Cortical Stimulation Concurrent With Skilled Motor Training Improves Forelimb Function and Enhances Motor Cortical Reorganization Following Controlled Cortical Impact

Background. Electrical and magnetic brain stimulation can improve motor function following stroke in humans, rats, and nonhuman primates, especially when paired with rehabilitative training (RT). Previously, we found in rodent stroke models that epidural electrical cortical stimulation (CS) of the ipsilesional motor cortex (MC) combined with motor RT enhances motor function and motor cortical plasticity. It was unknown whether CS following experimental traumatic brain injury (TBI) would have similar effects. Objective. To test the effects of CS combined with motor training after moderate/severe TBI on behavioral outcome and motor cortical organization. Methods. Following unilateral controlled cortical impact (CCI) over the caudal forelimb area of the MC in adult male rats, forelimb reach training was administered daily for 9 weeks concurrently with subthreshold, 100-Hz monopolar CS or no-stimulation control procedures. The rate and magnitude of behavioral improvements and changes in forelimb movement representations in the injured MC as revealed by intracortical microstimulation were measured. Results. CCI resulted in severe motor impairments persisting throughout the 9 weeks of training in both groups, but CS-treated animals had significantly greater behavioral improvements. CS also increased wrist motor cortical representation, one of the main movements used in the training task, when compared with RT alone. However, the overall recovery level was modest, leaving animals still extremely impaired. Conclusions. These data suggest that CS may be useful for improving rehabilitation efficacy after TBI but also raise the possibility that the CS parameters that are highly effective following stroke are suboptimal after moderate/severe TBI.