Aberrant resting-state oscillatory brain activity in Parkinson's disease patients with visual hallucinations: An MEG source-space study

Abstract

To gain insight into possible underlying mechanism(s) of visual hallucinations (VH) in Parkinson's disease (PD), we explored changes in local oscillatory activity in different frequency bands with source-space magnetoencephalography (MEG). Eyes-closed resting-state MEG recordings were obtained from 20 PD patients with hallucinations (Hall+) and 20 PD patients without hallucinations (Hall-), matched for age, gender and disease severity. The Hall+ group was subdivided into 10 patients with VH only (unimodal Hall+) and 10 patients with multimodal hallucinations (multimodal Hall+). Subsequently, neuronal activity at source-level was reconstructed using an atlas-based beamforming approach resulting in source-space time series for 78 cortical and 12 subcortical regions of interest in the automated anatomical labeling (AAL) atlas. Peak frequency (PF) and relative power in six frequency bands (delta, theta, alpha1, alpha2, beta and gamma) were compared between Hall+ and Hall-, unimodal Hall+ and Hall-, multimodal Hall+ and Hall-, and unimodal Hall+ and multimodal Hall+ patients. PF and relative power per frequency band did not differ between Hall+ and Hall-, and multimodal Hall+ and Hall- patients. Compared to the Hall- group, unimodal Hall+ patients showed significantly higher relative power in the theta band (p = 0.005), and significantly lower relative power in the beta (p = 0.029) and gamma (p = 0.007) band, and lower PF (p = 0.011). Compared to the unimodal Hall+, multimodal Hall+ showed significantly higher PF (p = 0.007). In conclusion, a subset of PD patients with only VH showed slowing of MEG-based resting-state brain activity with an increase in theta activity, and a concomitant decrease in beta and gamma activity, which could indicate central cholinergic dysfunction as underlying mechanism of VH in PD. This signature was absent in PD patients with multimodal hallucinations.

A Review on Tramiprosate (Homotaurine) in Alzheimer's Disease and Other Neurocognitive Disorders

“…Central cholinergic dysfunction has been reported in Parkinson's disease (PD) patients with early gait disturbances ( 69 ), visual hallucinations ( 70 ), REM sleep behavior disorder ( 71 ), dysphagia ( 72 ), cognitive decline ( 73 ), and olfactory impairment ( 74 , 75 ). Thus, treatment with tramiprosate (or ALZ-801) alone or associated with cholinesterase inhibitors (CEI) may be considered in these PD subtypes to improve cholinergic transmission.…”

Hallucinations, somatic‐functional disorders of PD‐DLB as expressions of thalamic dysfunction

“…The pattern is rhythmic, typical of thalamocortical spindling activity and is classified in progressive scores ranging from the random presence to stable presence or presence intermingled with the slower rhythmic or arrhythmic theta‐delta activity because of cortical disconnection . Diffuse theta activity has been recorded during hallucinations and hallucinatory delusional states …”

“…6,27,28 Diffuse theta activity has been recorded during hallucinations and hallucinatory delusional states. 32,89,90,107,108 In physiologic conditions, theta bursts are recorded from thalamic nuclei during the switch from waking states to sleep, 31 and theta appears with a predominant frontal distribution, at the onset of sleep, corresponding to the N1 sleep phase and often at the beginning of REM sleep, replacing desynchronization. 109 Instead, continuous theta activity is observed during REM sleep in PD patients and REM sleep behavior disorder of PD-RBD.…”

Cortical source imaging of resting-state MEG with a high resolution atlas: An evaluation of methods

“…Second, source localization methods are commonly conducted at the vertex level. It is typical in the analysis of spatially distributed resting-state data to parcellate the source-localized data into a small number of regions of interest (ROIs) for measuring functional connectivity (Tewarie et al, 2014;Colclough et al, 2016;Brookes et al, 2016;Dauwan et al, 2019). One commonly used template for cortical parcellation is the AAL atlas (Tzourio-Mazoyer et al, 2002), which is based on anatomical landmarks.…”