COMPARISON OF VISUAL COGNITIVE PROCESSING SPEED IN PARKINSON’S DISEASE AND ALZHEIMER’S DISEASE USING A NOVEL WAGON WHEEL ILLUSION-BASED METHOD

Introdution: Cognitive slowing (bradyphrenia) is considered a core feature of Parkinson’s disease (PD) in addition to motor bradykinesia; however, objective methods to quantify cognitive processing speed remain limited. Using WWI-FPS/15, a newly developed visual cognitive processing speed assessment based on the wagon wheel illusion, we quantitatively compared visual cognitive processing speed between PD and Alzheimer’s disease (AD).
Methods: We developed a video-based task in which rotating gears were displayed at randomly varying speeds. Participants identified the rotational speed at which the gear was perceived as rotating counterclockwise three consecutive times. WWI-FPS/15 (Wagon Wheel Illusion–Frames Per Second/15) was defined as the rotational speed divided by 15 degrees. Participants were prospectively enrolled between December 2023 and May 2025. PD was diagnosed according to the Movement Disorder Society 2015 criteria (probable or definite), and AD was diagnosed based on the NIA-AA/IWG-2 biomarker-based biological framework. Neuropsychological assessments (MMSE, MoCA-J, Cog-Eval) and WWI-FPS/15 were performed. Visual cognitive processing speed was compared between PD and AD using multivariate logistic regression analysis, adjusting for age and educational background.
Results: Forty-four participants were analyzed (19 normal controls, 13 AD, and 12 PD). Mean WWI-FPS/15 scores were lower in PD (39.8 ± 7.6) than in AD (42.8 ± 3.7). Multivariate analysis demonstrated significantly lower WWI-FPS/15 scores in PD compared with AD after adjustment for age and educational background (p < 0.0139).
Conclusions: WWI-FPS/15 revealed significantly lower visual cognitive processing speed in Parkinson’s disease than in Alzheimer’s disease, suggesting characteristic cognitive slowing in PD.