Early deafened bilateral cochlear implant users show ITD sensitivity at different pulse rates

N Roßkothen-Kuhl; AN Buck; R Laszig; JW Schnupp

doi:10.1055/s-0039-1686485

Laryngo-Rhino-Otologie, Inhaltsverzeichnis

CC BY-NC-ND 4.0 · Laryngorhinootologie 2019; 98(S 02): S149
DOI: 10.1055/s-0039-1686485

Abstracts

Otology

Early deafened bilateral cochlear implant users show ITD sensitivity at different pulse rates

Autoren

N Roßkothen-Kuhl

¹Universitätsklinikum Freiburg, Klinik für Hals-Nasen-Ohrenheilkunde, Freiburg
AN Buck

²Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, Hong Kong, SAR China
R Laszig

¹Universitätsklinikum Freiburg, Klinik für Hals-Nasen-Ohrenheilkunde, Freiburg
JW Schnupp

²Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, Hong Kong, SAR China

Abstract

Volltext

Sound localization is one of the major challenges for bilateral cochlear implant (CI) users. One reason is their limited perception of binaural cues, especially interaural time difference (ITD). While studies on human implantees hypothesize that the issue lies in the lack of early sensory input, we have shown on neonatally deafened, CI-implanted rats that ITD sensitivity can be developed independent from early sensory input if the bilateral CIs are synchronized. Here, we investigate to what extent the pulse rate influences the ITD performance of early deaf CI users.

We used rats to study binaural hearing with electrical intracochlear stimulation. Deafness was induced neonatally by kanamycin and verified by measuring auditory brainstem responses. In young adulthood, CI electrodes were inserted into both cochleae. ITD sensitivity at different pulse rates (50, 300, 900 Hz) was studied by training CI-implanted rats on a sound lateralization task. Binaural, biphasic stimuli were presented via experimental processors.

All neonatally deafened CI-rats showed microsecond ITD sensitivity when provided with precise ITD cues right from stimulation onset. Within the rats' physiological range of +/- 120µs, good ITD discrimination was found independent from the pulse rate although the performance was slightly better for lower rates. This ITD performance compares with that achieved by normal hearing rats.

These results have important clinical implications, as they suggest that even early deafened CI patients with clinical stimulation rates of around 900 Hz should be able to use ITDs for sound localization when stimulated bilaterally synchronized from the time of bilateral CI implantation.