THE N400 IN A SEMANTIC CATEGORIZATION TASK ACROSS 6 DECADES

Objectives: To characterize the effects of normal aging on the amplitu de, latency and scalp distribution of the N400 congruity effect. Metho ds: Event-related brain potentials (ERPs) were recorded from 72 adults (half of them men) between the ages of 20 and 80 years (12/decade) as they performed a semantic categorization task. Participants listened to spoken phrases (e.g. 'a type of fruit' or 'the opposite of black') followed about I s later by a visually-presented word that either did or did not fit with the sense of the preceding phrase; they reported t he word read and whether or not it was appropriate. ERP measurements ( mean amplitudes, peak amplitudes, peak latencies) were subjected to an alysis of variance and linear regression analyses. Results: All partic ipants, regardless of age, produced larger N400s to words that did not fit than to those that did. The N400 congruity effect (no-fit ERPs - fit ERPs) showed a reliable linear decrease in the amplitude (0.05-0.0 9 mu V per year, r = 0.40) and a reliable linear increase peak latency (1.5-2.1 ms/year, r = 0.60) with age. Conclusions: In sum, the N400 s emantic congruity effect at the scalp gets smaller, slower and more va riable with age, consistent with a quantitative rather than qualitativ e change in semantic processing (integration) with normal aging. (C) 1 998 Elsevier Science Ireland Ltd. All rights reserved.