Maturation of Auditory Processing in Children With Dyslexia Compared to Average-reading Children

Asymmetry, Auditory Processing and Reading Skills in Phonological Dyslexic Children Compared to Average-reading Children

The hypothesis of central auditory processing disorders has been advanced to explain the anomalies of the grapheme/phoneme combination in some dyslexia. These phonological disorders may be linked to abnormalities of the efferent (medial olivocochlear) system modulation and of cortical asymmetry. Indeed, the efferent system has an asymmetry in relation to handedness. Thus, in right-handed subject, it is predominant on the right side. In contrast, in the subject-handed dyslexic, the efferent system tends to be right-lateralized or non-lateralized. However, after an audio-visual training, normal lateralization can appear. This maturation of the efferent system lateralization during reading acquisition seems to have a particular profile in dyslexics with phonological disorder, especially if it is persistent. This finding allows to consider new prognostic evaluation and speech therapy rehabilitation in the dyslexic child.

Common inclusion criteria

• Native French speaker and french education
• No medical treatment for behavior or neurological disorders (as epilepsy)
• Normal or corrected vision
• Right-handed children (Edinburgh tets (Oldfield, 1971): >+50%)
• Normal ORL examination
• No hearing loss : hearing thresholds not above 15 dB between 250 and 4 000 Hz
• Presence of Otoacoustic Emissions (Total amplitude < 5 dB or SNR > 3dB for at least 3 frequency bands between 1 and 4 kHz)
• Normal level of intellectual development
• Regular school attendance

For the normal reading children

• Aged from 6 to less than 11
• Normal reading level

For the dyslexic children

• Aged from 8 to less than 11
• Diagnostic of dyslexia made by a complet check-up during the 6 last months before the inclusion

Exclusion Criteria

• Neurological or psychiatric disease incompatible with the testing procedure
• Ear disease during more than 6 months
• Normal reading children who have repeat a year
• Previous speech therapy for normal reading children
• Not corrected visual acuteness
• Schooling in a foreign language
• Foreign language spoken at home with both parents
• Known hearing deficit
• Invalid social security