Evidence of echoic memory with a multichannel cochlear prosthesis

Short-term memory was examined in a subject with a multichannel cochlear prosthesis. Serial recall for lists of digits revealed what are widely regarded as the principal hallmarks of echoic memory, namely the recency effect and the suffix effect. Thus, probability of recall increased for the last one or two digits, except when a nominally irrelevant but spoken item was appended to the to-be-remembered list. It appears, therefore, that a multichannel cochlear implant can give rise to not only the perception of, but also an echoic memory for, speech. As with normal subjects, the suffix effect did not occur with a nonspeech suffix, implying that the echoic memory from the prosthesis shows normal sensitivity to the distinction between speech and nonspeech.     

Deaf animal models for studies of a multichannel cochlear prosthesis

Pathological alterations of the cochlea were studied in three different deaf animal (cat) populations. The ototoxic drug neomycin sulfate, was administered in one experimental series by direct infusion into the cochlear perilymph; a second group was given a series of intramuscular injections of the drug; and in a third experiment a mechanical lesion was made in the basilar membrane of the basal turn and the animals subsequently deafened by systemic neomycin. Hearing losses were tracked by monitoring thresholds of auditory brainstem responses to click stimulation. These deaf cat preparations fairly efficiently model pathologies recorded in man and are highly predictable over an acceptable time frame. Such preparations are of practical value for experiments involving intracochlear electrical stimulation (e.g., with model cochlear prosthesis electrodes).     

Speech tracking in the evaluation of a multichannel cochlear prosthesis

Individual speech tracking data were analyzed in relation to other variables in 11 adult users of the Nucleus multichannel cochlear implant. Patients were categorized according to postoperative speech tracking results. The resultant groups could also be differentiated on the basis of postoperative MAC scores, surgeon's rating of overall success, and duration of deafness before implantation. The speech tracking paradigm appears to be a useful technique for the evaluation of performance with a cochlear prosthesis.     

Vestibular evoked myogenic potentials evoked by multichannel cochlear implant - influence of C levels

CONCLUSIONS: This study showed that vestibular evoked myogenic potentials (VEMPs) evoked by cochlear implant (CI), could be related to the comfortable level (C level), particularly in the channels that are closer to the apical turn of the cochlea. OBJECTIVE: The purpose of this study was to investigate the correlation between VEMPs and C level of each channel. SUBJECTS AND METHODS: We investigated 24 children who underwent cochlear implantation. VEMPs were recorded from the operated ears with the CI switched 'off' or 'on'. To investigate the correlation between VEMPs and C level, we selected 13 patients with Nucleus 24 (SPrint), and divided them into group A (normal VEMPs) and B (absence of VEMPs). In these children, all the 22 electrodes were active, and were mapped in the same frequency range for each channel. RESULTS: Twenty children (83%) showed no VEMPs with the CI 'off'. Among them, 10 elicited VEMPs with the CI 'on', but the other 10 did not. In all channels, the mean C levels of CI were higher in group A than in group B. The p values in channels 1-12 were >0.10, in channels 13-16 were 0.06-0.09, and in channels 17-22 were 0.05-0.06, which were lower but not statistically significant.     

Neuromagnetic responses from a deaf subject to stimuli presented through a multichannel cochlear prosthesis

Neuromagnetic responses to stimuli presented through a 4-channel cochlear prosthesis were recorded from a deaf subject. The topography of the responses agreed with activation of the supratemporal auditory cortex. The responses to tone pips, noise/square-wave sequences, and to intermittent frequency modulation of a continuous tone resembled those obtained from subjects with normal hearing, being consistent with the good performance of this subject with his implant.     

Speech recognition by a deaf-blind multichannel cochlear implant patient

A case study of the first deaf-blind patient implanted with a Nucleus 22 channel cochlear prosthesis is presented. The patient's preimplant evaluation data, using a powerful hearing aid and vibro-tactile device, are compared with results obtained 8 months postimplant. Preimplant testing indicated no consistent response to sound. Postimplant testing showed ability to comprehend some open set speech with hearing alone through the cochlear implant including ability to utilize the telephone without a code system. The postimplant data suggest potential benefit for other postlingually deaf-blind individuals from multichannel cochlear stimulation.     

多通道人工耳蜗在语前聋儿童及青少年中的应用

目的　通过对植入人工耳蜗的语前聋儿童和青少年的听力和语言能力的评估 ,探讨我国儿童在使用人工耳蜗后的听力和言语能力发展规律及影响因素。方法　 2 5例行人工耳蜗植入的语前聋儿童及青少年患者参与本组测试。选用《聋儿听觉言语康复评估方法》作为测试材料 ,分别进行声音、言语声和环境声的辨别 ,数词、单字词、双字词、3字词、韵母、声母、声调、封闭项列短句的识别 ,开放项列字词和开放项列短句识别 ,语言清晰度 ,模仿句长 ,听话识图和看图说话等方面测试。结果　受试者术后均能感知到声音 ,辨别不同类别的声音。封闭项列测试结果全部大于机会水平 ,正确识别率随人工耳蜗使用时间而不断增加 ,随植入时年龄的增长而呈下降趋势。术后约半年显现开放项列识别能力 ,使用人工耳蜗后对患儿的言语发育具有较大帮助。结论　尽早对语前聋患儿植入人工耳蜗及进行术后康复 ,以达改善听力 ,提高语言能力 ,促进身心全面发展的目的。     

多通道人工耳蜗在语前聋儿童及青少年中的应用

目的 通过对植入人工耳蜗的语前聋儿童和青少年的听力和语言能力的评估,探讨我国儿童在使用人工耳蜗后的听力和言语能力发展规律及影响因素。方法 ２５例行人工耳蜗植入的语前聋儿童及青少年患者参与本组测试。选用《聋儿听觉言语康复评估方法》作为测试材料,分别进行声音,言语声和环境声的辨别,数词,单字词,双字词,３字词,韵母,声母,声调,封闭项列短句的识别,开放项列字词和开放项列短句识别,语言清晰度,模仿句长,     

Intra-aural reflexes elicited by a cochlear prosthesis in monkeys

Objective audiological tests are needed for pre- and postsurgical evaluation of cochlear prosthesis patients who are unable to give reliable subjective responses. In this study we demonstrated that contralateral intra-aural reflexes were elicited by a cochlear prosthesis in the monkey. Reflex variables measured include threshold, latency and amplitude. These findings indicate that the electrically elicited intra-aural reflex response may be useful to evaluate the peripheral auditory system in subjects with sensory deafness.     

Temporal-gap detection by cochlear prosthesis users

Minimum-detectable gaps for sinusoidal stimuli were measured for three users of a multi electrode cochlear prosthesis as functions of stimulus level, frequency, and electrode place within the cochlea. Stimulus level was scaled by sensation level and by growth-of-loudness functions generated for each condition by direct magnitude estimation. Minimum-detectable gaps decreased with increase in either sensation level or loudness, up to a plateau. When compared at equal sensation levels, the minimum-detectable gaps decreased with frequency increases. The frequency effect on minimum-detectable gaps is reduced if the data are considered at equal loudness. Comparison across place of stimulation within the cochlea showed minimum-detectable gaps to be shorter for more basal electrode placement at low stimulus levels. No differences in minimum-detectable gap as a function of place were found at higher stimulus levels.     

Otopathology in a case of multichannel cochlear implantation

The histopathology of the temporal bones of a patient who died of unrelated causes 10 weeks following cochlear implantation using a Richards Ineraid® device is presented. Deafness was caused by a prolonged course of intravenous gentamycin therapy 5 years prior to implantation. The electrode array of the cochlear implant was left in situ throughout histologic preparation and sectioning. Despite displacement and disruption of supporting structures of the inner ear, particularly in the 6-to-15-mm range as measured from the round window, there was no significant difference in the mean densities of spiral ganglion cells in the implanted and unimplanted sides. This case is presented as evidence that despite significant disruption of supporting elements of the inner ear, which is common during cochlear implantation, there appears to be little effect on the residual spiral ganglion cell count, at least in the short term.     

Magnetic fields from the auditory cortex of a deaf human individual occurring spontaneously or evoked by stimulation through a cochlear prosthesis

In a postlingually deaf individual, the magnetic field evoked by stimulation through a cochlear prosthesis (extracochlear electrodes) as well as of the spontaneous magnetoencephalogram was measured over the hemisphere contralateral to the prosthesis (CP), and the results were compared with those obtained from normal-hearing subjects. The latency of the 2 best developed waves M100 and M200 turned out to be prolonged in the CP patient by approximately 40 ms. The amplitude of wave M100 was significantly diminished, while wave M200 was only poorly developed. Location and direction of the equivalent current dipole (ECD) calculated for wave M100 was in good agreement with normal data, whereas the dipole moment was only about one third of the average dipole moment found in normals. Furthermore, evidence was obtained for another magnetic field wave, preceding the delayed auditory wave M100, which exhibits the same latency, ECD location and direction as reported in the literature for the somatosensory evoked magnetic field. This wave probably results from stimulation, through the intratympanic electrodes, of somatosensory nerves innervating the tympanic cavity. A potential clinical application of neuromagnetic measurements is discussed: The calculation of the ECD moment from the auditory cortical magnetic field evoked by electrical stimulation at the promontory would allow to estimate, prior to CP implantation, the number of persisting, excitable nerve fibres.     

Consonant production in children receiving a multichannel cochlear implant

Consonant production was investigated in 29 children participating in the federal Food and Drug Administration's clinical trials of the Nucleus WSP-III cochlear implant. Speech samples were collected preimplant and 1 year postimplant. A significantly greater number of children produced stop, nasal, fricative, and glide consonants postimplant. Voiced stop consonants were used by more children than the voiceless cognates; however, voiceless fricatives were used more than voiced fricatives. Visible places of articulation were used more frequently than less visible places of articulation. Comparisons to Smith's data (J Speech Hear Res 1975;18:795-811) revealed qualitative similarities but postimplant, quantitative differences were observed. Post hoc analyses of the data revealed some sounds were influenced more by an implant than other sounds and suggest the role of an implant upon spontaneous speech is complex.     

Experiments with a thinfilm multichannel electrode for cochlear implantation

A series of experiments with a thinfilm multichannel cochlear implant is presented. A number of surgical difficulties at implantation on temporal bones were experienced. In vitro measurements of the electrode's technical properties revealed 1) large variations in the impedance, and 2) good separation between channels. From a theoretical point of view this complicated type of electrode is interesting, but a number of modifications are necessary before it may be used for implantation in man.     

Insertional trauma of multichannel cochlear implants

Insertional trauma to the cochlea from three different multichannel cochlear implant electrodes was evaluated in a single-blind controlled study in fresh human temporal bones. Sixteen fresh human temporal bones were implanted with one of three types of multichannel electrodes (Symbion/InnerAid, Cochlear/Nucleus®, or Storz/UCSF). Seven temporal bones were used as controls where a cochleostomy only was created. The temporal bones were evaluated histologically and cochlear histograms of the trauma were created. Although the three electrode designs caused damage which was unlikely to hinder implant performance, a distinct pattern of trauma was seen with each of the three electrode types. The least traumatic of the three electrode designs in this study was the Nucleus type. The degree of insertional trauma may be relevant to changing indications for insertion of cochlear implants as well as for patients with device failure who require reimplantation.     

Unit responses at cochlear nucleus to electrical stimulation through a cochlear prosthesis

Afferent auditory fibers of the guinea pig cochlea were electrically stimulated with current introduced through electrodes in the scala tympani. Thresholds were determined for unit responses recorded in the ventral cochlear nuclei to a sinusoid of 98 Hz from response-rate growth functions versus stimulus intensity. Suprathreshold response rates for most units grew rapidly from threshold to saturation at 2-15 dB above threshold. Peristimulus time histograms were collected for responses to single sinusoids and combinations of two and five sinusoids ranging from 86 to 134 Hz. Spike occurrences were highly synchronous with individual cycles of the pure sinusoids, but responses to the more complex waveforms occurred primarily to the more intense peaks. The amplitude envelope was thus a major contributor to responses to multiple sinusoids. Destruction of cochlear structures with neomycin increased unit thresholds and produced some changes in waveform encoding.     

Perception of speech pattern contrasts using a multichannel cochlear implant

The ability to perceive for suprasegmental and eight segmental speech pattern contrasts was measured on 16 adult cochlear implantees using the Nucleus multichannel prosthesis with either F0-F2 (n = 9) or F0-F1-F2 (n = 7) coding. The results of this study indicated the following: (1) The Nucleus device provided significant access to the majority of suprasegmental and segmental speech contrasts. (2) Both one- and two-format coding strategies provided good access to speech pattern contrasts. (3) Considerable intersubject differences in performance were observed, but there was no evidence to suggest that these were related to either processing scheme. (4) Although the accessibility of speech contrasts varied, the pattern of perceptual performance was interpreted in terms of an acoustic/phonetic hierarchy. (5) The Speech Pattern Contrast (SPAC) test appears to be a practical procedure for analyzing the perception of phonologically salient information about the suprasegmental and segmental components of speech.     

Clinical trials with a 22-channel cochlear prosthesis

During 1984, six patients have been implanted with a 22-channel cochlear prosthesis. The device features a programmable wearable speech processor using a speech feature encoding strategy. A strict clinical protocol was followed, and no patients have been lost to follow-up. All patients are regular users of the device and have shown a restoration of hearing sensation in response to acoustic stimuli. Pure tone averages ranged from 20 to 47 dB HL and speech detection thresholds varied from 15 to 32.5 dB HL. All patients have shown a recognition of a large variety of environmental sounds, and an improvement in speech recognition ability when the device is used in conjunction with lipreading. Speech reception thresholds using spondee words without lipreading were obtained in three patients at levels of 27.5 to 55 dB HL and one patient had an open-set speech discrimination score (w-22 word list) of 42% without lipreading. In addition, two of the patients show an ability to have limited interactive conversation without the use of lipreading.