The magnetic mismatch field elicited by words and phonological non-words

The speech-evoked magnetic mismatch field was measured using a 49-channel gradiometer. The standard stimuli were words in one condition and phonological non-words in another condition. The deviants were non-words throughout. The equivalent current dipole fitted to the mismatch field was deeper inside the brain and its dipole moment was stronger for non-word than word standards. The factor structure of field amplitude, source dipole moment, and depth suggested that the lexicality conditions differed in source surface area and depth, but not in source current density. This lexicality effect is compatible with a modular rather than an interactive view of the relationship between lexical and phonetic representation.