Severity‐Dependent Effects of Parkinson's Disease on Perception of Visual and Vestibular Heading

Abstract

Objectives Parkinson's disease (PD) commonly affects visuospatial navigation causing postural instability and falls. Our overarching aim was to examine the visual and vestibular systems governing visuospatial navigation in PD. We hypothesize that PD affects vestibular and visual motion perception but to a different extent. The effects of PD on motion perception are dependent on the severity of the disease. Methods The two‐alternative‐forced‐choice task objectively measured the motion perception during two experiments. One experiment examined the vestibular motion perception with en bloc movement of the platform. The second experiment tested the visual motion perception using an immersive virtual reality goggle. Results We found that accuracy, threshold, and precision of vestibular perception were more impaired in advanced‐PD patients compared to those with a mild form of the disease. The parameters also correlated with the disease duration, overall axial motor impairment causing postural instability and falls, and subjective rating of the balance function. Such changes were present but less severe in visual motion perception. Conclusion We conclude that PD affects motion perception in the visual and vestibular domains in a severity‐dependent manner. The impact of the disease in the vestibular domain is more severe compared to the visual domain. © 2020 International Parkinson and Movement Disorder Society

Does vestibular motion perception correlate with axonal pathways stimulated by STN DBS in Parkinson's disease?

“…Our recent study examined the rst part of the hypothesis and the ndings suggested that stimulating the dorsal subthalamic region correlates with vestibular heading perception [8]. Visual heading perception was minimally affected in PD; and DBS did not create a signi cant effect on heading motion perception cued by optic ow [5,8]. Here, we examine the second part of our hypothesis and test if STN DBS induced activations of white-matter pathways create the change we observed vestibular heading perception of subjects with PD.…”

“…For left-sided heading, the observed improvement occurred when VTA center was located more anterior and dorsal to the STN in the contralateral hemisphere. This is an important insight because left is the direction that is impaired most in PD in a severity-dependent matter [5]. Left is also the motion direction that current stimulation settings appear to create minimal improvement [8].…”

“…The ability to perceive self linear motion, aka heading perception, is instrumental for maintaining gait and postural stability during locomotion. A recent study found a severity-dependent impairment in heading perception in PD [5]. The impairment was prominent when the participants relied on vestibular sensory information, but there were no signi cant effects on the visually cued heading perception.…”

“…Low R 2 values represent a perception trend that do not follow the expected S-shaped psychometric curve. In other words, for patients with low R 2 values, incremental increase in heading direction angles does not translate to a gradual improvement in the vestibular perception performance normally observed in an age-matched control group [1,5,8]. This results in relatively atter psychometric curve ts with values closer to zero.…”

“…2A). Our previous reports provide the detailed information on our experimental protocol and data analysis [5,8]. In summary, the task had a total of 99 trials, which were comprised of a step of forward movement in a heading direction randomly chosen from 0°, 5°, 10°, 20°, and 30° degrees to the right (indicated by positive degrees) or to the left (indicated by negative degrees) as can be seen in Fig.…”