SEARCH · PubMed Health

Results for “Cochlear Implants”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,693 records · Page 94Linked to original sources

PubMed2002

Frequency mapping in cochlear implants.

OBJECTIVE: To understand the short-term ("acute") effects of parametric variations to the frequency-to-electrode mapping on phoneme identification by Nucleus-22 cochlear implant listeners. METHODS: Phoneme recognition was measured in five Nucleus-22 cochlear implant listeners using custom four-channel continuous interleaved sampler (CIS) processors. For the four-channel processors, speech signals were band-pass filtered into four broad frequency bands. The temporal envelope in each band was extracted by half-wave rectification and low-pass filtering at 160 Hz. The extracted envelope was then transformed to electric currents by a power function with an exponent of 0.2. The resulting electric currents were delivered to four electrode pairs (18,22), (13,17), (8,12), (3,7). The effect of frequency-to-electrode mapping was investigated by systematically varying the parameters of band-pass filters while fixing the electrode locations. Experiment 1 measured phoneme recognition as a function of the slope of band-pass filters. The slope of band-pass filters varied from 48 dB/octave to 6 dB/octave; the corner frequencies of band-pass filters were not varied. Experiment 2 measured phoneme recognition as a function of the distribution of band-pass filters across a fixed overall frequency range. The frequency divisions of a fixed overall frequency range were systematically varied from a logarithmic to a linear distribution. Experiment 3 measured phoneme recognition as a function of the bandwidth of the band-pass filters. The bandwidth of each filter varied from 0.2 to 2 octaves; the center frequencies for each band were not varied. No practice or feedback was provided for subjects in all experiments. RESULTS: The slope of the band-pass filters had little effect on both vowel and consonant recognition. A slight performance drop was observed for only the shallowest slope condition (6 dB/octave). In contrast, the distribution of the band-pass filters had a strong effect on vowel recognition but a weak effect on consonant recognition. Best performance was achieved when a logarithmic or near-logarithmic frequency distribution was used to divide the overall frequency range. The bandwidth of the band-pass filters had a moderate effect on both vowel and consonant recognition. Vowel scores dropped significantly when the bandwidth of filters was too broad, whereas consonant scores dropped significantly when a narrower bandwidth was used. CONCLUSION: Under "acute" testing conditions, phoneme recognition with a four-channel CIS strategy seems to be only mildly affected by the slope of the band-pass filters, but can be significantly affected by the distribution of filters as well as the bandwidth of the filters. Optimal or near-optimal performance can be achieved with a logarithmic frequency distribution. Vowels are more susceptible to broad bandwidths, whereas consonants are more susceptible to narrow bandwidths.

Adult↗

PubMed1981

Results following cochlear implantation and rehabilitation.

Nine post-lingually deafened adults received single-electrode cochlear implants and afterwards participated in a rehabilitation program. For these nine patients the average threshold sensitivity in soundfield was significantly better with use of the cochlear prosthesis than with hearing aid amplification in the same ear prior to implantation. Significant changes also occurred in discrimination of environmental sounds, recognition of words and stress patterns, and in speechreading skill. Certain aspects of phonation (harshness, control of intensity, and habitual pitch). and some articulation problems improved, while inflection abnormalities were not altered. Data concerning daily hours of implant activation, an indicator of patient acceptance, reveal that seven of the nine use their cochlear prosthesis for at least eight hours per day. These results suggest that the single electrode cochlear implant is a clinically useful tool in the rehabilitation of selected profoundly deaf individuals.

Adult↗

PubMed1991

Cochlear implants as a contraindication to magnetic resonance imaging.

Magnetic resonance imaging poses little risk to the majority of patients undergoing scanning. However, cochlear implantation should pose a contraindication to this imaging process. This conclusion is based on several findings of in vitro testing of three cochlear implants: the 3M/House and 3M/Vienna designs and the Nucleus device. Specifically, tremendous torques are generated by each of these devices when they are introduced into the coil of a magnetic resonance imager; in addition, the 3M products not only were noted to induce an electrical current, but also were significantly magnetized and rendered afunctional. The clinical implications are discussed.

Cochlear Implants↗

PubMed1998

Role of speech therapy and sign language prior to cochlear implantation.

The speech therapist should assess and develop the communication skills of the deaf child prior and after a cochlear implantation. The goals are first the acquisition of a useful communication system by the deaf child (for avoiding a cognitive stimulation lack) and parallely the acquisition of good oral language competencies. The different modes of communication useable in the profoundly deaf education are presented. Exclusive sign language use is not indicated in implanted children. It is well demonstrated that an exclusive oral communication is associated with an insufficient knowledge of the oral language. The total communication (combination of listening, speech reading, signing with or without finger spelling) is a defective communication mode with a bad representation of the morpho-syntactic and the phonologic aspects of the oral language. The best choice seems to be the simultaneously use of a spoken language and a manually coding of their phonological structures. The limits of this alternative are discussed.

Child↗

PubMed1995

[Signal processing and clinical results with the French cochlear implant Digisonic].

The Digisonic is a totally digitised multichannel cochlear implant remarkable for the versatility of its sound signal processing. Owing to its flexible and articulated array, its 15 electrodes are usually introduced in the scala tympani. A special version of this device has been designed to be used in case of total obstructed cochlea. It consists of separated electrodes which may be inserted one by one in the inner ear in different holes gently drilled in the bony cochlea. The possibilities of the microprocessor allow the speech therapist to carefully select the best width and mean value of each frequency band respectively devoted to each functional electrode. These parameters may be adapted to progressively improve the patient's hearing performances as a function of his phonemic discrimination and or the number and the tonotopy of his functional electrodes. Moreover, owing to the versatility of this digitised emitter a lot of speech coding strategies may be easily programmed as a function of eventual desiderata. Its high miniaturisation leads this implant to be particularly useful for young children. Results of our 38 first implanted patients (age 2-74; mean 42) including 7 cases of totally obstructed cochlea are reported.

Adolescent↗

PubMed2004

Factors affecting speech understanding in gated interference: cochlear implant users and normal-hearing listeners.

Previous work [Nelson, Jin, Carney, and Nelson (2003), J. Acoust. Soc. Am. 113, 961-968] suggested that cochlear implant users do not benefit from masking release when listening in modulated noise. The previous findings indicated that implant users experience little to no release from masking when identifying sentences in speech-shaped noise, regardless of the modulation frequency applied to the noise. The lack of masking release occurred for all implant subjects who were using three different devices and speech processing strategies. In the present study, possible causes of this reduced masking release in implant listeners were investigated. Normal-hearing listeners, implant users, and normal-hearing listeners presented with a four-band simulation of a cochlear implant were tested for their understanding of sentences in gated noise (1-32 Hz gate frequencies) when the duty cycle of the noise was varied from 25% to 75%. No systematic effect of noise duty cycle on implant and simulation listeners' performance was noted, indicating that the masking caused by gated noise is not only energetic masking. Masking release significantly increased when the number of spectral channels was increased from 4 to 12 for simulation listeners, suggesting that spectral resolution is important for masking release. Listeners were also tested for their understanding of gated sentences (sentences in quiet interrupted by periods of silence ranging from 1 to 32 Hz as a measure of auditory fusion, or the ability to integrate speech across temporal gaps. Implant and simulation listeners had significant difficulty understanding gated sentences at every gate frequency. When the number of spectral channels was increased for simulation listeners, their ability to understand gated sentences improved significantly. Findings suggest that implant listeners' difficulty understanding speech in modulated conditions is related to at least two (possibly related) factors: degraded spectral information and limitations in auditory fusion across temporal gaps.

Adult↗

PubMed1997

Effect of high-frequency electrical stimulation of the auditory nerve in an animal model of cochlear implants.

HYPOTHESIS: Electrical stimulation of the cochlea at high rates induces significant adaptation of the auditory nerve. BACKGROUND: A new development of cochlear implants is the use of speech processors delivering electrical pulses on the implanted electrodes at high rates, such as 1,000 pulses per second (pps) and above. Such a stimulation mode allows subjects with cochlear implants to reach excellent understanding of speech. METHODS: Long Evans-rats received implantation of stimulating electrodes in the left cochlea. Two hundred-millisecond trains of short (20 microns) monophasic pulses were delivered in 50% duty cycle at 500 microA above threshold. The pulse rate in the train was increased from 100 pps to 1,500 pps. Electrically evoked auditory brainstem responses (EABR) were recorded. The amplitude of the compound action potential of the auditory nerve to each single pulse in the train was measured as the first vertex positive wave (WAVE I) of the EABR. RESULTS: At 100 and 200 pps, WAVE I amplitudes to each pulse were large and remained stable throughout the pulse train. For increasing pulse rates, WAVE I amplitudes progressively decreased during the first 40 to 50 ms of the train and reached 80% at 300 pps to 15% at 1,500 pps of the maximal amplitude observed for the first pulse in the train. CONCLUSIONS: The decrease of the WAVE I amplitude in response to high-rate pulsatile stimulation reflects an adaptation of the auditory nerve due, at least in part, to the refractory period of auditory nerve fibers.

Acoustic Stimulation↗

PubMed1999

Specific language growth in young children using the CLARION cochlear implant.

General and specific language growth was evaluated in 10 children who had received the CLARION Multi-Strategy Cochlear Implant during the clinical trial. The mean age at implantation was 37 months, and the children were followed for 18 months thereafter. Language comprehension and use were assessed with the Peabody Picture Vocabulary Test, the Reynell Developmental Language Scales, and mean length of utterance (MLU). The mean vocabulary scores indicated a 42-month increase in 18 months. The mean language comprehension increased from 20.4 to 40.8 months, and language use increased from 21.5 to 38.1 months. The mean MLU increased from 1.8 words to 4.8 words during the test period. Results indicated the children learned language at the same rate as their hearing peers of the same language age (except for vocabulary, which was faster), but retained a language delay relative to their hearing peers of the same chronological age.

Child, Preschool↗

PubMed2001

Vocabulary acquisition rate after pediatric cochlear implantation and the impact of age at implantation.

OBJECTIVE: studies of early vocabulary development after pediatric cochlear implantation show growth rates that approach normality. Do these growth rates continue to rise over time and, therefore, allow a 'catch up' with ideal scores for age, or do they decline after an initial peak. Could age at implantation be a decisive factor in that process? DESIGN: retrospective study (mean follow-up 4 years). PATIENTS: pre-lingually deaf children implanted between 1988 and1999, who serially performed Peabody Picture Vocabulary Test-Revised (PPVT), (37 patients) and Expressive One-word Picture Vocabulary Test-Revised (EOWPVT), (35 patients). OUTCOME MEASURES: the mean rates of age equivalent scores were determined for the whole follow-up period and analyzed further for two post-implant periods (the two halves of follow-up duration of individual patients). After sub-grouping by age at implantation (younger or older than 5 years old), the same analysis was executed for each subgroup. RESULTS: the mean EOWPVT rate of the earlier period was higher than that of the later period (1.33 vs. 0.67, P<0.01) and the mean PPVT rate of the earlier period was higher than that of the later period (0.72 vs. 0.5). The latter difference was not statistically significant (P>0.05). Within subgroups by age at implantation, the PPVT mean rates were stable for younger implanted patients (0.56 for both periods) and dropped for the older implanted sub-group (0.87-0.43, P>0.05). The EOWPVT mean rates declined significantly for the older patients group (1.72-0.55, P<0.01) but insignificantly for the younger patients (0.99-0.77, P>0.05). CONCLUSIONS: vocabulary acquisition rates decline in the post-implantation period. This is more pronounced with older implanted children and the EOWPVT rates. This information on the time course development of vocabulary after implantation would be valuable in counseling and planning habilitation in addition to candidate selection.

Age Factors↗

PubMed1998

Imaging and cochlear implant.

The auditory pathway imaging may be morphologic and/or functional. The high resolution computed tomography and the magnetic resonance imaging (MRI) provide an evaluation of the anatomical and structural landmarks useful for a safe and successful cochlear implantation. The electrical stimulations supplied by the cochlear implant give rise to ascending electrochemical activities reaching the cortex. These activities can be recorded with scalp electrodes by Evoked Potentials (EP) or fields techniques and eventually translated in isochronic or isopotential brain mapping. These techniques provide a very sharp temporal resolution with an imprecise spatial resolution. The late auditory EP of implantees are closely comparable to the responses of normal hearing people. The neuronal metabolism's increase is associated with a cerebral blood flow increase. Comparing regional cerebral blood flow (rCBF) between two or more conditions allows the localisation of brain areas involved in a fixed task. Single photon or positron emission tomography and functional MRI (fMRI) demonstrate cBF changes associated with an auditory stimulation. (f)MRI is contraindicated in cochlear implantees.

Brain↗

PubMed2001

A neural network model for optimizing vowel recognition by cochlear implant listeners.

Due to the variability in performance among cochlear implant (CI) patients, it is becoming increasingly important to find ways to optimally fit patients with speech processing strategies. This paper proposes an approach based on neural networks, which can be used to automatically optimize the performance of CI patients. The neural network model is implemented in two stages. In the first stage, a neural network is trained to mimic the CI patient's performance on the vowel identification task. The trained neural network is then used in the second stage to adjust a free parameter to improve vowel recognition performance for each individual patient. The parameter examined in this study was a weighting function applied to the compressed channel amplitudes extracted from a 6-channel continuous interleaved sampling (CIS) strategy. Two types of weighting functions were examined, one which assumed channel interaction, and one which assumed no interaction between channels. Results showed that the neural network models closely matched the performance of five Med-EI/CIS-Link implant patients. The resulting weighting functions obtained after neural network training improved vowel performance, with the larger improvement (4%) attained by the weighting function which modeled channel interaction.

Algorithms↗

PubMedDate not supplied

Speech recognition abilities of adults using cochlear implants with FM systems.

Speech recognition was evaluated for ten adults with normal hearing and eight adults with Nucleus cochlear implants (CIs) at several different signal-to-noise ratios (SNRs) and with three frequency modulated (FM) system arrangements: desktop, body worn, and miniature direct connect. Participants were asked to repeat Hearing in Noise Test (HINT) sentences presented with speech noise in a classroom setting and percent correct word repetition was determined. Performance was evaluated for both normal-hearing and CI participants with the desktop soundfield system. In addition, speech recognition for the CI participants was evaluated using two FM systems electrically coupled to their speech processors. When comparing the desktop sound field and the No-FM condition, only the listeners with normal hearing made significant improvements in speech recognition in noise. When comparing the performance across the three FM conditions for the CI listeners, the two electrically coupled FM systems resulted in significantly greater improvements in speech recognition in noise relative to the desktop soundfield system.

Adult↗

PubMed2004

Cochlear implantation in adults with prelingual deafness. Part I. Clinical results.

OBJECTIVES/HYPOTHESIS: To examine the hypothesis that the newer generations of cochlear implants could provide considerable speech understanding to late-implanted, prelingually deaf adult patients. STUDY DESIGN: Retrospective review. METHODS: Speech perception scores of 103 patients with long-term prelingual deafness obtained from the recent clinical trials were compared with other previously published results. RESULTS: Unlike patients receiving implants in early childhood, the audiologic performance of most patients with long-term prelingual deafness rapidly approached asymptotic levels within 1 year after implantation. Beginning at 3 months postimplantation, statistically significant improvement was noted in their speech perception scores compared with their preimplant levels. However, the average performance plateau achieved by this group of patients was significantly below the levels published for postlingual patients. No statistically significant differences were observed between the test scores at any testing interval among patients with different devices. CONCLUSIONS: Most patients with long-term prelingual deafness achieve their performance plateau within 1 year after implantation. The results suggest that patient characteristics, rather than device properties, are likely to be the major contributing factor responsible for the observed audiologic outcomes.

Adolescent↗

PubMed1998

Cochlear implants in children: an analysis of use over a three-year period.

OBJECTIVE: This study aimed to determine whether children continue to wear their cochlear implant systems 1 and 3 years after implantation. STUDY DESIGN: The design was a prospective study based on the analysis of forced-choice questionnaires on implant use completed independently by parents and teachers. SETTING: The study was performed at a dedicated pediatric cochlear implant program in a tertiary referral center in the United Kingdom. PATIENTS: All 85 consecutively implanted children who had reached the 1-year interval after implantation and 37 children who had reached the 3-year assessment interval after implantation participated. The patients represented all socioeconomic status groups, the entire range of educational settings, and often lived at a considerable distance from the implant center. MAIN OUTCOME MEASURES: Parents and local teachers were asked to describe implant use in the following categories: 1) all of the time; 2) most of the time; 3) some of the time; and 4) none of the time. RESULTS: One year after implantation, parents and teachers, respectively, rated 79 (93%) and 82 (96%) children as full-time users (category 1). Parents rated six children (7%) as users most of the time (category 2), and teachers rated three children (4%) as users most of the time. No child was rated as an occasional or nonuser (category 3 or 4). At 3 years after implantation, 33 (89%) and 34 (95%) children were rated as full-time users (category 1) by parents and teachers, respectively. Parents judged four children (11%) and teachers rated two children (5%) to be users most of the time (category 2). Again, no child was rated in category 3 or 4 as an occasional or nonuser. CONCLUSIONS: The majority of implanted children use their implant systems all of the time over a 3-year period after implantation when selected appropriately and given appropriate follow-up.

Child↗

PubMed2002

Rapid development of cortical auditory evoked potentials after early cochlear implantation.

The aim of our research was to estimate the time course of development and plasticity of the human central auditory pathways following cochlear implantation. We recorded cortical auditory-evoked potentials in 3-year-old congenitally deaf children after they were fitted with cochlear implants. Immediately after implantation cortical response latencies resembled those of normal-hearing newborns. Over the next few months, the cortical evoked responses showed rapid changes in morphology and latency that resulted in age-appropriate latencies by 8 months after implantation. Overall, the development of cortical response latencies for the implanted children was more rapid than for their normal-hearing age-matched peers. Our results demonstrate a high degree of central auditory system plasticity during early human development.

Analysis of Variance↗

PubMed2006

[The application of 3D reconstruction of CT scans for the observation of the cochlear implanted electrode location].

OBJECTIVE: To discuss the different methods of computed tomography (CT) scans and three dimensional reconstruction of inner ear with implanted electrodes, and to evaluate the value and image features of these methods. METHOD: Six cochlear implant (MEDEL Combi 40+, Advanced Bionics) recipients were involved in this study. The implanted electrodes of all patients were examined on the seventh postoperative day. The data of the CT scans was transferred to workstation for three dimensional reconstruction by volume rendering (VR), average intensity projection (AIP) and surface shaded display (SSD). RESULT: The three methods of three dimensional reconstruction provided satisfactory image of implanted electrode including the shape and the special relationship of the electrode in the inner ear. The insertion depth of the electrode can be evaluated directly. Moreover, each of the electrode pairs can be identified clearly. CONCLUSION: Postoperative evaluation of the implanted electrode with three methods of CT scans with three dimensions reconstruction of inner ear provide more accurate image of the special relationship of the electrode in the cochlear canal with direct demonstration of electrode insertion depth in the cochlea.

Child, Preschool↗

PubMed1991

Cochlear implants, acquisitions and controversies in the adult patient.

The cochlear implant field is rapidly progressing in the clinical field. This progress has produced new information regarding choice of devices, selection criteria, and surgical techniques. Some of these points remain controversial, and the authors try to determine their real value.

Adult↗

PubMed1999

Growth factors, auditory neurones and cochlear implants: a review.

The total number and the integrity of the auditory neurones available for stimulation govern the benefits that patients can derive from cochlear implants. Although electrical stimulation of the cochlea has been reported to promote auditory neuronal survival, this trophic effect is insufficient to regenerate de novo fibres. Hence, any agent that can maximize the number of, or regenerate functional auditory neurones would be of great benefit. Several studies have identified various growth factors crucial to the normal development of auditory neurones. In addition, in vitro studies have demonstrated that several growth factors are important for the maintenance, rescue and repair of adult auditory neurones. In vivo studies confirm the in vitro findings, reporting that specific growth factors are able to support auditory neuronal survival following injury or trauma, and in lower species growth factors have been associated with regenerating auditory neurones. In addition to their trophic actions, several growth factors have also been reported to affect ion channels thus the electrical response of neuronal fibres. Indeed, growth factors have been reported to enhance neuronal excitation and to improve the efficacy of synaptic transmission. Taken in concert, these effects suggest that exogenous growth factors delivered to the cochlea may improve the transmission of the electrical stimuli from the implanted electrode to the auditory pathway. Further studies are warranted to investigate how the adjunct delivery of growth factors with the cochlear implant may constitute a better treatment for hearing-impaired individuals.

Adult↗