title: Parkinsonian deficits in context-dependent regulation of standing postural control.
abstract: This study explored whether patients with Parkinson's disease alter the regulation of upright standing according to constraints imposed by the environmental context. The provision of context-dependent adaptations was inferred from the presence of adjustments to standing postural control that would serve to reduce fall risk when balance was challenged by a threatening environmental context. Participants were asked to stand as still as possible in two environmental context conditions that differed in the level of imposed postural threat: LOW threat and HIGH threat. Eight levodopa dependent patients with Parkinson's disease (PD) and eight age-matched control subjects (CTRL) provided the subject sample. PD patients were tested following a 12-h withdrawal of anti-Parkinsonian medications and approximately 1h post-medication. The CTRL group showed altered postural control in the HIGH threat condition, in a manner that was indicative of appropriate context-dependent regulation of standing. PD patients, in the non-medicated or medicated states, did not modify stance regulation when the environmental context heightened postural threat. Our results extend the current understanding of Parkinsonian deficits in the context-dependent regulation of postural control to include upright standing.
authors.affiliation: Balance Research Laboratory, Department of Kinesiology, University of Lethbridge, Canada. l.brown@uleth.ca
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Brown
authors.forename: Jon B
authors.initials: JB
authors.lastname: Doan
authors.forename: Ian Q
authors.initials: IQ
authors.lastname: Whishaw
authors.forename: Oksana
authors.initials: O
authors.lastname: Suchowersky
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D020734:Parkinsonian Disorders / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011312:Pressure; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology; D019415:Torque