A behavioural model of bilateral cochlear implantation. (360G-Wellcome-079759_Z_06_Z)

Unilateral cochlear implantation (CI) restores partial hearing to patients: they often understand speech, but only in quiet conditions, and have severe sound localization deficits. Normal listeners hear speech-in-noise and localize sounds better with two ears, utilizing interaural level differences (ILDs) and interaural time-delays (ITDs). For these reasons, bilateral CI has been trialled. Bilateral implantees show improved localization and ILD sensitivity, but moderate ITD thresholds, with highly variable results. Effects of auditory experience, age at hearing loss or deafness duration may account for this variability. We have developed an animal model of bilateral CI, with the aim of maximizing binaural benefits of CI in humans, whilst utilizing CI as a tool to study the development and plasticity of the neural mechanisms underlying binaural processing. Ferrets will be deafened, bilaterally implanted and chronically stimulated in infancy. Once they are mature, we will assess their ability to localize sound and to process binaural cues using behavioural and electrophysiological techniques that are currently in use in this laboratory. We will then examine the effects of age at hearing loss and duration of deafness on the development of these measures. Lastly, potential benefits of auditory training and an experimental processing strategy, designed to better-preserve ITD cues, will be assessed.