the second. Performance was at chance on blank trials, and cats with complete cord transection failed to discriminate. Lesioned cats did not orient or otherwise react to any nonrewarded stimulus below the level of the lesion. A total of 532 units were recorded under light barbiturate anesthesia from the hind paw projection near the tip of the ansate sulcus in these and other similarly prepared cats. Three-fourths of the units found before and acutely after the cord lesions were made were driven by hind limb stimulation. Only 27% of the units recorded 10 or more days afterwards could be driven. Of these driven units, 15 (38%) responded to foreleg stimulation, 13 exclusively so. No such units were found in intact or acutely lesioned cats.