Effects of stimulus modality and response mode on the P300 event-related potential differentiation of young and elderly adults.

The P300 event-related brain potential (ERP) was examined in 14 young (20 - 29 years of age) and 16 elderly (60 - 82 years of age) adult subjects during the performance of auditory and visual discrimination tasks requiring silent counting or key pressing in response to target stimuli. P300 latencies were longer in elderly (vs young) adults and in visual (vs auditory) tasks, and visual tasks elicited larger P300 amplitudes than auditory tasks in both age groups. Neither stimulus modality nor response mode affected P300 differentiation of young and elderly subjects. Steeper P300 anterior-posterior scalp amplitude gradients were seen in the young (vs elderly) adults, regardless of stimulus or response type. Examination of inter-subject variability with the coefficient of variation (CV) statistic found the lowest (i.e., best) CV values to be exhibited in the visual task requiring the counting of target stimuli. Implications of the findings are discussed in relation to P300 applications in the clinical assessment of dementia and aging-associated cognitive alterations.