title: Attention modulates step initiation postural adjustments in Parkinson freezers.
abstract: BACKGROUND
  In view of freezing of gait's circumstances of occurrence in Parkinson's disease, attentional resources appear to be involved in step initiation failure. Anticipatory postural adjustments (APAs) are essential because they allow unloading of the stepping leg and so create the conditions required for progression. Our main objective was to establish whether or not a change in attentional load during step initiation modulates APAs differently in patients with vs. without freezing of gait.
  
  
  METHODS
  Three groups of 15 subjects were recruited: elderly people and parkinsonian patients with or without freezing of gait. Attention was modulated before step execution by means of an auditory oddball discrimination task with event-related potential recording. The primary endpoint was the occurrence of inappropriate APAs following the attentional task, i.e. APAs not followed by a step after an intercurrent auditory stimulus.
  
  
  RESULTS
  In parkinsonian patients with freezing of gait, inappropriate APAs were recorded in 63% of the trials and were observed more frequently than in patients without freezing of gait (51%) and elderly controls (48%). Furthermore, inappropriate APAs in freezers were longer and more ample than in parkinsonian non-freezers and controls. Lastly, postural preparation was impaired in the parkinsonian patients.
  
  
  CONCLUSIONS
  Our results indicate that allocation of attentional resources during step preparation influences the release of APAs differently in freezers and non-freezers. Modulating attentional load is partly responsible for triggering an inappropriate motor program. This difficulty in focusing attention or resisting interference may contribute (at least in part) to the gait initiation failure observed in parkinsonian freezers.
authors.affiliation: Université Lille Nord de France, UDSL, France; Troubles cognitifs dégénératifs et vasculaires, EA1046, Lille 2, France; Neurology and Movement Disorders Department, Lille University Medical Center, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Tard
authors.affiliation: Université Lille Nord de France, UDSL, France; Troubles cognitifs dégénératifs et vasculaires, EA1046, Lille 2, France; Neurology and Movement Disorders Department, Lille University Medical Center, France.
authors.forename: Kathy
authors.initials: K
authors.lastname: Dujardin
authors.affiliation: Troubles cognitifs dégénératifs et vasculaires, EA1046, Lille 2, France; Clinical Neurophysiology Department, Lille University Medical Center, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Bourriez
authors.affiliation: Université Lille Nord de France, UDSL, France; Neurology and Movement Disorders Department, Lille University Medical Center, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Destée
authors.affiliation: Université Lille Nord de France, UDSL, France; Troubles cognitifs dégénératifs et vasculaires, EA1046, Lille 2, France; Clinical Neurophysiology Department, Lille University Medical Center, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Derambure
authors.affiliation: Université Lille Nord de France, UDSL, France; Troubles cognitifs dégénératifs et vasculaires, EA1046, Lille 2, France; Neurology and Movement Disorders Department, Lille University Medical Center, France.
authors.forename: Luc
authors.initials: L
authors.lastname: Defebvre
authors.affiliation: Université Lille Nord de France, UDSL, France; Troubles cognitifs dégénératifs et vasculaires, EA1046, Lille 2, France; Clinical Neurophysiology Department, Lille University Medical Center, France. Electronic address: arnaud.delval@chru-lille.fr.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Delval
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000368:Aged; D059031:Anticipation, Psychological / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology; D020233:Gait Disorders, Neurologic / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology
keywords: Attention; Freezing of gait; Gait initiation; Parkinson's disease; Postural adjustments