This study aimed to examine the effect of motor imagery (MI) coupled with voluntary movement on the excitability of spinal motor neurons and its impact on accuracy in movement. The study participants were eight healthy individuals (mean age: 20.1 years) with a Kinesthetic and Visual Imagery Questionnaire score of ≥3. First, the participants rested (rest). Second, the participants practiced adjusting finger-pinch forces at 20% of maximal voluntary contraction (MVC) using visual feedback (motor practice [MP]). Third, the participants adjusted the finger-pinch forces at 20% MVC without visual feedback (pinch task 1). Fourth, the participants performed MI. Fifth, the participants repeated pinch task 1 (pinch task 2). Sixth, the participants performed MI with actual motion using visual feedback (MP+MI). Seventh, the participants repeated pinch task 1 again (pinch task 3). Eighth, the participants rested again (rest 2). The F-waves were recorded in the rest, MP, MI, MP+MI, and rest 2 conditions. The indices of accuracy were measured for pinch tasks 1, 2, and 3. The accuracy in movement showed no significant differences among the tasks. The increase in the F-wave/M-wave amplitude ratio was determined by subtracting the value in the rest condition for each trial. Participants with improved accuracy showed moderately increased excitability of the spinal neurons.

Motor imagery undertaken after motor practice on the same side aids in maintaining motor accuracy. This study aimed to determine the effect of motor imagery after motor practice on the opposite side. Twenty healthy subjects were positioned in the supine position, and F-waves were recorded (rest 1). The subjects practiced adjustment pinch force with a target using the right hand. Subsequently, the subjects performed motor imagery to convert movements of the right hand to those of the left hand; the F-wave was recorded (motor imagery). Finally, the subjects attempted adjustment pinch force at a target, and motor accuracy was measured (pinch task). On another day, the subjects performed the control procedure for motor imagery and one more rest trial (rest 2) swapped. The index of motor accuracy was pinch force error from target force and to convert absolute value. Consequently, no difference was detected in the absolute error between the force recorded during motor imagery and that recorded during rest 2. However, the persistence of the F-wave was significantly increased for motor imagery than for rest 1. Motor imagery after motor practice on the opposite side did not improve motor accuracy to a great extent. However, the excitability of the spinal motor neurons increased after motor imagery.

Muscle evoked potential after electrical stimulation to the brain [Br(E)-MsEP] requires measures to reduce the drug-induced decrease in amplitude: Anesthetic Fade. In this observational study, we examined the effect of increasing stimulus intensity on amplitude values. In 528 spinal surgeries, 120 cases showed some waveform reductions. In the 120 cases, amplitude recoveries were observed in 65 cases (54.2%) by increasing stimulus intensity, and 9 cases (7.5%) showed the recovery by addition of double-train stimulation. In the 46 patients who failed to recover amplitude by increasing stimulus intensity, 28 patients recovered that after anesthetic and/or surgical interventions. 102 patients (85%) with amplitude recoveries had good neural prognosis. Postoperative neuropathy occurred in 11 (61%) out of 18 patients who showed reductions of less than 30% of baseline amplitude value in the final waveform. In the cases of the patients who Anesthetic fade was suspected, there was a tendency for amplitude recovery to be seen by increasing stimulus intensity.