Executive functions are impaired in patients with Parkinson's disease with visual hallucinations

Objectives: Although cognitive impairment has been identified as a risk factor for visual hallucinations (VHs), more specific neuropsychological deficits underlying such phenomena have not been established. Here, we investigate the link between executive dysfunction and the occurrence of VHs. Methods: We evaluated three groups-17 patients with Parkinson's disease (PD) with VHs, 20 patients with PD without VHs and 20 age-matched controls-on a battery of tests previously reported to evaluate executive functions, namely tests of inhibitory ability, short-term memory and working memory. Results: Differences were found on tests of inhibitory ability, for which the patient group with VHs showed impairment when compared with the non-hallucinating group. Conclusions: Patients with PD with VHs have substantially greater impairment of inhibitory ability than patients without VHs. These findings support interactive models of the genesis of visual hallucinations in PD.