Magnetic mismatch fields elicited by vowels and consonants.
Auditory-evoked mismatch fields (MMFs) elicited by vowel contrasts and plosive stop consonant place-of-articulation contrasts were recorded over the left hemisphere of neurologically and audiologically normal subjects. Two experiments were conducted: vowels were presented in isolation in experiment 1 and embedded in consonant-vowel syllables in experiment 2. Bestfit equivalent MMF sources were obtained using the model of a single, spatiotemporal current dipole in a sphere. In both experiments, MMF sources activated by place-of-articulation contrasts were later in latency and smaller in dipole moment amplitude than MMF sources excited by vowel contrasts. There was evidence, albeit not unambiguous, for the vowel-contrast MMF sources being located more posteriorly than the consonant-contrast MMF sources in experiment 1 and more laterally in experiment 2. In both experiments, the MMF source excited by the contrast between /da/ and /ga/ was more anterior than the MMF source excited by the contrast between /da/ and /ba/. The effects on latency and dipole moment may be interpreted to mirror differences in perceptual discriminability and auditory memory decay between consonantal place-of-articulation contrasts and vowel contrasts. Similarly, the effects on location may be interpreted to reflect featural specificity of the mismatch response. Interestingly, the dipole source analysis results show a correspondence to the pattern of preservation and loss of the mismatch response to vowel and consonant place-of-articulation contrasts recently observed in Wernicke's aphasia.
Diesch
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Institute of Psychology, Technical University of Berlin, Germany. dies0230@mailszrz.zrz.tu-berlin.de
Luce
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D000161:Acoustic Stimulation; D000328:Adult; D001921:Brain / Q000502:physiology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D010700:Phonetics; D013063:Speech Discrimination Tests; D013067:Speech Perception / Q000502:physiology*