SOMATOTOPY OF THE HUMAN ARM USING FMRI

WE describe a technique for mapping out human somatosensory cortex usi ng functional magnetic resonance imaging (fMRI). To produce cortical a ctivation, a pneumatic apparatus presented subjects with a periodic se ries of air puffs in which a sliding window of five locations moved al ong the ventral surface of the left arm in a proximal-to-distal or dis tal-to-proximal direction. This approach, in which the phase-delay of the stimulus can be used to produce somatotopic maps of somatosensory cortex, is based on a method used to generate retinotopic maps of visu al cortex; Functional images were acquired using an echoplanar 1.5T sc anner and a T2-weighted spiral acquisition pulse sequence. The period ic series of air puffs created phase-related activation in two cortica l regions of the contralateral parietal lobe, the posterior bank of th e central sulcus and a more posterior and lateral region.