Neurodegeneration
How does brain network activity relate to visual hallucinations?
Open access · cc by · source: Europe PMC
People with Parkinson's disease who experience visual hallucinations show abnormally high connectivity within the brain's default mode network compared to those without hallucinations, despite an overall decline in network connectivity caused by the disease itself.
Study at a glance
- Design
- Cross-sectional — Resting-state fMRI of Parkinson’s patients with vs without visual hallucinations and controls
- N
- N=38 · 24 Parkinson’s patients (12 with VH, 12 without) and 14 healthy controls
- Population
- Parkinson’s disease patients with and without visual hallucinations and healthy controls
- Outcome
- Overall DMN hypoconnectivity in PD with relatively higher DMN connectivity in hallucinators
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Parkinson's patients overall showed lower default mode network connectivity compared to healthy controls. However, patients who experienced visual hallucinations had significantly higher functional connectivity in specific default mode network regions—specifically the precuneus, posterior cingulate gyrus, and middle frontal gyrus—than patients without hallucinations. No differences in cortical thickness were found among the groups, indicating these network changes occur without detectable structural tissue loss.
Methodology
The researchers scanned 38 participants, including 24 individuals with Parkinson's disease—divided into 12 with visual hallucinations and 12 without—and 14 healthy controls. Each participant underwent resting-state functional MRI to measure brain network connectivity during rest. The authors also collected high-resolution structural scans to measure cortical thickness across the brain.
Limitations
The study does not establish a causal relationship between default mode network hyperconnectivity and the actual occurrence of hallucinations. Because the sample size was small, subtle structural differences or weak correlations between symptom severity and connectivity may have been missed. Additionally, because participants were cognitively intact and had relatively mild to moderate hallucinations, the findings may not apply to patients with severe cognitive decline or more extreme hallucinatory symptoms. Finally, patients were scanned while taking their regular dopaminergic medications, which could potentially influence network activity.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Resting-state functional connectivity within the default mode network is disrupted in neurodegenerative diseases like Alzheimer's and Parkinson's, directly correlating with cognitive decline or specific clinical symptoms.
Evidence for the claim as stated.
High functional connectivity is frequently interpreted as a healthy, adaptive feature (such as in creativity or cognitive compensation in aging), yet in other contexts, hyper-synchrony represents pathology, such as less specialized networks in Down Syndrome or visual hallucinations in Parkinson's.
Evidence for the claim as stated.
Patients with Parkinson's disease display an overall reduction in default mode network connectivity, yet those who experience visual hallucinations exhibit localized hyperconnectivity in specific default mode regions, such as the precuneus and posterior cingulate, without corresponding changes in cortical thickness.
Evidence for the claim as stated.
Functional network alterations, such as default mode network hyperconnectivity in Parkinson's patients with visual hallucinations, can exist independently without any detectable loss in cortical thickness.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
High functional connectivity is frequently interpreted as a healthy, adaptive feature (such as in creativity or cognitive compensation in aging), yet in other contexts, hyper-synchrony represents pathology, such as less specialized networks in Down Syndrome or visual hallucinations in Parkinson's.
Related papers in this topic
Same topic cluster — not a recommendation engine.
- How tau buildup shapes brain networks in dementia
- How does brain structure change in early Parkinson's disease?
- How does brain inflammation affect connectivity and thinking in AD?
- Can a new PET imaging tracer distinguish different tau diseases?
- Does brain region loss predict memory decline in Parkinson's?