title: Gamma band activity in an auditory oddball paradigm studied with the wavelet transform.
abstract: OBJECTIVE
  To examine the characteristics of evoked and induced gamma band oscillatory responses occurring during P300 development in an auditory oddball paradigm.
  
  
  METHODS
  A time-frequency analysis method was applied to an auditory oddball paradigm in 7 healthy subjects. This method combines a multiresolution wavelet algorithm for signal extraction and the Gabor transform to represent the temporal evolution of the selected frequency components. Phase-locked or evoked activity and also non-phase-locked activity were computed for both standard and target stimuli.
  
  
  RESULTS
  The gamma band frequency components differed between target and non-target stimuli processing. The study showed an early and mainly phase-locked oscillatory response appearing around 26--28 ms after both standard and target stimuli onset. This response showed a spectral peak around 44 Hz for both stimuli. A late oscillatory activity peaking at 37 Hz with a latency around 360 ms was observed appearing only for target stimuli. The latency of this late oscillatory activity had a high correlation (P=0.002) to the latency of the P300 wave.
  
  
  CONCLUSIONS
  EEG signal analysis with wavelet transform allows the identification of an early oscillatory cortical response in the gamma frequency range, as well as a late P300-related response.
authors.affiliation: Clinical Neurophysiology Unit, Department of Neurology, Clínica Universitaria, Facultad de Medicina, Universidad de Navarra, Pamplona, Spain.
authors.forename: I G
authors.initials: IG
authors.lastname: Gurtubay
authors.forename: M
authors.initials: M
authors.lastname: Alegre
authors.forename: A
authors.initials: A
authors.lastname: Labarga
authors.forename: A
authors.initials: A
authors.lastname: Malanda
authors.forename: J
authors.initials: J
authors.lastname: Iriarte
authors.forename: J
authors.initials: J
authors.lastname: Artieda
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000465:Algorithms; D004569:Electroencephalography / Q000379:methods* / Q000706:statistics & numerical data; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male