Authors of this prospective study examined how minor hallucinations in Parkinson’s disease (PD) relate to visual processing and cognitive impairment. Researchers evaluated 93 patients with PD, including 55 without minor hallucinations and 38 with minor hallucinations, using a visual categorization task with faces, objects, and face-like objects. Patients with minor hallucinations had lower accuracy for faces and objects, suggesting deficits in visual discrimination that were not explained by slower reaction times. When cognitive status was considered, patients with both minor hallucinations and mild cognitive impairment showed the greatest deficits, with lower accuracy and slower responses across stimulus types.
Event-related potential findings suggested a staged disruption in visual processing. Early sensory registration appeared intact, but patients with minor hallucinations showed reduced N170 amplitudes, suggesting impaired early visual encoding; increased N300 amplitudes, suggesting greater reliance on semantic or associative processing; and reduced P600 amplitudes, suggesting weakened late-stage monitoring or reality-checking. These abnormalities were most pronounced in patients with both minor hallucinations and cognitive impairment. The authors concluded that minor hallucinations in PD may arise from the combined effects of degraded visual input, altered top-down interpretation, and reduced cognitive control, with late-stage monitoring potentially relevant to loss of insight as cognition declines.
Reference: Pérez-Carasol L, Martinez-Horta S, Horta-Barba A, et al. Disrupted visual-to-semantic dynamics promote visual hallucinations in Parkinson’s disease. NPJ Parkinsons Dis. 2025 Dec 26;12(1):24. doi: 10.1038/s41531-025-01235-1.
