Co-Morbidity of APD and Reading Disabilities

Evelyne      Veuillet; Caroline      Bouilhol; Hung      Thai-Van

doi:10.2174/157339611796548429

Abstract

Auditory processing disorders (APDs) are associated with an inability to process auditory information which cannot be explained by abnormal hearing thresholds. This review focuses on APDs that are liable to be found in subjects with language-based learning disabilities such as dyslexia. Although the causal relationship between the presence of an APD and reading deficits is still poorly understood, it is clear that in many cases (estimated range between 30-50%) the presence of an APD may serve as a marker of language-based learning problems. While some dyslexic children can be characterized by poor performances in auditory temporal processing (resolution, masking, ordering, integration) they can also experience hearing difficulties with competing or degraded acoustic signals (for example, during dichotic listening or in the presence of a noisy background). Behavioural hearing deficits are not always found in dyslexic children; when present they may be explained, at least partly, by the task complexity which induces strong cognitive load. However, there is no doubt that the co-morbidity of APD and dyslexia can create difficulties in communication and academic skills. In addition to these behavioural indices of APD, evidence for abnormal function of the descending auditory pathway is provided in dyslexia. We here present preliminary results showing 1) differences in the developmental trajectories when normal reading and dyslexic children are compared for auditory descending pathway function and 2) deficient high level process (attention) which appears in literacy problems and auditory processing deficits (dichotic listening) through feedback connections from higher to lower areas. These abnormalities, in turn, may be accompanied by different behavioural manifestations of APD.

Keywords: Auditory processing disorder, dyslexia, psychoacoustic measurements, dichotic listening, auditory attention, auditory memory, auditory asymmetry, medial olivo-cochlear system, psychoacoustic measurements auditory memory