title: EEG coherence characteristics at rest and during a three-level working memory task in normal aging and mild cognitive impairment.
abstract: BACKGROUND
  The aim was to examine and compare the characteristics of intra- and inter-hemispheric EEG coherence in patients with mild cognitive impairment (MCI) and healthy controls at rest and during a working memory (WM) task having three levels.
  
  
  METHODS
  The subjects included 35 patients with MCI according to the DSM-IV criteria (mean age: 62.3+/-6.5 years) and 34 healthy controls (mean age: 57.4+/-4.0) selected from the community. All the subjects performed a simple calculation and recall task of WM with three levels of (WM1-3) while their EEG signal was recording. Inter- and intra-hemispheric EEG coherence was analyzed during the WM loads.
  
  
  RESULTS
  Intra- and inter-hemispheric coherence during the WM task showed a "drop-to-rise" tendency compared with that at-rest condition. There was significantly higher coherence in MCI patients than in controls during the WM task. Intra-hemispheric ortical connectivity diminished while inter-hemispheric connectivity dominated in the MCI patients during WM with increasing task difficulty.
  
  
  CONCLUSIONS
  MCI patients and normal controls may have differences in cortical connection and MCI patients have a cortical connection disturbance during WM tasks. With increasing task difficulty the MCI patients mobilized more inter-hemispheric than intra-hemispheric cognitive resources.
authors.affiliation: Department of Psychiatry, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China. Jiang_zju@mail.hz.zj.cn
authors.forename: Zheng-Yan
authors.initials: ZY
authors.lastname: Jiang
authors.forename: Lei-Lei
authors.initials: LL
authors.lastname: Zheng
authors.forename: En-Yan
authors.initials: EY
authors.lastname: Yu
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D003072:Cognition Disorders / Q000503:physiopathology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011597:Psychomotor Performance