Visual-spatial disembedding in Parkinson's disease.

Visual-spatial disembedding requires a person to visually scan the stimulus and allocate spatial selective attention to the locations of relevant stimuli. Parkinson's disease (PD) is often associated with visual-spatial deficits, but the influence of PD on disembedding is not entirely known. The goal of this study is to learn whether participants with PD have defective visuospatial disembedding and whether this defect responds to dopaminergic treatment. We also wanted to examine the relationship of disembedding with other cognitive processes and the different parkinsonian clinical symptoms. Participants were PD patients and matched controls. PD participants were tested "on" and "off" medications on the Hidden Patterns Test (HPT) and tests of frontal-executive functions. PD patients had difficulties in visual-spatial disembedding that were not related to medication status, illness duration or severity, or symptom presentation, but were related to other tasks requiring visual scanning in response to alterations in spatial allocation of attention. Lack of improvement with dopaminergic treatment suggests deficits in other neurotransmitter-neuromodulatory systems or degenerative processes in the frontal-striatal networks, cortex, or basal ganglia.