Somatosensory evoked fields to large-area vibrotactile stimuli

We describe a method to apply large-area vibrotactile stimuli, based on a v ibrating balloon, on the palms of both hands during evoked response studies . Magnetoencephalographic (MEG) signals were recorded with a whole-scalp ne uromagnetometer from six healthy subjects while they held their hands on a balloon which was made to vibrate by delivering tones to it through a louds peaker and a tube. The 200 Hz stimuli, presented once every 1 or 2 s in sep arate sessions, elicited prominent and replicable somatosensory evoked fiel ds (SEFs) and also auditory evoked fields (AEFs) due to the concomitant sou nd. Source modelling allowed reliable differentiation between bilateral act ivation of the primary somatosensory (SI) cortices (peaks at 46-61 ms after the stimulus onset) and of the supratemporal auditory cortices (peaks at 1 04-126 ms). These simple vibrotactile stimuli could be useful for rapid and reliable identification of the somatosensory and auditory cortices, for ex ample in presurgical evaluation of children. (C) 1999 Elsevier Science Irel and Ltd. All rights reserved.