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Abstract:
Children with specific language impairment (SLI) are
deficient in the perception of brief and rapidly changing speech
segments, such as consonant formant transitions. An additional
source of difficulty may arise from a backward masking effect on
the consonant formant transitions, by the following steady-state
vowel. This study examined the relative discriminability of the
speech segments within a consonant-vowel (CV) syllable. Behavioral
discrimination and the auditory event related potential (ERP)
components N1 and P2 were recorded in normal-hearing adults, along
with the mismatch negativity to deviant stimuli. Latencies and
amplitudes were analyzed. The stimuli were 1) full CV syllables (ba
and daí), 2) isolated consonant formant transitions (b and
dí), 3) vowels matching either the formant transition or the
full syllable duration (ëIí and ëeí) and 4)
simple tones matching the transition F2 onset frequencies of the
speech sounds. ERP data correlated well with the behavioral data,
in demonstrating that the discrimination of the speech sounds was
more difficult and required longer processing than that of the
tones. Formant transition discrimination was found to be similar to
that of the full syllables. Preliminary results indicate that the
vowel discrimination was relatively easier. These
electrophysiological measures can now be used to identify specific
phonological impairments in SLI children.
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