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Induced alpha band power changes in the human EEG and attention
W Klimesch1, M Doppelmayr, H Russegger
1Department of Physiological Psychology, University of Salzburg, Austria. wolfgang.klimesch@sbg.ac.at
Abstract:
Induced alpha power (in a lower, intermediate and upper band) which is deprived from evoked electroencephalograph (EEG) activity was analyzed in an oddball task in which a warning signal (WS) preceded a target or non-target. The lower band, reflecting phasic alertness, desynchronizes only in response to the WS and target. The intermediate band, reflecting expectancy, desynchronizes about 1 s before a target or non-target appears. Upper alpha desynchronizes only after a target is presented and, thus, reflects the performance of the task which was to count the targets. Thus, only slower alpha frequencies reflect attentional demands such as alertness and expectancy.