Basic auditory processing skills and phonological awareness in low-IQ readers and typically developing controls

We explore the relationships between basic auditory processing, phonological awareness, vocabulary, and word reading in a sample of 95 children, 55 typically developing children, and 40 children with low IQ. All children received nonspeech auditory processing tasks, phonological processing and literacy measures, and a receptive vocabulary task. Compared to age-matched controls, the children with low IQ and low reading skills were significantly impaired in auditory and phonological processing, whereas the children with low IQ and preserved reading skills were not. There were also significant predictive relations between auditory processing and single word reading. Poor auditory processing was not dependent on low IQ, as auditory processing was age appropriate in the low-IQ children who were good readers.

N1, P2 and T-complex of the auditory brain event-related potentials to tones with varying rise times in adults with and without dyslexia

Dyslexia is a learning difficulty affecting the acquisition of fluent reading and spelling skills due to poor phonological processing. Underlying deficits in processing sound rise time have also been found in children and adults with dyslexia. However, the neural basis for these deficits is unknown. In the present study event-related potentials were used to index neural processing and examine the effect of rise time manipulation on the obligatory N1. T-complex and P2 responses in English speaking adults with and without dyslexia. The Tb wave of the T-complex showed differences between groups, with the amplitudes for Tb becoming less negative with increased rise time for the participants with dyslexia only. Frontocentral N1 and P2 did not show group effects. Enhanced Tb amplitude that is modulated by rise time could indicate altered neural networks at the lateral surface of the superior temporal gyrus in adults with dyslexia. (C) 2011 Elsevier B.V. All rights reserved.

Auditory sensory deficits in developmental dyslexia: A longitudinal ERP study

The core difficulty in developmental dyslexia across languages is a "phonological deficit", a specific difficulty with the neural representation of the sound structure of words. Recent data across languages suggest that this phonological deficit arises in part from inefficient auditory processing of the rate of change of the amplitude envelope at syllable onset (inefficient sensory processing of rise time). Rise time is a complex percept that also involves changes in duration and perceived intensity. Understanding the neural mechanisms that give rise to the phonological deficit in dyslexia is important for optimising educational interventions. In a three-deviant passive 'oddball' paradigm and a corresponding blocked 'deviant-alone' control condition we recorded ERPs to tones varying in rise time, duration and intensity in children with dyslexia and typically developing children longitudinally. We report here results from test Phases 1 and 2, when participants were aged 8-10. years. We found an MMN to duration, but not to rise time nor intensity deviants, at both time points for both groups. For rise time, duration and intensity we found group effects in both the Oddball and Blocked conditions. There was a slower fronto-central P1 response in the dyslexic group compared to controls. The amplitude of the P1 fronto-centrally to tones with slower rise times and lower intensity was smaller compared to tones with sharper rise times and higher intensity in the Oddball condition, for children with dyslexia only. The latency of this ERP component for all three stimuli was shorter on the right compared to the left hemisphere, only for the dyslexic group in the Blocked condition. Furthermore, we found decreased N1c amplitude to tones with slower rise times compared to tones with sharper rise times for children with dyslexia, only in the Oddball condition. Several other effects of stimulus type, age and laterality were also observed. Our data suggest that neuronal responses underlying some aspects of auditory sensory processing may be impaired in dyslexia. © 2011 Elsevier Inc.