Basic fibroblast growth factor stimulates functional recovery after neonatal lesions of motor cortex in rats.

Rats were given bilateral lesions of the motor cortex on the tenth day of life, and then received a daily subcutaneously injection of either basic fibroblast growth factor (FGF-2) or vehicle for 7 consecutive days. In adulthood, they were trained and assessed on a skilled forelimb reaching task. Although all lesion groups were impaired at skilled reaching, the postnatal day 10-lesioned group that received FGF-2 was less impaired than the lesion group that received the vehicle. Furthermore, the lesioned rats that received FGF-2 showed a filling of the lesion cavity with tissue, whereas the lesioned vehicle-treated rats still had a prominent lesion cavity. The functionality of the tissue filling the cavity, tissue surrounding it, and tissue from the motor cortex (in control rats) was assessed using intracortical microstimulation, and showed that stimulation of some sites from the filled cavity could evoke movement. The rats were perfused and processed for Golgi-Cox staining. Medium spiny neurons from the striatum were drawn and analyzed, and the results suggest that postnatal day 10 lesions of the motor cortex induced an increase in the length and complexity of these cells compared with those of non-lesioned rats. Our results suggest that FGF-2 may play an important role in recovery from early brain damage.

Sensitivity of cortical movement representations to motor experience: evidence that skill learning but not strength training induces cortical reorganization.

The topography of forelimb movement representations within the rat motor cortex was examined following forelimb strength training. Adult male rats were allocated to either a Power Reaching, Control Reaching or Non-Reaching Condition. Power Reaching rats were trained to grasp and break progressively larger bundles of dried pasta strands with their preferred forelimb. Control Reaching animals were trained to break a single pasta strand and Non-Reaching animals were not trained. Power Reaching animals exhibited a progressive increase in the maximal size of the pasta bundle that could be retrieved during a 30-day training period. Kinematic analyses showed that this improvement was not due to a change in reaching strategy. Intracortical microelectrode stimulation was used to derive maps of forelimb movement representations within the motor cortex of all animals following training. In comparison to Non-Reaching animals, both Power Reaching and Control Reaching animals exhibited a significant increase in the proportion of motor cortex occupied by distal forelimb movement representations (wrist/digit) and a decrease in the proportion of proximal representations (elbow/shoulder). These results demonstrate that the development of skilled forelimb movements, but not increased forelimb strength, was associated with a reorganization of forelimb movement representations within motor cortex.