Reliability of P3 Event-Related Potential during Working Memory across the Spectrum of Cognitive Aging

Event related potentials (ERPs) offer unparalleled temporal resolution in tracing distinct electrophysiological processes related to normal and pathological cognitive aging. The stability of ERPs in older individuals, who inherently show more intraindividual variability in cognitive functions, has not been established. In this test-retest reliability study, 39 older individuals (age 74.10 (5.4) years; 23 (59%) women; 15 nonamyloid elevated, 16 amyloid elevated, 8 cognitively impaired) with scores on the Montreal Cognitive Assessment (MOCA) ranging between 3 and 30 completed a working memory (nback) test with three levels of difficulty at baseline and 2 week follow up. Stability of the ERP was evaluated on grand averaged task effects for both visits. P3 peak amplitude and latency were measured in frontal channels. P3 peak amplitude at Fz, our main outcome variable, showed excellent reliability in 0back (intraclass correlation coefficient (ICC), 95% confidence interval = 0.82 (0.67 to 0.90) and 1back (ICC = 0.87 (0.76 to 0.93), however, only fair reliability in 2back (ICC = 0.53 (0.09 to 0.75). Reliability of P3 peak latencies was substantially lower, with ICCs ranging between 0.17 for 2back and 0.54 for 0back. Generalized linear mixed models showed no confounding effect of age, group, or task difficulty on stability of P3 amplitude and latency of Fz. By contrast, MOCA scores tended to negatively correlate with P3 amplitude of Fz (p=0.07). We conclude that P3 peak amplitude and latency provide a stable measure of electrophysiological processes in older individuals. However, impaired cognition may affect the stability of the ERP response.