title: The modulatory effect of electrical stimulation on the excitability of the corticospinal tract varies according to the type of muscle contraction being performed.
abstract: Afferent input caused by electrical stimulation of a peripheral nerve increases corticospinal excitability during voluntary contractions, indicating that proprioceptive sensory input arriving at the cortex plays a fundamental role in modulating corticospinal excitability. The purpose of this study was to investigate whether the effect of electrical stimulation on the corticospinal excitability varies according to the type of muscle contraction being performed. Motor-evoked potentials (MEPs) were elicited by transcranial magnetic stimulation (TMS) during a shortening contraction, an isometric contraction, or no contraction of the first dorsal interosseous (FDI) muscle. In some trials, electrical stimulation of the ulnar nerve was performed at 110% of the sensory threshold or 110% of the motor threshold prior to TMS. Electrical stimulation involved either a train of 50 pulses at 10 Hz or a single pulse. Shortening contraction with the train of electrical stimuli significantly increased MEP amplitudes, and the increase was dependent on the type of stimulation. Isometric contraction with the train of electrical stimuli and electrical stimulation without voluntary contraction did not affect MEP amplitudes. A single pulse of electrical stimulation did not affect MEP amplitudes in any condition. Thus, electrical-stimulation-induced modulation of corticospinal excitability varied according to the type of muscle contraction performed and the type of stimulation. These results show that the type of contraction should be considered when using electrical stimulation for rehabilitation in patients with central nervous system lesions.
authors.affiliation: Department of Physical Therapy, Niigata University of Health and Welfare Niigata, Japan ; Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Saito
authors.affiliation: Faculty of Rehabilitation, Kanagawa University of Human Services Kanagawa ,Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sugawara
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Miyaguchi
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Hikari
authors.initials: H
authors.lastname: Kirimoto
authors.affiliation: Department of Physical Therapy, Niigata University of Health and Welfare Niigata, Japan ; Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tamaki
authors.affiliation: Department of Physical Therapy, Niigata University of Health and Welfare Niigata, Japan ; Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Onishi
keywords: corticospinal tract; electrical stimulation; excitability; transcranial magnetic stimulation; voluntary contraction