title: Cortical mechanisms of mirror therapy after stroke.
abstract: OBJECTIVE
  Mirror therapy is a new form of stroke rehabilitation that uses the mirror reflection of the unaffected hand in place of the affected hand to augment movement training. The mechanism of mirror therapy is not known but is thought to involve changes in cerebral organization. We used magnetoencephalography (MEG) to measure changes in cortical activity during mirror training after stroke. In particular, we examined movement-related changes in the power of cortical oscillations in the beta (15-30 Hz) frequency range, known to be involved in movement.
  
  
  METHODS
  Ten stroke patients with upper limb paresis and 13 healthy controls were recorded using MEG while performing bimanual hand movements in 2 different conditions. In one, subjects looked directly at their affected hand (or dominant hand in controls), and in the other, they looked at a mirror reflection of their unaffected hand in place of their affected hand. The movement-related beta desynchronization was calculated in both primary motor cortices.
  
  
  RESULTS
  Movement-related beta desynchronization was symmetrical during bilateral movement and unaltered by the mirror condition in controls. In the patients, movement-related beta desynchronization was generally smaller than in controls, but greater in contralesional compared to ipsilesional motor cortex. This initial asymmetry in movement-related beta desynchronization between hemispheres was made more symmetrical by the presence of the mirror.
  
  
  CONCLUSIONS
  Mirror therapy could potentially aid stroke rehabilitation by normalizing an asymmetrical pattern of movement-related beta desynchronization in primary motor cortices during bilateral movement.
authors.affiliation: UCL Institute of Neurology, London, UK h.rossiter@ucl.ac.uk.
authors.forename: Holly E
authors.initials: HE
authors.lastname: Rossiter
authors.affiliation: UCL Institute of Neurology, London, UK.
authors.forename: Mimi R
authors.initials: MR
authors.lastname: Borrelli
authors.affiliation: UCL Institute of Neurology, London, UK.
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Borchert
authors.affiliation: UCL Institute of Neurology, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Bradbury
authors.affiliation: UCL Institute of Neurology, London, UK.
authors.forename: Nick S
authors.initials: NS
authors.lastname: Ward
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002540:Cerebral Cortex / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D019018:Imagery, Psychotherapy / Q000379:methods*; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D013057:Spectrum Analysis; D000071939:Stroke Rehabilitation
keywords: MEG; beta oscillations; mirror therapy; motor cortex; stroke