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Abstract:
Abstract: We investigated hemispheric processing asymmetries
in auditory evoked M100 in response to speech sounds that differed
by a single phonetic feature (place of articulation): differential
response patterns for single-feature within-speech contrasts may
suggest that the hemispheres are performing different computations
on that feature. We presented consonant vowel syllables (CVs) that
differed in place of articulation cues but were otherwise matched
(/ba/, /da/, /ga/) and recorded from left and right auditory cortex
in 5 healthy adults. Evoked responses were simultaneously sampled
from both hemispheres using a twin 37-channel biomagnetometer
(MAGNES-II). We found differential activation patterns in the M100
component of the auditory evoked fields in response to CVs and
report two general effects: i) longer latencies in the left
hemisphere (M=113.66, SD=0.69) vs. the right (M=105.54, SD=1.92)
and ii) higher amplitudes in the right hemisphere (M=96.80,
SD=9.60) vs. the left (M=77.80, SD=5.07). In addition, a
within-subject analysis of each CV type revealed that M100
amplitude was systematically more variable across the three
syllables in the right hemisphere than in the left in our subjects,
perhaps reflecting differing neural mechanisms in the decoding of
place of articulation cues in left and right auditory areas.
Differential lateralization patterns for within-speech contrasts
may provide evidence that the hemispheres are performing differing
computations on speech sounds early in auditory cortical
processing.
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