Onset Weighting of Temporal Spatial Cues with bilateral Cochlear Implant Stimulation

Sound localization is one of the major challenges for bilateral cochlear implant (CI) users. Their ability to use binaural cues, especially interaural time differences (ITDs), falls below that of normal hearing peers. Our recent study on neonatally deafened (ND), CI implanted rats has shown that very good ITD sensitivity can be developed even in the absence of early sensory input if the CIs are synchronized. Here, we investigate onset weighting in ITD sensitivity between ND CI and normal hearing (NH) rats across different pulse rates.

Neonatal rat pups were deafened using kanamycin and bilaterally implanted with CIs as young adults. NH rats of the same age were additionally tested. Using a two-alternative forced choice task rats learned to lateralize pulse trains (biphasic electric stimuli delivered via CIs or acoustic clicks delivered over earphones). ITD values for individual pulses were jittered randomly, within the rat’s physiological range (+/-120 µs) at different pulse rates (50, 300, 900 Hz). Temporal Weighting Functions (TWFs) were calculated using multiple regression analysis to determine the perceptual weight of each pulse.

Comparable to NH humans, NH rats showed TWFs with strong onset weighting of ITDs across all frequencies. This could also be observed for CI rats, although the up-weighting of the first pulse decreased at higher frequencies and was of smaller magnitude.

Rat TWFs are fundamentally very similar to those found in humans, illustrating the suitability of rats as a model for human binaural hearing. The pulse rate dependence of onset ITD processing we observed in CI rats may also help to explain the poor ITD perception of early deafened CI users, given that current clinical CI processors are running at =900 Hz.

Taube Kinder lernen hören e. V.; Deutscher Akademischer Austauschdienst

Poster-PDF A-1746.PDF

Publication History

Article published online:
10 June 2020