TRANSIENT DEAFFERENTATION IN HUMANS INDUCES RAPID MODULATION OF PRIMARY SENSORY CORTEX NOT ASSOCIATED WITH SUBCORTICAL CHANGES - A SOMATOSENSORY-EVOKED POTENTIAL STUDY

Human somatosensory cortex (S1) is capable of rapid modification after temporary peripheral deafferentation but it is not known whether subc ortical changes contribute to this modulation. We recorded spinal, bra instem and cortical somatosensory evoked potentials (SEPs) to median n erve stimulation following anaesthetic block of the ipsilateral ulnar nerve. Spinal N13 and subcortical P14, N18 potentials remained unchang ed during the experiment. N20/P20, P27 and N30 cortical potentials, wh ich are generated in different subareas of the S1 (N20/P20, N30 in are a 3b; P27 in area 1), showed different increases in amplitude during t he anaesthesia, which were more marked for N20/P20 and N30 than for P2 7 potentials. These results suggest that changes in S1 neural activity induced by transient deafferentation may be primarily intracortical i n origin and appear to be segregated within the different subareas of the somatosensory cortex. Unmasking of pre-existing thalamo-cortical p rojections from median nerve territories, induced by ipsilateral ulnar nerve deafferentation, may be the mechanism underlying cortical SEP e nhancement. (C) 1997 Elsevier Science Ireland Ltd.