ON THE REASONS FOR THE DELAY OF P3-LATENCY IN HEALTHY ELDERLY SUBJECTS

The P3 component reaches its peak later in elderly subjects than in young subjects. The aim of this study was to repeat this finding in the usual auditory oddball task and to look for reasons for the delay by analysing other components and by applying another task, the visual Push / Wait task. It was found in the oddball that the age delay was present for mismatch negativity already but further increased until P3's peak. In the Push / Wait task, the size of the age delay was independent of another delay caused by reduced visual intensity of the stimuli. Further, the age delay had its onset after the occipital P140 component whereas the intensity delay was present before this component. Within the elderly, P3 latencies correlated between the auditory and the visual tasks, and the common factor extracted from both latencies correlated with a test of short-term memory span. It is concluded that the age delay of P3 is not due to a delay of perceptual encoding but perhaps due to delayed memory processes in the elderly. As usual, P3 amplitudes were larger and more parietally focussed in the young than in the elderly. Possible differences in motivation might account for this finding.