title: [Spectral analysis of EEG coherence in Alzheimer's disease].
abstract: BACKGROUND
  In analysis of the electrical activity of the brain, coherence is a measure of the degree of synchrony between two or more regions of the brain with regard to their frequency values over a unit of time.
  
  
  OBJECTIVE
  To explore the functional alterations caused by Alzheimer's disease (AD), by evaluating the behaviour of coherence over the whole spectrum of EEG frequencies.
  
  
  METHODS
  We studied a group of 42 patients with AD, according to criteria of the NINCDS ADRDA group. Partial coherence (e.g. between two derivations each time) was calculated within and between hemispheres, during a state of mental rest; the Z statistic was also determined by comparing the coherence values with the standard data for age, sex and functional state of the brain.
  
  
  RESULTS
  Significantly low coherence values were obtained for the frontal central regions of the left hemisphere (LH) and for the occipital parietal regions of the right hemisphere (RH) in the delta band. The same localisations were carried out for the theta band, in addition to the centrotemporal and temporal regions of the LH. The highest incoherence values were observed for the alpha and beta bands, more specifically in frontal central and occipital parietal derivations of the RH, and temporal derivations of the LH.
  
  
  CONCLUSIONS
  Non activated partial coherence acts as an indicator of the degree of functional disconnection between brain regions in AD. Studying activated coherence in these patients could contribute new elements to our knowledge about the functional disorders observed in this disease.
authors.affiliation: Instituto Nacional de Neurologia y Neurocirugia, La Habana, Cuba. pedrol@informed.sld.cu
authors.forename: P L
authors.initials: PL
authors.lastname: Calderón González
authors.forename: M A
authors.initials: MA
authors.lastname: Parra Rodríguez
authors.forename: J J
authors.initials: JJ
authors.lastname: Llibre Rodríguez
authors.forename: J V
authors.initials: JV
authors.lastname: Gutiérrez
mesh_terms: D000544:Alzheimer Disease / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D013057:Spectrum Analysis