title: Biologically-variable rhythmic auditory cues are superior to isochronous cues in fostering natural gait variability in Parkinson's disease.
abstract: Rhythmic auditory cueing improves certain gait symptoms of Parkinson's disease (PD). Cues are typically stimuli or beats with a fixed inter-beat interval. We show that isochronous cueing has an unwanted side-effect in that it exacerbates one of the motor symptoms characteristic of advanced PD. Whereas the parameters of the stride cycle of healthy walkers and early patients possess a persistent correlation in time, or long-range correlation (LRC), isochronous cueing renders stride-to-stride variability random. Random stride cycle variability is also associated with reduced gait stability and lack of flexibility.
  
  
  
  To investigate how to prevent patients from acquiring a random stride cycle pattern, we tested rhythmic cueing which mimics the properties of variability found in healthy gait (biological variability). PD patients (n=19) and age-matched healthy participants (n=19) walked with three rhythmic cueing stimuli: isochronous, with random variability, and with biological variability (LRC). Synchronization was not instructed.
  
  
  
  The persistent correlation in gait was preserved only with stimuli with biological variability, equally for patients and controls (p's<0.05). In contrast, cueing with isochronous or randomly varying inter-stimulus/beat intervals removed the LRC in the stride cycle. Notably, the individual's tendency to synchronize steps with beats determined the amount of negative effects of isochronous and random cues (p's<0.05) but not the positive effect of biological variability.
  
  
  
  Stimulus variability and patients' propensity to synchronize play a critical role in fostering healthier gait dynamics during cueing. The beneficial effects of biological variability provide useful guidelines for improving existing cueing treatments.
authors.affiliation: EuroMov, Université de Montpellier, Montpellier, France; Centro de Ciencias de la Complejidad (C3), Universidad Nacional Autónoma de México, Mexico. Electronic address: dobri.dotov@gmail.com.
authors.forename: D G
authors.initials: DG
authors.lastname: Dotov
authors.affiliation: EuroMov, Université de Montpellier, Montpellier, France; CHRU, Hôpital Gui-de-Chauliac, Montpellier, France.
authors.forename: S
authors.initials: S
authors.lastname: Bayard
authors.affiliation: CHRU, Hôpital Gui-de-Chauliac, Montpellier, France; Clinique Beau Soleil, Montpellier, France.
authors.forename: V
authors.initials: V
authors.lastname: Cochen de Cock
authors.affiliation: EuroMov, Université de Montpellier, Montpellier, France; CHRU, Hôpital Gui-de-Chauliac, Montpellier, France.
authors.forename: C
authors.initials: C
authors.lastname: Geny
authors.affiliation: CHRU, Hôpital Gui-de-Chauliac, Montpellier, France.
authors.forename: V
authors.initials: V
authors.lastname: Driss
authors.affiliation: Clinique du Parc, Montpellier, France.
authors.forename: G
authors.initials: G
authors.lastname: Garrigue
authors.affiliation: EuroMov, Université de Montpellier, Montpellier, France; Institut Universitaire de France (IUF), Paris, France.
authors.forename: B
authors.initials: B
authors.lastname: Bardy
authors.affiliation: EuroMov, Université de Montpellier, Montpellier, France; Institut Universitaire de France (IUF), Paris, France; International Laboratory for Brain, Music, and Sound Research (BRAMS), Montreal, Canada; Department of Cognitive Psychology, WSFiZ, Warsaw, Poland.
authors.forename: S
authors.initials: S
authors.lastname: Dalla Bella
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003463:Cues; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D010507:Periodicity; D016138:Walking
keywords: Cueing; Gait; Motor variability; Parkinson's disease; Rhythm; Synchronization