The N400 in a semantic categorization task across 6 decades.
OBJECTIVE
To characterize the effects of normal aging on the amplitude, latency and scalp distribution of the N400 congruity effect.


METHODS
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 1 s later by a visually-presented word that either did or did not fit with the sense of the preceding phrase; they reported the word read and whether or not it was appropriate. ERP measurements (mean amplitudes, peak amplitudes, peak latencies) were subjected to analysis of variance and linear regression analyses.


RESULTS
All participants, 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 (0.05-0.09 microV 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 semantic congruity effect at the scalp gets smaller, slower and more variable with age, consistent with a quantitative rather than qualitative change in semantic processing (integration) with normal aging.
Department of Cognitive Science, University of California, San Diego, La Jolla 92093-0515, USA. mkutas@ucsd.edu
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D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001245:Association Learning / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D004569:Electroencephalography; D004585:Electrooculography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000502:physiology; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D013702:Temporal Lobe / Q000502:physiology