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Abstract:
Abstract: Phonological theory shows that the phonemes of a
language are composed of sub-phonemic units known as features. The
phonemes /b/ and /p/ differ in voicing, but share the place of
articulation feature [labial] which distinguishes them from the
[alveolar] phonemes /d/ and /t/. Existing research has shown that
the generator of the Magnetic Mismatch Field (MMF) in human
auditory cortex reflects detailed language-specific phonetic
discrimination (Näätänen et al. 1997). Our previous
work has also shown that the MMF also reflects phonological
categorization due to the grouping of many acoustically disparate
sounds into phoneme categories or sub-phonemic feature categories
(Phillips et al. 1999ab). The current work extends these findings
to place of articulation feature contrasts, which are cued by
complex spectral contrasts. Evoked magnetic fields were recorded
using a whole head biomagnetometer while subjects passively
listened to sequences of standard and oddball stimuli. [labial]
stimuli were chosen randomly from a set of 8 synthetic syllables,
consisting of contrasting tokens of /bæ/, and /pæ/;
[alveolar] stimuli were chosen from a corresponding set of
/dæ/, and /tæ/ stimuli. There was a many-to-one ratio
at the level of phonological features, but not at the acoustic or
phonetic level. Comparison of responses to standard and deviant
stimuli revealed a MMF component which indicate that the generator
of the MMF can use rapid spectral cues to group sounds into
feature-level categories.
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