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Auditory steady state cortical responses indicate deviant phonemic-rate processing in adults with dyslexia.

Abstract：

OBJECTIVES:Speech intelligibility is strongly influenced by the ability to process temporal modulations. It is hypothesized that in dyslexia, deficient processing of rapidly changing auditory information underlies a deficient development of phonological representations, causing reading and spelling problems. Low-frequency modulations between 4 and 20 Hz correspond to the processing rate of important phonological segments (syllables and phonemes, respectively) in speech and therefore provide a bridge between low-level auditory and phonological processing. In the present study, temporal modulation processing was investigated by auditory steady state responses (ASSRs) in normal-reading and dyslexic adults. DESIGN:Multichannel ASSRs were recorded in normal-reading and dyslexic adults in response to speech-weighted noise stimuli amplitude modulated at 80, 20, and 4 Hz. The 80 Hz modulation is known to be primarily generated by the brainstem, whereas the 20 and 4 Hz modulations are mainly generated in the cortex. Furthermore, the 20 and 4 Hz modulations provide an objective auditory performance measure related to phonemic- and syllabic-rate processing. In addition to neurophysiological measures, psychophysical tests of speech-in-noise perception and phonological awareness were assessed. RESULTS:On the basis of response strength and phase coherence measures, normal-reading and dyslexic participants showed similar processing at the brainstem level. At the cortical level of the auditory system, dyslexic subjects demonstrated deviant phonemic-rate responses compared with normal readers, whereas no group differences were found for the syllabic rate. Furthermore, a relationship between phonemic-rate ASSRs and psychophysical tests of speech-in-noise perception and phonological awareness was obtained. CONCLUSIONS:The results suggest reduced cortical processing for phonemic-rate modulations in dyslexic adults, presumably resulting in limited integration of temporal information in the dorsal phonological pathway.

journal_name

Ear Hear

journal_title

Ear and hearing

authors

Poelmans H,Luts H,Vandermosten M,Boets B,Ghesquière P,Wouters J

doi

10.1097/AUD.0b013e31822c26b9

subject

Has Abstract

pub_date

2012-01-01 00:00:00

pages

134-43

issue

eissn

0196-0202

issn

1538-4667

journal_volume

pub_type

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Auditory steady state cortical responses indicate deviant phonemic-rate processing in adults with dyslexia.