Age-related differences during simple working memory decisions: ERP indices of early recognition and compensation...

Imaging data has identified frontal cortical activation in older adults during simple recognition tasks that relates positively with performance and could, therefore, be considered compensatory. However, in a previous electrophysiological study involving a Sternberg task with proactive interference manipulations, we observed a frontal positive scalp potential between 400 and 500 ms that was unique to older adults and predictive of poorer performance. These results led us to ask whether unique frontal activation in older adults serves a compensatory role only during relatively simple tasks when stimulus familiarity provides an unambiguous basis for response selection. In the current study, we tested this hypothesis by having younger and older adults complete a verbal Sternberg task without interference manipulations. In younger adults, we observed an early posterior negativity (90-120 ms) that predicted performance accuracy. Older adults failed to show this early negativity but did produce the expected frontal positivity. However, the frontal positivity was again associated with poorer performance. These data support the view that younger adults are able to bias early target discrimination to benefit response selection whereas older adults rely on later controlled processes that are not always effective in buffering against normative age-related decline.