Resumo

Introduction: Electroencephalography (EEG) provides a powerful tool for studying cortical plasticity, allowing investigation of pathologic brain pathways. As a result of direct trauma to neurons in a spinal cord injury (SCI), axons responsible for conveying messages to and from the cortex may be seriously damaged and thus limit the link between brain centers and the spinal cord. Demonstration of changes in brain activity of spinal cord injured rats submitted to training is very important as it has clear implications for understanding brain response to trauma after rehabilitation and may lead to future therapies that enhance regeneration, or inhibit secondary destruction of neural tissue. Objectives: The objectives of this study were to investigate the influence of treadmill training in functional motor recovery, and concurrently, for the first time, recording EEG changes in motor cortex of Wistar rats with moderate contusive SCI. Methods: All procedures were approved by the local Ethical Committee and performed in accordance with Mutlicenter Animal SCI Study. Wistar rats, 280-380g, were used to implant 32 Teflon coated tungsten sharp microwire (0.05mm diameter spaced by 0.5mm) in the left motor cortex. The set was fixated to the skull bone with cianoacrilate adhesive. After 10 days, they underwent contusive SCI at T9-T10 levels using NYU-Impactor device. For these surgical procedures, rats were anesthetized with Ketamine (100mg/kg), Xylazine (5mg/kg) and local Xylestesin. Animals were trained in a treadmill during 15 minutes, five times per week for two months after SCI. Trainings started on the 5th post operative day (POd). Rats motor cortex recordings occurred during freely behaving in an open field and treadmill training. Motor recovery was assessed with Basso, Beattie and Bresnahan (BBB) open field locomotor scale. These assessments were performed once before SCI for obtaining basal behaviors and on the 1st, 3rd, 5th, 7th POd and then weekly till two months. The functional motor behavior data were submitted to a repeated measure analysis of variance and the EEG data were submitted to spectral analysis using Welch periodogram. This technique is robust for small data sets and keeps frequency resolution. Results: Trained animals showed important functional recovery after treadmill training, being able to perform consistent and coordinated plantar steps (F5,11=30.34, p<0.05). We found that the EEG theta wave power decreased after SCI in freely behaving (6.5Hz ±0.8), and there was an increase during exercise (8Hz ±0.8), which might indicate an alertness or attentional state related to the task. Additionally, theta rhythm facilitates the sensorimotor integration occurring during dynamic motor performance. EEG beta wave power decreased soon after SCI (13.5Hz ±0.8) and it arouse as animals start to recover because of the treadmill training (15.5Hz ±0.8). At the end of the experiment, trained animals EEG features are similar to the pre injury recordings. Scientifically meaningful is the cortical beta-activity association with an up-regulation of sensory inputs that are relevant to the motor response organization. Conclusion: Sensorimotor integration can be facilitated in injured animals submitted to a specific rehabilitation program, thus our treadmill training induced functional recovery and motor cortex reorganization.