Mismatch negativity (MMN), an index of experience-dependent memory traces, was used to investigate the processing of lexical contrasts in the human brain.The MMN was elicited either by rare words presented among repetitive words or pseudowords, or by pseudowords presented among words. Phonetic and phonological contrasts were identical in all conditions. MMNs elicited by both word deviants were larger than that elicited by the deviant pseudoword. The presence of lexical contrast did not

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... tly alter the word-elicited MMNs, which were, however, distinct in amplitude and topography from the MMN evoked by pseudowords. Thus, our results indicate the existence of word-related MMN enhancement largely independent of the lexical status of the standard stimulus. This enhancement may re£ect the presence of a longterm memory trace for a spoken word. NeuroReport 13:521^525