EEG Cortical Connectivity Analysis of Working Memory Reveals Topological Reorganization in Theta and Alpha Bands

Abstract

Numerous studies have revealed various working memory (WM)-related brain activities that originate from various cortical regions and oscillate at different frequencies. However, multi-frequency band analysis of the brain network in WM in the cortical space remains largely unexplored. In this study, we employed a graph theoretical framework to characterize the topological properties of the brain functional network in the theta and alpha frequency bands during WM tasks. Twenty-eight subjects performed visual n-back tasks at two difficulty levels, i.e., 0-back (control task) and 2-back (WM task). After preprocessing, Electroencephalogram (EEG) signals were projected into the source space and 80 cortical brain regions were selected for further analysis. Subsequently, the theta- and alpha-band networks were constructed by calculating the Pearson correlation coefficients between the power series (obtained by concatenating the power values of all epochs in each session) of all pairs of brain regions. Graph theoretical approaches were then employed to estimate the topological properties of the brain networks at different WM tasks. We found higher functional integration in the theta band and lower functional segregation in the alpha band in the WM task compared with the control task. Moreover, compared to the 0-back task, altered regional centrality was revealed in the 2-back task in various brain regions that mainly resided in the frontal, temporal and occipital lobes, with distinct presentations in the theta and alpha bands. In addition, significant negative correlations were found between the reaction time with the average path length of the theta-band network and the local clustering of the alpha-band network, which demonstrates the potential for using the brain network metrics as biomarkers for predicting the task performance during WM tasks.

Better ears with eyes open: effects of multisensory stimulation with nonconscious visual stimuli on auditory learning

“…Tesche and Karhu (2000) report that auditory stimulus-evoked theta oscillations were related to neural networks encompassing, for example, the hippocampus. It is indeed expected that tasks like the one used here recruits a large network, consistently with findings that theta oscillations play an integrative role during cognitive demand (Sarnthein et al, 1998;Sauseng et al, 2010;Dai et al, 2017).…”

The Dynamic Properties of a Brain Network During Spatial Working Memory Tasks in College Students With ADHD Traits

“…Some studies investigating functional connectivity and brain networks of working memory using EEG/MEG (magnetoencephalography) in healthy subjects observed the connectivity between frontotemporal, central-parietal, and occipital areas during working memory tasks ( Chou et al, 2015 ; Wianda and Ross, 2019 ), and small-world network characteristics with a high clustering coefficient and low characteristic path length. These results imply that the brain regions involved in processing information consecutively while performing working memory tasks function efficiently ( Shahabi et al, 2014 ; Dai et al, 2017 ). Studies using EEG on ADHD patients to investigate functional connectivity and brain networks in working memory are limited.…”

Anterior cingulate cortex differently modulates fronto-parietal functional connectivity between resting-state and working memory tasks

“…Because of the presence of functional connectivity during resting-state, it would be more critical to investigate the relative changes of functional connectivity during working memory tasks. Electroencephalogram (EEG) studies typically show increased connectivity in the theta band and reduced connectivity in the alpha band between fronto-parietal regions (Babiloni et al, 2004; Dai et al, 2017; Sauseng, Klimesch, Schabus, & Doppelmayr, 2005). As blood-oxygen-level dependent (BOLD) signals measured by functional MRI (fMRI), the signal synchronizations between some of the fronto-parietal regions were found to be reduced during higher working memory load condition compared with control condition, although these regions were more activated in the same contrast (Di & Biswal, 2019).…”