Low-frequency signals support perceptual organization of implant-simulated speech for adults and children.

OBJECTIVE: Using signals processed to simulate speech received through cochlear implants and low-frequency extended hearing aids, this study examined the proposal that low-frequency signals facilitate the perceptual organization of broader, spectrally degraded signals. DESIGN: In two experiments, words and sentences were presented in diotic and dichotic configurations as four-channel noise-vocoded signals (VOC-only), and as those signals combined with the acoustic signal below 0.25 kHz (LOW-plus). Dependent measures were percent correct recognition, and the difference between scores for the two processing conditions given as proportions of recognition scores for VOC-only. The influence of linguistic context was also examined. STUDY SAMPLE: Participants had normal hearing. In all, 40 adults, 40 seven-year-olds, and 20 five-year-olds participated. RESULTS: Participants of all ages showed benefits of adding the low-frequency signal. The effect was greater for sentences than words, but no effect of diotic versus dichotic presentation was found. The influence of linguistic context was similar across age groups, and did not contribute to the low-frequency effect. Listeners who had poorer VOC-only scores showed greater low-frequency effects. CONCLUSION: The benefit of adding a low-frequency signal to a broader, spectrally degraded signal derives in some part from its facilitative influence on perceptual organization of the sensory input.

Cochlear Implants in Adults: Effects of Age and Duration of Deafness on Speech Recognition.

OBJECTIVE: Unexplained outcome variability exists among adults with cochlear implants (CIs). Two significant predictors are age and duration of deafness, with older patients and those with longer durations of deafness generally demonstrating poorer speech recognition. However, these factors are often highly correlated. Thus, it is unclear whether poorer outcomes should be attributed primarily to age-related declines or to the experience of auditory deprivation. Our aim was to examine the effects of aging and duration of hearing loss on outcomes for postlingually deaf adults with CIs. STUDY DESIGN: Retrospective review of adults who received CIs from 1983 to 2014. SETTING: Tertiary adult CI program. PATIENTS: Sixty-four adult patients with postlingual hearing loss beginning after age 12 years, full electrode insertion, normal cochlear anatomy, and availability of postoperative outcome measures. INTERVENTION: Cochlear implantation with 12 months or greater of device use. MAIN OUTCOME MEASURES: Postoperative pure-tone averages (0.5, 1, 2, and 3 kHz) and recognition of words in sentences (Hearing in Noise Test and AzBio). RESULTS: Age at postoperative testing had a negative partial correlation with AzBio scores, when controlling for duration of deafness, whereas duration of deafness had a positive partial correlation with AzBio scores, when controlling for age. No other effects were identified. CONCLUSION: Older age at testing was associated with poorer recognition of words in difficult sentences, suggesting that cognitive aging may negatively impact CI outcomes. Further studies are needed to examine how a long duration of auditory deprivation affects CI outcomes.