Altered Finger Representations in Sensorimotor Cortex of Musicians with Focal Dystonia: Precentral Cortex

Using functional magnetic resonance imaging (fMRI), finger representations were characterized in the precentral cortex of 11 normal musicians and 14 musicians with focal task-specific dystonia. Finger representations were identified from differential activation during repetitive movements of each finger relative to others. Despite group similarities in topography, abnormalities in representations of affected fingers were identified. For the finger showing chronic flexion (primary dystonic finger or PDF), the cortical “disparity” from its normal location and the distance to the adjacent finger were increased. By contrast, representational characteristics of the finger showing chronic extension (primary compensatory finger or PCF) did not differ significantly from the control group, but did differ from those of the PDF. Regardless of whether either finger's representation differed substantively from normal, the PCF consistently showed greater volume of activation than the PDF or other fingers. These findings reflect dysfunctional interactions between at least two fingers and their cortical representations.