Abnormalities in hubs location and nodes centrality predict cognitive slowing and increased performance variability in first-episode schizophrenia patients

Abstract

Introducing the Minimum Spanning Tree (MST) algorithms to neural networks science eliminated the problem of arbitrary setting of the threshold for connectivity strength. Despite these advantages, MST has been rarely used to study network abnormalities in schizophrenia. An MST graph mapping a network structure is its simplification, therefore, it is important to verify whether the reconfigured network is significantly related to the behavioural dimensions of the clinical picture of schizophrenia. 35 first-episode schizophrenia patients and 35 matched healthy controls underwent an assessment of information processing speed, cognitive inter-trial variability modelled with ex-Gaussian distributional analysis of reaction times and resting-state EEG recordings to obtain frequency-specific functional connectivity matrices from which MST graphs were computed. The patients’ network had a more random structure and star-like arrangement with overloaded hubs positioned more posteriorly than it was in the case of the control group. Deficient processing speed in the group of patients was predicted by increased maximal betweenness centrality in beta and gamma bands, while decreased consistency in cognitive processing was predicted by the betweenness centrality of posterior nodes in the gamma band, together with duration of illness. The betweenness centrality of posterior nodes in the gamma band was also significantly correlated with positive psychotic symptoms in the clinical group.

Disentangling age‐ and disease‐related alterations in schizophrenia brain network using structural equation modeling: A graph theoretical study based on minimum spanning tree

“…As the critical backbone of the original network, MST structure could reflect fundamental topological alterations in the brain network in schizophrenia. It is worth noting that despite a significant inconsistency in graph theoretical studies of schizophrenia (Fornito, Zalesky, Pantelis, & Bullmore, 2012; van den Heuvel & Fornito, 2014), our findings of a more centralized MST in schizophrenia were validated under three other parcellation schemes and resonate with two previous schizophrenia pathology studies based on resting‐state EEG paradigm (Jonak et al, 2019; Krukow et al, 2019). In the first study, higher leaf fraction and reduced network diameter in MSTs in several frequency bands was found in schizophrenia patients; in the second study, patients with longer illness duration were found to exhibit more star‐like MST, characterized by higher leaf fraction and tree hierarchy index (closer to 0.5).…”

“…Comparisons can then be made based on MSTs constructed in different individuals, thus avoiding arbitrary thresholding or normalization protocols employed in conventional graph theoretical studies. It has been demonstrated that MST is critical to global network communication (Van Mieghem & Magdalena, 2005; Van Mieghem & Van Langen, 2005; Wang, Hernandez, & Van Mieghem, 2008) and the disruption of MST structure has been found in various neuropsychiatric disorders (Stam et al, 2014), including in two schizophrenia electroencephalography (EEG) studies (Jonak, Krukow, Jonak, Grochowski, & Karakuła‐Juchnowicz, 2019; Krukow, Jonak, Karpiński, & Karakuła‐Juchnowicz, 2019). However, to the best of our knowledge, there was no previous study, which applied the MST approach, together with rs‐fMRI, to disentangle network‐level dysregulations in schizophrenia.…”

Widespread Reductions of Spontaneous Neurophysiological Activity in Leber’s Disease—An Application of EEG Source Current Density Reconstruction

“…After the segmentation, each epoch was visually inspected by a certified clinical neurophysiologist, who removed bad epochs containing artifacts (i.e., head or muscle movements, electrode cable movements, or jaw clenching) from the analysis. Finally, for each participant, 135 visual-artifact-free epochs were selected [ 14 ].…”

“…Electroencephalography (EEG) is another functional neuroimaging method that allows for the assessment of electrical potentials of the brain [ 13 , 14 ]. In comparison to fMRI, the application of EEG enables the accurate observation of the neural processes occurring in the brain cortex with very high temporal precision [ 15 ].…”

Manipulations of the Response-Stimulus Intervals as a Factor Inducing Controlled Amount of Reaction Time Intra-Individual Variability

“…IIV may also be used as a valid parameter in predictions regarding risk of dementia onset [20,21]. Of note, increased IIV explained a substantial part of processing speed deficit in schizophrenia and bipolar disorder [22,23], what is of special importance considering that slowdown is not only one of the most pronounced neuropsychological impairment in these groups, but also explain differences between patients and controls regarding all other cognitive dimensions [24][25][26].…”