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Results for “Auditory Threshold”

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At least 703 records · Page 39Linked to original sources

PubMed1989

Development of morphological and physiological changes in the cochlea induced by cytomegalovirus.

The effect of viral infection in the cochlea was investigated by inoculation of live cytomegalovirus or inactivated virus. Auditory thresholds were measured on the day of inoculation and on the terminal day. Two to 8 days following inoculation, the animals were killed and the cochleas were evaluated histologically. The compound nerve potential showed an increase in threshold prior to the cochlear microphonic, indicating the nerve was affected prior to the outer hair cells. All experimental cochleas contained inflammatory and cytomegalic inclusion cells and showed degenerative changes. The number of infected cells was small relative to the histopathology. Control cochleas had normal structure and function. The degeneration, therefore, might be mediated by inflammation as well as by the cytopathic effect of the virus. Viral infections, therefore, might be better managed with anti-inflammatory therapy in addition to antiviral agents.

Animals↗

PubMed1991

Optimization of automated hearing test algorithms: a comparison of data from simulations and young children.

A five-up, five-down automated staircase procedure was used to explore the effects of variable starting and stopping rules as they interact with infant behavior in influencing the accuracy and efficiency of infant auditory threshold testing. Results from 146 infants were compared to results from computer simulations (see accompanying article) in order to evaluate an infant response model used in the simulations. Results indicate that the automated procedure successfully discriminated between infants with normal versus abnormal tympanograms. In addition, the model accurately predicted infant results in terms of the effects of starting and stopping rules. The model was less useful in predicting the relationship between minimum response levels and false positive rates.

Algorithms↗

PubMed2003

Does repeated hyperbaric exposure to 4 atmosphere absolute cause hearing impairment? Study in Guinea pigs and clinical incidences.

HYPOTHESIS: Direct pressure applied on the inner ear cannot induce hearing loss. BACKGROUND: Three possible causes have been described in the literature for inner ear permanent lesions during scuba diving: pressure imbalance between the middle ear and the external ear, appearance of microbubbles in the internal ear, and direct effect of pressure on the inner ear. We seek to determine whether this last factor can be involved. METHODS: We submitted two groups of guinea pigs previously implanted with an electrode in the round window to a protocol of air diving in a hyperbaric chamber. Eardrums of animals in one of the two groups had been perforated beforehand. Twenty dives were practiced over 4 weeks. We chose dive parameters consistent with common sport diving: maximal pressure of 4 atmosphere absolute and duration of 30 minutes. Auditory threshold and cochlear spontaneous activity were recorded at regular intervals. Furthermore, we recorded spontaneous cochlear activity in Heliox 400-m and 600-m dives to determine whether our conclusions hold for "extreme" diving. RESULTS: In the group with perforated eardrums, no variation of those parameters were recorded, even in extreme diving. Important variations were noticed in the other group. CONCLUSIONS: Pressure applied directly on the inner ear during diving does not disturb cochlear activity.

Animals↗

PubMed2006

Protective properties of idebenone in noise-induced hearing loss in the guinea pig.

Idebenone is a synthetic analogue of coenzyme Q10 with antioxidant properties. The present study investigated the antioxidant activity of idebenone in the rescue of acoustic trauma. Noise-induced hearing loss was induced by exposing guinea pigs to a continuous pure tone and idebenone was injected intraperitoneally 1 h before noise exposure and once daily for 3 days. Guinea pigs treated with idebenone showed significantly smaller auditory threshold shifts than unprotected control animals. Missing and apoptotic cells were identified with scanning electron microscopy and terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assay. Protected animals presented a lesser extent of both apoptotic activation and hair cell loss in the organ of Corti. Our results suggest an antioxidant function of idebenone in protection from noise-induced hearing loss and provide a rationale for exploring therapeutic strategies in humans.

Acoustic Stimulation↗

PubMed1992

Functional/metabolic modulation of the brain stem lesions caused by 1,3-dinitrobenzene in the rat.

To determine whether neuronal activity plays a role in the localisation of brain stem lesions in 1,3-dinitrobenzene intoxication we produced asymmetrical changes in auditory input by rupturing the left tympanic membrane in Fischer rats. This raised the auditory threshold on that side from 57-63 dB to 104-122 dB. It also decreased glucose utilisation in the ipsilateral cochlear nucleus and significantly increased utilisation in the contralateral nucleus, resulting in a relative deficit of 72 +/- 6%. Similarly, tympanic membrane rupture led to decreased glucose utilisation in the contralateral and increased utilisation in the ipsilateral inferior colliculus. Additional exposure to "white noise" prevented the decrease in glucose utilisation in the contralateral inferior colliculus. Dosing with dinitrobenzene (10 mg/kg in 4 doses over 48 hr) to otherwise normal rats produces symmetrical vasculonecrotic lesions in these regions, but in animals with left tympanic membrane rupture the severity of morphological changes in the ipsilateral cochlear nucleus and the contralateral inferior colliculus were substantially reduced. Additional exposure to "white noise" increased the degree of damage in the ipsilateral cochlear nucleus and contralateral inferior colliculus. These findings indicate that altered auditory function in rats, with its associated metabolic consequences exercises a significant role in the development of brain stem damage in auditory pathways following dinitrobenzene intoxication.

Acoustic Stimulation↗

PubMed1978

Adaptive testing in audiology.

A general approach to adaptive testing of the up-down type is described. Audiological applications of the procedure are described, including measurement of the auditory threshold, estimating the spread of the subject's response curve, testing for sequential response dependencies, and finding PB-max. Guidelines are provided for the practical implementation of these procedures using relatively simple rules for controlling stimulus levels and for estimating the parameters of interest. Also described is the Simplical Method, a multivariate adaptive procedure which, like the transformed up-down method, is relatively efficient yet involves simple rules of adjustment and of estimation. The Simplical Method has been used in the adaptive fitting of a wearable master hearing aid and an example of this application is given.

Audiometry↗

PubMed2001

Ginkgo biloba extract EGb 761 or pentoxifylline for the treatment of sudden deafness: a randomized, reference-controlled, double-blind study.

In a randomized, prospective, double-blind study involving 72 patients, the therapeutic efficacy of ginkgo extract EGb 761 (n = 37) was compared to that of pentoxifylline (n = 35) for the treatment of sudden deafness. The two therapeutic schedules were equally well tolerated and showed a statistically significant equivalence in improvement or in return to normal of the auditory thresholds in the two patient groups. Furthermore, no differences were found between the treatment groups with regard to the criteria for a return to normal of speech discrimination and reduction of the tinnitus which arose at the same time as the sudden hearing loss. The patient's subjective assessment of the treatment with regard to improvement in hearing and reduction in tinnitus suggested that Ginkgo biloba extract was more beneficial than pentoxifylline. In summary, it was shown that treatment of sudden deafness with ginkgo special extract EGb 761 was as effective as treatment with pentoxifylline.

Adult↗

PubMed2006

Age-dependent degeneration of the stria vascularis in human cochleae.

OBJECTIVE: Aging is a common cause of acquired hearing impairments. This study investigated age-related morphologic changes in human cochleae, with a particular focus on degeneration of the stria vascularis (SV) and the spiral ganglion (SG). STUDY DESIGN: Retrospective case review. METHODS: The study group comprised 91 temporal bones from individuals aged 10 to 85 years who had no history or audiometric findings suggestive of specific causes of cochlear degeneration. We quantified the SV and SG atrophy at each cochlear turn using morphometric measurements. Correlations of the SV and SG atrophy with age, audiometric patterns of hearing loss, and auditory thresholds were statistically investigated. RESULT: The SV and the SG both showed a tendency for progressive atrophy to develop with age. However, statistically significant correlations were observed between aging and SV atrophy only in the apical and basal cochlear turns. These findings were consistent with those reported previously in gerbils. No significant correlations were detected between SV or SG atrophy and audiometric findings. CONCLUSION: SV atrophy appears to be the most prominent anatomic characteristic of aged human cochleae.

Adolescent↗

PubMed1995

Cisplatin in children: hearing loss correlates with iris and skin pigmentation.

Pigmentation is reported to affect cisplatin-induced ototoxicity in adult humans. The hearing loss is worse in people with brown irises, than in those with blue irises. We assessed the hypothesis that cisplatin-treated children with dark irises suffer more deterioration in auditory thresholds than do those with less pigmentation. For the 19 children whose data met the requirements of this observational retrospective study, we found a weak correlation (Spearman's r = 0.50; p < 0.05) of high frequency hearing loss (at 4000 Hz) and pigmentation. Blue or hazel-eyed children averaged 2.9 dB worsening at 4000 Hz, in contrast to 14.2 dB worsening for brown or black-eyed children. Pigmentation may account for some of the individual susceptibility to cisplatin ototoxicity. We suggest that iris colour be included in future reports of cisplatin-related hearing loss.

Adolescent↗

PubMed1997

The ototoxicity of trichloroethylene: extrapolation and relevance of high-concentration, short-duration animal exposure data.

Inhalation exposure to high concentrations of 1,1, 2-trichloroethylene (TCE) has been shown to damage hearing in the mid-frequency range in the rat. The present study directly evaluated the adequacy of high-concentration, short-term exposures to TCE for predicting the neurotoxicity produced by longer duration exposures. Adult male Long-Evans rats (n = 10-12 per group) were exposed to TCE via inhalation (whole body) in 1-m3 stainless steel flow-through chambers for 6 hr/day, 5 days/week. The following exposures were used: 1 day (4000-8000 ppm), 1 week (1000-4000 ppm), 4 weeks (800-3200 ppm), and 13 weeks (800-3200 ppm). Air-only exposed animals served as controls. Auditory thresholds were determined for a 16-kHz tone 3-5 weeks after exposure using reflex modification audiometry. Results replicated previous findings of a hearing loss at 16 kHz for all exposure durations. The dB15 concentrations (concentration that increases thresholds by 15 dB) for 16-kHz thresholds were 6218, 2992, 2592, and 2160 ppm for the 1-day, 1-week, 4-week and 13-week exposures, respectively. These data demonstrate that the ototoxicity of TCE was less than that predicted by a strict concentration x time relationship. These data also demonstrate that simple models of extrapolation (i.e., C x t = k, Haber's Law) overestimate the potency of TCE when extrapolating from short-duration to longer-duration exposures. Furthermore, these data suggest that, relative to ambient or occupational exposures, the ototoxicity of TCE in the rat is a high-concentration effect.

Administration, Inhalation↗

PubMed1975

Psychophysical evaluation of toxic effects on sensory systems.

Toxic effects on sensory systems have rarely been evaluated by psychophysical methods. As examples of possible applications four studies are described. Sodium salicylate and kanamycin, both reported to produce hearing deficits in man, have also been demonstrated to affect auditory thresholds in monkeys. With the latter drug the deficits measured were found to be correlated with specific loss of receptor cells in the cochlea. Pheniprazine, known to induce red-green color blindness, was found to disrupt a wavelength discrimination in pigeons. Trans 11-amino-10,11-dihydro-5-(3-dimethylaminopropyl)-5,10-expoxy-5H-dibenzo[a,d]-cycloheptene dihydrochloride, which was found to bleach the tapidum lucidum in dogs when given subacutely, was found to decrease sensitivity to light. The loss in sensitivity measured by behavioral techniques was correlated with the loss of coloration of the tapidum. Monkeys, not having a tapidum, did not show a similar effect.

Acoustic Stimulation↗

PubMed1980

Aspects of frequency discrimination in passerine birds and pigeons.

With the use of a positive reinforcement operant technique, pulsed-tone, frequency difference limens (DLs) were measured in two Icterid passerine species, the redwing blackbird (Agelaius phoeniceus) and the brown-headed cowbird (Molothrus ater). Direct comparisons were made with two nonpasserine control (pigeon) subjects. Blackbirds were more sensitive than pigeons to frequency changes above 1.0 kHz but less sensitive below 1.0 kHz. Measured DLs in all these birds were within the range of nonhuman mammals but higher than those of humans. The lowest delta f/f ratio for all birds occurred at 4.0 kHz, a frequency for which they exhibit minimal absolute auditory thresholds and which is a dominant component in the song of the redwing. As in humans, blackbird sensitivity at 1.0 and 2.0 kHz declined as sensation level (SL) was decreased, but at 4.0 kHz, sensitivity showed no clear dependence on SL. At 8.0 kHz, near the upper limit of blackbird hearing, sensitivity increased with a decrease in SL. This latter frequency is a dominant component in the song of the cowbird. Differences in frequency sensitivty were also found as a function of the direction of frequency shift from the standard: Upward shifts produced lower DLs at 1.0 and 2.0 kHz, and downward shifts produced lower DLs at 8.0 kHz.

Animals↗

PubMed2000

Experience with a yes-no single-interval maximum-likelihood procedure.

The report in 1993 by Green [J. Acoust. Soc. Am. 93, 2096-2105 (1993)] describing the application of a new psychophysical method requiring few trials and little time to measure auditory thresholds has generated considerable interest among experimentalists. The procedure uses a single-interval stimulus presentation, requests a yes-no decision by subjects, and implements a maximum-likelihood calculation to determine the next trial stimulus level within an adaptive track, as well as the final threshold estimate. Data are presented here describing separate experiences with this procedure in two laboratories in both detection and discrimination tasks. Issues addressed include comparisons with more traditional psychophysical methods, variability in threshold estimates, experimental time required, and possible minor modifications to improve the basic procedure. Results using this procedure are comparable in terms of variability of estimates to those emerging from more lengthy procedures. However, because it may be difficult for some listeners to maintain a consistent criterion and because attentional lapses may be costly, experimenters must be willing to monitor performance closely and repeat some tracks in cases where excessively high variability is noted. Further, this procedure may not be suitable for tasks for which the form of the psychometric function is not well-established. Modifications allowing a variable slope parameter in the maximum-likelihood evaluations of psychometric functions may be of benefit.

Attention↗

PubMed1979

Non-simultaneous auditory masking in the goldfish, Carassius auratus.

Auditory thresholds were determined for 500 HZ pure tone pulses of 15, 25 and 50 ms duration presented leading, following or simultaneously with noise pulses of 50 or 250 ms duration. Masking by the noise decreased: (i) with an increase in tone pulse duration; (ii) with a shortening of the noise pulse duration; and (iii) as the interval between tone and noise pulses was increased from 0 to 350 ms. The effect of the noise was independent of whether the noise led or followed the pure tone. It is suggested that the most significant factor affecting masking was the duration of the interval between tone and noise, and that the site for the interactions between signals is central to the inner ear.

Animals↗

PubMed1988

Masking patterns in the bullfrog (Rana catesbeiana). I: Behavioral effects.

A psychophysical technique based on reflex modification was used to measure masked auditory thresholds in the bullfrog (Rana catesbeiana). Masked thresholds were converted to critical ratios to describe the frequency selectivity of the bullfrog's hearing. The bullfrog's critical ratio function is complex. At low frequencies (100-600 Hz), it increases gradually with tone frequency at a rate of about 4 dB/octave. At high frequencies (1000-2500 Hz), the rate of increase with tone frequency is steeper (9 dB/octave). Critical ratios are lowest at frequencies around 1000 Hz (about 18 dB). Unlike effects previously reported in another anuran species, the green treefrog, the bullfrog's critical ratio function is not parallel to its pure-tone audiogram. Moreover, the relationship of the bullfrog's critical ratio function to the spectral composition of its species-specific vocalizations is not as compelling as in the green treefrog.

Acoustic Stimulation↗

PubMedDate not supplied

Toluene-induced hearing loss in rats evidenced by the brainstem auditory-evoked response.

Behavioral results showing that toluene causes hearing loss in rats precipitated an electrophysiologic study of the auditory thresholds of these rats using the brainstem auditory-evoked response (BAER). Twenty-three-day-old male Fischer-344 rats had been exposed to 1400 or 1200 ppm toluene 14 hrs/day, for 4 or 5 weeks while a control group was exposed only to air. The rats were tested 2.5 mo after termination of the exposures. BAERs, recorded with 25-gauge needle electrodes placed over the nose and posterior skull, were evoked by 100-microseconds-duration clicks and 1-msec-duration tone pips at eight intensities. Thresholds for the appearance of BAERs in the toluene-exposed rats were elevated by 13 to 27 dB, and latency-intensity functions were consistent with the occurrence of sensorineural hearing loss. The amplitudes of the third and fifth components of the BAER were attenuated at high stimulus intensities in the toluene-exposed rats. These behavioral and electrophysiologic results are apparently the first to indicate the ototoxicity of toluene in experimental animals.

Animals↗

PubMed1993

Lateral asymmetries in auditory acuity distinguish hallucinating from nonhallucinating schizophrenic patients.

Bilateral absolute auditory thresholds for frequencies ranging from 250 to 8000 Hz were examined on two occasions in schizophrenic patients and normal control subjects. Patients were classified as hallucinators and nonhallucinators on the basis of symptom ratings on both occasions. Previous evidence of better right than left ear acuity in schizophrenia was replicated but was found to characterize nonhallucinating patients only. Hallucinators showed no lateral asymmetry and inferior right ear acuity as compared with that in nonhallucinators. The results were reliable on retest. Brief Psychiatric Rating Scale scores of positive and negative symptoms in some cases differentiated hallucinators from nonhallucinators. The relationship of verbal hallucinations and right ear-left temporal lobe functions is discussed, together with complexities in cerebral laterality-syndrome relationships.

Adult↗

PubMed1988

Underwater audiogram of a false killer whale (Pseudorca crassidens).

Underwater audiograms are available for only a few odontocete species. A false killer whale (Pseudorca crassidens) was trained at Sea Life Park in Oahu, Hawaii for an underwater hearing test using a go/no-go response paradigm. Over a 6-month period, auditory thresholds from 2-115 kHz were measured using an up/down staircase psychometric technique. The resulting audiogram showed hearing sensitivities below 64 kHz similar to those of belugas (Delphinapterus leucas) and Atlantic bottlenosed dolphins (Tursiops truncatus). Above 64 kHz, this Pseudorca had a rapid decrease in sensitivity of about 150 dB per octave. A similar decrease in sensitivity occurs at 32 kHz in the killer whale, at 50 kHz in the Amazon River dolphin, at 120 kHz in the beluga, at 140 kHz in the bottlenosed dolphin, and at 140 kHz in the harbor porpoise. The most sensitive range of hearing was from 16-64 kHz (a range of 10 dB from the maximum sensitivity). This range corresponds with the peak frequency of echolocation pulses recorded from captive Pseudorca.

Acoustic Stimulation↗