Abnormal Cross Frequency Coupling of Brain Electroencephalographic Oscillations Related to Visual Oddball Task in Parkinson's Disease with Mild Cognitive Impairment

Abstract

Parkinson's disease (PD) is a movement disorder caused by degeneration in dopaminergic neurons. During the disease course, most of PD patients develop mild cognitive impairment (PDMCI) and dementia, especially affecting frontal executive functions. In this study, we tested the hypothesis that PDMCI patients may be characterized by abnormal neurophysiological oscillatory mechanisms coupling frontal and posterior cortical areas during cognitive information processing. To test this hypothesis, event-related EEG oscillations (EROs) during counting visual target (rare) stimuli in an oddball task were recorded in healthy controls (HC; N = 51), cognitively unimpaired PD patients (N = 48), and PDMCI patients (N = 53). Hilbert transform served to estimate instantaneous phase and amplitude of EROs from delta to gamma frequency bands, while modulation index computed ERO phase-amplitude coupling (PAC) at electrode pairs. As compared to the HC and PD groups, the PDMCI group was characterized by (1) more posterior topography of the delta-theta PAC and (2) reversed delta-low frequency alpha PAC direction, ie, posterior-to-anterior rather than anterior-to-posterior. These results suggest that during cognitive demands, PDMCI patients are characterized by abnormal neurophysiological oscillatory mechanisms mainly led by delta frequencies underpinning functional connectivity from frontal to parietal cortical areas.

Pathobiology of Cognitive Impairment in Parkinson Disease: Challenges and Outlooks

“…PD-MCI patients compared to HCs were characterized by more frequent posterior topography of the δ-θ phase-amplitude coupling (PAC) and reversed δ-low frequency α PAC direction, i.e., posterior-to-anterior rather than anterior-to-posterior. This suggested that they showed abnormal neurophysiological oscillatory mechanisms mainly led by δ frequencies underpinning FC from frontal to parietal cortical areas [ 309 ].…”

Beta–Gamma Phase-Amplitude Coupling as a Non-Invasive Biomarker for Parkinson’s Disease: Insights from Electroencephalography Studies

“…It can increase neural information flow and improve the behavioral performance of actions controlled by distant neural populations [ 40 ]. Abnormalities in PAC have been connected to disruptions in higher-order cognitive processes such as alpha–gamma PAC decrease, which was detected in Alzheimer’s dementia patients in comparison to healthy controls [ 46 ], while topographical changes in delta–theta PAC were observed in PD patients with mild cognitive impairment during a visual oddball task [ 47 ]. Apart from its crucial role in higher-order cognitive processes [ 20 ], a significant impact of PAC can be attributed to coordinating neural populations responsible for movement execution [ 15 ].…”