Visual working memory in Parkinson's disease patients using real-world visual objects and perceptual organization.

BACKGROUND

Many studies reported impairment of working memory performance in Parkinson's disease (PD) patients. However, it is largely unknown whether different characteristics of the memory items could affect the performance of visual working memory in PD patients.

METHODS

In this study, we employed two types of stimuli - real-world objects and Gestalt organization, which may primarily evoke top-down modulation of high-level cognitive functions and bottom-up processing of low-level visual function, respectively, to investigate their effects on visual working memory performance in patients with PD compared to healthy controls.

RESULTS

Experiment 1 used real-world objects and simple color blocks as memory materials, and we found that the overall memory performance of the PD group and the control group showed deficits for real objects compared to simple colors. While healthy individuals showed deficits only under high memory load, PD patients experienced difficulties for memorizing real-world object even under low memory load, indicating a reduction in visual working memory capacity. Experiment 2 used Gestalt illusory contours as memory materials, and it showed that PD patients obtain the memory gain of Gestalt organization when memorizing task-relevant orientations rather than task-irrelevant colors, indicating that the memory benefits are acquired when the features constituting illusory are relevant to the task.

CONCLUSIONS

Our findings suggest that PD patients do not benefit from top-down modulation induced by memorizing real-world objects, but can improve through Gestalt organization, indicating that bottom-up perceptual grouping remains intact in PD and revealing a functional divergence between low-level and high-level visual and cognitive abilities in PD.