title: Changes of excitability in M1 induced by neuromuscular electrical stimulation differ between presence and absence of voluntary drive.
abstract: The aim of this study is to investigate excitability changes in the human motor cortex induced by variable therapeutic electrical stimulations (TESs) with or without voluntary drive. We recorded motor-evoked potentials (MEPs) from extensor and flexor carpi radialis (FCR) muscles at rest and during FCR muscle contraction after the application of TES on FCR. TES application conditions were changed intensities, frequencies, and trains. In addition, to evaluate the contribution of M1 inhibitory circuits to the effects of TES application, we also recorded MEPs using paired-pulse transcranial magnetic stimulation. In resting muscle states, an increase in TES intensity resulted in an increase in MEP ratio in both the muscles. In contrast, when TES was applied to FCR during contraction, MEP ratios of both the muscles decreased with increased number of pulse trains. However, under both the states, MEP ratios decreased induced by paired-pulse transcranial magnetic stimulation in extensor carpi radialis to which TES was not applied. Excitability changes in M1 induced by TES application were reversibly modulated depending on the presence or absence of voluntary drive. This study showed that the therapy and the voluntary drive of the target muscles act together, and complement the effects of each other, which may be beneficial for optimizing the rehabilitation if the therapy accompanies voluntary drive.
authors.affiliation: Division of Physical Therapy, Faculty of Health and Social Work, Kanagawa University of Human Services, Heisei-cho, Yokosuka, Kanagawa, Japan. sugawara-k@kuhs.ac.jp
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sugawara
authors.forename: Shigeo
authors.initials: S
authors.lastname: Tanabe
authors.forename: Toshio
authors.initials: T
authors.lastname: Higashi
authors.forename: Takamasa
authors.initials: T
authors.lastname: Tsurumi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kasai
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D004328:Drive; D004599:Electric Stimulation Therapy / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000294:innervation; D006225:Hand / Q000294:innervation; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation; D009415:Nerve Net / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D019415:Torque; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D014836:Volition / Q000502:physiology*; D014953:Wrist / Q000294:innervation; D055815:Young Adult