Objective: To investigate unisensory and multisensory self-motion perception mediated by the visual and vestibular systems in PD.

Background: Parkinson’s disease (PD) is classically characterized by a decline in motor function. However, non-motor symptoms (including cognitive, sensory and perceptual deficits) are becoming increasingly recognized as an important part of the disease. Specifically perceptual deficits may infact underly deficits in motor function for example gait and balance.

Methods: Nineteen PD participants and 23 age-matched control were tested in a self-motion perception task in a 3D motion simulator. [figure1] Stimuli comprised vestibular (inertial motion), visual (optic flow) and combined vestibular-visual cues. Two levels of visual noise were tested: 100% motion coherence (i.e., no visual noise) and 65% coherence (35% noise). Cues in the multisensory combined condition were presented simultaneously but with a discrepancy (cue conflict) of ± 6 degrees between the modalities to allow comparison of multisensory integration optimality versus Bayesian predictions. [figure2] Disease severity was measured with the UPDRS motor part.

Results: PD patients had significantly higher visual thresholds of self-motion perception vs. controls yet there was no significant difference between groups in the vestibular condition. [figure3] With 65% coherence visual thresholds correlated positively with motor UPDRS (r=0.68, p=0.01). [figure4] In cue conflict conditions PD patients suboptimally overweight visual cues. [figure5]

Conclusions: PD patients demonstrated a selective impairment of self-motion perception from visual (but not vestibular) cues which was more marked with more severe disease. Yet visual cues were overweighted in PD. These results suggest a specific deterioration of visual self-motion perception in PD, which might contribute to balance and gait disorders. This work was presented at the 26th Israel Society for Neuroscience Annual Meeting in December 2017.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/visual-deficits-of-self-motion-perception-in-parkinsons-disease/