title: Memory-related EEG power and coherence reductions in mild Alzheimer's disease.
abstract: OBJECTIVE
  To examine memory-related EEG power and coherence over temporal and central recording sites in patients with early Alzheimer's disease (AD) and normal controls.
  
  
  METHODS
  EEG was recorded from central (Fz, Cz and Pz) and temporal (T3 and T4) electrodes while ten very mild AD patients and ten controls performed a Sternberg-type memory scanning task with three levels of working memory load. Spectral power in delta (0-3 Hz), theta (3-5 Hz), lower alpha1 (5-7 Hz), lower alpha2 (7-9 Hz), upper alpha (9-11 Hz) and beta (15-30 Hz) was averaged for temporal and central electrodes. Coherence was averaged between central electrodes, between central and right temporal electrodes and between central and left temporal electrodes.
  
  
  RESULTS
  While behavioral performance of very mild AD patients did not differ significantly from that of normal controls, findings suggest that normal controls but not AD patients respond to memory demands by increasing upper alpha power over temporal cortex. When compared with normal controls, AD patients had reduced upper alpha coherence between central and right temporal cortex.
  
  
  CONCLUSIONS
  Results are consistent with previous research on the role of upper alpha in semantic memory and suggest that very mild AD may inhibit selective synchronization of upper alpha in temporal lobes. Reduced coherence between central and temporal cortex is discussed in light of a neurological model of AD that hypothesizes reduced electrocortical efficiency and a breakdown of neural network communication to temporal lobes possibly resulting from temporal lobe atrophy.
authors.affiliation: Mercer's Institute for Research on Ageing, St. James's Hospital, Dublin, Ireland. michael.hogan@nuigalway.ie
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hogan
authors.forename: Gregory R J
authors.initials: GR
authors.lastname: Swanwick
authors.forename: Jochen
authors.initials: J
authors.lastname: Kaiser
authors.forename: Michael
authors.initials: M
authors.lastname: Rowan
authors.forename: Brian
authors.initials: B
authors.lastname: Lawlor
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000503:physiopathology; D002540:Cerebral Cortex / Q000503:physiopathology; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D012720:Severity of Illness Index