Abnormal Auditory Cortical Activation in Dyslexia 100 msec after Speech Onset
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© 2002 MIT Press. This is the final version of the article: Helenius, Päivi ; Salmelin, Riitta ; Richardson, Ulla ; Leinonen, Seija ; Lyytinen, Heikki. 2002. Abnormal Auditory Cortical Activation in Dyslexia 100 msec after Speech Onset. Journal of Cognitive Neuroscience. Volume 14, Issue 4. P. 603-617. ISSN 0898-929X (printed). DOI: 10.1162/08989290260045846, which has been published in final form at http://www.mitpressjournals.org/doi/abs/10.1162/08989290260045846#.VVmkumOkuSo
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2002
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Mcode
Degree programme
Language
en
Pages
603-617
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Journal of Cognitive Neuroscience, Volume 14, Issue 4
Abstract
Reading difficulties are associated with problems in processing and manipulating speech sounds. Dyslexic individuals seem to have, for instance, difficulties in perceiving the length and identity of consonants. Using magnetoencephalography (MEG), we characterized the spatio-temporal pattern of auditory cortical activation in dyslexia evoked by three types of natural bisyllabic pseudowords (/ata/, /atta/, and /a a/), complex nonspeech sound pairs (corresponding to /atta/ and /a a/) and simple 1-kHz tones. The most robust difference between dyslexic and non-reading-impaired adults was seen in the left supratemporal auditory cortex 100 msec after the onset of the vowel /a/. This N100m response was abnormally strong in dyslexic individuals. For the complex nonspeech sounds and tone, the N100m response amplitudes were similar in dyslexic and nonimpaired individuals. The responses evoked by syllable /ta/ of the pseudoword /atta/ also showed modest latency differences between the two subject groups. The responses evoked by the corresponding nonspeech sounds did not differ between the two subject groups. Further, when the initial formant transition, that is, the consonant, was removed from the syllable /ta/, the N100m latency was normal in dyslexic individuals. Thus, it appears that dyslexia is reflected as abnormal activation of the auditory cortex already 100 msec after speech onset, manifested as abnormal response strengths for natural speech and as delays for speech sounds containing rapid frequency transition. These differences between the dyslexic and nonimpaired individuals also imply that the N100m response codes stimulus-specific features likely to be critical for speech perception. Which features of speech (or nonspeech stimuli) are critical in eliciting the abnormally strong N100m response in dyslexic individuals should be resolved in future studies.Description
Keywords
auditory cortical activation, dyslexia, speech onset
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Citation
Helenius, Päivi & Salmelin, Riitta & Richardson, Ulla & Leinonen, Seija & Lyytinen, Heikki. 2002. Abnormal Auditory Cortical Activation in Dyslexia 100 msec after Speech Onset. Journal of Cognitive Neuroscience. Volume 14, Issue 4. P. 603-617. ISSN 0898-929X (printed). DOI: 10.1162/08989290260045846.