Comparison of Responses from Brainstem Neurons to Electrical and Acoustic Stimulation: Implications for Electrical ITD Processing in the Lateral Superior Olive

Tag / Zeit: 17.08.2021, 08:40-09:00
Raum: Schubert 1+2
Typ: Regulärer Vortrag
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Zusammenfassung: Our ability to localize sound sources is predominantly derived from the capacity of our brain to detect sub-millisecond Interaural Time Differences (ITD) in the arrival of sounds between the two ears. Unfortunately, ITD-sensitivity is severely limited in bilateral Cochlear Implant (CI) users. Neuronally, ITD-sensitivity is based on the comparison of the relative strength and timing of excitatory and inhibitory inputs from the two ears in the brainstem. Current psychophysical and physiological data imply that contrary to normal hearing listeners, ITD-sensitivity in CI users is mostly governed by the lateral superior olive (LSO) pathway. To gain better insight into the processing along this pathway during electrical stimulation and to identify potential bottlenecks for electrical ITD-sensitivity, we utilized electrophysiology in rodents and computer modelling. We obtained in vivo recordings from single brainstem neurons in response to acoustic and electrical click trains. We found hyper-acuity and hyper-precision for both the excitatory and the inhibitory pathway during electrical compared to acoustical stimulation. A physiologically plausible model of the LSO pathway (Klug et al., 2020) was able to faithfully replicate these results and suggests that the impaired ITD-sensitivity of CI users might be due to an impairment of the integration process in LSO neurons.