Abstract:

Objective To explore the activation of motor cortex and brain lateralization of healthy male subjects during mirror visual feedback (MVF) of dominant and non-dominant hands.
Methods From March to September, 2021, 17 right-handed male subjects were recruited in Shenyang Sport University. The eego^TMmylab electroencephalography (EEG) system was applied to acquire the EEG and surface electromyography (sEMG) signals of digital extensor muscle during MVF. The subjects were completed unilateral finger stretching exercise, including left/right hand MVF and left/right hand visual feedback (VF). Each paradigm was repeated 80 trials, and the four paradigms were divided into two experiments, with one week between each experiment. The time-domain characteristics of sEMG signals and the time-frequency characteristics of α-band (8 to 13 Hz) and β-band (13 to 20 Hz) EEG signals which were closely related to motion were analyzed. Activation and asymmetry of motor cortex during MVF in dominant and nondominant hands were measured with event-related desynchronization/synchronization (ERD/ERS) and asymmetric index (AI).
Results When the relaxed hand was right hand, the sEMG amplitude of digital extensor muscle were more in MVF and VF than in resting state (P < 0.05). In α bands, the main effect of training state on ERD/ERS was significant (F = 14.125, η_p² = 0.469, P = 0.002), and it was higher in MVF than in VF. In β band, the main effect of training state on ERD/ERS was significant (F = 9.704, η_p² = 0.378, P = 0.007), the interaction effect of moving hand and training state was significant on ERD/ERS (F = 8.014, η_p² = 0.334, P = 0.012); for VF, ERD/ERS was higher in right hand movement than in left hand movement (F = 7.267, η_p² = 0.312, P = 0.016); for right hand movement, ERD/ERS was higher in MVF than in VF (F = 17.530, η_p² = 0.523, P = 0.001). At the position of C4 electrode, ERD/ERS was higher in right hand movement than in left hand movement under VF (t = -3.201, P = 0.006, Cohen's d = 0.776), and ERD/ERS was higher in MVF than in VF under right hand movement (t = -4.060, P = 0.001, Cohen's d = 0.985). Main effect of training state was significant on AI at β band (F = 5.796, η_p² = 0.266, P = 0.028), and it was higher in MVF than in VF.
Conclusion MVF may improve the activity of motor cortex neurons on the ipsilateral side of the motor hand through recruitment of frontal and parietal mirror neurons and reduction of interhemispheric and intracortical inhibitory activities, and it is more effective for the dominant hand training.

Key words: mirror visual feedback, unilateral movement, electroencephalography, event-related de-synchronization/synchronization