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Hearing and Donuts (Brain and Bagels) Seminar

October 28, 2022 @ 8:30 am - 9:30 am

Agudemu Borijigin, Ph.D.
Postdoctoral fellow
Binaural Hearing and Speech Lab (Litovsky), Waisman Center

Topic: Improving speech localization in cochlear implant listeners using a specialized processor with novel stimulation strategies

Individuals with severe-to-profound hearing loss are typically candidates for cochlear implants (CIs). In the past two decades there has been a transformation in care such that many patients are provided with CIs in both ears, i.e., bilateral CIs (BiCIs), instead of just one. Although BiCIs lead to better spatial hearing and speech understanding in noise, recipients continue to perform worse than typical hearing listeners. This is partly because clinical speech coding strategies do not accurately encode binaural cues such as interaural time differences (ITDs)—cues that are essential for sound localization and segregation of speech in noise. One reason that clinical speech processors do not accurately encode ITDs is that they discard temporal fine structure information and stimulate all electrodes with high-rate pulses (~1,000 per second). At this high rate, ITDs are neither usable nor perceived by the brain. The conundrum is that high-rate stimulation is important for speech intelligibility, while low-rate stimulation is needed for ITD sensitivity. To address the conundrum, the Litovsky lab has been using a novel approach—mixed rate stimulation strategy to test the idea that sending high- and low-rate stimulations to different electrodes could restore ITD sensitivity while retaining speech intelligibility. Recent research on mixed rate strategy suggests that not all CI recipients receive the same benefits from using a mixed rate strategy, especially for listening in noise.

The proposed work seeks to test the hypothesis that, for the mixed rate strategy to be truly effective, the strategy needs to be customized for each individual CI patient, such that the low-rate stimulation for ITD sensitivity is delivered to the location along the cochlea that has the “best” response to stimulation, in other words where neural health status is the most optimal. This study will use a unique bilaterally-synchronized and portable research processor—the CCi-MOBILE, to address this question. For each BiCI recipient, two “mixed rate” strategies will be tested: whereby low-rate ITDs are delivered to either the “best” or “worst” ITD binaural pairs of electrodes; the remaining electrode pairs receive standard high-rate stimulation. Using these two mixed rate strategies, as well as participants’ “all-high” rate clinical strategy, listeners will then be tested on the localization of single words in quiet, or in speech-shaped noise. Results will be discussed in the context of whether participants could better localize speech both in quiet and noise using a mixed rate strategy, due to the addition of ITD information through low-rate stimulation. More importantly, it will reveal the possible impact of specifying the stimulation site for the low-rate ITD information on the effectiveness of the mixed rate strategy.

Learn more about the Hearing and Donuts Seminar Series


October 28, 2022
8:30 am - 9:30 am
Event Category:


Waisman Center
1500 Highland Ave
Madison, WI 53705