Affiliations: Department of Neuroscience, Neurosurgery, Uppsala University, Uppsala, Sweden | Department of Neuroscience, Neurophysiology, Uppsala University, Uppsala, Sweden
Note: [] Corresponding author: Niklas Marklund, Department of Neuroscience, Section for Neurosurgery, Uppsala University, Entrance 85, 2nd Floor, Uppsala University Hospital, S-75185 Uppsala, Sweden. Tel.: +46 18 6114937; Fax: +46 18 55 86 17; E-mail: niklas.marklund@neuro.uu.se
Abstract: Purpose: Recovery is limited following traumatic brain injury (TBI) since injured axons regenerate poorly and replacement of lost cells is minimal. Behavioral improvements could instead be due to plasticity of uninjured brain regions. We hypothesized that plasticity of the uninjured hemisphere occurs contralateral to a focal TBI in the adult rat. Thus, we performed cortical mapping of the cortex contralateral to the TBI using intracortical microstimulation (ICMS). Methods: A focal TBI was induced using the weight-drop technique (n = 5) and sham-injured animals were used as controls (n = 4). At five weeks post-injury, ICMS was used to map the motor area contralateral to the injury. Motor responses were detected by visual inspection and electromyography (EMG). Results: In sham- and brain-injured animals, numerous fore- and hindlimb motor responses contralateral to the stimulation (ipsilateral to the injury) were obtained. Compared to sham-injured controls, there was a markedly increased (p < 0.05) number of fore- and hindlimb responses ipsilateral to the stimulation after TBI. Conclusion: Following focal TBI in the rat, our data suggest reorganization of cortical and/or subcortical regions in the uninjured hemisphere contralateral to a focal TBI leading to an altered responsiveness to ICMS. Although we cannot exclude that these changes are maladaptive, it is plausible that this plasticity process positively influences motor recovery after TBI.
Keywords: Traumatic brain injury, motor cortex, mapping, microstimulation, motor evoked potential
