Functional EEG network analysis in schizophrenia: Evidence of larger segregation and deficit of modulation.
Higher mental functions depend on global cerebral functional coordination. Our aim was to study fast modulation of functional networks in schizophrenia that has not been previously assessed.



Graph-theory was used to analyze the electroencephalographic (EEG) activity during an odd-ball task in 57 schizophrenia patients (18 first episode patients, FEPs) and 59 healthy controls. Clustering coefficient (CLC), characteristic path length (PL) and small-worldness (SW) were computed at baseline ([-300 0] ms prior to stimulus delivery) and response ([150 450] ms post-stimulus) windows. Clinical and cognitive assessments were performed.



CLC, PL and SW showed a significant modulation between baseline and response in controls but not in patients. Patients obtained higher CLC and SW at baseline, lower CLC and higher PL at response, and diminished modulation of CLC and SW as compared to controls. In patients, CLC and SW modulation were inversely associated to cognitive performance in executive tasks and directly associated to working memory. Similar patterns were observed in FEPs. CLC and SW during the baseline were inversely associated to their respective modulation magnitudes.



Our results are coherent with a hyper-segregated network at baseline (higher CLC) and a decreased modulation of the functional connectivity during cognition in schizophrenia.
Biomedical Engineering Group, Department TSCIT, ETS Ingenieros de Telecomunicación, University of Valladolid, Spain.
Javier
J
Gomez-Pilar
Psychiatry Department, School of Medicine, University of Valladolid, Spain.
Alba
A
Lubeiro
Biomedical Engineering Group, Department TSCIT, ETS Ingenieros de Telecomunicación, University of Valladolid, Spain; Instituto de Investigación en Matemática (IMUVA), University of Valladolid, Spain; Neuroscience Institute of Castilla y León (INCYL), University of Salamanca, Spain.
Jesús
J
Poza
Biomedical Engineering Group, Department TSCIT, ETS Ingenieros de Telecomunicación, University of Valladolid, Spain; Instituto de Investigación en Matemática (IMUVA), University of Valladolid, Spain; Neuroscience Institute of Castilla y León (INCYL), University of Salamanca, Spain.
Roberto
R
Hornero
Clinical Neurophysiology Service, University Hospital of Valladolid, Valladolid, Spain.
Marta
M
Ayuso
Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain; Psychiatry Service, University Hospital of Alava, Spain.
César
C
Valcárcel
Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain; Psychiatry Service, University Hospital of Alava, Spain.
Karim
K
Haidar
Psychiatry Service, University Hospital of Valladolid, Valladolid, Spain.
José A
JA
Blanco
Neuroscience Institute of Castilla y León (INCYL), University of Salamanca, Spain; Psychiatry Service, University Hospital of Valladolid, Valladolid, Spain.. Electronic address: vicente.molina@uva.es.
Vicente
V
Molina
D000328:Adult; D004569:Electroencephalography / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D059907:Functional Neuroimaging; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D012559:Schizophrenia / Q000503:physiopathology*; D055815:Young Adult
Complex network theory; Electroencephalography; Evoked response; Schizophrenia