LANGUAGE-SPECIFIC PHONEME REPRESENTATIONS REVEALED BY ELECTRIC AND MAGNETIC BRAIN RESPONSES

There is considerable debate about whether the early processing of sou nds depends on whether they form part of speech. Proponents of such sp eech specificity postulate the existence of language-dependent memory traces, which are activated in the processing of speech(1-3) but not w hen equally complex, acoustic non-speech stimuli are processed. Here w e report the existence of these traces in the human brain, We presente d to Finnish subjects the Finnish phoneme prototype /e/ as the frequen t stimulus, and other Finnish phoneme prototypes or a non-prototype (t he Estonian prototype /(o) over tilde/) as the infrequent stimulus. We found that the brain's automatic change-detection response, reflected electrically as the mismatch negativity (MMN)(4-10), was enhanced whe n the infrequent, deviant stimulus was a prototype (the Finnish /o/) r elative to when it was a non-prototype (the Estonian /(o) over tilde/) . These phonemic traces, revealed by MMN, are language-specific, as /( o) over tilde/ caused enhancement of MMN in Estonians. Whole-head magn etic recordings(11,12) located the source of this native-language, pho neme-related response enhancement, and thus the language-specific memo ry traces, in the auditory cortex of the left hemisphere.