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Abstract:
Abstract: We examined the incidence and character of phantom
sensations after SCI, and the association between phantom percepts
and cortical reorganization using fMRI. Subjects with SCI between
T3 and T12 received a detailed questionnaire (N = 14), and a
selected subset (N = 5) were scanned during punctate tactile and
motor stimulation conditions (1.5T). We recorded 24 distinct
phantom sensations (10/14 subjects). Reference zones (RZ) were
present in 7 phantom sensations, and none of these followed a
pattern predicted by somatotopic reorganization of the postcentral
gyrus (PoCG). Activation patterns observed with fMRI supported this
finding: Subject 4 had RZs on his right and left forearms that
projected sensations to the level of injury on the ipsilateral
chest (T7). Correspondingly, stimulation of these RZs activated
foci in the PoCG chest and forearm representations with
non-activated regions of cortex interposed, while stimulation of
adjacent, non-RZ regions activated only the forearm
representations. In 7 runs during non-RZ forearm stimulation in SCI
subjects, chest-area activity was observed in only 1 run:
Similarly, in previous studies from our laboratory using this
stimulus in normal subjects, 1/10 (1.5T) and 0/5 (3T) runs
activated the chest region. Our findings are consistent with
cuneate nucleus reorganization, where the chest and forearm
representations are predicted to be adjacent in humans (Florence et
al., 1988).
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