Differential effects of pain and spatial attention on digit representationin the human primary somatosensory cortex

Reorganization of primary somatosensory cortex subsequent to either reduced or enhanced peripheral input is well established. Recently, plastic change s following arm amputation in humans were shown to correlate with phantom l imb pain. This raised the question whether spatial attention and pain may c ause cortical reorganization in the absence of deafferentation. Using non-i nvasive neuroelectric imaging to study the digit representation in the huma n primary somatosensory cortex, we report a delayed shift of the representa tion of digits 2-3 due to pain on the digits 4-5, which outlasted the pain by several minutes. In contrast, reorganization during spatial attention wa s less pronounced, was seen almost immediately and only during the conditio n. These data indicate that spatial attention and pain without peripheral d eafferentation cause cortical reorganization by different mechanisms. The d ifferential time course of reorganizational effects observed at the cortex may be due to modulation of the lemniscal pathways by nociceptive input fro m the spinal cord dorsal horn. NeuroReport 11:1289-1293 (C) 2000 Lippincott Williams & Wilkins.