Latency of the P3 event-related potential: normative aspects and within-subject variability.

A growing body of research has focused on the P3 (P300) event-related potential as an electrophysiological correlate of selective attention. The present investigation examines the intrasubject test-retest reliability of the auditory evoked P3 latency measure for neurologically and audiologically normal young adults aged 22-34 years across test sessions separated by 2-4 weeks (N = 9) and across trials within one test session (N = 20). In a target-selection ('oddball') paradigm, subjects mentally counted infrequent 2 kHz tone bursts (targets) randomly interspersed within a sequence of 1 kHz tone bursts (non-targets). A strong positive correlation was demonstrated between latencies of test sessions I and II. An analysis of variance did not demonstrate statistically significant latency differences as a function of either tests or trials for the test-retest group (N = 9). Although analysis of variance demonstrated a statistically significant difference between trials within one test session for 20 subjects, the small mean latency difference between trials (4.7 msec) is interpreted as being clinically unimportant. The stability of P3 latency found in this study over a period of 2-4 weeks supports its application to the study of normal and disordered cognitive processes.