EEG alpha activity and the ERP to target stimuli in an auditory oddball paradigm.

Peak-to-peak amplitudes of the N1P2 and N2P3 components in the target ERPs from a fixed interstimulus interval auditory oddball paradigm were investigated as a function of within-subject pre-stimulus levels of alpha activity. Fourteen subjects were each presented with 600 auditory stimuli in a two-tone auditory oddball paradigm which required a button-press to targets, presented with 50% probability. Pre-stimulus alpha activity at Pz was assessed for each trial by digital filtering from 8 to 13 Hz, and alpha RMS amplitude was used to sort the ERPs at Pz and Cz. A direct relationship was obtained between component amplitudes at both Pz and Cz and pre-stimulus alpha level at Pz. Component latencies were strongly related to post-stimulus alpha peaks and troughs. These data confirm the intimate relationship between central nervous system activation, as evidenced by spontaneous EEG in the pre-stimulus period, and the ERP resulting from stimulus presentation.