Motor Imagery Facilitates the Spinal Motor Neurons Without Hemispheric Asymmetry

Purpose: To determine possible hemispheric differences of motor imagery in facilitating the anterior horn cells. Methods: We conducted a side-to-side comparison of motor imagery to counter rest-induced suppression of spinal motor neurons in 10 right-handed healthy adults using the F wave as a measure of excitability. Studies consisted of sequential recording of F waves from the abductor pollicis brevis with 100 supramaximal stimuli applied to the median nerve on three consecutive sessions: (1) after standardized hand exercise to establish the baseline; (2) after immobilizing abductor pollicis brevis bilaterally for 3 hours, with one side assigned to relaxation task and the other side to motor imagery task; and (3) after standardized hand exercise to assess a recovery. The same sequence was repeated, switching the side of relaxation and motor imagery tasks. Results: F-wave persistence and average amplitude showed a significant decrease (P < 0.01) from baseline after relaxation task, recovering quickly after exercise, but no change (P > 0.05) after motor imagery task. The results showed no significant differences (P > 0.05) between dominant and non-dominant hands. Conclusion: Motor imagery facilitates the spinal motor neurons without hemispheric asymmetry.