Differences between the tactile sensitivity on the anterior torso of normal individuals and those having suffered complete transection of the spinal cord

Using the method of limits and a magnitude estimation procedure, the sense of touch was examined at multiple sites on the anterior torso of normal sub jects. Their performance was compared with the performance of individuals h aving experienced a functionally complete spinal cord transection more than 6 months prior to the tests. Near the insentient regions of the spinal cor d-injured patients there was a zone wherein the threshold for light touch w as elevated and variable. Within this same transition zone, estimates of th e magnitude of a brushing stimulus increased as a linear function of distan ce from the border for approximately 12 cm away from insentient skin. Throu ghout the rest of the thorax, spinal cord-injured patients displayed touch thresholds 67% higher than normals and, at the same test sites, spinal cord -injured patients offered estimates of the intensity of the brushing stimul us that: averaged 62% higher than normal subjects. The greater intensity of the sensations experienced by spinal cord-injured patients with even very weak stimuli and the smaller range within which they were able to scale sti mulus intensity, produced a situation wherein the patients made frequent er rors of judgement even on skin regions far from the body parts affected by the lesion. These observations support the hypothesis that spinal cord lesi ons interrupt tonic modulatory mechanisms having global influences on the s ense of touch. This loss produces an elevation of the touch threshold and a reduction of the normal dynamic range of tactile sensory perception for al l skin surfaces on the anterior torso.