title: Effects of amplitude cueing on postural responses and preparatory cortical activity of people with Parkinson disease.
abstract: OBJECTIVE
  Persons with Parkinson disease (PD) are unable to modify their postural responses, and show an associated increase in cortical preparatory activity for anticipated postural perturbations. In this study we asked whether participants with PD could modify their postural responses and cortical preparatory activity when cued to focus on increasing movement amplitude before a series of predictable postural perturbations.
  
  
  METHODS
  Twelve participants with PD performed postural responses to 30 identical backward surface translations. We cued participants to focus on increasing movement amplitude, and examined the effects of cueing by measuring postural responses (center-of-pressure initial rate of change, automatic postural response stability, peak trunk flexion, peak ankle extension) and preparatory cortical activity (electroencephalographic measures of contingent negative variation, alpha and beta event-related desynchronization).
  
  
  RESULTS
  Participants with PD modified their postural responses during the amplitude trials by increasing trunk flexion, slowing center-of-pressure initial rate of change, and decreasing automatic postural response stability. However, no significant differences in contingent negative variation amplitude or alpha or beta event-related desynchronization were observed with versus without amplitude cueing.
  
  
  CONCLUSIONS
  Persons with PD were able to modify their feet-in-place postural responses with amplitude cueing. These changes were not associated with changes in cortical preparation during amplitude cue trials, suggesting that other regions or measures of brain function were responsible for changes in postural responses. Future studies are needed to determine the effects of long-term amplitude-cueing practice on cortical preparation and postural stability.Video Abstract available. See Video (Supplemental Digital Content 1, http://links.lww.com/JNPT/A78) for more insights from the authors.
authors.affiliation: Infant Neuromotor Control Laboratory (B.A.S.), Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California; Human Motion Analysis Laboratory (J.V.J.), Department of Rehabilitation and Movement Science, University of Vermont, Burlington, Vermont; and Balance Disorders Laboratory (F.B.H.), Department of Neurology, Oregon Health and Science University, and Portland Veterans Affairs Medical Center, Portland, Oregon.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Smith
authors.forename: Jesse V
authors.initials: JV
authors.lastname: Jacobs
authors.forename: Fay B
authors.initials: FB
authors.lastname: Horak
mesh_terms: D000368:Aged; D002540:Cerebral Cortex / Q000503:physiopathology*; D003463:Cues; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*