title: Resting-state connectivity in the prodromal phase of schizophrenia: insights from EEG microstates.
abstract: BACKGROUND
  Resting-state EEG microstates are thought to reflect the momentary local states and interactions of distributed neural networks in the brain. Several changes in resting-state EEG microstates have been described in acutely ill patients with schizophrenia, but it is not known whether these represent trait or state abnormalities. The present study aimed to investigate this issue by assessing EEG microstate characteristics in high-risk individuals (HR) and clinically stable first-episode patients with schizophrenia (SZ) with low symptom levels, compared to each other and healthy controls (HC).
  
  
  METHODS
  Participants were 18 HR, 18 SZ, and 22 HC subjects. 64-channel resting-state EEG recordings were used for microstate analyses. Microstates were clustered into four classes (A-D) according to their topography. Temporal parameters and topographies of microstates were compared among groups.
  
  
  RESULTS
  Microstate class A displayed higher coverage and occurrence in HR than SZ and HC, while microstate class B covered significantly more time in SZ compared to both HR and HC. Microstate class B displayed an aberrant spatial configuration in SZ, and to a lesser extent also in HR, compared to HC, with patients exhibiting significantly higher activity in the vicinity of the left posterior cingulate.
  
  
  CONCLUSIONS
  Microstate abnormalities observed in HR were similar to those previously reported in acutely ill patients with schizophrenia. Moreover, there was evidence that HR and SZ might share specific disturbances in brain functional connectivity. These findings raise the possibility that certain abnormalities in resting-state EEG microstates might be associated with an increased risk for psychosis.
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany. Electronic address: c.andreou@uke.de.
authors.forename: Christina
authors.initials: C
authors.lastname: Andreou
authors.affiliation: The KEY Institute for Brain-Mind Research, University Hospital of Psychiatry, CH-8032 Zurich, Switzerland.
authors.forename: Pascal L
authors.initials: PL
authors.lastname: Faber
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Leicht
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schoettle
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Nenad
authors.initials: N
authors.lastname: Polomac
authors.affiliation: Developmental Neurophysiology, Center for Molecular Neurobiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Ileana L
authors.initials: IL
authors.lastname: Hanganu-Opatz
authors.affiliation: The KEY Institute for Brain-Mind Research, University Hospital of Psychiatry, CH-8032 Zurich, Switzerland.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Lehmann
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mulert
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D012146:Rest / Q000502:physiology*; D012559:Schizophrenia / Q000503:physiopathology*; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
keywords: At-risk mental state; Connectivity; EEG; Microstates; Resting-state; Schizophrenia