Comparisons of P300s from standard oddball and omitted paradigms: Implications to exogenous/endogenous contributions

Purpose: To compare the amplitude, latency, morphology, and threshold of the auditory P300 using standard oddball and omitted paradigms. Research Design: P300 waveforms were measured from the Cz electrode site. Frequent stimuli for both paradigms were 1000 Hz tone bursts. Target stimuli for the standard oddball paradigm were 2000 Hz tone bursts and an omitted stimulus, or silent gap, for the omitted paradigm. Study Sample: Fifteen bilaterally normal-hearing young adults. Results: There were significantly lower amplitudes, poorer morphology, and higher thresholds for the P300 using an omitted paradigm compared to the standard oddball paradigm. Conclusion: These results suggest that the auditory P300 could have a larger exogenous component than traditionally thought.