Comparison of the intersubject and intrasubject variability of exogenous and endogenous auditory evoked potentials

The variability, both between subjects (intersubject variability) and within subjects (intrasubject variability), of the P300 event-related potential was compared to that of early and middle latency components using coefficients of variation. For each of five waveform components, 12 amplitude measures (two trials on each of six measurement occasions) and 12 latency measures were obtained for each of eight subjects. P300 intersubject variability was comparable to that of the most stable early components (ABR waves III and V), both in terms of amplitude and latency. Intrasubject variability was considerably greater for P300 than for the early components; even so, multiple waveforms collected from the same subject tended to fit within an envelope bounded by +/- 1 standard deviation form the mean (averaged) response to oddball stimuli. The variability of MLR component Pa exceeded that of all other components.