Compensation Aids Skilled Reaching in Aging and in Recovery from Forelimb Motor Cortex Stroke in the Rat

Compensatory movements mediate success in skilled reaching for food after stroke to the forelimb region of motor cortex (MtCx) in the rat. The present study asks whether the neural plasticity that enables compensation after motor stroke is preserved in aging. In order to avoid potential confounding effects of age-related negative-learning, rats were trained in a single pellet reaching task during young-adulthood. Subgroups were retested before and after contralateral forelimb MtCx stroke via pial stripping given at 3, 18, or 23 months of age. Over a two-month post-stroke rehabilitation period, end point measures were made of learned nonuse, recovery, retention, and performance ratings were made of reaching movement elements. Prior to stroke, young and aged rats maintained equivalent end point performance but older rats displayed compensatory changes in limb use as measured with ratings of the elements of forelimb movement. Following stroke, the aged groups of rats were more impaired on end point, movement, and anatomical measures. Nevertheless, the aged rats displayed substantial recovery via the use of compensatory movements. Thus, this study demonstrates that the neural plasticity that mediates compensatory movements after stroke in young adults is preserved prior to and following stroke in aging.