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Cochlear Implants in Adults - Research

1. An overall view of research by Margaret Skinner, Laura Holden and Tim Holden

Since 1989, the major goal of our clinical research with adult cochlear implant recipients has been to determine how to program an individual's speech processor to provide the best understanding of speech. The processor has the capability of activating the implanted electrodes in a variety of different ways, separately or in combination. Therefore it is necessary to adjust the processor that optimizes this activation in a way that is customized for each individual. For each study, two or three sets of adjustments have been chosen for comparison in a rigorous research design. Between six and twelve adults from our program participated in each study which covered a period of one to five months in weekly, two hour sessions

Results of these studies have demonstrated the significant improvement in speech recognition by research subjects for certain speech coding strategies. Two examples are the Nucleus 22 multipeak speech coding strategy (MPEAK) in 1989, and the spectral peak speech coding strategy (SPEAK) in 1994. We also have found improvement with certain settings, for example, assignment of frequency bands of incoming sound to electrodes in the inner ear.

Recent experimental results with the Nucleus 24 device have shown that it is also important to have more than one speech coding strategy available. We have found that individuals differ in the strategies they use to optimize their understanding of speech and which they prefer to use in everyday life. With the preferred strategy, they can communicate with greater ease in face-to-face conversation and on the telephone.

Analysis of individuals' responses to words presented during testing has revealed that individuals differ in their speech recognition patterns across speech coding strategies. When this analysis is complete, we hope it will suggest ways to modify selection of speech processor parameters for improved speech recognition and to develop training tasks for aural rehabilitation.

In another area of research, we are collaborating with colleagues in the Department of Radiology to determine the precise position of the cochlear implant electrode array in the inner ear of our patients. Our past studies have confirmed that there is great variation in the dimensions of the human inner ear. When the surgeon inserts the electrode array into the inner ear it is done essentially blindly, relying on resistance to determine the stopping point. Therefore, radiological information is critical to tell us where the array is in relation to auditory neurons in each person's ear.

In another area of research, we are collaborating with colleagues in the Department of Radiology to determine the precise position of the cochlear implant electrode array in the inner ear of our patients. Our past studies have confirmed that there is great variation in the dimensions of the human inner ear. When the surgeon inserts the electrode array into the inner ear it is done essentially blindly, relying on resistance to determine the stopping point. Therefore, radiological information is critical to tell us where the array is in relation to auditory neurons in each person's ear.

Our present collaboration is designed to enhance our ability to identify the position of the electrode array. Having gained this knowledge, we will compare each electrode's position with behavioral measures of the softest to loudest sound heard and inner ear recordings of auditory neurons' response to stimulation of each electrode. It is hoped that this analysis will provide a new basis for choosing speech processor adjustments that will lead to even better understanding of speech.

2. An overall view of research by Susan Binzer

For a number of years, cochlear implant recipients in our program and their partners have filled out a questionnaire called the Communication Profile for the Hearing Impaired (CPHI). They respond to the CPHI before and after cochlear implantation so we can evaluate their assessment of the degree of benefit from the implant. Recent analysis of their responses to the CPHI has shown that their perceived level of benefit agrees well with their success in understanding speech with their implants. Our findings suggest that the CPHI is a valuable tool for evaluating the psychosocial benefits of a cochlear implant.

CPHI results for four recipients were unusual in that the patients appeared to deny typical reactions to communication problems. We investigated the belief systems and coping mechanisms of these four individuals. We discovered that in everyday living, these individuals appear to cope well and have accepted the limitations of deafness. Analysis of their narratives suggests that their belief systems, including their strong spiritual faith, assisted them in achieving acceptance of their condition rarely seen amongst their hearing-impaired peers. Ongoing research is designed to evaluate other aspects of psychosocial benefit of cochlear implantation and hearing rehabilitation.

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Copyright 2014 Washington University School of Medicine
Copyright 2014 Washington University School of Medicine