• dementia;
  • psychomotor speed;
  • Stroop test;
  • visual hallucination;
  • vivid dream

Objective –  We investigated executive function in Parkinson’s disease (PD) patients, and focused on executive dysfunction in PD with hallucinations, but without dementia.

Methods –  PD patients were classified by cognitive or neuropsychotic status as PD group, PD with vivid dreaming group, PD with hallucinations group and Parkinson’s disease dementia (PDD) group. Psychomotor speed tests, the Stroop test, a verbal fluency test and the Self-rating Depression Scale were performed.

Results –  The PDD group showed poorer scores in every test compared with the PD group. The PD with hallucinations group showed results similar to those of the PDD group, while the PD with vivid dreaming group was similar to the PD group.

Conclusions –  The study suggests that PD patients with hallucinations, not extensive enough to qualify as dementia, already have executive dysfunction similar to that seen in PDD patients. Executive dysfunction may be an important substrate for hallucinations even when dementia is not yet apparent.