Motor imagery is the mental rehearsal of a movement within working memory. Reduction of spinal motor neuron excitability has been demonstrated after stroke, and motor imagery may increase spinal motor neuron excitability in patients with a motor deficit. However, spinal motor neuron excitability varies depending on the imagery strategy used. In this study, we examined spinal motor neuron excitability during kinesthetic, somatosensory, and combined imagery. Healthy adult volunteers (n=14) were recruited for F-wave recording. The F-wave was measured during relaxation to determine baseline levels, followed by measurement during the three imagery trials performed in a random order. In the somatosensory imagery (SI) trial, participants imagined tactile and pressure perception of the thumb finger pulp during holding a pinch meter. In the kinesthetic imagery (KI) trial, participants imagined muscle contraction during isometric thenar muscle activity at 50% maximal voluntary contraction. In the combined KI and SI trial, participants performed the KI and SI simultaneously. After F-wave recording, participants evaluated the difficulty of each imagery trial using a five-point Likert scale. Persistence during SI and KI was significantly higher than that at rest. The F/M amplitude ratio during KI was significantly higher than that at rest. The five-point Likert scale score of the combined KI and SI was significantly lower than that of KI. KI may increase spinal motor neuron excitability over that of SI. Thus, it is important to consider the sensory modality chosen for imagery during rehabilitation.
aGraduate School of Health Sciences, Graduate School of Kansai University of Health Sciences
bClinical Physical Therapy Laboratory, Faculty of Health Sciences, Kansai University of Health Sciences, Kumatori, Japan
Correspondence to Yoshibumi Bunno, PT, PhD, Graduate School of Health Sciences, Graduate School of Kansai University of Health Sciences, 2-11-1, Wakaba, Kumatori, Sennan, Osaka 590-0482, Japan Tel: +81 724 538 374; fax: +81 724 538 798; e-mail: email@example.com
Received November 6, 2018
Accepted February 3, 2019