title: Interactions Among Learning Stage, Retention, and Primary Motor Cortex Excitability in Motor Skill Learning.
abstract: BACKGROUND
  Previous studies have shown that primary motor cortex (M1) excitability is modulated by motor skill learning and that the M1 plays a crucial role in motor memory. However, the following questions remain: (1) At what stage do changes in M1 excitability occur? (2) Are learning-induced changes in leg M1 excitability associated with motor memory? Here, we did two experiments to answer these questions.
  
  
  RESULTS
  In experiment 1, subjects learned a visuomotor tracking task over two consecutive days. Before and after the task in Day 1, we recorded input-output curves of the motor evoked potentials (I-O curve) produced in the tibialis anterior muscle by transcranial magnetic stimulation. We found that the changes in M1 excitability were affected by learning stage. In addition, the changes in M1 excitability in Day 1 were correlated with the retention. In experiment 2, we recorded I-O curves before learning, after the fast-learning stage, and after learning. We found no changes in M1 excitability immediately after the fast-learning stage. Furthermore, a significant relationship between the length of slow-learning stage and the changes in M1 excitability was detected.
  
  
  CONCLUSIONS
  Previous studies have suggested that optimal motor commands are repeatedly used during the slow-learning stage. Therefore, present results indicate that changes in M1 excitability occur during the slow-learning stage and that such changes are proportional to motor skill retention because use-dependent plasticity occur by repetitive use of same motor commands during the slow-learning stage.
authors.affiliation: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Hirano
authors.affiliation: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Kubota
authors.affiliation: Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Aichi, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Tanabe
authors.affiliation: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Koizume
authors.affiliation: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan. Electronic address: funase@hiroshima-u.ac.jp.
authors.forename: Kozo
authors.initials: K
authors.lastname: Funase
mesh_terms: D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000502:physiology; D009044:Motor Cortex / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Learning stage; Motor skill learning; Performance retention; Primary motor cortex excitability