Graph-based analysis of brain connectivity in schizophrenia

Abstract

The present study evaluated brain connectivity using electroencephalography (EEG) data from 14 patients with schizophrenia and 14 healthy controls. Phase-Locking Value (PLV), Phase-Lag Index (PLI) and Directed Transfer Function (DTF) were calculated for the original EEG data and following current source density (CSD) transformation, re-referencing using the average reference electrode (AVERAGE) and reference electrode standardization techniques (REST). The statistical analysis of adjacency matrices was carried out using indices based on graph theory. Both CSD and REST reduced the influence of volume conducted currents. The largest group differences in connectivity were observed for the alpha band. Schizophrenic patients showed reduced connectivity strength, as well as a lower clustering coefficient and shorter characteristic path length for both measures of phase synchronization following CSD transformation or REST re-referencing. Reduced synchronization was accompanied by increased directional flow from the occipital region for the alpha band. Following the REST re-referencing, the sources of alpha activity were located at parietal rather than occipital derivations. The results of PLV and DTF demonstrated group differences in fronto-posterior asymmetry following CSD transformation, while for PLI the differences were significant only using REST. The only analysis that identified group differences in inter-hemispheric asymmetry was DTF calculated for REST. Our results suggest that a comparison of different connectivity measures using graph-based indices for each frequency band, separately, may be a useful tool in the study of disconnectivity disorders such as schizophrenia.

Reduced interhemispheric and increased intrahemispheric connectivity in schizophrenia brain networks

“…This was seen during eyes open and closed. Comparing schizophrenia to healthy controls at rest, Olejarczyk and Jernajczyk showed DTF influence originating from central, parietal and occipital electrodes towards all electrodes in both groups, and no influence from frontal (polar) or temporal electrodes (Olejarczyk and Jernajczyk, 2017). Although they did not show the differences in network strength, we believe that the DTF influence reductions we found for central and parieto-occipital regions are in line with their findings.…”

“…Data were rereferenced to average (Dien, 1998), followed by reference electrode standardisation (REST) (Yao, 2001;Dong et al, 2017), using electrode positions estimated by the BESA four-shell spherical model. REST reduces volume conduction and reference bias and is recommended for network analysis, especially in high-density setups with more than 60 (preferably 100) electrodes (Chella et al, 2016;Olejarczyk and Jernajczyk, 2017).…”

“…More recently, network analysis to assess brain connectivity rather than activity has gained importance in neurophysiological research (Fornito and Bullmore, 2015). Several studies have shown that brain connectivity is also disturbed in schizophrenia patients during resting state (Andreou et al, 2014(Andreou et al, , 2015Unschuld et al, 2014;Alonso-solís et al, 2015;Olejarczyk and Jernajczyk, 2017;Larsen et al, 2018) and in individual task-related EEG measurements such as the auditory oddball (Bachiller et al, 2015).…”

Development of a Machine Learning Based Algorithm To Accurately Detect Schizophrenia based on One-minute EEG Recordings

“…Page 3217 F20.0 diagnosed paranoid schizophrenia, who were hospitalized at the Institute of Psychiatry and Neurology in Warsaw, Poland, and 14 healthy controls (7 males: 26.8 ± 2.9, 7 females: 28.7 ± 3.4 years) [28]. The patients had to undergo a medication washout of at least seven days.…”

Graph Signal Processing of Low and High-Order Dynamic Functional Connectivity Networks Using EEG Resting-State for Schizophrenia: A Whole Brain Breakdown

“…A recent EEG study at resting-state explored aberrant functional brain connectivity induced by schizophrenia adopting three connectivity estimators, alternative network metrics and two reference systems (Olejarczyk and Jernajczyk, 2017). They revealed the inter-hemispheric asymmetric group-difference using DTF granger causality estimator at resting-state.…”