title: Motor strategies and excitability changes of human hand motor area are dependent on different voluntary drives.
abstract: The present study examined whether there were different voluntary drives between intended and non-intended muscle contractions. In experiment 1, during intended and non-intended muscle contractions, electromyograms (EMGs) were recorded from the first dorsal interosseous (FDI) and extensor carpi radialis (ECR) muscles when force levels were varied from 10% to 50% maximal voluntary contraction (MVC) in 10% MVC steps. In experiment 2, using transcranial magnetic stimulation, motor-evoked potentials (MEPs) were recorded from the FDI muscle when EMGs were varied from 10% to 40% EMGmax (EMG activities during MVC) in 10% EMGmax steps during intended and non-intended muscle contractions. In experiment 3, at 10% MVC force level MEPs were recorded before and after practice. The results showed that, in the FDI muscle, EMGs during intended muscle contractions were larger than those during non-intended ones at higher force levels (30-50% MVC). In the ECR muscle, reverse results were observed. At comparable EMG levels of the FDI muscle MEPs were the same during intended and non-intended muscle contractions. After practice, MEPs during intended muscle contraction became larger than those during non-intended at 10% MVC force level, while EMGs were the same between two muscle contractions. It is concluded that motor strategies and excitability changes of hand motor area are different during intended and non-intended muscle contractions, and these differences are due to the different voluntary drives of intended and non-intended. The present findings may contribute to the understanding of rehabilitation for patients suffering from damages of the central motor system.
authors.affiliation: Division of Sports and Health Sciences, Graduate School for International Development and Cooperation, Hiroshima University, 1-5-1 Kagamiyama, Higashihiroshima, 739-8529 Japan.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Ni
authors.forename: Nan
authors.initials: N
authors.lastname: Liang
authors.forename: Makoto
authors.initials: M
authors.lastname: Takahashi
authors.forename: Takamasa
authors.initials: T
authors.lastname: Yamashita
authors.forename: Susumu
authors.initials: S
authors.lastname: Yahagi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Toshio
authors.initials: T
authors.lastname: Tsuji
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kasai
mesh_terms: D000328:Adult; D001519:Behavior / Q000502:physiology; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006225:Hand / Q000033:anatomy & histology / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology