[Effects of aging on contingent negative variation and reaction time]

Contingent negative variations (CNV) were recorded at Cz for young, middle-aged and elderly groups of male and female subjects loaded with simple and discriminative sensory-motor tasks. Each task consisted of repeated single trials in which a warning signal (S1) of click tone was followed 4.0 s later by an imperative visual signal (S2) to which a quick motor response was required. The reaction time to S2 was also measured. In the simple task, a white circle of S2 was presented at probability of 75% on CRT screen, whereas in the discriminative task the subject was given either a green or red circle of S2 on CRT and asked to respond only to a green S2 with key-pressing. The negative component of the S1-S2 interval which was referenced as a baseline voltage during the 500 ms pre-S1 epoch was averaged over at least 12 single trials in each task. The reaction times were averaged over the trials in each task and used as a mean reaction time. A whole mean CNV amplitude averaged over the S1-S2 interval and 16 segmented CNV amplitudes of 250 ms epoch during the S1-S2 interval as well as the mean reaction time, number of erroneous responses and heart rates during both rest and task loading were obtained for each task. These parameters were submitted to 4-way ANOVA (age (3 levels) X gender (2) X task (2) X session (2)). The following age-related changes were observed: the whole mean CNV amplitude and the middle and late components of the segmented CNV decreased significantly with age.(ABSTRACT TRUNCATED AT 250 WORDS)