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PubMed2003

Distribution of catestatin-like immunoreactivity in the human auditory system.

Chromogranin A (CgA) belongs to the family of chromogranin peptides which are contained in large dense-core vesicles. The novel CgA fragment catestatin (bovine CgA(344-364); RSMRLSFRARGYGFRGPGLQL) is a potent inhibitor of catecholamine release by acting as a nicotinic cholinergic antagonist. Catestatin is a recently characterized neuropeptide, consisting of 21 amino acids, which might play an autocrine regulatory role in neuroendocrine secretion through its interaction with different nicotinic acetylcholine receptor subtypes. This study investigates for the first time the distribution of this peptide in the human auditory system using immunohistochemistry. A high density of catestatin-like immunoreactivity (catestatin-LI) is located in the spiral ganglion cells. In the dorsal cochlear nucleus, a high density of catestatin-LI consists of varicose fibers, immunoreactive varicosities and immunoreactive neurons. A moderate density is detected in the ventral cochlear and the medial vestibular nucleus. A low density is found in the inferior colliculus and superior olivary complex. The study indicates that catestatin is distinctly distributed in the auditory system, suggesting a role as a neuromodulatory peptide. Further studies should elucidate a possible interaction with other neurotransmitters in the auditory system.

Aged↗
PubMed1988

Projections of the cochlear nuclei and nucleus laminaris to the inferior colliculus of the barn owl.

The barn owl determines the directions from which sounds emanate by computing the interaural differences in the timing and intensity of sounds. These cues for sound localization are processed in independent channels originating at nucleus magnocellularis (NM) and nucleus angularis (NA), the cochlear nuclei. The cells of NM are specialized for encoding the phase of sounds in the ipsilateral ear. The cells of NA are specialized for encoding the intensity of sounds in the ipsilateral ear. NM projects solely, bilaterally, and tonotopically to nucleus laminaris (NL). NL and NA project to largely nonoverlapping zones in the central nucleus of the inferior colliculus (ICc), thus forming hodological subdivisions in which time and intensity information may be processed. The terminal field of NL occupies a discrete zone in the rostromedial portion of the contralateral ICc, which we have termed the "core" of ICc. The terminal field of NA surrounds the core of ICc and thus forms a "shell" around it. The projection from NL to the core conserves tonotopy. Low-frequency regions of NL project to the dorsal portions of the core whereas higher-frequency regions project to more ventral portions. This innervation pattern is consistent with earlier physiological studies of tonotopy. Physiological studies have also suggested that NL and the core of ICs contain a representation of the location of a sound source along the horizontal axis. Our data suggest that the projection from NL to the core preserves spatiotopy. Thus, the dorsal portion of NL on the left, which contains a representation of eccentric loci in the right hemifield, innervates the area of the right ICc core that represents eccentric right loci. The more ventral portion of the left NL, which represents loci close to the vertical meridian, innervates the more rostral portions of the right core, which also represents loci near the vertical meridian.

Afferent Pathways↗
PubMed1993

Organization of the nucleus magnocellularis and the nucleus laminaris in the barn owl: encoding and measuring interaural time differences.

The circuit from the cochlear nucleus magnocellularis to the nucleus laminaris supports the encoding and measurement of interaural time differences in the auditory brainstem. Specializations for the encoding of temporal information include the few and/or short dendrites and thick axons of the magnocellular and laminaris neurons, and the high degree of convergence in the circuit. Magnocellular cells have large cell bodies covered with somatic spines. The cells have few dendrites, and the number of dendrites decreases from low to high best frequency regions of the nucleus. Magnocellular neurons receive both auditory nerve terminals and GABAergic terminals with symmetric synapses and terminals filled with pleomorphic vesicles. The axonal projections of magnocellular neurons to the nucleus laminaris form maps of interaural time difference. About 100 magnocellular afferents from each side converge on each laminaris neuron, and the terminals from each side do not occupy separate domains on the cell. These terminals form punctate asymmetric synapses on both the dendrites and the cell bodies of laminaris neurons. Laminaris neurons also receive GABAergic terminals which form symmetric synapses. Laminaris neurons have oval cell bodies covered with very short dendrites. The cells in the low best frequency region of the nucleus laminaris have longer dendrites.

Animals↗
PubMed1997

Perception of rhythmic and sequential pitch patterns by normally hearing adults and adult cochlear implant users.

OBJECTIVE: This study compares the musical perception of 17 adult recipients of the Nucleus cochlear implant using two different formant extraction processing strategies (F0F1F2 and MPEAK). DESIGN: Over a 12 mo period, participants were alternately switched between two strategies every 3 mo. Performance was evaluated using three measures of rhythmic and sequential pitch perception. RESULTS: Three individuals performed significantly better with the MPEAK strategy on one particular rhythm task, 11 participants performed better with the MPEAK strategy on another rhythm task, and no significant differences were found between the two strategies on a sequential pitch pattern task. CONCLUSIONS: Neither strategy seems clearly superior for perception of either sequential pitch or rhythmic patterns.

Adult↗
PubMed1992

Patient performance with two types of multiple electrode intracochlear implant.

The functional results of 9 persons implanted with the Symbion Ineraid and 8 persons implanted with the Nucleus cochlear implant with the F0, F1, F2 coding strategy are reported. All patients were postlingually totally deaf, the patients implanted with the Symbion Ineraid were all above 40 years of age, while the Nucleus patients were with one exception under 40 years of age. The CID Everyday Sentences Test, the Helen Test and the Speech Tracking Test showed that all patients improved their communication skills when sound through the implant was added to lip-reading. The patients' ability to understand without lip-reading was tested with the CID everyday sentences test, with the Helen test, with spondees, with three-choice vowels and with a consonant confusion test. These showed that all 9 Symbion Ineraid patients achieved some degree of open speech understanding. Four of the 8 Nucleus patients achieved some degree of open speech understanding. Difference limen tests for intensity and frequency indicated that 2 of the Nucleus patients who did not achieve open speech understanding probably had extensive cochlear nerve damage, while the remaining 2 Nucleus patients without open speech understanding had good frequency and intensity discrimination.

Acoustic Stimulation↗
PubMed1985

The development of innervation patterns in the avian cochlea.

The sequence of developmental events leading to the innervation of the cochlea and the differentiation of its receptor cells has been studied in chick embryos with Golgi methods. We describe the morphogenesis of cochlear ganglion cell peripheral processes from their appearance in early embryos to the formation of their mature endings on hair cells in the basilar papilla (organ of Corti) of prehatching chicks. In the stage of peripheral fiber outgrowth, embryonic days 3-5, the fibers emerge from the ganglion cell bodies and grow, in a uniform fashion, toward the undifferentiated receptor epithelium of the otocyst. In the stage of the invasion of the otocyst by the peripheral fibers, embryonic days 6-7, some fibers enter the epithelium directly after reaching it, others enter after traveling some distance longitudinally beneath its basal lamina. The invading fibers appear to encounter resistance at the basal lamina, but, once within the epithelium, at embryonic days 8-9, they form a surfeit of branches in columnar zones oriented radially toward the surface. In early synaptogenesis (embryonic days 8-9) hair cells first become apparent. They differentiate from primitive epithelial cells. These cells withdraw their basal processes, which appear to accompany the growing fibers into the superficial epithelium. At embryonic days 11-13, the stage of mid-synaptogenesis, the fibers develop large, bulbous, preterminal and terminal swellings, which are located below the bases of the hair cells; the surplus branches atrophy or withdraw. Efferent axons are first seen in the epithelium at this time. In late synaptogenesis (embryonic days 14-17), the preterminal swellings disappear and the endings transform into mature foot-shapes at the bases of the hair cells. These morphological changes during the development of the peripheral endings are comparable to those of cochlear axons in nucleus magnocellularis (cochlear nucleus). During mid-synaptogenesis, when the ganglion cells develop swellings in the periphery, their central axons ramify extensively. Late in synaptogenesis, while the peripheral swellings disappear, there is a corresponding condensation of the central terminals to form the end-bulbs of Held. Thus, specific connections of the cochlear ganglion cells and their target cells in the ear and brain may result from two sequential developmental phases: (1) loosely organized and overabundant initial growth of branches from the fibers entering their target tissue; (2) reorganization of these fibers with the disappearance or resorption of the surplus branches during the transformation of their endings into mature synaptic arrangements.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1978

Some observations on the binding patterns of alpha-bungarotoxin in the central nervous system of the rat.

Patterns of alpha-bungarotoxin (alphaBuTX) binding within the brain of the rat have been studied following one of the two procedures: (1) the intraventricular injection of 125I-labeled toxin followed by a survival period of 1--8 days before aldehyde perfusion, or (2) the incubation of fresh cryostat sections of brain tissue in dilute solutions of radioactive toxin. Appropriate controls with nicotine, curare, atropine and native alphaBuTX established that specific nature of the binding. The principal observations were that toxin binding sites are predominantly associated with central areas of the brain in direct receipt of sensory inputs (the main and accessory olfactory bulbs, superior colliculus, ventral lateral geniculate nucleus, cochlear nuclei, the substantia gelatinosa of the spinal cord and spinal trigeminal nucleus, the principal sensory nucleus of the trigeminal, and the dorsal column nuclei) and with limbic areas of the brain (hippocampus, amygdala, olfactory tubercle, medial mammillary nucleus, and the dorsal tegmental nucleus of Gudden). Toxin was not found to bind to cranial motor nuclei with the exception of the dorsal motor nucleus of the vagus and the nucleus ambiguus. The discrete distribution of clusters of silver grains within the granule layer of cerebellar folia I, IX, and X is described as well as the heavy labeling of the inferior and accessory olivary nuclei. In many areas of the brain silver grains were found to overlie cell bodies. It is suggested that this may reflect the presence of both membrane-bound toxin and internalized ligand following initial binding to a membrane receptor site. An attempt was made to correlate the localization of toxin binding sites with the terminal distributions of previously described cholinergic pathways. There appears to be a reasonably good agreement between the distribution of toxin receptors and proposed sites of cholinergic transmission within the hippocampus, interpeduncular nucleus and cerebellum. In most other cases however, lack of data precluded such correlations. The anatomical relationship of alphaBuTX binding activity and neurotransmitters other than acetylcholine is also considered.

Animals↗
PubMed1993

Distribution of the inositol 1,4,5-trisphosphate receptor, P400, in adult rat brain.

The distribution of the inositol 1,4,5-trisphosphate receptor protein, P400, was investigated in adult rat brain by immunocytochemistry with the monoclonal antibody 4C11 raised against mouse cerebellar inositol 1,4,5-trisphosphate receptor protein. Immunoreactive neuronal cell bodies were detected in the cerebral cortex, the claustrum, the endopiriform nucleus, the corpus callosum, the anterior olfactory nuclei, the olfactory tubercle, the nucleus accumbens, the lateral septum, the bed nucleus of the stria terminalis, the hippocampal formation, the dentate gyrus, the caudate-putamen, the fundus striatum, the amygdaloid complex, the thalamus, the caudolateral part of the hypothalamus, the supramammillary nuclei, the substantia nigra, the pedunculopontine tegmental nucleus, the ventrotegmental area, the Purkinje cells in the cerebellum, the dorsal cochlear nucleus, the subnucleus oralis and caudalis of trigeminal nerve, and the dorsal horn of the spinal cord. Immunoreactive fibres were found in the medial forebrain bundle, the globus pallidus, the stria terminalis, the pyramidal tract, the spinal tract of trigeminal nerve, and the ventral horn of spinal cord. Nerve fibres forming a dense plexus ending in terminal-like boutons were detected in relation to nonimmunoreactive neurons of the dentate, interpositus, and fastigial nuclei of the cerebellum and around neurons of the vestibular nuclei. This receptor protein binds a specific second messenger, inositol 1,4,5-trisphosphate, which produces a mobilization of intracellular Ca2+ and a modulation of transmitter release.

Animals↗
PubMed2002

Intrinsic neuronal properties of the chick nucleus angularis.

In vitro whole cell recording revealed intrinsic firing properties and single-cell morphology in the cochlear nucleus angularis (NA) of the chick. We classified three major classes of neurons: one-spike, damped, and tonic. A delayed inward rectifying current was observed in all classes during hyperpolarization injections. One-spike neurons responded with a single spike to depolarizing current injection and had small (stubby) radiate dendritic trees. Damped neurons responded with only a few spikes at the onset of positive current injection. More positive current inputs led to a damped response. Damped cell dendrites had a planar orientation parallel to the isofrequency axis in NA. Tonic cells produced trains of action potentials in response to a depolarizing current injection. Three variations of the tonic type had multipolar morphology, with dendrites oriented either radially (I and III) or perpendicular to the tonotopic axis (II; vertical). Tonics I and III differed in the shape of their action potential undershoot. Thus NA is both physiologically and morphologically heterogeneous.

Action Potentials↗
PubMed1995

Analytic importance of the coding features for the discrimination of vowels in the cochlear implant signal.

The present study considers the analytic importance of the excitation pulse features delivered by a Nucleus cochlear implant using the F0F1F2 strategy. Four cochlear implant patients and 10 speakers uttering two 48-item lists constructed from four basic French vowels participated in this study. Patterns were presented to the patients and played at the input of an acquisition system in order to record the pulse features. Confusion matrices obtained with the patients and with automatic recognition procedures were then compared in order to find out the best-matching models simulating the patients' performances, out of 255 possibilities. The automatic recognition was carried out according to fuzzy logic based on the elementary features of the pulses coding the vowels. Results show that the essential features strongly depended on the subject.

Adult↗
PubMed1988

Origin of ascending projections to an isofrequency region of the mustache bat's inferior colliculus.

The inferior colliculus of the mustache bat is similar in most respects to the inferior colliculus of more commonly studied mammals, but one isofrequency contour, the dorsoposterior division, is greatly overrepresented. The present study utilizes this specialization of the auditory system in the mustache bat to determine the total set of ascending projections to a single isofrequency contour of the inferior colliculus. Within the dorsoposterior division, neurons are all very narrowly tuned to 60 kHz, the major component of this bat's echolocation call. The afferent projections to this isofrequency contour were identified by making deposits of horseradish peroxidase (HRP) within the dorsoposterior division after physiologically defining its borders. Two other frequency representations are present in the central nucleus of the inferior colliculus of the mustache bat, the anterolateral division in which there is an orderly progression of frequencies from 59 down to 20 kHz, and the medial division in which frequencies from 63-120 kHz are represented. In additional experiments, the afferent projections to the medial and anterolateral divisions were examined, providing an anatomical description of the tonotopicity of the lower auditory nuclei. Deposits of HRP in the DPD labeled cells in each of the lower brainstem auditory nuclei that have previously been shown to project to the entire central nucleus of the inferior colliculus. The ascending projections to the dorsoposterior division include contralateral projections from the cochlear nucleus and inferior colliculus, ipsilateral projections from the medial superior olive, ventral and intermediate nuclei of the lateral lemniscus, and bilateral projections from the lateral superior olive and dorsal nucleus of the lateral lemniscus. In most of the nuclei, labeled cells were confined to specific portions of the nuclei, often forming "slabs" of labeled cells across the rostrocaudal extent of most nuclei. These slabs presumably represent the 60 kHz representation in each of the lower nuclei. When deposits of HRP were made into other frequency band representations of the inferior colliculus, in either the medial or anterolateral division, labeled cells again formed slabs in each lower nucleus. However, the location of the slab varied as a function of the best frequency of neurons at the deposit site, and labeled cells were not present within the 60 kHz representation. These results show the general tonotopy of the mustache bat's brainstem auditory nuclei, and with respect to the dorsoposterior division, clearly reveal the total set of projections to a single isofrequency region.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed2004

Histologic evaluation of the tissue seal and biologic response around cochlear implant electrodes in the human.

HYPOTHESIS: Histopathologic study of the tissue seal and biologic response around cochlear implant electrodes in patients who had received a cochlear implant during life could provide clues concerning the pathogenesis of meningitis after cochlear implantation. BACKGROUND: Bacterial meningitis has been reported as an infrequent complication of cochlear implantation using a variety of electrode designs. The cause of meningitis in cochlear implant recipients has not been firmly established. In an analogous surgical situation, namely stapedectomy, delayed meningitis could occur as a complication of ipsilateral acute suppurative otitis media in which there was open communication between the middle ear and perilymph. METHODS: Twenty-one temporal bones from 20 individuals who had undergone cochlear implantation during life were studied by light microscopy. All sections passing through the cochleostomy site and electrode track were examined to evaluate the tissue seal at the cochleostomy, the presence or absence of an extracochlear electrode sheath, and finally, to seek evidence of a cellular inflammatory response near the electrode. These data were compared with clinical data, including electrode system used, the number of years between implantation and death, type of tissue used at surgery, and the age and sex of the patients. RESULTS: The 21 specimens included cases implanted with the Symbion Ineraid, Cochlear Corporation Nucleus 22-channel, Cochlear Corporation Nucleus 24-channel, a Cochlear Corporation Nucleus single channel, and Advanced Bionics Clarion C1 devices. At the cochleostomy site, and just within the cochlea, there was a robust fibrous and bony tissue response in all 21 ears and in most cases, there was a fibrous sheath surrounding the electrode in the middle ear. No recognizable open communication or potential communication between the middle ear and the inner ear was seen in any of the 21 ears. An inflammatory cellular response, including mononuclear leukocytes, histiocytes, and foreign body giant cells, were present in 12 of the 21 temporal bones (57%) and was most intense at the cochleostomy site. No statistically significant relationship was found between the presence or absence of inflammatory cells and the type of tissue graft used at surgery. CONCLUSIONS: The histologic evidence presented in this study does not support open communication between the middle and the inner ear as part of the pathogenesis of bacterial meningitis as a late complication after cochlear implantation. Rather, the finding of a cellular inflammatory response in 12 of 21 temporal bones suggests that late hematogenous contamination and colonization of the implant is a much more likely pathogenic mechanism. This putative mechanism has implications for possible strategies to prevent meningitis after cochlear implantation.

Aged↗
PubMed2000

Pathology of Madras type of motor neuron disease (MMND)--a histological and immunohistochemical study.

A neuropathological report of Madras type of motor neuron disease (MMND) is presented and the differences from other forms of MND are discussed. An 18-year-old girl presented with nerve deafness and slowly progressive bulbo-spinal muscular atrophy, characteristic of MMND. Post-mortem examination of the spinal cord showed a severe loss of anterior horn cells, prominent dilatation of vessels, diffuse, but sparse sprinkling of microglial cells and lymphocytes, and demyelination and sclerosis of the ventrolateral columns. Neuronal depletion and marked gliosis was noted in the cochlear nucleus on both sides, while other bulbar motor nuclei were also involved. The cochlear nerve showed demyelination and axonal loss. Trigeminal and vestibular ganglia revealed features of ganglionitis. The possibility of an inflammatory aetiology for MMND needs to be considered.

Adolescent↗
PubMed1998

Stability of the cochlear implant array in children.

OBJECTIVE: To determine cochlear implant electrode stability in the young patient. Electrode migration due to future skull growth was a concern that led to prohibiting implantation in children less than 2 years of age. Recently, the high level of performance achieved by young implantees has led to a re-evaluation of this lower age limit, requiring an assessment of the effects of skull growth over time. STUDY DESIGN: Prospective radiographic analysis of electrode position of cochlear implants in young children. METHODS: Twenty-seven children implanted with the Nucleus (Cochlear Corp., Denver, CO) or Clarion (Advanced Bionics Inc., Sylmar, CA) multi-channel cochlear prostheses were subjects for this study. Follow-up radiographic studies were obtained for a period of 1 month to 5 years after implantation. The age at time of implantation ranged from 14 months to 5 years. An intraoperative modified Stenver's view plain radiograph was obtained as a baseline. After implantation, on a yearly basis transorbital Stenver's and base views were obtained for comparative purposes. Additional radiographs were obtained whenever a change in performance or electrode map caused suspicion for extrusion. Electrode position was determined using a computer graphics enhancement technique whereby image contrast filters enhanced the visibility of the electrode array and surrounding bony structures. RESULTS: An analysis of the data revealed no migration of the electrode array over time. CONCLUSIONS: The confirmation of the stability of the electrode array alleviates the concern of the effects of skull growth on cochlear implantation in young children.

Child, Preschool↗
PubMed1991

The monaural nuclei of the lateral lemniscus in an echolocating bat: parallel pathways for analyzing temporal features of sound.

In echolocating bats, three cell groups in the lateral lemniscus are conspicuous for their large size and high degree of differentiation. These cell groups are the intermediate nucleus (INLL), columnar nucleus (VNLLc), and multipolar cell area (VNLLm). All receive projections from the contralateral cochlear nucleus. Previous anatomical studies suggest the hypothesis that these nuclei are important for analyzing the temporal structure of sound. To investigate this possibility, we recorded responses of single units in the INLL, VNLLc, and VNLLm of Eptesicus fuscus. The results show that each cytoarchitectural division contains a complete tonotopic representation. Certain response properties are common to all three nuclei. First, virtually all units are monaural. Second, all are broadly tuned to frequency; their average Q10dB value of 9.1 is considerably lower than values measured in the inferior colliculus of Eptesicus. Third, most units have little or no spontaneous activity. Fourth, all have short integration times, responding robustly to stimuli less than 5 msec in duration. The broad tuning, lack of spontaneous activity, and short integration time all make these neurons well suited for the accurate encoding of temporal information. Although there are many similarities, there are also important differences among nuclei. The clearest evidence of specialization is in VNLLc. Neurons here are more broadly tuned than those in INLL or VNLLm, have no spontaneous activity, and always respond with one spike per stimulus. The latency of the spike is precisely locked to the stimulus onset, with variability from trial to trial as low as 0.03 msec. In addition, the latency remains constant over large variations in frequency or intensity. In INLL and VNLLm, response patterns are about equally distributed between tonic, chopping, and phasic; there are no single-spike constant-latency responses of the type seen in VNLLc, although some choppers and pausers do respond with constant first-spike latency. The results indicate that VNLLc is specialized to encode very precisely the onset of sound; the other nuclei may encode ongoing properties of a sound.

Acoustic Stimulation↗
PubMed1994

Reduced retinal activity increases GFAP immunoreactivity in rat lateral geniculate nucleus.

Dynamic regulation of astrocytic processes by the electrical activity of local neurons has been previously described in chick cochlear nucleus. The present study extends this observation by showing that astrocytes in the rat lateral geniculate nucleus (LGN) also increase their immunoreactivity for glial fibrillary acidic protein (GFAP) soon after deprivation of afferent visual neuronal activity. Within 6 h of enucleation, which eliminates a major source of afferent input to the contralateral LGN, GFAP immunoreactivity increases relative to the ipsilateral LGN. A similar increase in GFAP immunoreactivity can be induced by intraocular injections of tetrodotoxin, demonstrating that a reversible manipulation of optic nerve electrical activity is sufficient to regulate LGN astrocytes. This rapid response to activity deprivation is less dramatic than the gliotic reaction observed 3 weeks following deafferentation, by which time afferent terminals have degenerated. These results support the notion that regulation of astrocytic processes by neural activity may play an important role in activity-dependent synaptic regulations in the various sensory systems of vertebrates.

Animals↗
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

Recognition of speech presented at soft to loud levels by adult cochlear implant recipients of three cochlear implant systems.

OBJECTIVE: The purpose of this study was to conduct a large-scale investigation with adult recipients of the Clarion, Med-El, and Nucleus cochlear implant systems to (1) determine average scores and ranges of performance for word and sentence stimuli presented at three intensity levels (70, 60, and 50 dB SPL); (2) provide information on the variability of scores for each subject by obtaining test-retest measures for all test conditions; and (3) further evaluate the potential use of lower speech presentation levels (i.e., 60 and/or 50 dB SPL) in cochlear implant candidacy assessment. DESIGN: Seventy-eight adult cochlear implant recipients, 26 with each of the three cochlear implant systems, participated in the study. To ensure that the data collected reflect the range of performance of adult recipients using recent technology for the three implant systems (Clarion HiFocus I or II, Med-El Combi 40+, Nucleus 24M or 24R), a composite range and distribution of consonant-nucleus-consonant (CNC) monosyllabic word scores was determined. Subjects using each device were selected to closely represent this range and distribution of CNC performance. During test sessions, subjects were administered the Hearing in Noise Test (HINT) sentence test and the CNC word test at three presentation levels (70, 60, and 50 dB SPL). HINT sentences also were administered at 60 dB SPL with a signal-to-noise ratio (SNR) of +8 dB. Warble tones were used to determine sound-field threshold levels from 250 to 4000 Hz. Test-retest measures were obtained for each of the speech recognition tests as well as for warble-tone sound-field thresholds. RESULTS: Cochlear implant recipients using the Clarion, Med-El, or Nucleus devices performed on average equally as well at 60 compared with 70 dB SPL when listening for words and sentences. Additionally, subjects had substantial open-set speech perception performance at the softer level of 50 dB SPL for the same stimuli; however, subjects' ability to understand speech was poorer when listening in noise to signals of greater intensity (60 dB SPL + 8 SNR) than when listening to signals presented at a soft presentation level (50 dB SPL) in quiet. A significant correlation was found between sound-field thresholds and speech recognition scores for presentation levels below 70 dB SPL. The results demonstrated a high test-retest reliability with cochlear implant users for these presentation levels and stimuli. Average sound-field thresholds were between 24 and 29 dB HL for frequencies of 250 to 4000 Hz, and results across sessions were essentially the same. CONCLUSIONS: Speech perception measures used with cochlear implant candidates and recipients should reflect the listening challenges that individuals encounter in natural communication situations. These data provide the basis for recommending new candidacy criteria based on speech recognition tests presented at 60 and/or 50 dB SPL, intensity levels that reflect real-life listening, rather than 70 dB SPL.

Adult↗