title: Small-world networks and disturbed functional connectivity in schizophrenia.
abstract: Disturbances in "functional connectivity" have been proposed as a major pathophysiological mechanism for schizophrenia, and in particular, for cognitive disorganization. Detection and estimation of these disturbances would be of clinical interest. Here we characterize the spatial pattern of functional connectivity by computing the "synchronization likelihood" (SL) of EEG at rest and during performance of a 2Back working memory task using letters of the alphabet presented on a PC screen in subjects with schizophrenia and healthy controls. The spatial patterns of functional connectivity were then characterized with graph theoretical measures to test whether a disruption of an optimal spatial pattern ("small-world") of the functional connectivity network underlies schizophrenia. Twenty stabilized patients with schizophrenia, who were able to work, and 20 healthy controls participated in the study. During the working memory (WM) task healthy subjects exhibited small-world properties (a combination of local clustering and high overall integration of the functional networks) in the alpha, beta and gamma bands. These properties were not present in the schizophrenia group. These findings are in accordance with a partially inadequate organization of neuronal networks in subjects with schizophrenia. This method could be helpful for diagnosis and evaluation of the severity of the disease, as well as understanding the pathophysiologic mechanisms underlying cognitive dysfunction in schizophrenia.
authors.affiliation: University of Crete, Medical Division, 71409 Iraklion Crete, Greece. michelosifis@yahoo.com
authors.forename: Sifis
authors.initials: S
authors.lastname: Micheloyannis
authors.forename: Ellie
authors.initials: E
authors.lastname: Pachou
authors.forename: Cornelis Jan
authors.initials: CJ
authors.lastname: Stam
authors.forename: Michael
authors.initials: M
authors.lastname: Breakspear
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Bitsios
authors.forename: Michael
authors.initials: M
authors.lastname: Vourkas
authors.forename: Sophia
authors.initials: S
authors.lastname: Erimaki
authors.forename: Michael
authors.initials: M
authors.lastname: Zervakis
mesh_terms: D000328:Adult; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000453:epidemiology; D009415:Nerve Net / Q000503:physiopathology*; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D012720:Severity of Illness Index