After brain injury, survived neuronal cells complement impaired functions by remodeling the neural network. Previous study has shown that motor map reorganization is a form of neural network remodeling, which plays important role for functional recovery. Despite many factors have been known to affect the motor map, diaschisis and rehabilitative therapy for example, little is known as to how or when motor map reorganization occurs and rehabilitative therapy modifies it. In the present study, the spatiotemporal changes of motor map were investigated using intracortical microstimulation (ICMS) techniques.
Rats were assigned to either sham or photothrombosis (PT) groups, and further allocated into rehabilitative or non-rehabilitative groups. After 3 weeks training of skilled forelimb reaching test, stroke were induced in caudal forelimb area (CFA). Rehabilitative therapy was carried out by continuing the skilled forelimb training for 4weeks after operation. To investigate the spatiotemporal changes of motor cortex, ICMS were performed at a day before the operation, 1, 4, 10-12, 18-19 or 31-33 days after operation.
After PT stroke, the success rates of reach test were decreased to about 10% of the pre-PT values. Without rehabilitative therapy, though success rates recovered slightly in first 2 weeks, significant recovery was not exist at 28 days after stroke. In the rats with rehabilitative therapy, success rates were recovered with time and achieved 80% of the pre-PT value 4 weeks after stroke.
In ICMS study, almost complete destruction of CFA were confirmed. Rostral forelimb area (RFA) was also significantly reduced, although RFA was located away from the infarction area. In non-rehabilitative rats, no RFA recovery was observed until 2 weeks after stroke and only the partial recovery was achieved even 4 weeks after stroke. In contrast, rehabilitative rat showed significant RFA recovery as soon as 2 weeks after stroke, and the size of RFA 4 weeks after stroke was larger than pre-PT values.
These results indicate that rehabilitation therapy accelerates and enhances motor map reorganization.