Age differences in the contingent negative variation (CNV): reduced frontal activity in the elderly.

The effects of distraction on the contingent negative variation (CNV) were investigated in a group of 11 elderly (mean = 72.2 years) and a group of 12 young (mean = 23.3 years) subjects. Scalp electrical activity was recorded from midline sites at frontal, central, and parietal locations. Three experimental conditions included Recall, No Recall, and Control situations. In the Recall, or distraction condition, spoken consonant-vowel-consonant (CVC) letters were presented concurrently with the CNV signal interval and were recalled by the subjects after each trial. The No Recall condition was similar to the Recall task except that subjects were not required to repeat the CVSs. The Control condition presented a standard S1 - S2 CNV situation without CVCs. Amplitudes of the CNV, reaction times (RTs), and heart rate (HR) served as indices of distraction. The effects of distraction for both age groups indicated reduced CNVs, lengthened RTs, and elevated HRs. However, a significant age by electrode interaction revealed that while CNV amplitudes at central and parietal sites were comparable between age groups, amplitudes at the frontal placement were consistently reduced in the elderly compared to the young in all conditions. The finding of diminished frontal activity, as measured by the CNV, suggests a process of selective cortical aging and possible cellular loss which may be linked to performance deficits.