Comparison of event related potentials (ERPs) distributions obtained with three reference systems: linked binaural, mean reference, extracephalic.

Event related potentials (ERPs) to auditory and visual oddball paradigms were recorded from 19 scalp derivations in 10 controls. Three different reference systems were used: the linked earlobes (LE), the computer calculated mean reference (MR), and a calibrated sterno-vertebral extracephalic reference (EC). The distribution of ERPs was represented on single plane maps (quadratic interpolation, 4-NN method). With LE reference N2, P3a-P3b had no polarity reverted counterparts on the scalp. With EC reference a negativity was recorded on T3-T4 (and partly T5-T5) derivations with the same latency as P3a-P3b vertex component. With MR the N2, P3a-P3b components at vertex were paralleled by polarity reverted counterparts on anterior frontal, temporal and occipital derivations.