Browsing by Author "Gunduz, Duygu Hunerli"

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Citation - WoS: 9
Citation - Scopus: 8
Abnormal Cross Frequency Coupling of Brain Electroencephalographic Oscillations Related To Visual Oddball Task in Parkinson's Disease With Mild Cognitive Impairment
(Sage Publications Inc, 2023) Bayraktaroglu, Zubeyir; Akturk, Tuba; Yener, Görsev; de Graaf, Tom A.; Hanoglu, Lutfu; Yildirim, Ebru; Gunduz, Duygu Hunerli
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.
Citation - WoS: 2
Resting-State Eeg Findings in Differentiating Alzheimer's Disease From Amnestic Mild Cognitive Impairment and Healthy Elderly Controls
(Galenos Publ House, 2021) Kayal, Ozgecan; Gunduz, Duygu Hunerli; Yerlikaya, Deniz; Yener, Görsev
Objective: We aimed at investigating alterations in Resting-State electroencephalography (rsEEG) patterns of individuals with amnestic mild cognitive impairment (aMCI), and Alzheimer's disease (AD). Materials and Methods: Twenty healthy controls (HC) with 20 aMCI, and 20 AD patients were included in the study. EEG data was recorded for 4 minutes of eyes-closed condition according to the International 10-20 system. EEG rhythms of interest were delta (0.5-3.9 Hz), theta (4-7.8 Hz), alpha 1 (8-10.4 Hz), alpha 2 (10.5-13 Hz), and beta (13-30 Hz). The discriminatory power of rsEEG between groups was evaluated using the receiver operating characteristic analysis. Correlations among cognitive scores and power values of rsEEG were analyzed using Pearson correlation analysis. Results: We observed effects on delta [F-(2.57): 8.353; p=0.001}, theta [F-(2.57): 5.038; p=0.010}, alpha 1 [F-(2.57): 3.837; p=0.027}, and alpha 2 [F-(2.57): 4.209; p=0.020} power between groups. Moreover, interaction effects for anterior-posterior electrode location x group on delta [F-(6.171): 2.621; p=0.038}, and theta [F-(6.171): 3.537; p=0.020} power were also detected. AD group demonstrated decreased delta power in frontal, central and parietal locations (for all; p<0.040) compared to HC and aMCI groups. In addition, the AD group also had decreased alpha and alpha1 power in comparison with HC (for all; p<0.026). Furthermore, we recorded a sensitivity of 80.0% and a specificity of 80.0% of delta power when using the cut-off score of >1.71 to identify AD from aMCI at central electrodes, and >1.73 to identify AD from HC at parietal electrodes. Moderate correlations were also detected among cognitive scores and rsEEG rhythms. Conclusion: This study revealed the importance of delta and theta activity in rsEEG both as an electrophysiological indicator of cognitive status in AD and as a discriminatory tool for detecting aMCI.