Deviations in effective connectivity explain different hallucination subtypes in Parkinson’s disease psychosis
M. Vignando, D. Ffytche, N. Mazibuko, G. Palma, Anjali Bhat, M. Montagnese, Sonali Dave, Y. Tai, L. Batzu, V. Leta, K. R. Chaudhuri, Caroline H. Williams Gray, M. Mehta
Nature Mental Health June 1, 2026 DOI: 10.1038/s44220-026-00669-7 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational case-control study using dynamic causal modeling of EEG Peer reviewed |
|---|---|
| Sample size | 38 |
| Population | People with Parkinson's disease, 20 with visual hallucinations and 18 without |
| Measures | Visual mismatch negativity task, dynamic causal modeling, source reconstruction |
| Key findings | People with Parkinson's disease and visual hallucinations showed reduced top-down and enhanced bottom-up connectivity in ventral visual and prefrontal regions during a visual mismatch negativity task, suggesting deficits in sensory prediction updating and overreliance on visual input. Connectivity patterns differed by hallucination complexity, and task-related source-reconstructed activity correlated positively with normative serotonergic 5-HT2A receptor distribution. |
Abstract
Psychosis and visual hallucinations (VH) in Parkinson’s disease (PD) substantially impact patient outcomes, yet the underlying neural mechanisms remain unclear, limiting effective treatments. Here we used dynamic causal modeling to leverage the fast temporal dynamics captured with electroencephalography data during a visual mismatch negativity task in people with PD with (N = 20) and without (N = 18) VH to examine effective connectivity. We found reduced top-down and enhanced bottom-up connectivity in ventral visual and prefrontal regions during task performance in PD-VH, suggesting deficits in sensory prediction updating and an overreliance on visual input. Connectivity patterns differed with hallucination complexity, with complex VH being associated with altered top-down and bottom-up right-hemisphere connectivity, and multimodal hallucinations to more widespread bilateral disruption. Increased task activity, as computed with source reconstruction, correlated positively with normative serotonergic 5-HT2A receptor distribution. These findings highlight specific neural targets for early therapeutic interventions, supporting a transdiagnostic computational architecture of hallucinations. In this study, Vignando et al. investigate neural alterations in visual processing in people with Parkinson’s disease with visual hallucinations compared with those without visual hallucinations.