P300 component identification in auditory oddball and novel paradigms using source analysis techniques: reduced latency variability in the elderly.

P300 latency variability in normal subjects limits its diagnostic applicability as a test for cognitive function. One of the causes of variation is the overlap in P300 (P3A and P3B) components resulting in inaccurate latency determination. Recently, we have shown that identification of P3A and P3B components using source analysis techniques significantly reduces P300 latency variability in healthy younger subjects. Here, we included a novel paradigm to enhance sensitivity and investigated the efficiency of the source analysis technique in reducing the P300 latency variability in healthy older subjects. Data were recorded with a 128-channel EEG system in 28 healthy subjects (aged 53-82 years, 12 males). We used a standard two-tone and a novel three-tone auditory oddball paradigm and an established source analysis technique, and compared the latencies to those obtained with conventional P300 analysis. The source analysis method identified both P3A and P3B components in a substantially larger percentage of subjects (93% versus 32%) than the conventional method. Both for the standard and novel paradigm, the source analysis method yielded a later mean P3B latency (361.4 versus 344.2 milliseconds, P = 0.017, and 374.4 milliseconds versus 354.3 milliseconds, P = 0.014, respectively) with a smaller standard deviation (15.8 versus 26.2 milliseconds, P = 0.013, and 18.9 versus 30.0 milliseconds, P = 0.052, borderline significant, respectively) than the conventional P300 method, for subjects aged 50 to 70 years. When applying the source analysis technique, as in young healthy subjects, a considerable reduction of P300 latency variability was thus found in healthy older subjects aged 50 to 70 years for both paradigms. This may have important consequences for applications of clinical event-related potential research in the early diagnosis of dementia, because the first signs of this disease are mostly observed in this age category.