Functional Brain Connectivity Patterns Associated with Visual Hallucinations in Dementia with Lewy Bodies

Abstract

Background: The presence of recurrent, complex visual hallucinations (VH) is among the core clinical features of dementia with Lewy bodies (DLB). It has been proposed that VH arise from a disrupted organization of functional brain networks. However, studies are still limited, especially investigating the resting-state functional brain features underpinning VH in patients with dementia. Objective: The aim of the present pilot study was to investigate whether there were any alterations in functional connectivity associated with VH in DLB. Methods: Seed-based analyses and independent component analysis (ICA) of resting-state fMRI scans were carried out to explore differences in functional connectivity between DLB patients with and without VH. Results: Seed-based analyses reported decreased connectivity of the lateral geniculate nucleus, the superior parietal lobule and the putamen with the medial frontal gyrus in DLB patients with VH. Visual areas showed a pattern of both decreased and increased functional connectivity. ICA revealed between-group differences in the default mode network (DMN). Conclusion: Functional connectivity analyses suggest dysfunctional top-down and bottom-up processes and DMN-related alterations in DLB patients with VH. These impairments might foster the generation of false visual images that are misinterpreted, ultimately resulting in VH.

A systematic review on resting state functional connectivity in patients with neurodegenerative disease and hallucinations

“… Severe cerebrovascular disease; primary psychiatric disorders; severe ocular diseases N.A. Pezzoli et al (2021a ) 7 DLB VH 16 DLB NH 2.57 (1.4) 2.13 (1.31) 75.29 (5.09) 73.5 (6.65) NPI to assess presence, severity and frequency Recurrent, complex hallucination Severe cerebrovascular disease; history of psychiatric disorders; severe eye pathology impairing visual acuity N.A. Walpola et al (2020) 18 PD H 20 PD NH 20 HC 7.6 (5) 5.7 (3.2) 67.5 (6.7) 63.7 (6.6) - MDS-UPDRS (question 2) Score ≥ 1, having VH (including minor (passage or illusions) or complex hallucinations N.A.…”

“…Fourty% of the studies only stated the presence of hallucinations based on specific assessments as inclusion criteria. Specifically, Pezzoli and colleagues (2021a) used the Neuropsychiatric Inventory (NPI) to determine the presence of hallucinations, Walpola and colleagues (2020) selected a score higher than 1 on the question related to hallucinations and psychosis of the Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), Hepp and colleagues (2017) classified patients as hallucinator if their score was higher than 1 on the Scales for Outcomes in Parkinson Disease Psychiatric Complications, and Franciotti and colleagues (2015) examined the presence of complex hallucinations through the Parkinson Psychosis Rating Scale (PPRS).…”

“…The studies were conducted in five different countries. Three studies were conducted in Hong Kong ( Yao et al, 2016 , Yao et al, 2015 , Yao et al, 2014 ), three in Italy ( Zorzi et al, 2021 , Pezzoli et al, 2021a , Franciotti et al, 2015 ), two in Australia ( Walpola et al, 2020 , Shine et al, 2015 ), one in Spain ( Bejr‐kasem et al, 2019 ), and one in The Netherlands ( Hepp et al, 2017 ).…”

“…A recent meta -analysis focusing on voxel-based morphometry (VBM) revealed the reduced volumes of frontal, occipital, occipitotemporal and parietal brain regions in patients with neurodegenerative diseases suffering from hallucinations as compared with those without hallucinations ( Pezzoli et al, 2021a ). However, an influential view on brain functioning conceived the relation between structure and function based on the dynamic communication between brain regions, balancing between integration and segregation ( Sporns, 2012 ).…”

A Multimodal Neuroimaging and Neuropsychological Study of Visual Hallucinations in Alzheimer’s Disease

“…In addition, the chosen imaging modalities might have not been suitable to clarify the mechanisms at the basis of VH in AD. There is evidence that altered functional connectivity, detected using resting-state functional MRI (fMRI), may be related to VH in patients with PD and DLB, especially in the default mode network (DMN) [49][50][51]. According to Shine et al [52], VH in PD would be facilitated by the presence of disrupted engagement of attention networks, including overactivity of the DMN.…”