Brain dynamics in the active vs. passive auditory oddball task: exploration of narrow-band EEG phase effects.
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.
Barry
Robert J
RJ
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
Rushby
Jacqueline A
JA
Smith
Janette L
JL
Clarke
Adam R
AR
Croft
Rodney J
RJ
Wallace
Mark J
MJ
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