Memory traces for inflectional affixes as shown by mismatch negativity.

Mismatch negativity (MMN), an index of experience-dependent memory traces, was used to investigate the processing of grammatical affixes in the human brain. The MMN was elicited by either a verb stem or an inflected verb form, phonetic contrasts being identical in both conditions. The topography of the mismatch responses showed clear left-hemispheric laterality in both conditions. However, the MMN to the inflected form occurred later than that for the stem. Furthermore, the inflected stimulus produced MMN maximal in centroparietal sites, whereas stem-elicited MMN was more profound at more frontal sites. We suggest that these features of the MMN to inflected form indicate delayed activation of left-lateralized perisylvian cell assemblies that function as cortical memory traces of inflectional affixes.