Visuospatial transformation impairments in Parkinson's disease.

Some previous studies have reported impairments in Parkinson's disease (PD) that affect performance on visuospatial tasks. The aim of this study was to further elucidate the underlying cognitive impairment to visuospatial processing in PD. Nondementing PD patients and neurologically normal, age-matched controls completed two tasks of visuospatial transformation. In Task 1, observers made perceptual matching judgments about the shape equivalence of two upright or rotated 2D novel patterns. Task 2 used a recognition memory paradigm in which participants first memorized a target object at a specific orientation and then made target/nontarget judgments to targets or visually similar distractors at varying orientations. Analyses of the regression slopes between response times and angular disparity showed that PD is associated with impairments affecting spatial transformation during image normalization in both tasks. The results also showed that the patients were more impaired, relative to controls, at spatial transformation during the perceptual matching of two images, than in the recognition memory task. It is suggested that PD can result in deficits affecting spatial transformation processes that are modulated by working memory and task demands.