1. WAISMAN
CENTER
2019 ARO Meeting
Baltimore, MD
PS621
Listening effort in bilateral cochlear implant users with asymmetric across-ear performance in speech perception
Emily Burg1, Tanvi Thakkar1, Shelly P. Godar1, Matthew B. Winn2, Ruth Y. Litovsky1
1University of Wisconsin-Madison, Madison, WI 2Univsersity of Minnesota, Minneapolis, MN
Binaural Hearing and Speech Laboratory
INTRODUCTION
METHODS
RESULTS
Speech intelligibility and pupil dilation
Participants
11 adults with BiCIs.
Stimuli
Harvard IEEE sentences spoken by a woman.
Stimuli were presented at 65dB SPL-A.
Determining the “better” ear
Previous word recognition scores for each ear were compared. If there was no difference, the participant’s preferred ear was labeled the “better” ear.
Examining asymmetry more closely revealed a subtle relationship with bilateral performance
Individuals with hearing loss experience elevated listening effort relative to normal hearing individuals, and effortful listening gives rise to stress, fatigue, and social withdrawal.1,2,3
Individuals with severe-to-profound hearing loss can improve listening performance with bilateral cochlear implants (BiCIs).4
However, factors like electrode placement and neural survival can cause asymmetries between ears.
It has been shown that listeners with small speech asymmetries between ears perform best when listening bilaterally compared to either ear alone, and that individuals with large asymmetries perform best when listening with only their better ear. 5
It is unknown how bilateral implantation influences listening effort, particularly when there are differences in speech perception abilities between ears.
Subject ID
Age (yrs)
Better ear
Inter- implant delay (yrs)
BiCI experience (yrs)
IDI 52
Right
0.6
4.6
ICW 25
18.6
4.9
ICK 75
Left
1.0
7.2
IBY 55
4.2
7.3
IDG 70
2.0
7.7
ICJ 69
0.0
8.8
IBK 78
6.0
9.8
ICD 61
10.0
IBZ 51
1.3
11.0
IBL 72
4.8
12.8
ICB 67
2.8
12.9
Figure 2:
On average, participants scored lowest in speech and exerted the most effort with the poorer ear only.
Mean speech scores were similar for better ear and bilateral listening, but the latter required slightly more effort.
Three subjects scored below 50% correct in their poorer ear (IBL, ICW, ICJ) and demonstrated greater pupil dilation than in their better ear, suggesting that they remained engaged in the task even when performance was low.
Less effort or engagement B.
Better A.
r2 =0.34 A. B.
r2=0.01
Figure 2A. Percentage of correctly repeated words and 2B. peak pupil dilation in each listening condition. Participants are ordered from small to large speech asymmetry.
Figure 4A. Speech intelligibility (p=0.06) and 4B. pupil dilation (p=0.77) in the bilateral condition as a function of speech between ears.
Subject ID
IBY
IBZ
IDI
IBK
ICD
ICB
IDG
ICK
IBL
ICW
ICJ
Speech Asymmetry 0% 3% 4% 7%
10%
12%
22%
45%
53%
55%
Table 2. Difference in speech intelligibility between ears for each participant.
There was a modest association between asymmetry and speech intelligibility in the bilateral condition. This suggests that it may be a predictor of performance, but not effort.
Is increased effort in the bilateral condition due to large asymmetries across ears?
Table 1. Participant demographics (ordered by years of bilateral experience).
Large vs. small asymmetry: differences from better ear to bilateral listening reflect influence of poorer ear
What other factors are related to listening effort in BiCI users?
Listeners with large speech asymmetry (difference=45-55%)
Listeners with small speech asymmetry (difference=0-22%)
Figure 3. Comparison of speech scores and pupil dilation between better ear and bilateral conditions for A,B) participants with small asymmetries and C,D) large asymmetries in speech intelligibility between ears.
Speech Intelligibility
Pupil Dilation A. C. D. B.
Figure 3:
Overall, there was no consistent trend in intelligibility from the better ear to bilateral condition across groups (A,C). Most participants exhibited slightly greater pupil dilation in the bilateral vs. better ear condition (B,D).
A portion of participants with small asymmetries (A,B) had higher intelligibility in the bilateral vs. better ear condition. For some individuals this was accompanied by a decrease in pupil dilation (e.g. ICD), and for others an increase (e.g. IDI).
Participants with large asymmetries (C,D) did not exhibit any consistent relationship between better ear and bilateral conditions.
Less effort or engagement
Better
How can we measure
listening effort?
Pupillometry: As tasks get harder and cognitive load increases, pupil size also increases.5
Listening Conditions
Bilateral
Poorer ear only
Better ear only
Pupil dilation as a function of
bilateral experience
Less effort or engagement
More effort or engagement
r2=0.08
r2=0.04
r2=0.24
Task
Three conditions were tested: Better ear only, Poorer ear only, and Bilateral.
Listeners repeated target sentences presented in quiet from a loudspeaker at 0° azimuth. Responses were scored by an experimenter.
Peak pupil dilation during the post-stimulus wait period was used to evaluate listening effort (Figure 1).3
Participants completed 30 trials per condition.
Trials with significant artifacts were discarded from analysis. 6
Remaining trials were averaged into a single pupil track, and plotted as proportion change from baseline.
PURPOSE
To determine the impact of asymmetry in speech intelligibility on bilateral listening in individuals with BiCIs.
We hypothesized that small asymmetries would facilitate decreased pupil dilation for bilateral compared to better ear listening due to binaural redundancy.
2) Alternatively, large asymmetries would result in similar or increased pupil dilation for bilateral compared to better ear listening due to discrepancies between signals which could hinder performance.
Less Effort
More Effort
Figure 1. Example of two pupil tracks.
Baseline
Stimulus
Wait
Response
Proportion change re: baseline
Time relative to stimulus offset (s)
0.80.6
0.4
0.2
-0.2
Figure 5. Pupil dilation as a function of bilateral experience for better ear (p=0.40), bilateral (p=0.57), and poorer ear (p=0.13) conditions.
SUMMARY
For individuals with both small and large asymmetries, there were no noticeable trends in speech intelligibility or pupil dilation from the better ear to bilateral condition (Figure 3).
When treating asymmetry on a continuum, we found that there was a subtle inverse relationship between asymmetry and intelligibility in the bilateral condition. No relationship was observed between asymmetry and pupil dilation in the bilateral condition, suggesting that asymmetry may impact performance but not listening effort/engagement (Figure 4).
Secondary analyses revealed that bilateral experience did not predict pupil dilation in the bilateral condition (Figure 5).
We plan to test a larger sample in order to further explore these relationships and what they may indicate about effort or engagement in BiCI users.  
ACKNOWLEDGEMENTS: We would like to thank all of the individuals who participated in this study. This work was supported by NIH-NIDCD (R01DC to RYL) and in part by NIH-NICHD (U54HD to Waisman Center).
1Edwards, B. (2007). The future of hearing aid technology. Trends in amplification, 11(1),
2Hughes, S. E., Hutchings, H. A., Rapport, F. L., McMahon, C. M., & Boisvert, I. (2018). Social connectedness and perceived listening effort in adult cochlear implant users: A grounded theory to establish content validity for a new patient-reported outcome measure. Ear and hearing, 39(5),
4Litovsky, R. Y., Parkinson, A., Arcaroli, J., Peters, R., Lake, J., Johnstone, P., & Yu, G. (2004). Bilateral cochlear implants in adults and children. Archives of Otolaryngology–Head & Neck Surgery, 130(5),
5Litovsky, R., Parkinson, A., Arcaroli, J., & Sammeth, C. (2006). Simultaneous bilateral cochlear implantation in adults: a multicenter clinical study. Ear and hearing, 27(6),
6Winn, M. B., Wendt, D., Koelewijn, T., & Kuchinsky, S. E. (2018). Best Practices and Advice for Using Pupillometry to Measure Listening Effort: An Introduction for Those Who Want to Get Started. Trends in hearing, 22.
3Zekveld, A. A., Kramer, S. E., & Festen, J. M. (2010). Pupil response as an indication of effortful listening: The influence of sentence intelligibility. Ear and hearing, 31(4),