title: Modulating the motor system by action observation after stroke.
abstract: OBJECTIVE
  Much recent interest surrounds the use of action observation, which is observing another individual performing a motor task, in stroke rehabilitation, to promote motor recovery by engaging similar brain regions to action execution. This may be especially useful in individuals with limited mobility. Here, we assess how cortical motor activity during action observation is affected by stroke and by stroke-related motor deficits.
  
  
  METHODS
  We used functional MRI to compare brain activity during right and left hand action observation in right-handed nondisabled participants and participants who were right-handed before left hemisphere stroke. All participants performed the same actions after their functional MRI.
  
  
  RESULTS
  Nondisabled participants show greater bilateral cortical motor activity when observing actions made using the left hand, whereas participants with stroke show greater ipsilesional cortical motor activity when observing actions made using the right (paretic) hand (P<0.05; corrected). For both groups, action processing is modulated by motor capability: cortical motor activity is greater when observing the hand with lower motor scores (P<0.05; corrected). Furthermore, for stroke, the extent of ipsilesional activity correlates with lesion volume (P=0.049), in a pattern that suggests adaptive plasticity.
  
  
  CONCLUSIONS
  We found that action observation activates specific motor plans in damaged motor circuits after stroke, and this activity is related to motor capability to perform the same actions. Cortical motor activity during action observation may be relevant to motor learning, and to motor relearning in stroke rehabilitation.
authors.affiliation: Division of Biokinesiology and Physical Therapy, Brain and Creativity Institute, University of Southern California, Los Angeles, CA, USA. kathleenalice@gmail.com
authors.forename: Kathleen Alice
authors.initials: KA
authors.lastname: Garrison
authors.forename: Lisa
authors.initials: L
authors.lastname: Aziz-Zadeh
authors.forename: Savio Waiho
authors.initials: SW
authors.lastname: Wong
authors.forename: Sook-Lei
authors.initials: SL
authors.lastname: Liew
authors.forename: Carolee Joyce
authors.initials: CJ
authors.lastname: Winstein
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping / Q000295:instrumentation / Q000379:methods; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D020772:Internal Capsule / Q000473:pathology / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology*; D009069:Movement Disorders / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D009415:Nerve Net / Q000473:pathology / Q000503:physiopathology*; D009483:Neuropsychological Tests; D020521:Stroke / Q000150:complications / Q000473:pathology / Q000503:physiopathology*
keywords: action observation; mirror neuron system; plasticity; rehabilitation; stroke