Effect of two interaural phase conditions for binaural exposures on threshold shift.
Explore the source record for details and available documents.
Audiometry↗
SEARCH · PubMed Health
Results for “Auditory Threshold”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Construction of a dummy head after new measurements of thresholds of hearing.
Explore the source record for details and available documents.
Auditory Threshold↗
Nonconstant quality of auditory filters in the porpoises, Phocoena phocoena and Neophocaena phocaenoides (Cetacea, Phocoenidae).
Simultaneous tone-tone masking in conjunction with the envelope-following response (EFR) recording was used to obtain tuning curves in porpoises Phocoena phocoena and Neophocaena phocaenoides asiaeorientalis. The EFR was evoked by amplitude-modulated probes with a modulation rate of 1000 Hz and carrier frequencies from 22.5 to 140 kHz. Equivalent rectangular quality QERB of the obtained tuning curves varied from 8.3-8.6 at lower (22.5-32 kHz) probe frequencies to 44.8-47.4 at high (128-140 kHz) frequencies. The QERB dependence on probe frequency could be approximated by regression lines with a slope of 0.83 to 0.86 in log-log scale, which corresponded to almost frequency-proportional quality and almost constant bandwidth of 3-4 kHz. Thus, the frequency representation in the porpoise auditory system is much closer to a constant-bandwidth rather that to a constant-quality manner.
Animals↗
Hybrid measurement of auditory steady-state responses and distortion product otoacoustic emissions using an amplitude-modulated primary tone.
A maximum auditory steady-state response (ASSR) amplitude is yielded when the ASSR is elicited by an amplitude-modulated tone (f(c)) with a fixed modulation frequency (f(m) = 40 Hz), whereas the maximum distortion product otoacoustic emission (DPOAE) level is yielded when the DPOAE is elicited using a fixed frequency ratio of the primary tones (f2/f1 = 1.2). When eliciting the DPOAE and ASSR by the same tone pair, optimal stimulation is present for either DPOAE or ASSR and thus adequate simultaneous DPOAE/ASSR measurement is not possible across test frequency f2 or f(c), respectively. The purpose of the present study was to determine whether the ASSR and DPOAE can be measured simultaneously without notable restrictions using a DPOAE stimulus setting in which one primary tone is amplitude modulated. A DPOAE of frequency 2f1-f2 and ASSR of modulation frequency 41 Hz were measured in ten normal hearing subjects at a test frequency between 0.5 and 8 kHz (f2 = f(c)). The decrease in the DPOAE level and the loss in ASSR amplitude during hybrid mode stimulation amounted, on average, to only 2.60 dB [standard deviation (SD) = 1.38 dB] and 1.83 dB (SD = 2.38 dB), respectively. These findings suggest simultaneous DPOAE and ASSR measurements to be feasible across all test frequencies when using a DPOAE stimulus setting where the primary tone f2 is amplitude modulated.
Acoustic Impedance Tests↗
Acoustic trauma: single neuron basis for the "half-octave shift".
Exposure to an intense pure tone can induce a loss of hearing sensitivity. If this loss recovers, then the desensitization is regarded as a temporary threshold shift (TTS). At the single auditory neuron level this TTS was monitored as a loss of sensitivity at the neuron's most sensitive or characteristic frequency (CF). When pure-tone exposures were presented at frequency intervals measured from the neuron CF, then a frequency half an octave below the CF was the most effective for inducing a CF TTS. All exposure frequencies higher than half an octave below the CF produce a marked reduction in TTS growth with intensity, when compared to lower exposure frequencies. This behavior is such that, with increasing exposure frequency higher than the -1/2-octave point, the intensity needed to produce a given TTS grew faster than the neuron sensitivity. However, below the -1/2-octave point all exposure frequencies were similarly behaved. Strong similarities exist between the frequency-specific requirements for TTS and the mechanical and neural nonlinearities found in other studies. This suggests that the half-octave shift may well be a direct result of basilar membrane nonlinearities.
Acoustics↗
Diversity of adaptation patterns in responses of eighth nerve fibers in the bullfrog, Rana catesbeiana.
The firing patterns of eighth nerve fibers in the bullfrog, Rana catesbeiana, were analyzed for responses to long duration tone bursts at best excitatory frequency ( BEF ) and at frequencies along the upper and lower boundaries of the excitatory tuning curve of each fiber. These firing patterns were used as an index of the degree of short-term adaptation of each fiber. Amphibian papilla fibers (with BEFs 100-1000 Hz) exhibited marked diversity in their firing patterns to BEF tones, ranging from very flat or tonic (sustained responses throughout the duration of the stimulus) to very peaked or phasic (responding primarily or exclusively to stimulus onset). Moreover, the degree of short-term adaptation shown by an individual fiber varied with stimulating frequency. The firing patterns of amphibian papilla fibers tended to become more tonic as stimulus frequency was lowered below BEF ; conversely, as stimulus frequency was increased above BEF , firing patterns either showed little change from that at BEF , or became more phasic. A similar frequency dependence of adaptation has not been reported in responses of mammalian eighth nerve fibers with comparable BEFs . The firing patterns of basilar papilla fibers ( BEFs greater than 1000 Hz) remained similar in response to both BEF and non- BEF tones. These data reveal that the firing patterns and degrees of short-term adaptation of amphibian papilla fibers vary considerably across the tuning curve, whereas those of basilar papilla fibers remain relatively more constant with changes in stimulating frequency.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Partial dissociation of spontaneous otoacoustic emissions and distortion products during aspirin use in humans.
Otoacoustic emissions (OAEs) of two types--spontaneous and evoked distortion products--were studied before, during, and following a period of aspirin use. As previously reported, aspirin consumption uniformly reduced the spontaneous OAEs (SOAEs) to unmeasurable or extremely low levels. Aspirin consumption also reduced the amplitude of the evoked distortion products (EDPs) but did not eliminate them entirely. The amplitude of the EDP and its change with aspirin consumption were related to both the proximity of the EDP to the frequency of the SOAE and to the level of the primaries producing the EDP. At low primary levels, even with the SOAE absent (due to aspirin consumption, or suppression), EDPs near the SOAE frequency were 10-20 dB higher than when they were 100 Hz away from the SOAE frequency.
Acoustic Stimulation↗
Noise level, inner hair cell damage, audiometric features, and equal-energy hypothesis.
Rabbits were exposed to 2- to 7-kHz noise either for a short duration at a high sound-pressure level (15 or 30 min at 115 dB SPL), or a long duration at a low level (512 h at 85 dB SPL). The high-level exposure produced a hearing loss in the frequency range 2-6 kHz, whereas the low-level exposure gave maximum hearing loss at 12-20 kHz. The 115-dB exposure caused significantly more damage to inner hair cells than the 85-dB exposure. The implications of the present results for evaluating audiograms, equal-energy hypothesis, risk criteria, and subjective auditory features are pointed out.
Animals↗
Binaural-level functions in ferret auditory cortex: evidence for a continuous distribution of response properties.
Many previous studies have subdivided auditory neurons into a number of physiological classes according to various criteria applied to their binaural response properties. However, it is often unclear whether such classifications represent discrete classes of neurons or whether they merely reflect a potentially convenient but ultimately arbitrary partitioning of a continuous underlying distribution of response properties. In this study we recorded the binaural response properties of 310 units in the auditory cortex of anesthetized ferrets, using an extensive range of interaural level differences (ILDs) and average binaural levels (ABLs). Most recordings were from primary auditory fields on the middle ectosylvian gyrus and from neurons with characteristic frequencies >5 kHz. We used simple multivariate statistics to quantify a fundamental coding feature: the shapes of the binaural response functions. The shapes of all 310 binaural response surfaces were represented as points in a five-dimensional principal component space. This space captured the underlying shape of all the binaural response surfaces. The distribution of binaural level functions was not homogeneous because some shapes were more common than others. Despite this, clustering validation techniques revealed no evidence for the existence of discrete, or partially overlapping, clusters that could serve as a basis for an objective classification of binaural-level functions. We also examined the gradients of the response functions for the population of units; these gradients were greatest near the midline, which is consistent with free-field data showing that cortical neurons are most sensitive to changes in stimulus location in this region of space.
Acoustic Stimulation↗
Comparison of response properties of inferior colliculus neurons of two inbred mouse strains differing in susceptibility to audiogenic seizures.
Explore the source record for details and available documents.
Acoustic Stimulation↗
Auditory brainstem response: recent developments in recording and analysis.
During the past 25 years since the 'discovery' of the ABR, clinicians world-wide have exploited the clinical utility of this evoked response with many different populations. The 1970s and 1980s saw the development of ABR protocols for increasing the reliability and validity of the response in various clinical situations. Now, in the last decade of the century, advanced technology and the development of increasingly sophisticated software allows more flexibility in these measurements. Thus, ABR testing continues to evolve at a rapid pace. The main focus for ABR in the 1990s has been on developing techniques to improve the quality of the response, decrease the time in which it takes to record the response, and minimize human error through objective response analysis. Some of the major recent developments were reviewed in this chapter. The intent of this review is to provide the researcher and the clinician with an understanding of the underlying principles of the techniques which will be, and are already, available to them on their ABR equipment. Many of these techniques are promising for use with newborns, children, and difficult-to-test populations where time is a limiting factor in the amount of information that can be obtained. We encourage any and all clinicians to experiment with these techniques to determine how each technique might contribute to their particular clinic protocols. As with any new technique, there will be a learning curve associated with understanding the underlying principles, mastering the technical requirements, and realizing the most valuable clinical applications of these methods. Once the procedures become familiar to clinicians and applied in varied clinical settings, it is likely that the neurodiagnostic and audiologic value of ABR will be profoundly enhanced.
Auditory Threshold↗
Single-dipole analyses of the N100m are not suitable for characterizing the cortical representation of pitch.
In several previous studies, the deflection N100m of the auditory evoked field (AEF), occurring about 100 ms after the onset of a sound, has been used to investigate whether complex tones are represented in the auditory cortex by their spectrum or their periodicity pitch. However, the results partially contradict each other. Moreover, the basic assumption that N100m originates from a single cortical source has been questioned. To gain clarity, the AEF elicited by a complex tone with a periodicity of 4 ms (pitch 250 Hz) and a spectrum between 1000 and 2000 Hz was compared with the AEF in response to pure tones of 250 and 1000 Hz, respectively (on 12 subjects). While a previous analysis [Audiol Neurootol 2001;6: 263-278] was exclusively devoted to the N100m latency, this article presents source analyses with two variants of a single-dipole model (moving dipole and fixed dipole). Earlier reports, suggesting that N100m arises from a cortical source representing the pitch rather than the spectrum of the sound, could not be reproduced, independent of the method used. It appears that an investigation of the functional organization of the human auditory cortex based on N100m source modeling requires a much higher degree of sophistication than a single-dipole model can provide.
Audiometry, Pure-Tone↗
Travelling wave motion along the pigeon basilar membrane.
The basilar membrane (BM) motion in the pigeon was measured using the Mössbauer technique. Tonotopic frequency mapping and travelling wave motion were observed over the basal 35% of the BM. The sensitivity and sharpness of the BM tuning depended on the physiological condition of the cochlea. The observed amplitude responses did not match the frequency threshold tuning curves of single primary auditory fibers.
Acoustic Stimulation↗
Auditory brainstem potentials in uraemia.
Evoked response audiometry was carried out to assess the viability of the auditory pathway in haemodialysed patients. The latency of the waves III and V and I-V interpeak latencies were significantly longer in the renal patients compared to the control group. The I-V interpeak latency was longer in 8 of our 13 patients than the upper limit (4.38 ms) in our laboratory. The possible cause for the central auditory dysfunction may be multifactorial, including the effect of metastatic calcifications, repeated occurrence of disequilibrium syndrome, or some small, molecular, toxic, metabolic substance. The significance of the different factors may vary among different haemodialysis centres.
Adult↗
The influence of aging on auditory brainstem response and electrocochleography in the elderly.
Auditory brainstem responses and simultaneous transtympanic electrocochleographies were investigated in 92 subjects aged between 50 and 89 years with normal hearing or mild presbycusis. Subjects were classified into four age-related groups: 16 subjects in the sixth decade, 28 in the seventh decade, 32 in the eighth decade and 16 in the ninth decade. Thirty young subjects with normal hearing aged 20-29 years were chosen as controls. The result showed progressive delay of wave I (or action potential: AP), wave III and wave V and lengthening of the interpeak intervals (IPIs) of waves III-V and I-V in the subjects aged 50-79 years. In the subjects in the ninth decade, shortening of IPIs of waves I-III and I-V was noted in spite of further delays of wave I. The amplitude of APs on electrocochleography decreased in the groups with mild presbycusis. Both the lengthening and shortening of IPIs might be electrophysiological alterations occurring with aging in the central auditory pathways.
Age Factors↗
Electric response audiometry: the morphology of normal responses.
Explore the source record for details and available documents.
Adult↗
Comparison of the intrasubject repeatability of auditory brain stem and middle latency responses elicited in young children.
The auditory brain stem response (ABR) and middle latency response (MLR) were studied in 48 young children (96 ears). The responses were elicited using low intensity stimuli (30-dB nHL clicks) and simultaneously were recorded on a dual time base. Both the ABR and MLR were elicited in 70 ears. In 12 ears, just one response was recorded (ABR in eight ears and the MLR in four ears). In 14 ears, neither response was recorded. Test-retest analysis on the same subject demonstrated that the ABR was more repeatable and easier to identify than the MLR. The test-retest difference was determined for the amplitude and latency of the ABR and MLR waveforms. The test-retest latency difference for wave Pa was found to be 3.6 times larger than for wave V. The normalized test-retest amplitude difference for P phi-Na, Na-Pa, and Pa-Nb was found to be two to three times larger than for wave V. These data support the conclusion that the ABR, rather than the MLR, should be used to measure hearing in young children. The authors also advocate using minimal high pass (HP) filtering when recording the ABR in a sedated or sleeping child. Muscle artifact was not found to be a problem. The authors suggest the use of minimal HP filtering so that phase-shift distortion is minimized and a larger response amplitude can be recorded.
Audiometry, Evoked Response↗
Effects of preoperative electrical stimulability and historical factors on performance with multichannel cochlear implant.
We investigated the relationship between results of preoperative transtympanic electrical promontory stimulation, duration of deafness, postoperative implanted psychophysical results, and postoperative speech and speech sound recognition as indicated by a battery of five tests. Our subjects were 10 patients implanted with the Cochlear Corporation multielectrode implant, 1 year postimplantation, with a minimum of 17 active electrodes programmed in the bipolar + 1 mode. The results indicated that preoperative promontory thresholds, the slope of the threshold function, and the duration of auditory deprivation are excellent predictors of postoperative speech and speech sound recognition in the auditory (processor alone) mode. These results have significant implications for patient selection and counseling.
Adolescent↗