title: MEG spectral profile in Alzheimer's disease and mild cognitive impairment.
abstract: OBJECTIVE
  In this study, we applied a novel procedure to calculate the mean frequency from the Magnetoencephalography (MEG) signals of 22 patients with Alzheimer's Disease (AD), 22 patients with mild cognitive impairment (MCI), and 21 healthy controls. A significant mean frequency decrease was expected in pathological groups. MCI subjects are expected to show intermediate mean frequency values between AD patients and controls.
  
  
  METHODS
  MEG signal was obtained from a whole-head 148 channels magnetometer in a resting condition. We estimated the power spectral density from the MEG signal by means of the Fourier transform of the autocorrelation function. Then, we computed the mean frequency for each subject.
  
  
  RESULTS
  Mean frequency was higher in controls (12.46 +/- 2.00 Hz, mean +/- SD) than in MCI subjects (10.82 +/- 2.21 Hz) with significant differences (P < 0.05). Moreover, mean frequency values in MCI subjects were higher than in AD patients (9.06 +/- 2.48 Hz, P < 0.05). We also detected a decrease of 0.17 Hz per year in mean frequency from normal subjects' MEG (P < 0.05)
  
  
  CONCLUSIONS
  Results demonstrated that the approach adopted for the calculation of a mean frequency score seems to be adequate and sensitive to detect differences between normal aging, cognitive deterioration and AD. In addition, data may contribute to the theoretical discussion on the nature of mild cognitive impairment and its similitudes with Alzheimer's disease.
  
  
  CONCLUSIONS
  This paper may be considered a first step to obtain a reliable measure which summarizes spectral information, and might be of a potential clinical interest.
authors.affiliation: Centro de Magnetoencefalografía Dr Pérez-Modrego, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Fernández
authors.forename: Roberto
authors.initials: R
authors.lastname: Hornero
authors.forename: Agustín
authors.initials: A
authors.lastname: Mayo
authors.forename: Jesús
authors.initials: J
authors.lastname: Poza
authors.forename: Pedro
authors.initials: P
authors.lastname: Gil-Gregorio
authors.forename: Tomás
authors.initials: T
authors.lastname: Ortiz
mesh_terms: D000367:Age Factors; D000368:Aged; D000544:Alzheimer Disease / Q000503:physiopathology*; D001931:Brain Mapping; D003072:Cognition Disorders / Q000503:physiopathology*; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D013057:Spectrum Analysis