Cerebral Cortex Advance Access originally published online on February 1, 2006
Cerebral Cortex 2007 17(1):1-8; doi:10.1093/cercor/bhj129
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Feature Article |
Alpha Phase Reset Contributes to the Generation of ERPs
1 Department of Physiological Psychology, University of Salzburg, Salzburg, Austria, 2 Institute of Medical Psychology, University of Tübingen, Tübingen, Germany
Address correspondence to Univ. Prof. Dr Wolfgang Klimesch, Department of Physiological Psychology, Institute of Psychology, University of Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria. Email: wolfgang.klimesch{at}sbg.ac.at.
An unresolved question in electroencephalogram (EEG) research is whether event-related potentials (ERPs) are generated by phase-reset or evoked response. We analyzed data of a visual feature detection task and will show 1) phase concentration in the alpha frequency range, 2) ongoing alpha activity prior to stimulus onset, 3) evoked alpha oscillation in the ERP, 4) lack of power increase during phase concentration, 5) decrease in amplitude variance during early evoked components preceding a decrease in power, and 6) the same cortical sources for induced prestimulus power and evoked poststimulus power. Because none of these data provide unequivocal evidence for phase reset, we additionally tested the basic assumption of the evoked model, which is the additivity of the evoked response on the basis of a simulation approach. Our findings suggest that nonadditive processes—typical for a phase reset—are involved in the generation of the ERP. Thus, together with the other findings this study provides unequivocal evidence for phase resetting in the human EEG.
Key Words: alpha • EEG • ERP • oscillations • phase • phase resetting