One important indicator of neurocognitive function is the P3 (or P300) response, evidenced in by the production of a large positive waveform with a peak between 300 ms. and 700 ms. after the presentation of a target stimulus. The P3 response is elicited by infrequently presented target stimuli in a stream of more frequently occurring non-target stimuli in auditory and visual target detection tasks. Frequency domain analysis of EEG recording suggests that the theta band event related oscillation (ERO) is a major constituent of the P3 response. Two target detection tasks, one visual, the other auditory, were used for this study. The response was recorded from frontal, central and parietal scalp locations. All six collaborating sites used identical experimental procedures and EEG acquisition hardware and software. Electrical activity was amplified 10,000 times using Neuroscan amplifiers and was recorded continuously over a bandwidth of 0.02–100.0 Hz on a Neuroscan system. Estimates of EROs, the localized power of non-stationary evoked potential time series, were obtained using the S-transform, a time-frequency representation method.
