title: Quantitative EEG in Alzheimer's disease: cognitive state, resting state and association with disease severity.
abstract: BACKGROUND
  Quantitative electroencephalogram (qEEG) recorded during cognitive tasks has been shown to differentiate between patients with Alzheimer's disease (AD) and healthy individuals. However, the association between various qEEG markers recorded during mnestic paradigms and clinical measures of AD has not been studied in detail.
  
  
  OBJECTIVE
  To evaluate if 'cognitive' qEEG is a useful diagnostic option, particularly if memory paradigms are used as cognitive stimulators.
  
  
  METHODS
  This study is part of the Prospective Registry on Dementia in Austria (PRODEM), a multicenter dementia research project. A cohort of 79 probable AD patients was included in a cross-sectional analysis. qEEG recordings performed in resting states were compared with recordings during cognitively active states. Cognition was evoked with a face-name paradigm and a paired-associate word list task, respectively. Relative band powers, coherence and auto-mutual information were computed as functions of MMSE scores for the memory paradigms and during rest. Analyses were adjusted for the co-variables age, sex, duration of dementia and educational level.
  
  
  RESULTS
  MMSE scores explained 36-51% of the variances of qEEG-markers. Face-name encoding with eyes open was superior to resting state with eyes closed in relative theta and beta1 power as well as coherence, whereas relative alpha power and auto-mutual information yielded more significant results during resting state with eyes closed. The face-name task yielded stronger correlations with MMSE scores than the verbal memory task.
  
  
  CONCLUSIONS
  qEEG alterations recorded during mnestic activity, particularly face-name encoding showed the highest association with the MMSE and may serve as a clinically valuable marker for disease severity.
authors.affiliation: AIT Austrian Institute of Technology GmbH, A-1220 Vienna, Austria. Electronic address: heinrich.garn@ait.ac.at.
authors.forename: Heinrich
authors.initials: H
authors.lastname: Garn
authors.affiliation: AIT Austrian Institute of Technology GmbH, A-1220 Vienna, Austria. Electronic address: markus.waser@ait.ac.at.
authors.forename: Markus
authors.initials: M
authors.lastname: Waser
authors.affiliation: Vienna University of Technology, A-1220 Vienna, Austria. Electronic address: manfred.deistler@tuwien.ac.at.
authors.forename: Manfred
authors.initials: M
authors.lastname: Deistler
authors.affiliation: Department of Neurology, Graz Medical University, A-8036 Graz, Austria. Electronic address: reinhold.schmidt@medunigraz.at.
authors.forename: Reinhold
authors.initials: R
authors.lastname: Schmidt
authors.affiliation: Department of Neurology, Vienna Medical University, A-1090 Vienna, Austria. Electronic address: peter.dal-bianco@meduniwien.ac.at.
authors.forename: Peter
authors.initials: P
authors.lastname: Dal-Bianco
authors.affiliation: Department of Neurology, Linz General Hospital, A-4020 Linz, Austria. Electronic address: gerhard.ransmayr@akh.linz.at.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Ransmayr
authors.affiliation: Department of Neurology, Vienna Medical University, A-1090 Vienna, Austria. Electronic address: josef.zeitlhofer@meduniwien.ac.at.
authors.forename: Josef
authors.initials: J
authors.lastname: Zeitlhofer
authors.affiliation: Department of Neurology, Graz Medical University, A-8036 Graz, Austria. Electronic address: helena.schmidt@medunigraz.at.
authors.forename: Helena
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Department of Neurology, Graz Medical University, A-8036 Graz, Austria. Electronic address: stephan.seiler@medunigraz.at.
authors.forename: Stephan
authors.initials: S
authors.lastname: Seiler
authors.affiliation: Department of Neurology, Innsbruck Medical University, A-6020 Innsbruck, Austria. Electronic address: guenther.sanin@i-med.ac.at.
authors.forename: Guenter
authors.initials: G
authors.lastname: Sanin
authors.affiliation: Department of Neurology, Linz General Hospital, A-4020 Linz, Austria. Electronic address: georg.caravias@akh.linz.at.
authors.forename: Georg
authors.initials: G
authors.lastname: Caravias
authors.affiliation: Department of Neurology, Vienna Medical University, A-1090 Vienna, Austria. Electronic address: peter.santer@meduniwien.ac.at.
authors.forename: Peter
authors.initials: P
authors.lastname: Santer
authors.affiliation: Dr. Grossegger & Drbal GmbH, A-1190 Vienna, Austria. Electronic address: office@alphatrace.at.
authors.forename: Dieter
authors.initials: D
authors.lastname: Grossegger
authors.affiliation: Dr. Grossegger & Drbal GmbH, A-1190 Vienna, Austria. Electronic address: w.fruehwirt@alphatrace.at.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Fruehwirt
authors.affiliation: Department of Neurology, Innsbruck Medical University, A-6020 Innsbruck, Austria. Electronic address: thomas.benke@i-med.ac.at.
authors.forename: Thomas
authors.initials: T
authors.lastname: Benke
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications* / Q000235:genetics; D001057:Apolipoproteins E / Q000235:genetics; D001245:Association Learning / Q000502:physiology; D058256:Brain Waves / Q000502:physiology; D003072:Cognition Disorders / Q000209:etiology*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008609:Mental Status Schedule; D008875:Middle Aged; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D012146:Rest / Q000502:physiology*
chemical_list: D001057:Apolipoproteins E
keywords: Alzheimer's disease; Cognitive state; Quantitative EEG; Resting state