title: Induction of cortical plasticity for reciprocal muscles by paired associative stimulation.
abstract: BACKGROUND
  Paired associative stimulation (PAS) is widely used to induce plasticity in the human motor cortex. Although reciprocal inhibition of antagonist muscles plays a fundamental role in human movements, change in cortical circuits for reciprocal muscles by PAS is unknown.
  
  
  METHODS
  We investigated change in cortical plasticity for reciprocal muscles during PAS. PAS consisted of 200 pairs of peripheral electric stimulation of the right median nerve at the wrist at a frequency of 0.25 Hz followed by transcranial magnetic stimulation of the left M1 at the midpoint between the center of gravities of the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles. Measures of motor cortical excitability included resting motor threshold (RMT), GABAA-mediated short-interval intracortical inhibition (SICI), and GABAB-mediated long-interval intracortical inhibition (LICI).
  
  
  RESULTS
  Motor evoked potential amplitude-conditioned LICI for the FCR muscle was significantly decreased after PAS (P = 0.020), whereas that for the ECR muscle was significantly increased (P = 0.033). Changes in RMT and SICI for the FCR and ECR muscles were not significantly different before and after PAS. Corticospinal excitability for both reciprocal muscles was increased during PAS, but GABAB-mediated cortical inhibitory functions for the agonist and antagonist muscles were reciprocally altered after PAS.
  
  
  CONCLUSIONS
  These results implied that the cortical excitability for reciprocal muscles including GABAB-ergic inhibitory systems within human M1 could be differently altered by PAS.
authors.affiliation: Graduate School of Medical Sciences, Kitasato University Kanagawa, Japan ; School of Allied Health Sciences, Kitasato University Kanagawa, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
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: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sugawara
authors.affiliation: School of Allied Health Sciences, Kitasato University Kanagawa, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: School of Allied Health Sciences, Kitasato University Kanagawa, Japan.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: School of Allied Health Sciences, Kitasato University Kanagawa, Japan.
authors.forename: Ikuyo
authors.initials: I
authors.lastname: Ishizaka
authors.affiliation: Department of Rehabilitation Science, Nagoya University Graduate School of Medicine Nagoya, Japan.
authors.forename: Sumio
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Graduate School of Medical Sciences, Kitasato University Kanagawa, Japan ; School of Allied Health Sciences, Kitasato University Kanagawa, Japan.
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Matsunaga
authors.affiliation: Graduate School of Medical Sciences, Kitasato University Kanagawa, Japan ; School of Allied Health Sciences, Kitasato University Kanagawa, Japan.
authors.forename: Michinari
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare Niigata, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Onishi
mesh_terms: D000328:Adult; D004558:Electric Stimulation / Q000379:methods*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D011963:Receptors, GABA-A / Q000378:metabolism; D018080:Receptors, GABA-B / Q000378:metabolism; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014953:Wrist / Q000502:physiology; D055815:Young Adult
chemical_list: D011963:Receptors, GABA-A; D018080:Receptors, GABA-B
keywords: Human; magnetic stimulation; motor evoked potential; paired associative stimulation; reciprocal inhibition