Tactile stimulation of the hand causes bilateral cortical activation: a functional magnetic resonance study in humans

The purpose of the present study was to assess the somatotopy of the cortic al sensory representation of the fingers using a natural tactile stimulatio n of the glabrous skin. Multislice echoplanar imaging techniques were utili zed to investigate blood oxygen level dependent (BOLD) signal changes as a measure of cortical activation. Repetitive sensory stimulation of the glabr ous skin of digit II-III and digit IV-V resulted in a multifocal signal inc rease in a restricted area near the central sulcus in the contralateral hem isphere with a considerable overlap between the activated areas of digit II -III and digit IV-V. In addition, in all subjects tactile stimulation resul ted in ipsilateral signal increase near the central sulcus, which was 15-22 % of the contralateral effect. Stimulation of digit II-III caused significa ntly (P < 0.05) more activated voxels than digit IV-V in the contralateral hemisphere for both hands and for the left hand in the ipsilateral hemisphe re. These findings suggest an ipsilateral activation of the primary somatos ensory cortex during a natural tactile stimulation of the digits in humans. (C) 1999 Elsevier Science ireland Ltd. All rights reserved.