Three challenges for future research on cochlear implants

Abstract

Cochlear implants (CIs) often work very well for many children and adults with profound sensorineural (SNHL) hearing loss. Unfortunately, while many CI patients display substantial benefits in recognizing speech and understanding spoken language following cochlear implantation, a large number of patients achieve poor outcomes. Understanding and explaining the reasons for poor outcomes following implantation is a very challenging research problem that has received little attention despite the pressing clinical significance. In this paper, we discuss three challenges for future research on CIs. First, we consider the issue of individual differences and variability in outcomes following implantation. At the present time, we still do not have a complete and satisfactory account of the causal underlying factors that are responsible for the enormous individual differences and variability in outcomes. Second, we discuss issues related to the lack of preimplant predictors of outcomes. Very little prospective research has been carried out on the development of preimplant predictors that can be used to reliably identify CI candidates who may be at high risk for a poor outcome following implantation. Other than conventional demographics and hearing history, there are no prognostic tools available to predict speech recognition outcomes after implantation. Finally, we discuss the third challenge — what to do with a CI-user who has a poor outcome. We suggest that new research efforts need to be devoted to studying this neglected clinical population in greater depth to find out why they are doing poorly with their CI and what novel interventions and treatments can be developed to improve their speech recognition outcomes. Using these three challenges as objectives for future research on CIs, we suggest that the field needs to adopt a new narrative grounded in theory and methods from Cognitive Hearing Science and information processing theory. Without knowing which specific biological and neurocognitive factors are responsible for individual differences or understanding the underlying sensory and neurocognitive basis for variability in performance, it is impossible to select a specific approach to habilitation after a deaf adult or child receives a CI. Deaf adults and children who are performing poorly with their CIs are not a homogeneous group and may differ in many different ways from each other, reflecting the dysfunction of multiple brain systems associated with both congenital and acquired deafness. Hearing loss is not only an ear issue, it is also a brain issue too reflecting close links between perception and action and brain, body and world working together as a functionally integrated information processing system to support robust speech recognition and spoken language processing after implantation.

A Preliminary Study of the Effects of Attentive Music Listening on Cochlear Implant Users’ Speech Perception, Quality of Life, and Behavioral and Objective Measures of Frequency Change Detection

“…Even with speech coding strategies that provide temporal fine structure of the signal, CI users generally do not seem to benefit from it (Riss et al, 2011). Additionally, other factors that may limit pitch change detection include neuralelectrode interface (e.g., the distance between the electrode and neural elements), neural deficits related to sound deprivation, and cognitive function decline (Di Nardo et al, 2010;Limb and Roy, 2014;Pisoni et al, 2018).…”

Leveraging interdisciplinary perspectives to optimize auditory training for cochlear implant users

“…However, to date, there is no comprehensive set of predictors that can reliably account for differences in outcome performance observed with the device. That is, while a substantial portion our current knowledge base has justified the efficacy of the CI in order to demonstrate a benefit of the device at an implementation level (e.g., Pisoni, Kronenberger, Harris, & Moberly, 2017), we have a more limited understanding as to why a CI works well for some patients, yet poorly for others. As a result, the current evidence base does not account for why patients with comparable language status, medical history, demographic background, and device may perform differently with the implant (e.g., Moberly, Bates, Harris, & Pisoni, 2016;Pisoni, Cleary, Geers, & Tobey, 1999).…”

Evaluating hearing performance with cochlear implants within the same patient using daily randomization and imaging based fitting - The ELEPHANT study

“…CI performance appears to have reached a plateau in the last 30 years and despite an increase in scientific publications [2], a substantial amount of challenges await future research. For example, a CI user's individual gradient of improvement is still hard to predict [3] , disappointing outcomes remain hard to explain [4], speech perception in difficult listening situations remains extremely challenging for most CI users [5], and the quality of sound generated by CI stimulation is often considered unnatural and robotic despite decades of development [4,6].…”