Evaluating Cortical Stimulation as a Therapeutic Adjunct to Motor Skills Rehabilitation Training in a Rodent Model of Traumatic Brain Injury
McCarthy, Jordan J.
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Various studies in animal models of stroke have found that motor impairments caused by stroke can be greatly reduced if the injured area of the motor cortex is electrically stimulated while the animal performs motor skills rehabilitation tasks. This rehabilitation and stimulation combination therapy is very effective, as animals receiving combination therapy are significantly less impaired than animals receiving only rehabilitation after stroke. This study evaluated the behavioral effects of combining cortical stimulation to the affected motor cortex with motor skills rehabilitation training after traumatic brain injury (TBI) to determine if cortical stimulation holds the same benefits for TBI as it does for stroke in reducing motor impairments after injury. In this study, rats were initially trained to a criterion level of proficiency on a skilled single-pellet reaching task. Rats then received a controlled cortical impact (CCI) to the area of the motor cortex corresponding to their preferred reaching limb, and electrodes were implanted over the perilesional tissues near the injury site. Nine days after surgery, rats began a seven-week rehabilitation training program in one of four conditions: 100 Hz anodal stimulation during training, 100 Hz cathodal stimulation during training, 100 Hz bipolar stimulation during training, or no stimulation during training. The behavioral effects of rehabilitation and stimulation were assessed throughout the study with weekly single-pellet reaching test probes that evaluated qualitative aspects of 12 distinct motor movements in the reaching task. Overall, no significant differences in reaching performance were found between any of the four groups. These results suggest that 100 Hz anodal, cathodal, and bipolar stimulation are not effective adjuncts to motor skills rehabilitation training in the rodent CCI model of TBI. However, future studies should test different combinations of frequency, intensity, and polarity parameters, because it is possible that a different combination of stimulation parameters could be an effective therapeutic adjunct to motor skills rehabilitation training after TBI.