On the relationship between background EEG and the P300 event-related potential.

Background EEG was recorded from 24 subjects under eyes open/closed conditions for 5 min. The P3(00) event-related brain potential (ERP) was elicited with auditory stimuli when eyes were open/closed in the same subjects. Target stimulus probability was manipulated (0.20, 0.40, 0.60, 0.80) in different blocks under each eyes open/closed condition. Spectral analysis indicated that EEG power between 8 and 12 Hz demonstrated a similar scalp distribution as the P3 component of the ERP for the electrode sites employed. Spectral power and mean frequency were modestly correlated with P3 amplitude and peak latency primarily in the slower EEG bands, with associations observed across probability conditions and often strongest when target stimulus probability was .20. The results suggest that differences between individuals for EEG variation may contribute to P3 component variability, especially at the parietal recording site and under low target stimulus probability conditions when the P3 is largest and most stable.