title: Phase synchronization of the ongoing EEG and auditory EP generation.
abstract: OBJECTIVE
  We investigated the role of phase synchronization of the spontaneous electroencephalogram (EEG) in auditory evoked potential (EP) generation in a sample of healthy individuals.
  
  
  METHODS
  Auditory responses were obtained from 20 healthy subjects following a double stimulus paradigm, using two identical tone bursts (S1 and S2) separated by 0.5s. Single-trial auditory evoked potentials were decomposed into sinusoidal, exponentially decaying/increasing components using the piecewise Prony method (PPM). Pre- and post-stimulus phase histograms were compared to determine the degree of phase synchronization produced by auditory stimulation.
  
  
  RESULTS
  Analysis of single responses revealed that the S1 stimuli produced phase synchronization in the 2-8Hz frequency range, with little or no concomitant amplitude increase. A significantly reduced phase effect was seen in response to S2 stimuli.
  
  
  CONCLUSIONS
  Stimulus-induced phase synchronization of the ongoing EEG is a major mechanism for the generation of auditory EP components with a latency in the 50-250ms range.
  
  
  CONCLUSIONS
  The fact that the EP components accessed here are generated through phase synchronization implies that the ensemble-averaged EP will not resemble the single trial response, and it would certainly be misleading to consider the single trial response as an amplitude-scaled version of the ensemble average.
authors.affiliation: Department of Electrical and Computer Engineering, University of Houston, Houston, TX, USA. bjansen@uh.edu
authors.forename: Ben H
authors.initials: BH
authors.lastname: Jansen
authors.forename: Gopal
authors.initials: G
authors.lastname: Agarwal
authors.forename: Anant
authors.initials: A
authors.lastname: Hegde
authors.forename: Nashaat N
authors.initials: NN
authors.lastname: Boutros
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001921:Brain / Q000502:physiology*; D003344:Cortical Synchronization; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D012016:Reference Values