Effect of consistent electric stimulation on auditory perception in cochlear implant users
Holder, Jourdan Taylor
The primary goal of this project was to investigate the relationship between daily cochlear implant (CI) use and speech recognition outcomes in postlingually deafened, adult CI recipients. This goal was addressed using four related experiments. First, a correlational analysis of daily CI use measured via data logging in the CI software and speech recognition outcomes showed a strong, significant correlation (rs = 0.61, p < 0.0001, 95% Confidence Interval [0.54, 0.69]) in a sample of 300 patients. This finding motivated experiment two, which aimed to evaluate the impact of increased CI use on speech recognition performance and assess one potential underlying mechanism. The results of the second experiment showed that speech recognition can be improved with more consistent daily CI use. On average, participants’ (n = 20) speech recognition improved by 3.0-, 2.4-, and 7.0-percentage points per hour of increased use for words, sentences, and sentences in noise, respectively. The one potential underlying mechanism that we assessed, spectral processing, was a significant mediator of the change, but only accounted for a small amount of the variance. Experiment three explored other commonly studied factors thought to contribute to CI outcome variability but have not yet been studied in combination with daily CI use: electrode location, neurocognitive measures, and CI programming. This experiment was not adequately powered to draw firm conclusions, but results showed a significant correlation between a measure of inhibitory control (Stroop test) and all measures of speech recognition. Lastly, in experiment four, we designed a questionnaire to identify daily CI use habits and barriers to daily CI use. The Cochlear Implant Use Questionnaire (CIUQ) was developed and administered to 100 CI recipients. It was immediately useful for identifying and overcoming barriers to CI use with our study participants, and it showed evidence of construct validity via a significant correlation with daily CI use. In summary, this dissertation project discovered a novel correlation between daily CI use and speech recognition in adults, provided evidence that more consistent daily CI use causes improved speech recognition, and created a tool to help patients identify and overcome barriers to more consistent CI use.