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

Abstract

The purpose of the present study was to assess the somatotopy of the cortical sensory representation of the fingers using a natural tactile stimulation of the glabrous skin. Multislice echoplanar imaging techniques were utilized to investigate blood oxygen level dependent (BOLD) signal changes as a measure of cortical activation. Repetitive sensory stimulation of the glabrous skin of digit II–III and digit IV–V resulted in a multifocal signal increase in a restricted area near the central sulcus in the contralateral hemisphere with a considerable overlap between the activated areas of digit II–III and digit IV–V. In addition, in all subjects tactile stimulation resulted in ipsilateral signal increase near the central sulcus, which was 15–22% of the contralateral effect. Stimulation of digit II–III caused significantly ( 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 hemisphere. These findings suggest an ipsilateral activation of the primary somatosensory cortex during a natural tactile stimulation of the digits in humans.