Comparison of speech recognition ability with different speech processing strategies by Korean cochlear implantees

Speech perception performance in experienced cochlear-implant patients receiving the SPEAK processing strategy in the Nucleus Spectra-22 cochlear implant

Sixteen experienced cochlear implant patients with a wide range of speech-perception abilities received the SPEAK processing strategy in the Nucleus Spectra-22 cochlear implant. Speech perception was assessed in quiet and in noise with SPEAK and with the patients' previous strategies (for most, Multipeak) at the study onset, as well as after using SPEAK for 6 months. Comparisons were made within and across the two test sessions to elucidate possible learning effects. Patients were also asked to rate the strategies on seven speech recognition and sound quality scales. After 6 months' experience with SPEAK, patients showed significantly improved mean performance on a range of speech recognition measures in quiet and noise. When mean subjective ratings were compared over time there were no significant differences noted between strategies. However, many individuals rated the SPEAK strategy better for two or more of the seven subjective measures. Ratings for "appreciation of music" and "quality of my own voice" in particular were generally higher for SPEAK. Improvements were realized by patients with a wide range of speech perception abilities, including those with little or no open-set speech recognition.

Performance over time of adult patients using the Ineraid or nucleus cochlear implant

This study examined the average and individual performance over time of 49 adult cochlear implant subjects. Subjects were randomly assigned to receive either the Ineraid cochlear implant, with analog processing, or the Nucleus cochlear implant, with feature-extraction processing. All subjects had postlingual profound bilateral sensorineural hearing loss and received no significant benefit from hearing aids before implantation. Group data were examined in two ways. First, only subjects who had complete data over the test period were examined. Second, an analysis of all available data was carried out by mixed linear-model analysis. In this analysis, to account for missed follow-ups at the planned intervals, data consisting of the observations closest in time to the planned test times were modeled by natural splines with knots at the planned follow-up times. Contrasts between all pairs of planned follow-up times for each device were tested, as were contrasts between devices at each planned follow-up time. Results indicated little difference between the performance of the Ineraid and Nucleus subjects in their level of performance or their rate of learning. Postimplantation performance was typically superior to preimplantation performance within 9 months, and continued to improve up to 18-30 months depending on the speech perception measure. In some subjects, improvements in speech perception measures were observed up to four or five years postimplantation. There was also evidence that three subjects had a decrement in overall speech perception performance, although their postimplantation scores were always higher than their preimplantation scores. In at least one subjects this was likely a result of age-related cognition decrements.

A within-subject comparison of adult patients using the Nucleus F0F1F2 and F0F1F2B3B4B5 speech processing strategies

This study compares the Nucleus F0F1F2 and F0F1F2B3B4B5 (also known as "Multipeak") of "Mpeak") processing schemes in 17 patients wearing the Mini Speech Processor. All patients had at least 18 months implant experience using the F0F1F2 processing strategy. For this study, they were switched to the F0F1F2B3B4B5 processing strategy for 3 months. They then returned to using the F0F1F2 strategy for 3 months, then used the F0F1F2B3B4B5 strategy again for 3 months, and lastly used the F0F1F2 strategy for 3 months. Performance' was evaluated with both schemes after each interval, using speech recognition tests and subjective ratings. Overall, differences between the results for the two processing schemes were not large. Average performance was somewhat better for the F0F1F2B3B4B5 strategy for word and sentence identification, but not for any of the other speech measures. Superior performance was observed in 8 patients with the F0F1F2B3B4B5 strategy. However, 6 of the 8 individuals were significantly better on only one of the six speech measures in the test battery. The other 2 patients performed better on two of the speech measures. Superior performance was also observed in 3 patients with F0F1F2 strategy for consonant recognition. For the remaining patients, there was little difference in their performance with the two strategies. Information transmission analyses indicated that the F0F1F2B3B4B5 strategy transmitted consonant duration and frication cues more efficiently than F0F1F2. Experience with one strategy appeared to benefit performance with the other strategy.

Performance of adult Ineraid and Nucleus cochlear implant patients after 3.5 years of use

Forty-two postlingually deafened adult patients, 21 with a formant extraction version of the Nucleus cochlear implant and 21 with the Ineraid cochlear implant (analog processing), were evaluated on a series of speech perception tests after using their implants for about 3.5 years. A wide range of performance was observed across patients for both devices. All but 4 patients showed an enhancement in their lipreading ability with the implant. Word recognition averaged about 14-19% correct, and word recognition in sentences averaged about 43-49% correct for the two implant groups. Average performance was superior with the Ineraid implant on consonant recognition in noise. An information transmission analysis suggested that vowel perception was influenced by first- and third-formant frequency for the Nucleus, and first-formant and fundamental frequency for the Ineraid patients. It appeared that the Ineraid device was more effective, on average, at conveying information about consonant nasality and frication. For consonant perception, nasality and frication contributed most to the total information transmitted for both implant types. Both devices had difficulty conveying information about vowel second-formant frequency and consonant place information. These scores at 3.5 years are substantially elevated from preoperative performance and, overall, the patients clearly benefit from their implant.