Evaluating Listening Effort in Unilateral, Bimodal, and Bilateral Cochlear Implant Users.

OBJECTIVE: Evaluate listening effort (LE) in unilateral, bilateral, and bimodal cochlear implant (CI) users. Establish an easy-to-implement task of LE that could be useful for clinical decision making. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary neurotology center. METHODS: The Sentence Final Word Identification and Recall Task, an established measure of LE, was modified to include challenging listening conditions (multitalker babble, gender, and emotional variation; test), in addition to single-talker sentences (control). Participants listened to lists of sentences in each condition and recalled the last word of each sentence. LE was quantified by percentage of words correctly recalled and was compared across conditions, across CI groups, and within subjects (best aided vs monaural). RESULTS: A total of 24 adults between the ages of 37 and 82 years enrolled, including 4 unilateral CI users (CI), 10 bilateral CI users (CICI), and 10 bimodal CI users (CIHA). Task condition impacted LE (P < .001), but hearing configuration and listener group did not (P = .90). Working memory capacity and contralateral hearing contributed to individual performance. CONCLUSION: This study adds to the growing body of literature on LE in challenging listening conditions for CI users and demonstrates feasibility of a simple behavioral task that could be implemented clinically to assess LE. This study also highlights the potential benefits of bimodal hearing and individual hearing and cognitive factors in understanding individual differences in performance, which will be evaluated through further research.

The Impact of Neurocognitive Skills on Recognition of Spectrally Degraded Sentences.

BACKGROUND: Recent models theorize that neurocognitive resources are deployed differently during speech recognition depending on task demands, such as the severity of degradation of the signal or modality (auditory vs. audiovisual [AV]). This concept is particularly relevant to the adult cochlear implant (CI) population, considering the large amount of variability among CI users in their spectro-temporal processing abilities. However, disentangling the effects of individual differences in spectro-temporal processing and neurocognitive skills on speech recognition in clinical populations of adult CI users is challenging. Thus, this study investigated the relationship between neurocognitive functions and recognition of spectrally degraded speech in a group of young adult normal-hearing (NH) listeners. PURPOSE: The aim of this study was to manipulate the degree of spectral degradation and modality of speech presented to young adult NH listeners to determine whether deployment of neurocognitive skills would be affected. RESEARCH DESIGN: Correlational study design. STUDY SAMPLE: Twenty-one NH college students. DATA COLLECTION AND ANALYSIS: Participants listened to sentences in three spectral-degradation conditions: no degradation (clear sentences); moderate degradation (8-channel noise-vocoded); and high degradation (4-channel noise-vocoded). Thirty sentences were presented in an auditory-only (A-only) modality and an AV fashion. Visual assessments from The National Institute of Health Toolbox Cognitive Battery were completed to evaluate working memory, inhibition-concentration, cognitive flexibility, and processing speed. Analyses of variance compared speech recognition performance among spectral degradation condition and modality. Bivariate correlation analyses were performed among speech recognition performance and the neurocognitive skills in the various test conditions. RESULTS: Main effects on sentence recognition were found for degree of degradation (p = < 0.001) and modality (p = < 0.001). Inhibition-concentration skills moderately correlated (r = 0.45, p = 0.02) with recognition scores for sentences that were moderately degraded in the A-only condition. No correlations were found among neurocognitive scores and AV speech recognition scores. CONCLUSIONS: Inhibition-concentration skills are deployed differentially during sentence recognition, depending on the level of signal degradation. Additional studies will be required to study these relations in actual clinical populations such as adult CI users.

Bottom-Up Signal Quality Impacts the Role of Top-Down Cognitive-Linguistic Processing During Speech Recognition by Adults with Cochlear Implants.

HYPOTHESES: Significant variability persists in speech recognition outcomes in adults with cochlear implants (CIs). Sensory ("bottom-up") and cognitive-linguistic ("top-down") processes help explain this variability. However, the interactions of these bottom-up and top-down factors remain unclear. One hypothesis was tested: top-down processes would contribute differentially to speech recognition, depending on the fidelity of bottom-up input. BACKGROUND: Bottom-up spectro-temporal processing, assessed using a Spectral-Temporally Modulated Ripple Test (SMRT), is associated with CI speech recognition outcomes. Similarly, top-down cognitive-linguistic skills relate to outcomes, including working memory capacity, inhibition-concentration, speed of lexical access, and nonverbal reasoning. METHODS: Fifty-one adult CI users were tested for word and sentence recognition, along with performance on the SMRT and a battery of cognitive-linguistic tests. The group was divided into "low-," "intermediate-," and "high-SMRT" groups, based on SMRT scores. Separate correlation analyses were performed for each subgroup between a composite score of cognitive-linguistic processing and speech recognition. RESULTS: Associations of top-down composite scores with speech recognition were not significant for the low-SMRT group. In contrast, these associations were significant and of medium effect size (Spearman's rho = 0.44-0.46) for two sentence types for the intermediate-SMRT group. For the high-SMRT group, top-down scores were associated with both word and sentence recognition, with medium to large effect sizes (Spearman's rho = 0.45-0.58). CONCLUSIONS: Top-down processes contribute differentially to speech recognition in CI users based on the quality of bottom-up input. Findings have clinical implications for individualized treatment approaches relying on bottom-up device programming or top-down rehabilitation approaches.

Cognitive Functions in Adults Receiving Cochlear Implants: Predictors of Speech Recognition and Changes After Implantation.

HYPOTHESES: Significant variability in speech recognition outcomes is consistently observed in adults who receive cochlear implants (CIs), some of which may be attributable to cognitive functions. Two hypotheses were tested: 1) preoperative cognitive skills assessed visually would predict postoperative speech recognition at 6 months after CI; and 2) cochlear implantation would result in benefits to cognitive processes at 6 months. BACKGROUND: Several executive functioning tasks have been identified as contributors to speech recognition in adults with hearing loss. There is also mounting evidence that cochlear implantation can improve cognitive functioning. This study examined whether preoperative cognitive functions would predict speech recognition after implantation, and whether cognitive skills would improve as a result of CI intervention. METHODS: Nineteen post-lingually deafened adult CI candidates were tested preoperatively using a visual battery of tests to assess working memory (WM), processing speed, inhibition-concentration, and nonverbal reasoning. Six months post-implantation, participants were assessed with a battery of word and sentence recognition measures and cognitive tests were repeated. RESULTS: Multiple speech measures after 6 months of CI use were correlated with preoperative visual WM (symbol span task) and inhibition ability (stroop incongruent task) with moderate-to-large effect sizes. Small-to-large effect size improvements in visual WM, concentration, and inhibition tasks were found from pre- to post-CI. Patients with lower baseline cognitive abilities improved the most after implantation. CONCLUSIONS: Findings provide evidence that preoperative cognitive factors contribute to speech recognition outcomes for adult CI users, and support the premise that implantation may lead to improvements in some cognitive domains.

Total body phylloquinone and its turnover in human subjects at two levels of vitamin K intake.

The aims of this study were to determine the total body phylloquinone and its metabolic turnover in human subjects using a tracer dose of [5-H3]phylloquinone containing 4 MBq/mmol. Seven subjects aged 22 to 49 years were given 0.3 microg isotopic phylloquinone intravenously on a control diet (75 microg phylloquinone/d) and blood, urine and faeces were sampled periodically for 6 d. Five of these subjects were studied a second time after 3-8 weeks on a low-vitamin K diet (8 microg/d). The changes in the radioactivity of plasma phylloquinone with time were analysed by the method of residuals and fitted to a curve composed of two exponential components. The size of the exchangeable body pool was calculated by isotope dilution. Plasma phylloquinone levels fell during vitamin K restriction but the vitamin K-dependent coagulation factors did not change. After injection the first exponential decay curve t1/2 was 1.0 (sd 0.47) h in the subjects on the control diet and 0.49 (sd 0.27) h after vitamin K restriction. On the control diet, the second exponential t1/2 was 27.6 (sd 124) h that did not change on the low-vitamin K diet ( (sd 13.5) h). These results indicate that the turnover time for phylloquinone in human subjects is about 1.5 d. Urinary excretion of 3H-metabolites ranged from 30 % of the administered dose on the control diet to 38 % on the restricted diet and had the same turnover rate as the second component of the plasma decay curves. The exchangeable body pool of phylloquinone declined from about 1.0 microg/kg before restriction to lower values after vitamin K restriction. The faecal excretion of phylloquinone and its metabolites fell from 32 % of the administered dose on the control diet to 13 % on the restricted diet.