Functional Connectivity and Brain Networks in Schizophrenia

Abstract

Schizophrenia has often been conceived as a disorder of connectivity between components of large-scale brain networks. We tested this hypothesis by measuring aspects of both functional connectivity and functional network topology derived from resting-state fMRI time series acquired at 72 cerebral regions over 17 min from 15 healthy volunteers (14 male, 1 female) and 12 people diagnosed with schizophrenia (10 male, 2 female). We investigated between-group differences in strength and diversity of functional connectivity in the 0.06 -0.125 Hz frequency interval, and some topological properties of undirected graphs constructed from thresholded interregional correlation matrices. In people with schizophrenia, strength of functional connectivity was significantly decreased, whereas diversity of functional connections was increased. Topologically, functional brain networks had reduced clustering and small-worldness, reduced probability of high-degree hubs, and increased robustness in the schizophrenic group. Reduced degree and clustering were locally significant in medial parietal, premotor and cingulate, and right orbitofrontal cortical nodes of functional networks in schizophrenia. Functional connectivity and topological metrics were correlated with each other and with behavioral performance on a verbal fluency task. We conclude that people with schizophrenia tend to have a less strongly integrated, more diverse profile of brain functional connectivity, associated with a less hub-dominated configuration of complex brain functional networks. Alongside these behaviorally disadvantageous differences, however, brain networks in the schizophrenic group also showed a greater robustness to random attack, pointing to a possible benefit of the schizophrenia connectome, if less extremely expressed.

Reduced specialized processing in psychotic disorder: a graph theoretical analysis of cerebral functional connectivity

“…2010; Lynall et al. 2010; Micheloyannis 2012). The clustering coefficient is a measure of functional segregation, which is the ability for specialized processing to occur within highly interconnected brain regions (Rubinov and Sporns 2010).…”

“…2010; Lynall et al. 2010) or the reverse (longer characteristic path length) (Liu et al. 2008; Yu et al.…”

“…2010; Lynall et al. 2010). In other words, the evidence to date suggests that functional brain networks have a more random organization in patients with schizophrenia than in healthy controls.…”

Increased thalamic centrality and putamen–thalamic connectivity in patients with parkinsonian resting tremor

“…Of note, measures of within‐module degree and participation coefficient are dependent on optimal modularity estimates; therefore, we also examined the group differences in modularity to ensure that the centrality differences were not confounded by the deviations in modular partition qualities. Because the measured graph metrics are highly interdependent (Cao et al., 2014; Lynall et al., 2010) and our primary hypothesis relates to the bilateral thalami, no specific multiple corrections were needed. Statistical significance was thus set at p  < .05.…”

Structure and dynamics of functional networks in child-onset schizophrenia

“…The description of the large-scale human brain organization has allowed studying the hypothesis that some neuropsychiatric disorders are related to disarrays of connectivity between cortical areas. Indeed, aberrant structural patterns have been verified in the brain organization of subjects with autism, schizophrenia, depression, anxiety disorders, Alzheimer's disease and frontotemporal dementia (Supekar et al, 2008;He et al, 2008;Bassett et al, 2008;Bassett and Bullmore, 2009;Lynall et al, 2010;Menon, 2011). Revealing these disorder related differences has improved the understanding of how dysfunction of cognitive and emotion regulation processes are related to the altered brain network organization.…”