Auditory Steady State Cortical Responses Indicate Deviant Phonemic-Rate Processing in Adults With Dyslexia

Hanne Poelmans, Heleen Luts, Maaike Vandermosten, Bart Boets, Pol Ghesquière, Jan Wouters
2012 Ear and Hearing  
Corresponding author: Hanne Poelmans, O&N2, Herestraat 49 bus 721, 3000 Leuven, Belgium. Tel.: +32 16 33 04 95, Fax: +32 16 33 04 86, Hanne.Poelmans@med.kuleuven.be 1 This article has been published as: Poelmans, H., Luts, H., Vandermosten, M., Boets, B., Ghesquière, P., Wouters, J. (2012). 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
more » ... y 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 Hz, 20 Hz and 4 Hz. The 80 Hz modulation is known to be evoked in the brainstem, whereas the 20 Hz and 4 Hz modulations are mainly generated in the cortex. Furthermore, the 20 Hz and 4 Hz modulations provide an objective auditory performance measure related to phonemic-rate and syllabic-rate processing. In addition to neurophysiological measures, psychophysical tests of speech-innoise perception and phonological awareness were assessed. Results: Based on 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 to normal readers, whereas no group differences were found for the syllabic-rate. Furthermore, a relation between phonemic-rate ASSRs and psychophysical tests of speech-innoise perception and phonological awareness was obtained. Conclusions: These 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. Final published version is available at
doi:10.1097/aud.0b013e31822c26b9 pmid:21844810 fatcat:6lbzmzfbxneofhzm43iu45l3zu