Auditory mismatch responses to dynamic and static amplitude changes in typically developing and dyslexic children
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1
Centre for Neuroscience in Education, University of Cambridge, Uruguay
Phonological awareness deficits as measured by tasks requiring syllable, onset-rime and phoneme segmentation and/or manipulation are a core characteristic of developmental dyslexia. However, relatively little is known about the auditory antecedents of this phonological impairment. One auditory precursor to the development of phonological awareness may be the dynamic amplitude changes present at the onset of syllables that signal vowel onsets and therefore aid syllabic detection and onset-rime segmentation. In fact, rise-time perception has been shown to be impaired in dyslexic children and to predict phonological abilities in good and poor readers (Goswami et al., 2002, Goswami et al., submitted).
We measured the ERPs of 22 dyslexic and 24 typically developing children, all part of an ongoing longitudinal study investigating auditory processing in developmental dyslexia. The auditory thresholds of each child were also measured on a range of discrimination measures including amplitude rise-time and peak intensity discrimination. ERPs were recorded to 4 separate oddball streams (deviant probability of 0.1). Two amplitude rise-time changes (90 ms, 120 ms) and two peak intensity changes (61 dB, 68 dB) were presented. The deviant stimuli were held constant across the 4 conditions (15 ms rise, 75 dB) with the standard stimuli changed to create the oddball context. This allowed for a direct comparison of the mismatch responses to each of the four discriminations recorded. We hypothesized that dyslexic children would show a significant reduction in mismatch response to the smallest rise-time discrimination condition, commensurate with their poor behavioral discrimination of rise-time. Most behavioral studies have failed to find differences in discrimination of non-dynamic intensity cues, so we predicted no differences in the MMN responses for peak intensity across groups. While a classical frontally distributed MMN was observed in adult pilots across all conditions, a smaller frontal but right distributed mismatch response was observed in typically developing children. The same response was not found in dyslexic children. Links between the auditory discrimination thresholds, phonological awareness skills and mismatch responses of the children will be discussed.
Conference:
MMN 09
Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009.
Presentation Type:
Poster Presentation
Topic:
Poster Presentations
Citation:
Fosker
T,
Huss
M,
Fegan
N,
Szucs
D and
Goswami
U
(2009). Auditory mismatch responses to dynamic and static amplitude changes in typically developing and dyslexic children.
Conference Abstract:
MMN 09
Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications.
doi: 10.3389/conf.neuro.09.2009.05.076
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Received:
25 Mar 2009;
Published Online:
25 Mar 2009.
*
Correspondence:
Tim Fosker, Centre for Neuroscience in Education, University of Cambridge, Cambridge, Uruguay, tjf40@cam.ac.uk