title: Functional connectivity assessed by resting state EEG correlates with cognitive decline of Alzheimer's disease - An eLORETA study.
abstract: OBJECTIVE
  To explore neurophysiological biomarkers of Alzheimer's disease (AD), we investigated electroencephalography (EEG) of AD patients, and assessed lagged phase synchronization, a measure of brain functional connectivity.
  
  
  METHODS
  Twenty-eight probable AD patients and 30 healthy controls (HC) were enrolled. Forty seconds of artifact-free EEG data were selected and compared between patients with AD and HC. Current source density (CSD) and lagged phase synchronization were analyzed by using eLORETA.
  
  
  RESULTS
  Patients with AD showed significantly decreased lagged phase synchronization between most cortical regions in delta band relative to controls. There also was a decrease in lagged phase synchronization between the right dorsolateral prefrontal cortex (DLPFC) and the right posterior-inferior parietal lobule (pIPL) in theta band. In addition, some connections in delta band were found to be associated with cognitive function, measured by MMSE. This involved specifically interhemispheric temporal connections as well as left inferior parietal connectivity with the left hippocampus, lateral frontal regions, and the anterior cingulate cortex (aCC). Right temporal connections in delta band were related to global function, as estimated by CDR. No differences were found in CSD analysis between patients and HC.
  
  
  CONCLUSIONS
  Functional connectivity disruptions between certain brain regions, as measured with lagged phase synchronization, may potentially represent a neurophysiological biomarker of AD.
  
  
  CONCLUSIONS
  Our study indicated that AD and healthy elderly could have the different patterns of lagged phase synchronization.
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hata
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kazui
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan. Electronic address: ishii@psy.med.osaka-u.ac.jp.
authors.forename: Ryouhei
authors.initials: R
authors.lastname: Ishii
authors.affiliation: UCM-UPM Centre for Biomedical Technology, Department of Cognitive and Computational Neuroscience, Complutense University of Madrid, Madrid, Spain.
authors.forename: Leonides
authors.initials: L
authors.lastname: Canuet
authors.affiliation: The KEY Institute for Brain-Mind Research, University Hospital of Psychiatry, Zurich, Switzerland; Department of Psychiatry, Kansai Medical University, Osaka, Japan.
authors.forename: Roberto D
authors.initials: RD
authors.lastname: Pascual-Marqui
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan; Osaka Psychiatric Medical Center, Osaka, Japan.
authors.forename: Shunichiro
authors.initials: S
authors.lastname: Ikeda
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Kanemoto
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yoshiyama
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Iwase
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Takeda
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D003072:Cognition Disorders / Q000175:diagnosis / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000503:physiopathology*; D012146:Rest / Q000502:physiology
keywords: Alzheimer’s disease; CDR (Clinical Dementia Rating); Dementia; EEG; Functional connectivity; LORETA; Lagged phase synchronization; MMSE (Mini-Mental State Examination)