Understanding Factors Contributing To Variability In Outcomes of Cochlear-Implant Users

Abstract

Cochlear implants (CIs) are a beneficial and often life-changing treatment for individuals with profound sensorineural hearing loss. However, despite advances in device design and surgical techniques, clinicians continue to see a very wide range of outcomes for individual CI users. Some CI users are able to converse successfully over the phone and in noisy environments, while others struggle to communicate effectively even in quiet, one-on-one conversations. Clinical differences between patients, such as the onset and duration of deafness, and anatomical factors related to the electrode-to-neuron interface, explain relatively little of this overall variability in speech perception. This dissertation addresses various perceptual, cognitive, and social factors, such as spectral resolution, working memory, intellectual efficiency, social engagement, and coping strategies, which may account for some of the individual differences in speech understanding found in the CI population. First, the amount of variability inherent to difficult auditory tasks was assessed by measuring the variance in the perception of degraded speech in the normal-hearing population. Associations between the perception of degraded speech, working memory, and intellectual efficiency were also explored in CI users and both young and age-matched normal-hearing controls. The listening strategy of “filling in the blanks” or leveraging context to understand words that are not heard or misheard was also explored by using novel sentences with and without semantic context. Finally, ecological momentary assessments were used to assess social and listening behavior of CI users outside of the lab setting, by having participants complete short surveys on their smartphones while engaging in normal daily activities. Results indicate that listening difficulty associated with degraded speech perception and working memory abilities account for some variance seen in outcomes of CI users. Strategies such as leveraging semantic context and using visual cues to supplement auditory information are also widely used in the CI population. Finally, greater levels of social engagement were associated with better speech perception outcomes in individual CI users. These new insights into cognitive and social factors influencing outcomes in CI users could be used by clinicians to tailor rehabilitation and manage expectations in individual patients.