title: Cortical excitability in chronic stroke and modulation by training: a TMS study.
abstract: BACKGROUND
  A possible role for GABA in regulating cortical plasticity after stroke has been proposed.
  
  
  OBJECTIVE
  To investigate changes in intracortical inhibitory and facilitatory circuits in the affected hemisphere more than 6 months after stroke, as well as modulation of excitability by a single training session.
  
  
  METHODS
  A total of 22 patients >6 months after stroke were compared to age- and gender-matched healthy participants. Cortical excitability was assessed by transcranial magnetic stimulation (TMS), including paired-pulse stimulation, before and up to 30 minutes after a single 15-minute session of 1 Hz thumb abduction-adduction movements.
  
  
  RESULTS
  At baseline, TMS showed decreased intracortical inhibition in the affected hemisphere of patients (P = .004) compared to healthy participants. After training a short-lasting decline in motor evoked potentials was observed in both patients (P = .002) and healthy participants (P = .06). Moreover, in healthy participants, inhibitory activity decreased up to 30 minutes after training whereas no significant change was seen in the patients.
  
  
  CONCLUSIONS
  The findings indicate that inhibitory intracortical circuits are less active after stroke, and no change in inhibitory activity is evident after a single training session. This may indicate that intracortical disinhibition is beneficial during recovery and that an impaired capacity for modulation remains in the chronic stage of stroke.
authors.affiliation: Hammel Neurorehabilitation and Research Centre, CFIN, Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark. jbli@ki.au.dk
authors.forename: Jakob Udby
authors.initials: JU
authors.lastname: Blicher
authors.forename: Johannes
authors.initials: J
authors.lastname: Jakobsen
authors.forename: Grethe
authors.initials: G
authors.lastname: Andersen
authors.forename: Jørgen Feldbaek
authors.initials: JF
authors.lastname: Nielsen
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D002908:Chronic Disease / Q000534:rehabilitation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006225:Hand / Q000294:innervation / Q000503:physiopathology; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology / Q000534:rehabilitation; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology; D020521:Stroke / Q000503:physiopathology; D000071939:Stroke Rehabilitation; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D005680:gamma-Aminobutyric Acid