Differences between the tactile sensitivity on the anterior torso of normal individuals and those having suffered complete transection of the spinal cord
F. Saddiki-traki et al., Differences between the tactile sensitivity on the anterior torso of normal individuals and those having suffered complete transection of the spinal cord, SOMAT MOT R, 16(4), 1999, pp. 391-401
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.