Cochlear implants in young children.
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Adolescent↗
Biomedical subjects
R S Tyler
Publications and source records attributed to R S Tyler.
Tinnitus management.
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Combined Modality Therapy↗
Previous experience as a confounding factor in comparing cochlear-implant processing schemes.
It is of great importance to compare the relative merits of different cochlear-implant speech-processing strategies. Some groups have compared different strategies within single subjects, but usually the subject has prior experience with one strategy, and no allowance is made for this prior experience. We show in the present study that this is inappropriate. We tested one subject using the Melbourne (Cochlear Corp.) multichannel implant with the device set to process sounds in two different ways. In the first processing scheme, the device functioned normally, extracting information about voicing frequency, amplitude and second-formant frequency. This information activated the 21-channel device, determining pulse rate, pulse amplitude and electrode position (respectively). In the second processing scheme, a single electrode (with the largest dynamic range) was activated. This electrode coded overall amplitude and voicing frequency. The subject was tested on an audiovisual test of a 14-choice consonant recognition in the form /iCi/ over a period of over 4 months. During this time the subject used the 21-channel processor outside of the laboratory. Upon initial connection, there was little difference between the results obtained with the two schemes when tested in sound alone or in sound plus vision. However, after about 4 months, scores obtained with the 21-channel processor in sound plus vision were superior to the scores obtained with the one channel. This advantage came from a superiority in the features of voicing and nasality, but not place. Scores for sound-alone conditions between the two processing schemes remained similar for the 4-month period.(ABSTRACT TRUNCATED AT 250 WORDS)
Auditory Threshold↗
Iowa cochlear implant clinical project: results with two single-channel cochlear implants and one multi-channel cochlear implant.
Cochlear implants have become a realistic alternative for the management of profoundly deaf patients. A variety of implants with differing electrode designs and coding strategies have been developed by nine major implant centers around the world. Each center has their "star" patient, but objective comparisons between these different implant designs are unavailable. In order to determine the performance characteristics of the present generation of cochlear implants, comparison data are vital. We have developed an independent center where uniform objective comparisons of different cochlear implants can be performed longitudinally. This report will present results of nine patients implanted with three different cochlear implant prostheses. Four patients have been implanted with the Los Angeles (House) single-channel implant, three patients have received the Vienna (Hochmair) single-channel intracochlear device, and two patients have been implanted with the Melbourne (Clark) 21-channel unit. All patients have had 11 months or more of experience with their cochlear prostheses. The results of a comprehensive audiologic battery which includes audiovisual and environmental tasks are presented. All implants provide significant improvement in speechreading and sound awareness. The findings to date suggest that there is strong correlation between top-down cognitive processing (as reflected by lip reading skills) and performance with cochlear implants.
Adult↗
Cochlear implant comparisons.
The implantation of an electrode into the cochlea of profoundly hearing-impaired adults now promises to be a viable alternative for rehabilitation. In this article we describe six different kinds of cochlear implants, the single-channel devices developed in Los Angeles, Stanford, and Vienna, and the multichannel devices developed in Melbourne, San Francisco, and Utah. We then present results from our own patients implanted with the Los Angeles, Vienna, and Melbourne cochlear implants. All systems provide information about environmental sounds and prosody, which can improve lip-reading ability. Only our patients implanted with the Melbourne system have been able to recognize words in unknown sentences, although others have reported such spectacular performance with single-channel devices. We stress the importance of recorded tests, of material that is unfamiliar to the patient, and of avoiding multiple presentations of the test material.
Audiometry, Speech↗
Masking of tinnitus compared to masking of pure tones.
In 10 subjects with sensorineural tinnitus (associated with a sensorineural hearing loss and no apparent source for a tinnitus originating elsewhere), the minimum level required to mask the tinnitus was determined for tonal maskers at several masker frequencies. This tinnitus masking pattern was compared to a psychoacoustical tuning curve (PTC) in which the signal frequency and level were determined from tinnitus pitch and loudness matching. Different patterns emerged. One subject showed a near-normal PTC but required high-level maskers across the frequency range to mask the tinnitus. Another subject showed some frequency resolution in the PTC but required low-level maskers across the frequency range to mask the tinnitus. For the remaining eight subjects, the masker levels required to mask the tone were generally higher than those levels required to mask the tinnitus. In addition, it was noted that the tinnitus pitch-match frequency was sometimes associated with an increase or a decrease in threshold sensitivity, or it was found at the low-frequency edge of a steep high-frequency threshold loss. In other subjects there was no apparent relationship between the tinnitus pitch and the audiogram shape.
Adult↗
Factors influencing the masking level difference in cochlear hearing-impaired and normal-hearing listeners.
The masking level difference (MLD) at 500 Hz was examined in wide-band (960 Hz) and narrow-band (50 Hz) noise for normal-hearing subjects and subjects with symmetrical mild-to-moderate cochlear hearing loss. Monaural tasks of intensity discrimination, temporal resolution, and frequency resolution were performed in order to examine relationships between monaural dysfunction and MLD performance. Interaural time discrimination for a 500-Hz pure tone also was examined. The performance of the hearing-impaired subjects was poorer than that of the normal-hearing subjects for MLD, interaural delta t, and most monaural tasks. However, no significant relationships were found between monaural and MLD performance when effects of threshold were taken into account. MLDs were more reduced in wide-band noise than in narrow-band noise for the hearing-impaired subjects (when contrasted with normal-hearing subjects). MLD performance was correlated with interaural time discrimination, and it is suggested that one reason for poor MLD performance with hearing impairment may be poor temporal coding of stimulus-fine structure.
Adult↗
Postmasking effects of sensorineural tinnitus: a preliminary investigation.
In this study we provide some preliminary results of our attempt to measure the perception of tinnitus after the termination of a masker. The minimum level to mask tinnitus was determined for a 1-s masker in 10 subjects with sensorineural tinnitus. A continuous masker (parametrically varied in duration, frequency, and level) was then presented to the ear ipsilateral to the tinnitus. At the termination of the masker, subjects were required to press a button when their tinnitus "first returned" and a second button when it returned to "normal loudness." These response times were recorded automatically, and subjects reported what they heard after each trial. At low-level and short-duration maskers, the tinnitus typically was heard immediately after the masker termination. At higher levels and longer durations, different responses were observed. In two subjects, a silent interval was present after the masker, then the tinnitus returned at a softer loudness before returning to its premasker loudness. In one subject, the tinnitus was louder after the masker, and gradually returned to its premasker loudness. In another subject, the tinnitus returned immediately after the masker, but was softer than before. It then gradually increased to its premasker loudness. In the other two subjects, the tinnitus returned immediately to its normal loudness when the masker was terminated at all masker levels and durations. Higher level and longer duration maskers generally produced greater effects. Masker frequency, however, had little effect.
Adult↗
Initial Iowa results with the multichannel cochlear implant from Melbourne.
Two subjects who use the Melbourne multichannel cochlear implant were studied. Live-voice word, consonant, and vowel recognition tests, and a speech-tracking task were administered at regular intervals during the first 90 days after implantation. Results indicated 30-50% correct recognition of vowels (given 9 alternatives) and about 30-60% correct recognition of consonants (given 12 alternatives). Speech tracking showed from two to three times faster rates with the implant and vision compared to a vision-alone condition. After 3-4 months of implant experience, a number of recorded tests from the Minimal Auditory Capabilities battery and the Iowa Cochlear-Implant tests were then administered. These results indicated about 80% recognition of everyday sounds in a five-choice closed-set condition and about 50% recognition of everyday sounds in an open-set condition. The subjects were 50% correct at identifying the accented words in a sentence and about 50% correct at determining the number of syllables in a word. One subject was unable to recognize a sentence as a statement or a question. Background noise (+10 dB S/N) reduced their performance on a four-choice spondee test to chance. Both subjects were able to identify a sound as either a voice or a modulated noise at 95% correct, and both could recognize speaker sex at 95% correct. Neither could discriminate whether two (successive) sentences were spoken by the same speaker or by two different speakers. Remarkably, one subject identified 45% and the other 85% of the words in sentences that were preceded by a contextual picture using sound alone. One subject identified 13% of the words in sentences in sound alone even without contextual information.
Adult↗
Auditory filter asymmetry in the hearing impaired.
Thresholds for 2-kHz sinusoidal signals were determined in the presence of a notched-noise masker, for six normal-hearing listeners and 12 listeners with cochlear hearing losses. Following Patterson and Nimmo Smith [J. Acoust. Soc. Am. 67, 229-245 (1980)], conditions were used where the notch was placed both symmetrically and asymmetrically about the signal frequency. The auditory filter shape for both the low- and high-frequency side of the filter was calculated using the rounded-exponential form of the filter. In six hearing-impaired listeners, the auditory filter shape showed a shallow low-frequency skirt indicating pronounced susceptibility to the upward spread of masking. In two hearing-impaired listeners, the filter shape showed a shallow high-frequency skirt, indicating pronounced susceptibility to the downward spread of masking. Two other listeners with mild threshold losses had steeper and more symmetric filters than normal, suggesting either a small conductive loss or an attenuation factor of sensorineural origin not associated with a degradation of frequency resolution. In the remaining two listeners, the auditory filter had too little selectivity for its shape to be reliably determined.
Adult↗
Preliminary assessment of the Los Angeles, Vienna and Melbourne cochlear implants.
We tested four patients using the single-channel cochlear implant from Los Angeles, three patients using the single-channel cochlear implant from Vienna, and two patients using the multichannel cochlear implant from Melbourne. Tests from the MAC battery and the Iowa Cochlear Implant Battery were used. Most patients were able to identify some environmental sounds. Three of the patients had difficulty distinguishing between male and female voices, and three could not distinguish between a noise and a voice. All patients had difficulty discriminating between unknown speakers of the same sex. A four-choice spondee test in noise showed that all patients suffered drastically from background noise. In all cases there was an improvement in lipreading ability with the implant. On a sentence test with a contextual cue seven patients got some words with sound alone. Results obtained with the multichannel implant are superior on several tasks, but we have tested too few patients to allow us any firm conclusions.
Auditory Perception↗
Difficulties experienced by tinnitus sufferers.
Ninety-seven members of a tinnitus self-help group were asked to list the difficulties that they had as a result of their tinnitus. Seventy-two replies were returned from 22 men and 48 women (sex not reported in two cases) whose average age was 61 years. Tinnitus was associated with hearing difficulties in 53%, effects on lifestyle in 93%, effects on general health in 56%, and emotional difficulties in 70% of the sample. Getting to sleep was the most frequently mentioned difficulty, and many respondents indicated that they experienced depression, annoyance, and insecurity. The clinical application of this open-ended questionnaire are discussed.
Adult↗
The determination of tinnitus loudness considering the effects of recruitment.
We have attempted to determine a meaningful measure of tinnitus loudness that considers loudness recruitment. Sixteen subjects with sensorineural tinnitus adjusted the level of a pure tone so that it was (a) at threshold, (b) equal in loudness to the tinnitus, and (c) uncomfortably loud. The pure-tone frequency was (a) at the frequency of the tinnitus pitch, and (b) at the octave frequency between 500 and 4000 Hz having the pure-tone threshold closest to 0 dB HL. In addition, the subjects adjusted the level of a broadband noise so that it (a) was at threshold, (b) just masked the tinnitus, and (c) was uncomfortably loud. These measurements were performed both in the ear ipsilateral and in the ear contralateral to the tinnitus. Formulae based on abnormal loudness functions and uncomfortable loudness levels are presented that convert equal-loudness matches in dB sensation level (SL) into loudness in sones. The level of broadband noise (in dB SL) required to mask tinnitus was about the same in the ipsilateral and in the contralateral ear for most of our subjects, regardless of the ear in which the tinnitus was localized. This noise level (in dB SL) required to mask the tinnitus correlated well with the level (in dB SL) of a tone at the most normal frequency judged equal in loudness to the tinnitus.
Adult↗
Monaural and binaural auditory frequency resolution measured using bandlimited noise and notched-noise masking.
Several studies using bandlimited masking noise have indicated that NOSO frequency resolution is better than that for NOS pi. The present study examined NOSO and NOS pi frequency resolution with two different masking methods: bandlimited noise and notched noise. Noise spectrum levels of 10, 30, and 50 dB/Hz were used. Thresholds were determined for a 500-Hz signal, using a three-alternative forced-choice adaptive procedure, as a function of masker bandwidth and notchwidth. For NOSO presentation, 3-dB down points were comparable for the notched-noise and bandlimiting methods. For NOS pi presentation, 3-dB down points were generally greater for the bandlimiting method than the notched noise method. Furthermore, for NOS pi presentation, the 3-dB down estimate increased as noise level increased for the bandlimiting method, but stayed constant for the notched-noise method. It is suggested that the two masking methods measured different aspects of binaural processing.
Acoustic Stimulation↗
Frequency resolution and discrimination of constant and dynamic tones in normal and hearing-impaired listeners.
Frequency resolution and three tasks of frequency discrimination were measured at 500 and 4000 Hz in 12 normal and 12 hearing-impaired listeners. A three-interval, two-alternative forced-choice procedure was used. Frequency resolution was measured with an abbreviated psychoacoustical tuning curve. Frequency discrimination was measured for (1) a fixed-frequency standard and target, (2) a fixed-frequency standard and a frequency-transition target, and (3) frequency-transition standard and a frequency-transition target. The 50-ms frequency transitions had the same final frequency as the standards, but the initial frequency was lowered to obtain about 79% discrimination performance. There was a strong relationship between poor frequency resolution and elevated pure-tone thresholds, but only a very weak relationship between poor frequency discrimination and elevated pure-tone thresholds. Several hearing-impaired listeners had normal discrimination performance together with pure-tone thresholds of 80-90 dB HL. A slight correlation was found between word recognition and frequency discrimination, but a detailed comparison of the phonetic errors and either the frequency-discrimination or frequency-resolution tasks failed to suggest any consistent interdependencies. These results are consistent with previous work that has suggested that frequency resolution and frequency discrimination are independent processes.
Acoustic Stimulation↗
Sentence identification in noise and hearing-handicap questionnaires.
We compared the results of two hearing-handicap questionnaires (the Social Hearing-Handicap Index and the Hearing Measurement Scale) and the scores on three sentence-in-noise tests (CID sentences in continuous noise, BKB sentences in continuous noise and BKB sentences in noise modulated by the speech). Thirty subjects were tested, 6 with normal hearing, 11 with a mixed hearing loss, and 13 with a sensorineural hearing loss. Significant correlations were found among the sentence identification scores and the questionnaires, particularly those questions that dealt with the understanding of speech. Both the questionnaires and the sentence-identification scores were also highly correlated to pure-tone sensitivity.
Adolescent↗
Tinnitus pitch: a comparison of three measurement methods.
The most prominent pitch of tinnitus was measured in 10 subjects with sensorineural tinnitus. The pitch was determined with three different psychophysical procedures in the ear ipsilateral to the tinnitus; an Adaptive Method (Bracketing), a Method of Limits (ascending and descending), and the Method of Adjustment. Each procedure involved equating the pitch of a pure tone to the most prominent tinnitus pitch, and was repeated seven times on each subject. Although there was no statistically significant difference for the means and standard deviations among the different methods for the group data, there were some large differences in a few individuals. Many of the subjects produced pitch matches that covered a range of 1 octave, whereas others showed better consistency. The Method of Limits took longer to perform and resulted in more octave confusions than the other two methods. The Adaptive Method was also repeated five times for each subject in the ear contralateral to the tinnitus. Two subjects produced a tinnitus pitch match that was over 1/2 octave lower in the contralateral ear. We recommend that tinnitus pitch be measured in the ipsilateral ear with either the Method of Adjustment or the Adaptive Method. Because some patients are unreliable in their pitch matching we suggest repeating the match seven to nine times.
Auditory Threshold↗