title: Reduced after-effects following podokinetic adaptation in people with Parkinson's disease and freezing of gait.
abstract: BACKGROUND
  Gait dysfunction is common in people with Parkinson's disease (PD). Freezing of gait (FOG) is one such gait disturbance that significantly impacts mobility and quality of life in PD. Recent evidence suggests that cerebellar connectivity may differ in people with PD and FOG (PD+FOG) relative to those without FOG (PD-FOG). Investigation of gait adaptation, or the ability to change gait patterns in response to external perturbations, is cerebellum-dependent, is a practical means of probing cerebellar integrity and may provide additional insights regarding the FOG phenomenon.
  
  
  METHODS
  In this study, we investigated gait adaptation in PD and FOG by measuring after-effects, namely whole-body rotation, following stepping on a rotating disc in PD+FOG compared to PD-FOG and older healthy adults. We refer to the period of stepping on the rotating disc as the podokinetic (PK) stimulation and after-effects as podokinetic after-rotation (PKAR). Our primary measure of adaptation was the magnitude and rate of decay of the after-effects.
  
  
  RESULTS
  We noted that PKAR was diminished in PD+FOG compared to the other groups, indicating reduced storage of the adapted gait pattern in PD+FOG. In the PD groups, FOG explained about 20% of the variability in peak velocity. Furthermore, these differences were independent of stepping cadence or motor sign severity.
  
  
  CONCLUSIONS
  Our results show that gait adaptation is impaired in PD+FOG, suggesting the cerebellum may be differentially impacted in PD+FOG compared to PD-FOG. This supports previous neuroimaging evidence of cerebellar dysfunction in PD+FOG. Overall, these data further our understanding of gait deficits in PD+FOG.
authors.affiliation: Program in Physical Therapy, Washington University School of Medicine in St. Louis, 4444 Forest Park Ave., Campus Box 8502, St. Louis, MO 63108, USA. Electronic address: nemanichs@wusm.wustl.edu.
authors.forename: Samuel T
authors.initials: ST
authors.lastname: Nemanich
authors.affiliation: Program in Physical Therapy, Washington University School of Medicine in St. Louis, 4444 Forest Park Ave., Campus Box 8502, St. Louis, MO 63108, USA; Department of Anatomy and Neurobiology, Washington University School of Medicine in St. Louis, 660S. Euclid Ave., Campus Box 8108, St. Louis, MO 63110, USA; Department of Neurology, Washington University School of Medicine in St. Louis, 660S. Euclid Ave., Campus Box 8111, St. Louis, MO 63110, USA. Electronic address: earhartg@wusm.wustl.edu.
authors.forename: Gammon M
authors.initials: GM
authors.lastname: Earhart
mesh_terms: D000222:Adaptation, Physiological; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D020233:Gait Disorders, Neurologic / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D010300:Parkinson Disease / Q000503:physiopathology*; D011597:Psychomotor Performance; D011788:Quality of Life; D012399:Rotation; D013647:Task Performance and Analysis
keywords: After-effects; Freezing of gait; Locomotor adaptation; Parkinson disease