Event-related potential correlates of repetition priming and stimulus classification in young, middle-aged, and older adults.

Electrophysiological and behavioral measures were concurrently recorded from young, middle-aged, and elderly subjects during two classification tasks that required different levels of processing. In both tasks, a portion of stimuli repeated after lags of 2, 8, and 32 intervening items following their first presentation, although these repetitions were incidental to the primary task. All three age groups showed similar patterns of behavioral and event-related potential (ERP) responses associated with stimulus classification and item repetition. ERPs to repeated words were characterized by greater positive amplitude relative to words at first presentation. Similarly, ERPs elicited by items in a primed category were more positive compared with unprimed items. Reaction times were faster to both repeated and primed items. Behavioral and ERP effects were more marked when subjects were required to discriminate items based on meaning rather than on orthography. This study supports previous behavioral evidence suggesting that processes associated with repetition priming and stimulus classification are preserved with age, and demonstrates that ERPs are responsive to repetition throughout the life cycle. Implications for the cognitive processes underlying repetition effects are also discussed.