title: Brain dynamics in the active vs. passive auditory oddball task: exploration of narrow-band EEG phase effects.
abstract: OBJECTIVE
  We aimed to examine relationships between the phase of narrow-band electroencephalographic (EEG) activity at stimulus onset and the resultant event-related potentials (ERPs) in active vs. passive auditory oddball tasks, using a novel conceptualisation of orthogonal phase effects.
  
  
  METHODS
  This study focused on the operation of three recently-reported phase-influenced mechanisms, and ERP responses to the standard stimuli were analysed. Prestimulus narrow-band EEG activity (in 1 Hz bands from 1 to 13 Hz) at Cz was assessed for each trial using digital filtering. For each frequency, the cycle at stimulus onset was used to sort trials into four phases, for which ERPs were derived from both the filtered and unfiltered EEG activity at Fz, Cz and Pz.
  
  
  RESULTS
  Preferred brain states at various frequencies were indicated by approximately 20% differential occurrence within the orthogonal phase dimensions explored.
  
  
  CONCLUSIONS
  The preferred states were associated with more efficient processing of the stimulus, as reflected in differences in latency and/or amplitude of various ERP components, and provided evidence for the operation of the three separate phase-influenced mechanisms.
  
  
  CONCLUSIONS
  Both the occurrence of preferred brain states, and the mechanisms linking them to ERP outcomes focused on here, appeared relatively invariant across tasks, suggesting that they largely reflect reflexive brain processes.
authors: Brain & Behaviour Research Institute and School of Psychology, Department of Psychology, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia. robert_barry@uow.edu.au
authors: Robert J
authors: RJ
authors: Barry
authors: Jacqueline A
authors: JA
authors: Rushby
authors: Janette L
authors: JL
authors: Smith
authors: Adam R
authors: AR
authors: Clarke
authors: Rodney J
authors: RJ
authors: Croft
authors: Mark J
authors: MJ
authors: Wallace
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D003265:Contingent Negative Variation; D003627:Data Interpretation, Statistical; D004569:Electroencephalography / Q000706:statistics & numerical data*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male