SENSORY MAPPING IN A CONGENITALLY DEAF SUBJECT - MEG AND FMRI STUDIESOF CROSS-MODAL NON-PLASTICITY

It has been proposed that the auditory cortex of deaf subjects may pro vide an example of cross-modal compensatory plasticity. We investigate d whether sensory stimulation could elicit responses from auditory are as of a congenitally deaf subject. Neuromagnetic fields were recorded using a 37-channel biomagnetometer under conditions of: 1) visual stim ulation; 2) somatosensory stimulation; and 3) a simple motor task. Vis ual items were reversing checkerboards and single light spots, present ed in various portions of the visual field; somatosensory stimuli were pneumatic taps delivered to individual digit-segments and the lip; th e motor task was self-paced finger tapping. In addition, functional ma gnetic resonance imaging was used to observe the activation elicited b y full-field checkerboard and sign language stimuli. No responses to p assively presented visual or somatosensory stimuli were observed in th e auditory cortex. In contrast, somatosensory, motor, and visual corti ces revealed evoked magnetic responses comparable to those from contro l subjects, indicating canonical anatomic and physiological organizati on in these areas. These data suggest that primary projection areas do not reveal obvious plastic effects. We suggest that in the human audi tory cortex compensatory plasticity emerges primarily as a property of non-primary areas and is best observed under attentionally demanding conditions. (C) 1997 Wiley-Liss, Inc.