INITIAL CORTICAL REACTIONS TO INJURY OF THE MEDIAN AND RADIAL NERVES TO THE HANDS OF ADULT PRIMATES

The area 3b hand cortex of adult squirrel monkeys was mapped during th e first minutes to hours after transecting the radial and median nerve s to the hand. The objective was to evaluate initial cortical reaction s to this injury and to determine whether patterns and extents of cort ical change are similar in different individuals. There are 5 main fin dings. First, cortical aggregates related to ulnar nerve inputs from t he hand rapidly expanded to occupy an additional 21% of the cortical h and map. Second, face and forearm inputs, which normally activate area s adjacent to hand cortex, rapidly expanded into areas of 4% and 1% of the hand cortex respectively. Third, cortical changes involved shifts in receptive field locations that were initiated within minutes after injury. Fourth, the spatial patterns and extents of cortical change w ere similar in different individuals. Finally, the pattern of cortical change produced after this injury differed from the pattern seen afte r injury of the median and ulnar nerves. These rapid expansions are a beginning point from which further changes must progress; however, in contrast to changes accompanying chronic hand injuries, these initial cortical reactions do not appear dictated by use of uniniured inputs. (C) 1996 Wiley-Liss, Inc.