Objective A great deal of variability exists in the speech-recognition abilities of postlingually deaf adult cochlear implant (CI) recipients. A number of previous studies have shown that duration of deafness is a primary factor affecting CI outcomes; however, there is little agreement regarding other factors that may affect performance. The objective of the present study was to determine the source of variability in CI outcomes by examining three main factors, biographic/audiologic information, electrode position within the cochlea, and cognitive abilities in a group of newly implanted CI recipients. Design Participants were 114 postlingually deaf adults with either the Cochlear or Advanced Bionics CI systems. Biographic/audiologic information, aided sentence-recognition scores, a high resolution temporal bone CT scan and cognitive measures were obtained before implantation. Monosyllabic word recognition scores were obtained during numerous test intervals from 2 weeks to 2 years after initial activation of the CI. Electrode position within the cochlea was determined by three-dimensional reconstruction of pre- and postimplant CT scans. Participants' word scores over 2 years were fit with a logistic curve to predict word score as a function of time and to highlight 4-word recognition metrics (CNC initial score, CNC final score, rise time to 90% of CNC final score, and CNC difference score). Results Participants were divided into six outcome groups based on the percentile ranking of their CNC final score, that is, participants in the bottom 10% were in group 1; those in the top 10% were in group 6. Across outcome groups, significant relationships from low to high performance were identified. Biographic/audiologic factors of age at implantation, duration of hearing loss, duration of hearing aid use, and duration of severe-to-profound hearing loss were significantly and inversely related to performance as were frequency modulated tone, sound-field threshold levels obtained with the CI. That is, the higher-performing outcome groups were younger in age at the time of implantation, had shorter duration of severe-to-profound hearing loss, and had lower CI sound-field threshold levels. Significant inverse relationships across outcome groups were also observed for electrode position, specifically the percentage of electrodes in scala vestibuli as opposed to scala tympani and depth of insertion of the electrode array. In addition, positioning of electrode arrays closer to the modiolar wall was positively correlated with outcome. Cognitive ability was significantly and positively related to outcome; however, age at implantation and cognition were highly correlated. After controlling for age, cognition was no longer a factor affecting outcomes. Conclusion There are a number of factors that limit CI outcomes. They can act singularly or collectively to restrict an individual's performance and to varying degrees. The highest performing CI recipients are those with the least number of limiting factors. Knowledge of when and how these factors affect performance can favorably influence counseling, device fitting, and rehabilitation for individual patients and can contribute to improved device design and application.

Factors affecting open-set word recognition in adults with cochlear implants.

Like any other surgery requiring anesthesia, cochlear implantation in the first few years of life carries potential risks, which makes it important to assess the potential benefits. This study introdu

Development of Language and Speech Perception in Congenitally, Profoundly Deaf Children as a Function of Age at Cochlear Implantation

Objective: This study investigated factors contributing to the comprehension and production of English language by children with prelingual deafness after 4 to 7 yr of multichannel cochlear implant use. The analysis controlled for the effects of child and family characteristics so that educational factors most conducive to maximum implant benefit could be identified. Design: A battery of language tests were administered to 181 8- and 9-yr-old children from across the United States and Canada who received a cochlear implant by age 5. Tests of comprehension, verbal reasoning, narrative ability and spontaneous language production were administered either in speech and sign or in the child’s preferred communication mode. These constituted the Total Language measures. Spoken Language measures were derived from a speech-only language sample. Type and amount of educational intervention since implantation constituted the independent variables. Characteristics of the child and the family were considered intervening variables. A series of multiple regression analyses determined the amount of variance in Total Language and Spoken Language ability accounted for by the intervening variables and the amount of additional variance attributable to the independent variables. Results: More than half of the children (with performance intelligence quotients in the average range) exhibited language skills that were similar to those of hearing 8 to 9 yr olds on measures of verbal reasoning, narrative ability, utterance length, and lexical diversity. Significant predictors of language ability were similar for Total and for Spoken Language outcomes and included greater nonverbal intelligence, smaller family size, higher socio-economic status and female gender. Age at receiving an implant did not affect language outcome. After the variance due to these variables was controlled, the primary rehabilitative factors associated with linguistic outcome were amount of mainstream class placement and an educational emphasis on speech and auditory skills. Conclusions: Use of a cochlear implant has had a dramatic impact on the linguistic competence of profoundly hearing-impaired children. More than half of the children in this sample with average learning ability produced and understood English language at a level comparable with that of their hearing age mates. Such mature language outcomes were not typical of children with profound hearing loss who used hearing aids. Use of a visual (i.e., sign) language system did not provide the linguistic advantage that had been anticipated. Children educated without use of sign exhibited a significant advantage in their use of narratives, the breadth of their vocabulary, in their use of bound morphemes, in the length of their utterances and in the complexity of the syntax used in their spontaneous language. An oral educational focus provided a significant advantage for both spoken and total language skills. (Ear & Hearing 2003;24;46S–58S)

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Language skills of children with early cochlear implantation.

Eighty-seven primary-school children with impaired hearing were evaluated using speech perception, production, and language measures over a 3-year period. Forty-seven children with a mean unaided p...

Relationships Among Speech Perception, Production, Language, Hearing Loss, and Age in Children With Impaired Hearing

Hypothesis:Suboptimal cochlear implant (CI) electrode array placement may reduce presentation of coded information to the central nervous system and, consequently, limit speech recognition.Background:Generally, mean speech reception scores for CI recipients are similar across different CI systems, y

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Role of electrode placement as a contributor to variability in cochlear implant outcomes.

A group of 10 children, adolescents, and prelinguistically deafened adults were implanted with the 22-electrode cochlear implant (Cochlear Pty Ltd) at the University of Melbourne Cochlear Implant C...

Cochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception.

OBJECTIVES This study tested a combination of algorithms designed to improve cochlear implant performance in noise. A noise reduction (NR) algorithm, based on signal to noise ratio estimation was evaluated in combination with several directional microphone algorithms available in the Cochlear CP810 sound processor. DESIGN Fourteen adult unilateral cochlear implant users participated in the study. Evaluation was conducted using word recognition in quiet, sentence recognition in noise, and subjective feedback via questionnaire after a period of take-home use. Music appreciation was also evaluated in a controlled listening task. The sentence recognition task measured speech reception threshold for 50% morphemes correct. The interfering maskers were speech-weighted noise and competing talkers, which were spatially separated from the target speech. In addition, the locations of the noise maskers changed during the test in an effort to replicate relevant real-world listening conditions. SmartSound directionality settings Standard, Zoom, and Beam (used in the SmartSound programs Everyday, Noise, and Focus, respectively) were all evaluated with and without NR. RESULTS Microphone directionality demonstrated a consistent benefit in sentence recognition in all noise conditions tested. The group average speech reception threshold benefit over the Standard setting was 3.7 dB for Zoom and 5.3 dB for Beam. Addition of the NR algorithm further improved sentence recognition by 1.3 dB when the noise maskers were speech-weighted noise. There was an overall group preference for the NR algorithm in noisy environments. Group mean word recognition in quiet, preference in quiet conditions, and music appreciation were all unaffected by the NR algorithm. CONCLUSIONS Multimicrophone directionality was effective in improving speech understanding in spatially separated noisy conditions. The single-channel NR algorithm further enhanced speech intelligibility in speech-weighted noise for cochlear implant users while maintaining equivalent performance in quiet situations and when listening to music.

Combining directional microphone and single-channel noise reduction algorithms: a clinical evaluation in difficult listening conditions with cochlear implant users.

Objective: The aim of this study was to investigate whether a real-time noise reduction algorithm provided speech perception benefit for Cochlear™ Nucleus® cochlear implant recipients in the laboratory. Design: The noise reduction algorithm attenuated masker-dominated channels. It estimated the signal-to-noise ratio of each channel on a short-term basis from a single microphone input, using a recursive minimum statistics method. In this clinical evaluation, the algorithm was implemented in two programs (noise reduction programs 1 [NR1] and 2 [NR2]), which differed in their level of noise reduction. These programs used advanced combination encoder (ACE™) channel selection and were compared with ACE without noise reduction in 13 experienced cochlear implant subjects. An adaptive speech reception threshold (SRT) test provided the signal-to-noise ratio for 50% sentence intelligibility in three different types of noises: speech-weighted, cocktail party, and street-side city noise. Results: In all three noise types, mean SRTs for both NR programs were significantly better than those for ACE. The greatest improvement occurred for speech-weighted noise; the SRT benefit over ACE was 1.77 dB for NR1 and 2.14 dB for NR2. There were no significant differences in speech perception scores between the two NR programs. Subjects reported no degradation in sound quality with the experimental programs. Conclusions: The noise reduction algorithm was successful in improving sentence perception in speech-weighted noise, as well as in more dynamic types of background noise. The algorithm is currently being trialed in a behind-the-ear processor for take-home use.

Clinical evaluation of signal-to-noise ratio-based noise reduction in Nucleus® cochlear implant recipients.

The aim of this study was to assess auditory sequential, short-term-memory (SSTM) performance in young children using cochlear implants (CI group) and to examine the relationship of this performance to receptive language performance. Twenty-four children, 5 to 11 years old, using the Nucleus 22-electrode cochlear implant, were tested on a number of auditory and visual tasks of SSTM. The auditory memory tasks were designed to minimize the effect of auditory discrimination ability. Stimuli were chosen that children with cochlear implants could accurately identify with a reaction time similar to that of a control group of children with normal hearing (NH group). All children were also assessed on a receptive language test and on a nonverbal intelligence scale. As expected, children using cochlear implants demonstrated poorer auditory and visual SSTM skills than their hearing peers when the stimuli were verbal or were pictures that could be readily labeled. They did not differ from their peers with normal hearing on tasks where the stimuli were less likely to be verbally encoded. An important finding was that the CI group did not appear to have a sequential memory deficit specific to the auditory modality. The difference scores (auditory minus visual memory performance) for the CI group were not significantly different from those for the NH group. SSTM performance accounted for significant variance in the receptive language performance of the CI group. However, a forward stepwise regression analysis revealed that visual spatial memory (one of the subtests of the nonverbal IQ test) was the main predictor of variance in the language scores of the children using cochlear implants.

Pam W. Dawson

Papers

Cochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception.

Combining directional microphone and single-channel noise reduction algorithms: a clinical evaluation in difficult listening conditions with cochlear implant users.

Clinical evaluation of signal-to-noise ratio-based noise reduction in Nucleus® cochlear implant recipients.

Short-term auditory memory in children using cochlear implants

Short-term auditory memory in children using cochlear implants and its relevance to receptive language.