Phenomenology of visual hallucinations and their relationship to cognitive profile in Parkinson’s Disease patients: preliminary observations

Although the phenomenology of visual hallucinations (VHs) has been investigated, no study to date has related cognitive performance to the content of hallucinations, specifically whether participants who have familiar internally driven hallucinations differ in the executive function from patients with externally driven hallucinations. Here, we examine the relationship between executive function and the content of VHs in Parkinson’s disease (PD) patients. We evaluated three groups: 17 PD patients with internally driven memory-based VHs, 18 PD patients with externally driven non-memory-based VHs, and 20 PD patients without hallucinations on a series of tests previously reported to evaluate executive functions, specifically tests of inhibitory ability, short-term memory, and working memory. Differences were found on test of inhibitory ability with PD patients experiencing externally driven VHs having substantially greater impairment than patients with internally driven VHs. These findings indicate that the cognitive profile of patients may influence the content of the hallucinatory experience and could consequently have implications for treatment of the phenomenon.