title: Increase of theta/gamma ratio is associated with memory impairment.
abstract: OBJECTIVE
  In this study the theta/gamma ratio was investigated as early marker of cognitive decline.
  
  
  METHODS
  Forty-nine subjects with mild cognitive impairment (MCI) underwent EEG recording and MRI scan. The theta/gamma ratio of the relative power at the peak frequency was computed. Based on the tertiles values of the ratio, three groups with increasing values of theta/gamma ratio were obtained. The groups were characterized by the performance on cognitive tests. Changes in functional brain connectivity, as expressed by interhemisperic and intrahemispheric EEG linear coherence in the groups were also evaluated.
  
  
  RESULTS
  Increase in theta/gamma ratio was associated with impairment in memory tests. This relationship was confirmed by correlation and multiple regression analysis. An independent association was found between theta/gamma ratio and alpha3/alpha2 power ratio. Coherence analysis showed modifications of interhemispheric functional coupling on temporal regions on slow frequencies.
  
  
  CONCLUSIONS
  Theta/gamma ratio of relative power at peak frequency is significantly associated to memory decline. It could be a useful tool in detecting MCI subjects which are at major risk to develop Alzheimer's disease (AD) or other dementias.
  
  
  CONCLUSIONS
  A global modulation of brain rhythms could be driven by the pathological alterations of theta/gamma ratio.
authors.affiliation: IRCCS San Giovanni di Dio Fatebenefratelli, Department of Neurophysiology, 4, Pilastroni Road, 25125 Brescia, Italy. davide.moretti@afar.it
authors.forename: D V
authors.initials: DV
authors.lastname: Moretti
authors.forename: C
authors.initials: C
authors.lastname: Fracassi
authors.forename: M
authors.initials: M
authors.lastname: Pievani
authors.forename: C
authors.initials: C
authors.lastname: Geroldi
authors.forename: G
authors.initials: G
authors.lastname: Binetti
authors.forename: O
authors.initials: O
authors.lastname: Zanetti
authors.forename: K
authors.initials: K
authors.lastname: Sosta
authors.forename: P M
authors.initials: PM
authors.lastname: Rossini
authors.forename: G B
authors.initials: GB
authors.lastname: Frisoni
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000473:pathology / Q000503:physiopathology*; D008875:Middle Aged; D013057:Spectrum Analysis