title: Impaired tilt perception in Parkinson's disease: a central vestibular integration failure.
abstract: BACKGROUND
  Impaired balance control is a hallmark symptom in Parkinson's disease (PD). Altered sensory-motor integration contributes to the deficiency. We aimed to determine whether impaired vestibular signal processing added to the disorder. We exposed patients (N = 11; 68±6y) and age-matched healthy subjects (hS: N = 19; 65±11y) on a motion platform in complete darkness to two consecutive forward tilt movements (12 series; N = 24; overall 288 trials) and asked them to indicate which tilt was perceived larger. By combing tilt movements with translations we manipulated vestibular sensory input in order to investigate whether putative impairment resulted from a deficiency of the sensory organs (semicircular canals in 'single-SCC-cue-condition', otoliths in 'single-OT-cue-condition') themselves or to a sensory integration failure ('multi-cue-condition').
  
  
  RESULTS
  Tilt discrimination in the multi-cue-condition was inferior in patients compared to hS (p = 0.02). No significant differences between the two groups were found for both single-cue-conditions. Comparison of multi-cue-condition with a prediction resulting from the combination of both single-cue-conditions by optimal observer theory revealed that patients (p = 0.04), in contrast to hS, failed to efficiently combine SCC and OT information to improve tilt perception.
  
  
  CONCLUSIONS
  We found that PD patients distinguished forward tilts less precise than hS, suggesting impaired vestibular perception. Tilt discrimination in patients, moreover, did not improve as much as in hS in conditions where both SCC and OT information was available compared to conditions where only SCC or OT cues were activated. The latter provides evidence that tilt misperception in PD most likely results from an integration failure of vestibular signals.
authors: Department of Neurology, Zurich University Hospital, Zurich, Switzerland.
authors: Giovanni
authors: G
authors: Bertolini
authors: Department of Neurology, Zurich University Hospital, Zurich, Switzerland.
authors: Andrea
authors: A
authors: Wicki
authors: Department of Neurology, Zurich University Hospital, Zurich, Switzerland.
authors: Christian R
authors: CR
authors: Baumann
authors: Department of Neurology, Zurich University Hospital, Zurich, Switzerland.
authors: Dominik
authors: D
authors: Straumann
authors: Department of Neurology, Zurich University Hospital, Zurich, Switzerland.
authors: Antonella
authors: A
authors: Palla
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D003463:Cues; D003624:Darkness; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009038:Motion; D009039:Motion Perception; D010300:Parkinson Disease / Q000503:physiopathology*; D004856:Postural Balance; D011434:Proprioception; D014722:Vestibule, Labyrinth / Q000503:physiopathology*