Cognitive correlates of visual hallucinations in dementia associated with Parkinson's disease.

Background: There may be a relationship between cognitive impairment and visual hallucinations (VHs) in patients with Parkinson's disease (PD). The objective of this study was to compare the cognitive profile of hallucinating vs. nonhallucinating patients with Parkinson's disease dementia (PDD).

Methods: The cognitive profile of 86 PDD patients with hallucinations was compared with that of a carefully matched PDD group without hallucinations, all drawn from the baseline assessments of the EXPRESS study with rivastigmine. Logistic regression analysis was employed to identify cognitive measures that have an independent relationship with presence of hallucinations.

Results: Worse choice reaction time was the only independent predictor of hallucinations in the logistic regression. A further analysis of the reaction time tasks showed that response selection deficit as opposed to stimulus discrimination deficit was the main difference between the groups.

Discussion: These results indicate that attentional control is an important cognitive correlate of VHs in patients with PDD.