Event-related potentials (ERPs) were elicited with
auditory stimuli, and spectral analysis was performed on
the poststimulus electroencephalographic (EEG) activity
to assess how variables that influence the P300 affect
spectral parameters of the resultant ERP. In Experiment
1, a no-stimulus condition was compared with a single repeated
tone that was either ignored or counted. In Experiment
2, an auditory oddball paradigm was used in which the subject
ignored all stimuli, counted only the target, or counted
both the target and the standard stimuli in different conditions.
In Experiment 3, stimulus probability was manipulated in
separate conditions (.20, .50, .80), with the subject required
to count the target stimulus. Delta and theta band spectral
power increased whenever P300 amplitude increased. However,
as the attentional requirements increased across tasks,
alpha-1 and alpha-2 power and mean frequency increased.
The findings indicate that auditory stimulus processing
modulates the EEG more than just by adding ERP components
to the epoch.