An fMRI investigation of hand representation in paraplegic humans

Cortical reorganization can occur after deaf-ferentation due to loss of a limb, but the nature of the cortical reorganization after spinal cord injury (SCI) is still in debate.

Using a 1.5T MRI, we scanned paraplegic and noninjured participants during hand movement and palm stimulation, to determine whether longterm paraplegics would show different patterns of cortical activity from the noninjured participants.

The SCI group showed stronger activation in areas posterior, rather than superior, to the areas activated by non-SCIs. Conversely, the non-SCIs showed stronger activation in more anterior areas. The signal at each individual's maximally significant voxel had a greater modulation for the SCI group than for the non-SCIs, in response to movement.

In this study of sensory and motor representations within the same subjects, the authors show for the first time the increase in the BOLD fMRI signal modulation in SCI. The authors do not find evidence of expansion of the hand representation into nearby cortical areas, and they corroborate previous EEG studies indicating a posterior shift for hand motor representation after SCI, while showing that the sensory representation does not undergo a posterior shift of similar magnitude. The difference between the reorganization found here and the reorganization typically found following amputations suggests a rationale for the differences in neuropathic pain symptoms following a spinal cord injury or amputation.