title: Disinhibition of the premotor cortex contributes to a maladaptive change in the affected hand after stroke.
abstract: OBJECTIVE
  The mechanism of reorganization after stroke remains uncertain. Several studies that have measured reaction time (RT) delay by transcranial magnetic stimulation (TMS) have revealed some substrates responsible for the reorganization of motor recovery. In this study, we evaluated the RT delay and inhibitory functions by examining the silent period (SP) in the primary motor cortex (M1) and premotor cortex (PMC) of the affected hemisphere. Using these data, we investigated whether a change in the inhibitory system might influence motor recovery.
  
  
  METHODS
  This study was performed in 20 patients with chronic subcortical stroke. To evaluate the RT delay, TMS was applied to the affected hemisphere 100 ms after showing the cue that indicated paretic finger movement. The SP was induced by TMS over the affected hemisphere during voluntary contraction of the paretic hand.
  
  
  RESULTS
  The RT delays of the PMC were more prominent in patients with greater disability. The ratio of SP duration to RT delay in the PMC decreased with the decline in motor function. Moreover, upper arm function was better than hand function in patients with a decreased SP in the PMC.
  
  
  CONCLUSIONS
  The inhibitory function of the PMC was disturbed in patients with poor motor function. Stroke patients with poor motor ability appeared to depend not only on the motor pathway from M1 but also on other parallel motor circuits to move the paretic side. However, this brain reorganization might result in the sacrifice of function of the affected hand.
authors.affiliation: Department of Rehabilitation Medicine, Hospital of Hokkaido University, Sapporo, Japan. naoyuki@med.hokudai.ac.jp
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Takeuchi
authors.forename: Takeo
authors.initials: T
authors.lastname: Tada
authors.forename: Takayo
authors.initials: T
authors.lastname: Chuma
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Katsunori
authors.initials: K
authors.lastname: Ikoma
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005385:Fingers; D006225:Hand; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D010291:Paresis / Q000209:etiology / Q000503:physiopathology*; D011597:Psychomotor Performance; D011930:Reaction Time / Q000502:physiology; D020127:Recovery of Function; D020521:Stroke / Q000150:complications / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation