Functional Magnetic Resonance Imaging Study of the Central Auditory System After Single Sided Deafness

Overview

The objective is to study the relation between the reorganization of the central auditory system, and the psychophysical deficits in binaural hearing in subjects with single sided deafness.

Background Single sided deafness (SSD) and asymmetrical hearing loss are common hearing impairments, and their social consequences are well established. At the central auditory system level, the single sided deafness is associated with a reorganization of auditory temporal cortices that leads to a reduction of inter hemispheric asymmetry. Purpose : Our main objective is to study the relation between the reorganization of the central auditory system, namely the inter hemispheric asymmetry, and the psychophysical deficits in binaural hearing in subjects with SSD. Abstract : Binaural hearing enables spatial localization of the sound source and improves speech recognition in a competing noise. SSD and asymmetrical hearing loss are common hearing impairments, which affect 0.3 to 1/1000 children. In the adult population, this prevalence increases with age. The impact of SSD and asymmetrical hearing loss on quality of life indices is well established and some reports underline its consequences in children scholarship. Previous neuro-imaging and electro physiological studies highlighted the reduction of normal inter hemispheric asymmetry in subjects with SSD. To the best of our knowledge, there is no report about the relation between the central auditory system reorganization and its behavioural deficits. The investigators propose to conduct a study which analyzes the relationship between the reduction of inter hemispheric asymmetry and performance in binaural hearing tests. Thus, the auditory plasticity will be studied using functional magnetic resonance imaging and more specifically BOLD variations in auditory temporal cortices. A set of binaural hearing assessments will be performed, including speech recognition in noise and localization abilities. The correlation between the lateralization ratio and binaural measurements (speech reception threshold (SRT) in dichotic hearing, diotic hearing, reverse dichotic hearing) will be estimated. Likewise, the impact of SSD duration on cortical reorganization and binaural tests will be studied.

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