Cortical Network Analysis in Patients Affected by Schizophrenia

Abstract

In the present study, we studied the structural changes of the brain functional network in a group of schizophrenic (SCHZ) patients during a 2-back working memory task. Cortical signals were obtained from scalp EEG signals through the high-resolution EEG technique, which relies on realistic head models and linear inverse solutions. Functional networks were estimated by computing the spectral coherence--i.e. a measure of synchronization in the frequency domain--between the time series of all the available cortical sources. To analyze those cortical networks we followed a theoretical graph approach by computing the network density as the total number of links and the node degree as the number of links of each cortical source. The major result suggest that in the Alpha2 frequency band (11-13 Hz) the cortical functional networks of the SCHZ patients present the largest differences when compared with those of a group of control (CTRL) subjects. In particular, the structure of the SCHZ network altered radically during the memory task, as the number of links that were different from the REST condition increased sensibly with respect to the CTRL network. In addition, a compensatory mechanism was found in the SCHZ patients during the correct performance of the memory task where the node degree showed a frontal asymmetry with higher activation of the left frontal lobe--i.e. higher number of connections--in the Alpha2 frequency band.

Graph-based network analysis in schizophrenia

“…The same material was later analyzed with spectral analysis, coherence and construction of graphs from the coherence, and high-resolution EEG and graphs. These analyses showed the SWN disruption and, additionally, signs of hypofrontality with an asymmetry [62,63] . In another study with EEG signal recordings at rest, 40 young schizophrenics and 40 controls were estimated using a nonlinear method and the nonlinear correlation matrices were converted to weighted graphs.…”

“…2008: Liu et al [67] fMRI C, L, Eloc, Eglob, K, SWN 2009: Rubinov et al [64] EEG C, L, SWN 2009: Basset et al [66] MEG Cost efficiency 2010: Wang et al [77] fMRI SWN, efficiency 2010: van den Heuvel et al [40] DTI C, L, SWN 2010: De Vico Fallani et al [62] EEG Network density, degree 2010: Lynall et al [68] fMRI SWN, efficiency, hierarchy, degree dist, connectivity strength and diversity 2010: Alexander-Bloch et al [69] fMRI Modularity 2011: Jalili et al [65] EEG Degree, node strength, SWN, Eglob, modularity, centrality 2011: Zalesky et al [70] DTI SWN, nodal degree, C, L, efficiency 2011: Fornito et al [25] fMRI C, L, SWN, efficiency 2011: Yu et al [71] fMRI C, L, Eloc, Eglob, SWN 2011: Lord et al [79] fMRI…”

Differentiating transformational and non-transformational leaders on the basis of neurological imaging

“…For example, 90% coherence would indicate relatively high coupling or integration between brain locations, while 10% coherence would indicate relatively low coupling or differentiation between the locations. A sampling of EEG coherence studies includes, for example, examinations of cognition (Babiloni et al, 2010;Kislova & Rusalova, 2009;Martin-Loeches, Munoz-Ruata, Martinez-Lebrusant, & Gomez-Jari, 2001), heritability (van Baal, Boomsma, & de Geus, 2001;Van Beijsterveldt, Molenaar, de Geus, & Boomsma, 1998), gender differences (Hanlon, Thatcher, & Cline, 1999;Koles, Lind, & Flor-Henry, 2010), intelligence (Anokhin, Lutzenberger, & Birbaumer, 1999;Jausovec & Jausovec, 2003), and various clinical disorders (Babiloni et al, 2010;De Vico Fallani et al, 2010).…”

Exploring intermediate phenotypes with EEG: Working memory dysfunction in schizophrenia

“…Measures of functional connectivity in neural networks can be obtained through correlation analysis [160] or graph theory [15,36,145,155]. Networks with "small-world In summary, the reviewed studies suggest a relationship between impairments in synchronized oscillatory activity and perceptual and higher-level cognitive processing contributing to WM deficits in schizophrenia.…”