RECOVERY OF MOTOR FUNCTION AFTER FOCAL CORTICAL INJURY IN PRIMATES - COMPENSATORY MOVEMENT PATTERNS USED DURING REHABILITATIVE TRAINING

The recovery of skilled hand use after cortical injury was assessed in adult squirrel monkeys. Specific movement patterns used to perform a motor task requiring fine manual skill were analyzed before and after a small ischemic infarct (2.6-3.8 mm(2)) to the electrophysiologically identified hand area of the primary motor cortex (M1). After 1-3 week s of pre-infarct training, each monkey stereotypically used one specif ic movement pattern to retrieve food pellets. After injury to the hand area of M1, the monkeys were required to retrieve the pellets using t heir impaired forelimb. Immediately after the injury, the number of fi nger flexions used by the monkeys to retrieve the pellets increased, i ndicating a deficit in skilled finger use. After approximately I month of rehabilitative training, skilled use of the fingers appeared to re cover, indicated by a reduction in the number of finger flexions per r etrieval. The monkeys again retrieved the pellets using one specific m ovement pattern in most trials. Despite the apparent recovery of skill ed finger use after rehabilitative training, three of five monkeys ret rieved the pellets using stereotypic movement patterns different from those used before the injury. Thus, this study provides evidence that compensatory movement patterns are used in the recovery of motor funct ion following cortical injury, even after relatively small lesions tha t produce mild, transient deficits in motor performance. Examination o f electrophysiological maps of evoked movements suggests that the mode of recovery (re-acquisition of pre-infarct movement strategies vs dev elopment of compensatory movement strategies) may be related to the re lative size of the lesion and its specific location within the M1 hand representation.