ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Objective“Dead regions” are regions in the cochlea with no functioning inner hair cells (IHCs) and/or neurons. Amplification (using a hearing aid) over a frequency range corresponding to a dead region may not be beneficial and may even impair speech intelligibility. The objective of this article is to illustrate the use of psychophysical tuning curves (PTCs) as a tool for investigating dead regions and to illustrate the variety of audiogram configurations that can be associated with dead regions. We explore the influence of signal level and signal frequency to test the hypothesis that the frequency at the tip of the tuning curve defines the boundary of the dead region.DesignPTCs were measured for five subjects with sensorineural hearing loss who were suspected of having dead regions. One had a relatively “flat” loss, one had a mild mid-frequency loss and three had high-frequency losses, varying in severity from 70 dB to more than 120 dB. For each PTC, the level and frequency of the sinusoidal signal were fixed, and the level of a narrowband noise masker needed just to mask the signal was determined as a function of the masker frequency. When the signal falls in a frequency region that is not “dead,” the signal is detected via IHCs with characteristic frequencies (CFs) at or close to the signal frequency. In such a case, the tip of the PTC (the masker frequency at which the masker level is lowest) lies at or close to the signal frequency. When a dead region is present, the signal is detected via IHCs with CFs different from that of the signal frequency. In such a case, the tip of the PTC is shifted away from the signal frequency.ResultsPTCs with frequency-shifted tips (indicative of dead regions) were found for all subjects. The frequencies at the tips sometimes decreased slightly with increasing signal level. For the subject with a relatively flat loss, PTCs with tips close to 3000 Hz were obtained for signal frequencies of 400, 1000 and 1500 Hz. A PTC with a tip at 5000 Hz was found for a signal frequency of 6000 Hz. These results suggest that this subject had an “island” of surviving IHCs and neurons with CFs ranging from 3000 to 5000 Hz, with extensive dead regions on either side. For the subject with a mid-frequency loss, the pattern of results suggested a mid-frequency dead region. For the subjects with high-frequency loss, the results suggested the presence of high-frequency dead regions, in one case starting at a frequency where absolute thresholds were only slightly higher than normal.ConclusionsPTCs can be used to detect and delimit dead regions. Often, the frequency at the tip of the PTC can be used to defineapproximatelyone boundary of the dead region. However, the detection of beats can affect the shape of the PTC around the tip when the signal frequency lies just inside the dead region. The level of the signal can also have some effect on the frequency at the tip of the PTC. Very low signal levels can lead to variable results. Dead regions can start at frequencies where absolute thresholds are near normal.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveThe purpose of this research was to identify the gene responsible for a novel form of nonsyndromic, late-onset, bilateral, progressive, sensorineural hearing loss in a Michigan family of English descent. This report describes the audiologic aspects of the search.DesignFifty-eight members of the family served as subjects for the study. Family pedigree information was gathered from family interviews, family records, birth and death registration records and census data. Audiologic evaluation was used to describe the hearing loss (phenotype) and classify family members as affected or unaffected based on hearing status. These data then were used in a linkage analysis, a process in which the inheritance of a trait is compared with the inheritance of genetic markers and statistically significant associations are sought.ResultsThe team mapped the hearing loss to the long arm of chromosome 17 at band 17q25. The pattern of inheritance is autosomal dominant. The search for the gene is continuing using a candidate gene approach.ConclusionsThe hearing loss demonstrated by this mid-Michigan family is a novel form of nonsyndromic, genetic, late-onset, bilateral, progressive, sensorineural hearing loss. The locus of the gene, the 20th for autosomal dominant hearing loss, is at band 17q25 of chromosome 17.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveThe goal of this study was to estimate psychophysical levels using the electrically evoked compound action potential (EAP), measured with the Neural Response Telemetry capabilities of Cochlear Corporation’s Nucleus CI24M cochlear implant system.DesignTwelve postlingually deafened adults with at least 3 mo of implant experience with the CI24M were subjects in this study. EAP growth functions were successfully quantified on each active electrode of every subject. Correlation and regression analyses were performed between EAP measures and cochlear implant fitting psychophysics. Other information including performance, etiology and duration of hearing loss, and individual electrode impedance was considered.ResultsEAP thresholds were found to be highly correlated with psychophysical thresholds. The rate of EAP growth with increasing stimulation levels was also found to be correlated with the dynamic range of loudness limits and psychophysical thresholds in some subjects. No relationship was evident between EAP measures and speech perception tests.ConclusionsInformation from EAP growth function measurements may be used to estimate psychophysical information used in cochlear implant fitting but not to predict performance with the device.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveThe objective of the article is to provide an accurate model of the human cochlea with which potential distributions and thus neural excitation patterns around cochlear implant electrodes can be determined. Improvements on previous models of the implanted cochlea are that this model 1) includes the spiral nature of the cochlea as well as many other anatomical details (and it is a model of the human cochlear rather than the guinea pig cochlea), and 2) facilitates modeling of different electrode geometries, array locations and electrode separations without changing the structure of the model.DesignA three-dimensional spiraling finite element model of the human cochlea was created. The model incorporates the effect of neighboring canals and conduction along the fluid-filled canals of the cochlea. Potential distributions are used as inputs to a nerve fiber model to investigate auditory nerve excitation patterns around intracochlear electrode arrays.ResultsPotential distributions around intracochlear electrodes generated with the finite element model are presented. The effects of electrode separation, electrode geometry and array location on excitation threshold, excitation spread and ectopic excitation (i.e., excitation of nerve fibers at an undesirable location) are demonstrated.ConclusionsThe following conclusions should be considered preliminary, as their accuracy depends on the exactness of the underlying model. The spiraling geometry of the cochlea causes asymmetry in potential distributions. The location of electrodes along the length of the basilar membrane has a stronger influence on the site of excitation than the polarity of the leading phase of the stimulus. Array location is the primary parameter that controls excitation spread. Threshold currents and the effect of ongoing loss of peripheral dendrites on threshold currents can be limited by placing arrays close to the modiolus. Point electrode geometries are recommended above banded electrode geometries only when the array can be placed close to the modiolus. There is a tradeoff between array location and the degree of ectopic stimulation caused by a specific array location. Bimodal excitation patterns exist at comfortable stimulus intensities for longitudinal bipolar electrode configurations. It is shown that an electrode configuration with an electrode separation of approximately half that of the bipolar electrode separation of the Nucleus electrode can be used instead of radial and offset radial electrode configurations to create unimodal excitation patterns. The stimulation resolution of cochlear implant electrode arrays can potentially be improved by increasing the number of electrode contacts in an array.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveA method was developed to estimate the contralateral acoustic reflex threshold using shifts in wideband energy reflectance, admittance magnitude and power.DesignIn the first experiment contralateral reflex thresholds for a noise activator were estimated on three adult participants using reflectance, admittance and power measurements at frequencies from 250 to 8000 Hz. The reflex threshold was defined using a magnitude and a correlation technique, both having the property of examining the pattern of the reflex-induced shift across a fairly broad frequency range (250 to 2000 Hz). In the second experiment, the magnitude method was modified to include anFtest for the comparison of the magnitude of reflex-induced shifts in reflectance, admittance and power relative to response differences in a no-activator baseline condition. Data from four additional participants then were analyzed across a broader frequency range using a method that combined magnitude and correlation methods of estimating reflex thresholds.ResultsAcoustic reflex thresholds were obtained using reflectance, admittance and power-level measures in all subjects in both experiments. Individual reflex threshold estimates were as much as 24 dB lower than with the clinical system, with an average of approximately 14 dB lower for the three participants in the first experiment, and approximately 18 dB lower for the four participants in the second experiment.ConclusionsWideband measures of reflectance, admittance and power were successfully used to estimate acoustic reflex thresholds in seven participants. A reflex threshold test was devised based on the magnitude of the response shift in the presence of a contralateral activator, and the similarity of the response shift spectra across frequency between successive activator levels. Across all participants in the study, the new test yielded a more sensitive measure of the acoustic reflex threshold than the clinical method. This finding has both clinical and theoretical implications for the study of the acoustic reflex.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveThis study sought to describe the consonant information provided by amplification and by speechreading, and the extent to which such information might be complementary when a hearing aid user can see the talker’s face.DesignParticipants were 25 adults with acquired sensorineural hearing losses who wore the GN ReSound BT2 Personal Hearing System binaurally. Consonant recognition was assessed under four test conditions, each presented at an input level of 50 dB SPL: unaided listening without speechreading (baseline), aided listening without speechreading, unaided listening with speechreading, and aided listening with speechreading. Confusion matrices were generated for each of the four conditions to determine overall percent correct for each of 14 consonants, and information transmitted for place of articulation, manner of articulation, and voicing features.ResultsBoth amplification and speechreading provided a significant improvement in consonant recognition from the baseline condition. Speech-reading provided primarily place-of-articulation information, whereas amplification provided information about place and manner of articulation, as well as some voicing information.ConclusionsBoth amplification and speechreading provided place-of-articulation cues. The manner-of-articulation and voicing cues provided by amplification, therefore, were generally complementary to speechreading. It appears that the synergistic effect of combining the two sources of information can be optimized by amplification parameters that provide good audibility in the low-to-mid frequencies.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveTo investigate the applicability of the self-report inventory, Satisfaction with Amplification in Daily Life (SADL), at 2 wk postfitting.DesignThe SADL was completed by two groups of hearing aid users, one fitted 2 wk before completion, the other at least 1 yr before. All SADLs were completed as a paper and pencil exercise, without involvement of an audiologist or other clinic staff. All the aid users were Government funded, all were fitted with the same model hearing aid, all were over the age of 60 yr, and all were fitted and counselled by the same two audiologists. Comparisons were made of the two groups’ scores on each subscale and Global score, as well as on scores for each individual question.ResultsAll scores for subscales, Global score, and individual questions were higher at 2 wk postfitting than at 1 yr. Significant differences were found for subscales Positive Effect (p< 0.05), Service and Cost (p< 0.025), Negative Features (p< 0.001), as well as for the Global score (p< 0.001). The only subscale not resulting in a significant difference was Personal Image (p> 0.10). It was noted that Negative Features, such as background interference, acoustic feedback, and problems with telephone use, apparently take longer to be observed than Positive Effects such as improved communication and good sound quality.By contrast with some other reported studies, these results all display a reduction in self-reported outcome, rather than stability, or even improvement, over time. Among other possibilities, this finding may suggest the SADL measures something different to that measured by other inventories.ConclusionsThe results of this investigation suggest that, if the aim is to predict long-term satisfaction with aid fitting, 2 wk postfitting is too early for meaningful application of the SADL as an outcome measure. It is possible that an earlier stability in SADL scores might be obtained by inclusion of additional questions aimed at earlier detection of negative features. Such inclusions may detract from one of the SADL’s advantages, namely its brevity.It also is suggested that the long-term value of self-report methods will depend on development of rigorous and scientifically acceptable administration procedures, including appropriate times for application.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveTo evaluate the impact of low-threshold compression and hearing aid style (in-the-ear [ITE] versus behind-the-ear [BTE]) on the directional benefit and performance of commercially available directional hearing aids.DesignForty-seven adult listeners with mild-to-moderate sensorineural hearing loss were fit bilaterally with one BTE and four different ITE hearing aids. Speech recognition performance was measured through the Connected Speech Test (CST) and Hearing in Noise Test (HINT) for a simulated noisy restaurant environment.ResultsFor both the HINT and CST, speech recognition performance was significantly greater for subjects fit with directional in comparison with omnidirectional microphone hearing aids. Performance was significantly poorer for the BTE instrument in comparison with the ITE hearing aids when using omnidirectional microphones. No differences were found for directional benefit between compression and linear fitting schemes.ConclusionsNo systematic relationship was found between the relative directional benefit and hearing aid style; however, the speech recognition performance of the subjects was somewhat predictable based on Directivity Index measures of the individual hearing aid models. The fact that compression did not interact significantly with microphone type agrees well with previously reported electroacoustic data.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID