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PubMed1988

Binaural cochlear implantation: comparison of 3M/House and Nucleus 22 devices with evidence of sensory integration.

Direct comparison of the efficacy of cochlear implant designs has been difficult for several reasons. There have been wide variations in patients implanted and many differences in testing protocols for each device. In most instances, even a single patient may have unequal degrees of pathology and duration of deafness in the two ears. Implantation of a 3M/House device in the left ear and a Nucleus 22 device in the right ear of a 55-year-old woman, deafened to a similar degree and simultaneously in both ears by streptomycin, allows an opportunity to compare function under presumably similar circumstances. The Nucleus 22 cochlear implant was superior in this case in providing speech discrimination. Perhaps of greater interest, however, is evidence of a binaural effect. Presumably, central integration of sensory stimuli presented through two dissimilar processing strategies resulted in enhanced function on certain measures.

Cochlear Implants↗
PubMed2003

Binaural sensitivity as a function of interaural electrode position with a bilateral cochlear implant user.

Experiments were conducted with a single, bilateral cochlear implant user to examine interaural level and time-delay cues that putatively underlie the design and efficacy of bilateral implant systems. The subject's two implants were of different types but custom equipment allowed presentation of controlled bilateral stimuli, particularly those with specified interaural time difference (ITD) and interaural level difference (ILD) cues. A lateralization task was used to measure the effect of these cues on the perceived location of the sensations elicited. For trains of fixed-amplitude, biphasic current pulses at 100 pps, the subject demonstrated sensitivity to an ITD of 300 micros, providing evidence of access to binaural information. The choice of bilateral electrode pair greatly influenced ITD sensitivity, suggesting that electrode pairings are likely to be an important consideration in the effort to provide binaural advantages. The selection of bilateral electrode pairs showing sensitivity to ITD was partially aided by comparisons of the pitch elicited by individual electrodes in each ear (when stimulated alone with fixed-amplitude current pulses at 813 pps): specifically, interaural electrodes with similar pitches were more likely (but not certain) to show ITD sensitivity. Significant changes in lateral position occurred with specific electrode pairs. With five bilateral electrode pairs of 14 tested, ITDs of 300 and 600 micros moved an auditory image significantly from right to left. With these same pairs, ILD changes of approximately 11% of the dynamic range (in microApp) moved an auditory image from the far left to the far right-significantly farther than the nine pairs not showing significant ITD sensitivity. However, even these nine pairs did show response changes as a function of the interaural (or confounding monaural) level cue. Overall, insofar as the access to bilateral cues demonstrated herein generalizes to other subjects, it provides hope that the normal binaural advantages for speech recognition and sound localization can be made available to bilateral implant users.

Acoustic Stimulation↗
PubMed2000

Audiophonological results after cochlear implantation in 40 congenitally deaf patients: preliminary results.

The aim of this study is to evaluate the prognostic factors of audiophonological results in cochlear implant in congenitally deaf patients. Between 1991 and 1996. 40 congenitally deaf children underwent cochlear implantation in our department, at an average age of 7 years (median: 5 years). The results of speech therapy were evaluated with a mean follow-up of 2 years and were classified according to four criteria: perception of sound, speech perception, speech production and the level of oral language. For each criterion, a score was established ranging from zero to four. These scores were weighted according to age such that the results before and after implantation only reflected the changes related to the implantation. The prognostic factors for good results were: a good level of oral communication before implantation, residual hearing, progressive deafness and implantation at a young age. On the other hand, poor prognostic factors were: the presence of behavioral disorders and poor communication skills prior to implantation. Overall, the major prognostic factor for a good outcome appeared to be the preoperative level of oral language, even if this was rudimentary.

Adolescent↗
PubMed1986

Estimation of the number of patients who might be suitable for cochlear implant and similar procedures.

Data have been drawn from four sources to estimate the number of profoundly, bilaterally hearing impaired in Britain who might benefit from a rehabilitational programme which would include cochlear implants and other specialised aids. The sources were: the IHR National Study of Hearing; a total ascertainment survey of General Practitioners, ENT Consultants, Health Visitors etc. in the Wessex Health Region, which requested basic data on their profoundly, bilaterally hearing impaired patients; more detailed questionnaire data obtained directly from a subset of the patients identified in the ascertainment study; and the experience of various cochlear implant centres. Criteria are proposed to select candidates suitable for the initial research and development work on implant devices and to select those who might later be suitable for a routine clinical service with an established technique. Estimates of the corresponding numbers are given. Guidelines for identifying those who might benefit from acoustical aids are offered.

Auditory Threshold↗
PubMed2003

Noise improves suprathreshold discrimination in cochlear-implant listeners.

The present study aimed to examine the effect of noise on vowel-like suprathreshold discrimination in cochlear-implant listeners. The task was to detect an increment in level at the middle harmonic (400 Hz) in the background of a seven-harmonic complex from 100 to 700 Hz in 100-Hz steps. The task was performed in the absence (control) and presence of a white noise presented over a 20-35-dB range from inaudible to loud. The present result shows that discrimination of suprathreshold harmonic stimuli was significantly enhanced, particularly at the soft signal level, with suprathreshold noise. This result suggests that tuning of the noise level is required to optimize performance of different tasks in cochlear implants.

Adult↗
PubMed2006

Auditory and tactile processing in a postmeningitic deaf-blind patient with a cochlear implant.

The authors examined the neural function of a postmeningitic deaf-blind patient who regained his hearing with a multichannel cochlear implant. Auditory stimuli activated the temporal cortices of both sides in a manner similar to that of controls, reflecting the successful recruitment of the auditory cortex after implantation. The patient's occipital lobes were deactivated during the tactile language task, the results of which were completely different from those before cochlear implantation.

Adult↗
PubMed2000

Effects of phase duration and electrode separation on loudness growth in cochlear implant listeners.

Loudness estimates were obtained in a group of four adult subjects implanted with the Nucleus-22 multielectrode cochlear implant device, for a range of pulse amplitudes and different fixed phase durations and electrode separations. The stimulus was a 200-ms long train of biphasic pulses presented at 500 pulses/s. Subjects estimated loudness as a number from 0 ("don't hear it") to 100 ("uncomfortably loud"). Loudness was found to grow exponentially with pulse amplitude, at a rate that was dependent upon the phase duration as well as the electrode separation. An equation of the form L = e(lambda + gamma M)(D theta)I, where L is the estimated loudness, M is the separation between electrodes of a stimulating pair, D is the phase duration, I is current amplitude, and lambda, gamma, and theta are constants, appears to describe the observed data adequately. The findings are remarkably consistent across subjects.

Adult↗
PubMed2004

Pitch estimation of a deeply inserted cochlear implant electrode.

In this short communication, we evaluate the place-pitch relation of a newly designed, deeply inserted, cochlear implant electrode. The insertion depths ranged from 471 degrees to 662 degrees. Pitch perception was measured in eight subjects with monopolar stimulation on each electrode contact at intensities of 50% and 80% of the dynamic range. We observed a monotonic reduction of pitch estimate with insertion depth. For about half of the subjects, a flattening of the pitch estimate at the basal end of the electrode was seen, while for the other half, pitch continued to decrease monotonically up to the most apical part of the array. We conclude that deeper insertion could increase pitch range for at least some cochlear implant recipients, and could hence potentially increase group performance.

Adult↗
PubMed1994

Results of multichannel cochlear implants in congenital and acquired prelingual deafness in children: five-year follow-up.

Postlingually deafened children, using multichannel cochlear implants, have achieved substantial improvement in their speech perception abilities and, in many instances, the results are better than in postlingually deafened adults. It has been suggested that children with prelingually acquired and congenital deafness would not receive similar benefits, since they have not developed an auditory memory. The purpose of this study is to analyze the speech perception and production performance over time of prelingually deafened children who have been using a multichannel cochlear implant for 1-5 years. Preliminary results comparing the effects of age at implantation and etiology of deafness on performance are also examined.

Adolescent↗
PubMed1992

The effects of limiting the number of Nucleus 22 cochlear implant electrodes programmed on speech perception.

The purpose of this double-blind study was to evaluate systematically the effects of varying programmed electrodes on speech perception. The performance of five subjects implanted with the Nucleus 22-electrode cochlear implant was compared on the Four-Choice Spondee test, the Central Institute for the Deaf Sentence test, and Speech Tracking across the following conditions: (1) five most apical electrodes eliminated from the subject's MAP (stimulus parameters); (2) five most basal electrodes eliminated from subject's MAP; (3) the middle five electrodes eliminated from subject's MAP; and (4) subject's current MAP. Statistically significant differences were found for the Four-Choice Spondee test and both the auditory-only and auditory-plus-lipreading Speech Tracking measures. Three subjects demonstrated poorer performance on all test measures when the five electrodes from the apical portion of the array were not programmed. Two subjects performed equally well, regardless of MAP condition. Group means for all test measures present a trend of consistently poorer performance when the -5 Apex MAPs were utilized. A subjective rating scale was consistent with the perceptual tests, with all subjects best liking their current MAP and least liking the -5 Apex MAP. Results suggest that for some subjects, a fixed place code may control their ability to use spectral information for speech discrimination. For these subjects, first formant information (F1) traditionally coded on the most apical electrodes could not be utilized as effectively when coded on the adjacent middle electrodes.

Acoustic Stimulation↗
PubMed2006

Intra- and postoperative electrode impedance of the straight and Contour arrays of the Nucleus 24 cochlear implant: relation to T and C levels.

The objective of this study was to investigate electrode impedance in cochlear implant recipients in relation to electrically evoked stapedius reflex measurements during surgery, and to electrode design, stimulation mode, and T and C levels over a nine month period after surgery. Seventy-five implant recipients, implanted with a Nucleus straight electrode array or a Contour array, were included. The results show that: (1) during surgery electrode impedance decreases markedly after electrically evoked stapedius reflex measurements, (2) after surgery, during the period without stimulation until speech processor switch-on, impedance increases, (3) after processor switch-on impedance decreases. The lower impedance values after a period of stimulation are found at the higher T and C levels. Impedances of the straight array electrodes are lower than those of the Contour array. The difference corresponds mainly to their respective surface areas. In addition, the straight array shows a larger increase of impedance in the apical direction than the Contour array, probably because of the larger fluid environment around the basal electrodes of the straight array.

Adolescent↗
PubMed1996

Development of the facial recess: implications for cochlear implantation.

More attention is being focused on the growth and development of the facial recess because of the use of cochlear implantation in children over 2 years of age and the prospect of using implants in even younger children. The facial recess and the extended facial recess were measured in 123 temporal bones from 73 individuals ranging in age from 8 weeks in utero to 7 years after birth. The goals were to trace the development of the facial recess and to determine whether this area continues to grow into childhood. The facial recess enlarges throughout fetal life with the development of the facial canal and the tympanic annulus. Reichert's cartilage, seen early in utero in the facial recess, gradually resorbs but may persist in the newborn. In full-term infants, the facial recess reaches 3.25 mm at the oval window and 2.62 mm at the round window. The extended facial recess reaches 3.79 mm at the oval window and 3.04 mm at the round window. No statistically significant growth of the facial recess after birth could be demonstrated in this study. The data suggest that the facial recess is probably adult sized at birth and should allow surgical access for cochlear implantation in very young children.

Child, Preschool↗
PubMed1986

[Preliminary studies of deaf patients assessed for cochlear implantation].

Two techniques were employed to assess the suitability of deaf patients for cochlear implantation: electrical stimulation by means of ear canal electrode and promontorium electrode. The results of the ear canal tests indicate that the patients may be divided into three groups: I. non-usable dynamics, II. usable dynamics in low-frequency range, and III. usable dynamics over a wider frequency range. Comparable results were obtained via the promontory tests. Since the promontory tests showed a more accurate description of the subjective sensations, it is recommended that this test be performed with those patients who have been preselected on the basis of ear canal stimulation.

Auditory Pathways↗
PubMed2004

[CILAB--a PC-based laboratory speech processor for implementation and evaluation of new stimulation strategies for cochlear implants].

CILab is a computer-based versatile laboratory system for the implementation and evaluation of innovative stimulation strategies for cochlear implants. In contrast to existing laboratory systems the entire signal processing from the input signal to the creation of the data word for the implant is effected with the aid of a personal computer (PC). This permits rapid implementation of new stimulation strategies or psycho-acoustic tests. Real-time audio processing is also possible by using the CILab as a cochlear implant speech processor. The laboratory system has been employed with success for the evaluation of new strategies and numerous psycho-acoustic tests.

Acoustic Stimulation↗
PubMed2004

Deficits of non-verbal auditory perception in postlingually deaf humans using cochlear implants.

Temporal integration in the time domain of a few seconds was investigated with a subjective accentuation paradigm in 11 monochannel cochlear implant users, who showed auditory comprehension deficits. While listening to metronome beats generated at various frequencies, patients were asked to accentuate mentally every n-th beat and create an individual rhythmic pattern. The extent of temporal integration was defined as the duration of perceptual units consisting of subjectively grouped beats at particular metronome frequencies. The results indicate that there is reduced capacity for temporal integration in implant recipients, particularly for lower metronome frequencies, in comparison to normally hearing. These observations point to the coincidence of specific temporal processing disorders and deficits in auditory comprehension after cochlear implantation.

Acoustic Stimulation↗
PubMed2003

Optimizing the number of electrodes with high-rate stimulation of the clarion CII cochlear implant.

OBJECTIVE: This blind crossover study evaluates the effect of the number of electrodes of the Clarion CII cochlear implant on speech perception in silence and in noise using a "high-rate" continuous interleaved sampling (CIS) strategy. MATERIAL AND METHODS: Nine users of this implant with 3-11 months of experience of an 8-channel CIS strategy [833 pulses per second (pps)/channel, 75 micros/phase] were fitted in a random order with 8-, 12- and 16-channel CIS strategies (+/- 1,400 pps/channel, 21 micros/phase). After 1 month of exclusive use of each strategy the performance was tested with consonant-vowel-consonant words in silence (sound only) and in speech-shaped background noise with signal-to-noise ratios (SNRs) of + 10, + 5, 0 and -5 dB. RESULTS: With "high-rate" strategies most patients' speech understanding in noise improved, although the optimum number of electrodes was highly variable. Generally, faster performers benefited from more active electrodes, whilst slower performers deteriorated. If each patient's optimal strategy was determined by a weighted sum of the test results at +10, + 5 and 0 dB SNR, the average phoneme score improved from 57% to 72% at a SNR of + 5 dB, and from 46% to 56% at a SNR of 0 dB. The average phoneme score in silence was approximately 85% for all strategies. CONCLUSION: We conclude that speech perception (especially in noise) can improve significantly with "high-rate" speech processing strategies, provided that the optimum number of electrodes is determined for each patient individually.

Acoustic Stimulation↗