title: Conflicting and non-conflicting visual cues lead to error in gait initiation and gait inhibition in individuals with freezing of gait.
abstract: We asked whether conflicting visual cues influences gait initiation, gait inhibition and postural control in Parkinson's disease (PD) between freezers, non-freezers and healthy older adults.
  
  
  
  Twenty-five PD participants on dopaminergic medication and 17 healthy older adults were asked to initiate or refrain gait depending on visual cues: green GO (GG), green STOP (GS), red GO (RG), red STOP (RS). Center of pressure (CoP) displacement, variability and mean velocity (VCoP) in the anterior-posterior (AP) and medial-lateral (ML) directions and movement time (MT) were measured.
  
  
  
  Gait initiation: Both freezers and non-freezers were different from controls in GG and GS. In GS, freezers had smaller CoP displacement and velocity in both directions (p<0.01), while non-freezers had smaller VCoP in AP and ML (p<0.01). AP CoP displacement in GS was smaller in freezers compared to non-freezers (p<0.05). Freezers had longer MT compared to controls in GG and compared to both groups in GS (p<0.01). Gait inhibition: Controls and freezers had larger CoP displacement variability (p<0.05) and velocity (p<0.01) in both directions in RG compared to RS. No differences were seen in non-freezers. Three freezers initiated walking during the RG or RS conditions.
  
  
  
  Freezers were in general slower at initiating gait, displayed a more restrictive postural strategy and were more affected by the conflicting conditions compared to both controls and non-freezers. In freezers, the conflicting visual cues may have increased the cognitive load enough to provoke delays in processing the visual information and implementing the appropriate motor program.
authors.affiliation: School of Human Kinetics, Faculty of Health Sciences, Ottawa University, Canada.
authors.forename: Zacharie
authors.initials: Z
authors.lastname: Beaulne-Séguin
authors.affiliation: School of Human Kinetics, Faculty of Health Sciences, Ottawa University, Canada. Electronic address: jnantel@uottawa.ca.
authors.forename: Julie
authors.initials: J
authors.lastname: Nantel
mesh_terms: D000368:Aged; D003463:Cues; D005260:Female; D005684:Gait / Q000502:physiology; D020233:Gait Disorders, Neurologic / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D011187:Posture / Q000502:physiology
keywords: Freezers; Gait inhibition; Gait initiation; Incongruent visual information; Parkinson's disease