Maike Vollmer: Age-dependent effects of unilateral hearing loss on the processing of interaural time differences and possible readjustments by subsequent electric cochlear stimulation

Microsecond differences in the arrival time of sound between the two ears (interaural time differences, ITDs) are the primary cue for accurately localizing low-frequency sounds and for speech understanding in noise. There is increasing evidence that inhibitory connections are essential components in neural circuits that process ultrafast temporal information and contribute to precise ITD processing. Auditory deprivation can disturb the structural refinements of inhibitory inputs and produce long-lasting deficits in temporal acuity and ITD coding.
In an animal model for unilateral hearing the proposed project aims at understanding the functional relevance of inhibition for precise temporal information processing in the developing and adult auditory system. We plan to characterize the precise time course of critical period regulation of functional ITD coding and its association to certain stages of normative development. Based on these results, we plan to further determine whether the restoration of binaural hearing with a cochlear implant permits the recovery of ITD-relevant binaural integration and inter-hemispheric balance of neural activation in the early and adult unilaterally deafened auditory system. Deafness and stimulation induced functional changes will be correlated to synaptic and morphological rearrangements of inhibitory projections in auditory brainstem nuclei and will be compared with the predictions of computational models. Results will help identifying key principles of critical period plasticity for binaural integration and ITD processing and will provide insights into the timing and type of potential therapeutic approaches appropriate for restoration.