Somatotopic Arrangement of Eight Distinct Skin Areas in the Human Primary Somatosensory Cortex Derived from Functional Magnetic Resonance Imaging

Abstract

AO_SCPLOWBSTRACTC_SCPLOWBlood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) was used to investigate cortical activity associated with peripheral tactile stimuli in a small cohort of healthy humans. MR-safe automated pneumatic stimulators modeled after the Wartenberg pinwheel were used to generate tactile stimuli at regular intervals on eight disparate areas of skin. The phase-encoded BOLD responses of voxels in the cerebral cortex were characterized by the maximal normalized cross-correlation coefficients at time delays between an idealized response and the measure time course. Overall at the group level, the somatotopic organization of the somatosensory cortex (SI) follows the accepted homunculus model, but a noticeable amount of variation was observed between individual study participants. The surface areas of cortical regions in SI activated by tactile stimulation of different body parts were calculated, giving an estimate of cortical magnification factors. Data collected with the participant actively attending the stimuli were compared to data collected before the attention task. No significant attention-related changes were observed in the somatotopic maps or in time courses of voxels well-correlated to stimuli.