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.

At least 523 records · Page 29Linked to original sources

PubMed1992

Incidence of otitis media in CBA/J and CBA/CaJ mice.

The inbred CBA/J mouse has become a standard experimental animal for auditory study because of its lifelong good hearing. In a newly established mouse breeding colony that housed CBA/J and CBA/CaJ mice to reared as auditory subjects, otitis media frequently afflicted CBA/J mice, reaching an incidence of 90% in animals greater than 400 days of age. Otitis media was not found in CBA/CaJ mice. Three attempts to establish a colony that was free of otitis were unsuccessful. Although the primary pathogen was not clearly established, Pasteurella pneumotropica was isolated from infected bullae. Partial control of otitis media followed the introduction of tetracycline prophylaxis. The CBA/CaJ mice may be suitable replacements for CBA/J mice in studies that require inbred mice with good hearing, since their auditory thresholds did not differ significantly from those of otitis-free CBA/J mice.

Animals↗

PubMed1984

Past, present, and future applications of the auditory middle latency response.

For many years (auditory) middle latency response (MLR) reportedly has been an excellent electrophysiological procedure for estimating frequency specific auditory thresholds. Currently the 40 Hz potential, a derivative of the MLR, holds even greater promise for threshold testing. MLR also appears to have potentially valuable applications in the evaluation of functional hearing loss and assessment of higher auditory function. However, MLR is not without controversy. Questions of origin, filtering effects, and its use in pediatric assessment are current issues surrounding applications of MLR. The following article analyzes the values and limitations of MLR within the framework of past, present, and future research and clinical uses.

Acoustic Stimulation↗

PubMedDate not supplied

Audiological results in children with a cochlear implant.

Audiological data collected through June 1984 were analyzed for 126 children with the cochlear implant. Preimplant hearing aid results were compared to cochlear implant results at 6-month follow-up test intervals. Auditory thresholds to warble tones and speech stimuli, and auditory discrimination test scores were significantly better with the cochlear implant at all test intervals than preoperatively with a hearing aid. Electrical measurements were also monitored. Mean thresholds remained consistent over time. Electrical comfort levels increased slightly over time, indicating a widening of the electrical dynamic range. Results have been extremely encouraging. Some trends are beginning to develop, but more long-term data are needed to define the potential benefit of the implant in children.

Adolescent↗

PubMed2003

Human auditory steady-state responses.

Steady-state evoked potentials can be recorded from the human scalp in response to auditory stimuli presented at rates between 1 and 200 Hz or by periodic modulations of the amplitude and/or frequency of a continuous tone. Responses can be objectively detected using frequency-based analyses. In waking subjects, the responses are particularly prominent at rates near 40 Hz. Responses evoked by more rapidly presented stimuli are less affected by changes in arousal and can be evoked by multiple simultaneous stimuli without significant loss of amplitude. Response amplitude increases as the depth of modulation or the intensity increases. The phase delay of the response increases as the intensity or the carrier frequency decreases. Auditory steady-state responses are generated throughout the auditory nervous system, with cortical regions contributing more than brainstem generators to responses at lower modulation frequencies. These responses are useful for objectively evaluating auditory thresholds, assessing suprathreshold hearing, and monitoring the state of arousal during anesthesia.

Acoustic Stimulation↗

PubMedDate not supplied

The effects of middle ear muscle contraction on auditory and overload thresholds.

The present investigation examined psychophysically the frequency-specific and nonlinear attenuation of sound energy provided by middle ear muscle contraction in normal hearers. Aural overload and absolute auditory thresholds were measured at 500, 1 000 and 2 000 Hz prior to and during acoustic stapedial reflex contraction. Reflex contraction was elicited with contralateral broad-band noise. Results revealed that overload thresholds were elevated at 500 and 1 000 Hz and a slight decrease in overload threshold was apparent at 2 000 Hz during reflex contraction while absolute thresholds remained essentially unchanged. These data are consistent with previous psychophysical and physiological findings. The aural overload test having been derived directly from observations of cochlear microphonic saturation, moreover, affords direct comparison to results of electrophysiological experimentation.

Acoustic Stimulation↗

PubMed2005

[The thresholds comparison of auditory steady-state responses and auditory brain-stem response].

OBJECTIVE: To compare the thresholds of auditory brainstem response (ABR)and auditory steady-state responses (ASSR) in the same group of deaf children and give a clinical evaluation for ASSR after that. METHOD: Both kinds of thresholds have been recorded and analyzed of these deaf children. RESULT: The ABR thresholds are (85.82 +/- 12.39) and (82.70 +/- 14.93) dB nHL for left and right ears. At four testing frequencies of ASSR, the thresholds are (86.91 +/- 16.70), (90.32 +/- 16.11), (91.02 +/- 16.58), (89.80 +/- 17.08) and (85.15 +/- 18.16), (89.32 +/- 17.76), (90.41 +/- 18.87), (85.15 +/- 17.03) dB HL for left and right ears. The correlation coefficients between the ASSR and ABR of left and right ears are 0.622, 0.721, 0.757, 0.714 and 0.613, 0.732, 0.795, 0.739 at these frequencies respectively. These results showed significant correlation exiting. CONCLUSION: Reliable and frequency specific results could be obtained by ASSR so that it could be as a promising audiometry in clinic.

Acoustic Stimulation↗

PubMedDate not supplied

Preservation of residual hearing in children and post-lingually deafened adults after cochlear implantation: an initial study.

OBJECTIVE: To investigate whether the residual hearing of severely hearing-impaired children and adults could be preserved using the soft surgery approach. PATIENTS AND METHODS: This project employed a prospective study design. All testing and surgery took place in the Institute of Physiology and Pathology of Hearing, Warsaw, Poland. Twenty-six patients (7 children and 19 post-lingually deafened adults) with residual hearing were assessed. Subjects were assessed using conventional pure-tone audiometry at least 1 month prior to surgery. Cochlear implant surgery with a Med-El Combi 40/40+ standard electrode array was conducted, using the soft surgery approach. Pure-tone audiometry thresholds were re-assessed at least 1 month after surgery. The researchers assessed change in auditory thresholds using pure-tone audiometry to determine preservation of residual hearing. RESULTS: Sixteen of 26 patients (62%) retained their residual hearing within 5 dB HL of pre-operative scores. Only 5 of 26 patients (19%) lost all measurable residual hearing after cochlear implantation. This suggests that surgeons are often able to preserve residual hearing during cochlear implant surgery using the soft surgery technique. CONCLUSIONS: Preservation of residual hearing is an important consideration in cochlear implantation in the light of changing selection criteria for cochlear implant candidates, and as younger children are receiving implants. This is important, as we do not know yet the long-term effects of inner ear damage due to traumatic insertions of electrodes. This finding suggests a good prognosis for future possibilities of re-implantation.

Adolescent↗

PubMed1999

[New hearing test for functional deafness--the procedure to estimate the genuine hearing threshold].

This report describes a new procedure for examining functional deafness with binaural sound stimulation. This new hearing test can estimate the genuine pure tone hearing threshold quantitatively at every frequency by using the ordinary audiometer. In the case of the nonorganic deafness, even if the hearing disorders are bilateral or hemilateral, we believe that measuring auditory threshold separately, causes the deterioration of the threshold. Therefore, this procedure is designed so that the subject may not be aware of testing the auditory acuity of each ear, and utilizes the response of the phantom sound image in the head by simultaneous binaural presentation of sound stimulation. Our strategy is based on the following facts. If the normal subject has the same pure tone threshold level in both ears, the phantom sound image is formed in the median plane of the head by the equal suprathreshold tone level presented simultaneously in each ear. In the case of a unilateral auditory disorder, the sound image is localized to the center of the head only when sound stimulation louder than the threshold level of affected ear is given to both ears at the same time. Simultaneous binaural sound stimulation at a lower level than the threshold of the affected ear forms a lateralized sound image to the unaffected ear in the head. For patients with bilaterally similar hearing loss, the sound image is not formed if the stimulation is less than the threshold level of the pure tone. The band noise in the phase of each frequency with 50 dB HL was given binaurally to 10 normal hearing subjects, and the localization of the sound image formation was examined. This experiment confirmed that around the occipital region of the median plane in all subjects. Furthermore, comparing the formation threshold of the median plane image with the pure tone auditory threshold, proved that there was no significant difference statistically in either value. As a next step, 15 patients with unilateral sensorineural deafness were examined with this technique and we knew that the median sound images would not be formed with stimulation less than the pure tone auditory threshold of the affected ear. For clinical application, patients were classified into two groups with unilateral (6) and bilateral (2) functional deafness, and examined. Midline sound images definitely were formed with the lower magnitude of sound than the pure tone threshold by hemilateral nonorganic deafness. The difference of the forming threshold of the median sound image and the average of pure tone hearing level of the affected ear were maximum 100 dB, minimum 35 dB, and mean 69.4 dB. Furthermore, the difference of the median image forming threshold and the average hearing level of the unaffected ear were maximum 35 dB, minimum 0 dB, and mean 15.4 dB. In bilateral disorders, the midline plane sound image was formed with the corresponding level of the pure tone value in one subject, though the other one was determined by the maneuver method because it did not form a midline sound image. In conclusion, this examination can be readily used to estimate the genuine hearing threshold of the functional deafness.

Acoustic Stimulation↗

PubMed1979

Brainstem evoked potentials to tonepips in notched noise.

Notched noise can be used to mask the frequency spread of acoustic energy in the brief tonepips that are used to elicit brainstem evoked potentials. Brainstem responses to tonepips and notched noise can therefore be used to evaluate auditory thresholds at particular frequencies. These thresholds are more frequency-specific than those obtained using tonepips alone, and are accurate to within 20 dB of the conventional audiometric thresholds.

Acoustic Stimulation↗

PubMed1995

Developmental exposure to polychlorinated biphenyls (Aroclor 1254) reduces circulating thyroid hormone concentrations and causes hearing deficits in rats.

Developmental hypothyroidism causes growth deficits, motor dysfunction, and hearing disorders in humans and animals. Therefore, environmental toxicants, such as polychlorinated biphenyls (PCBs), may secondarily affect these endpoints via thyrotoxicity. In this study, Long-Evans rats were given Aroclor 1254 (po), at 0, 1, 4, or 8 mg/kg from Gestation Day 6 through Postnatal Day (PND) 21. We evaluated the offspring at various age intervals for circulating thyroid hormone concentrations [thyroid-stimulating hormone, and free and total triiodothyronine (T3) and thyroxin (T4)], body weight, eye opening, survival, motor activity development, auditory startle response, and auditory thresholds. Circulating T4 concentrations were sharply reduced in a dose-dependent fashion in PCB-exposed groups at PND 1, 7, 14, 21, and 30 but recovered to control levels by PND 45. Moderate reductions in T3 concentrations were apparent in the 4 and 8 mg/kg groups on PND 21 and 30. Deficits in body weight gain and early eye opening were apparent in the treated pups; by weaning, pup mortality was 20% in the 4 mg/kg group and 50% at the highest dose. Motor activity was also transiently reduced in 15 day old offspring from the 8 mg/kg group. At this dose, animals showed reduced auditory startle amplitudes at PND 24, but not when tested as adults. Importantly, Aroclor 1254 caused permanent auditory deficits (20-30 dB threshold shift) at the lowest frequency tested (1 kHz) in both the 4 and 8 mg/kg groups, whereas auditory thresholds were not significantly affected at higher frequencies (4, 16, 32, or 40 kHz). These data indicate that while some effects of Aroclor 1254 exposure are dissimilar to drug-induced hypothyroidism (e.g., age of eye opening), effects on hormone levels and body weight are comparable. Detection of auditory deficits in PCB-treated animals is a novel finding and may reflect the effects of thyroid hormone disruption on the development of the cochlea.

Acoustic Stimulation↗

PubMed1989

ABR threshold is a function of blood oxygen level.

In order to determine if there is a relation between auditory threshold and oxygen availability, cats were anesthetized, paralyzed and ventilated with room air and with hypoxic gas mixtures. Auditory nerve-brain stem evoked response (ABR) thresholds and arterial blood oxygen levels [partial pressures (PaO2) and percent saturation (SaO2)] were determined. The ABR threshold was unchanged as long as PaO2 was above 30 mm Hg (SaO2 greater than 45%). Below PaO2 20 mmHg (SaO2 less than 25%) the animal was not viable. Between these values, the hypoxia caused ABR threshold elevations which were reversible when the animal was again respirated with room air. ABR threshold was an inverse function of blood O2 level with an approximate 3.05 dB elevation for every mmHg decrease in PaO2 (2.89 dB/% SaO2). These findings are probably due to hypoxia induced depression of the endocochlear potential. Since ABR could be recorded in premature human neonates after at least 28 weeks gestation and since the human fetus in utero is also hypoxic, these results indicate that the fetus (greater than 28 weeks gestational age) has a sensorineural hearing loss in addition to a conductive loss.

Animals↗

PubMed1980

High-frequency sensitivity in infants.

Auditory thresholds were determined for infants and adults to half-octave bands of noise centered at 10,000 and 19,000 hertz. Adults were significantly more sensitive than infants at 10,000 hertz, but at 19,000 hertz, adults and infants had comparable thresholds.

Adult↗

PubMed1979

Evoked potential correlates of human information processing.

The late positive component (P3) of the feedback evoked potential was investigated in two tasks: the detection of near-threshold auditory stimuli, and the estimation of 1 s time intervals. When the intensity or probability of the threshold stimuli was varied in the detection task, it became apparent that the feedback P3 was related to the 'contingent probability' of confirming or disconfirming feedback given a particular response. In the time-estimation task the relative probabiliti-s of confirming and disconfirming feedback were altered by changing the time-window wherein a response was judged correct. In these experiments it was found that the feedback P3 component was highly dependent upon the probability of the feedback, and relatively independent of its confirming or disconfirming meaning. With decreasing probability of the feedback stimuli, the P3 component became larger, later, and somewhat more frontal.

Auditory Perception↗

PubMed1986

Consonant recognition in quiet and in noise with aging among normal hearing listeners.

Consonant recognition in quiet and in noise was investigated as a function of age for essentially normal hearing listeners 21-68 years old, using the nonsense syllable test (NST) [Resnick et al., J. Acoust. Soc. Am. Suppl. 1 58, S114 (1975)]. The subjects audited the materials in quiet and at S/N ratios of +10 and +5 dB at their most comfortable listening levels (MCLs). The MCLs approximated conversational speech levels and were not significantly different between the age groups. The effects of age group, S/N condition (quiet, S/N +10, S/N +5) and NST subsets, and the S/N condition X subset interaction were all significant. Interactions involving the age factor were nonsignificant. Confusion matrices were similar across age groups, including the directions of errors between the most frequently confused phonemes. Also, the older subjects experienced performance decrements on the same features that were least accurately recognized by the younger subjects. The findings suggest that essentially normal older persons listening in quiet and in noise experience decreased consonant recognition ability, but that the nature of their phoneme confusions is similar to that of younger individuals. Even though the older subjects met the same selection criteria as did younger ones, there was an expected shift upward in auditory thresholds with age within these limits. Sensitivity at 8000 Hz was correlated with NST scores in noise when controlling for age, but the correlation between performance in noise and age was nonsignificant when controlling for the 8000-Hz threshold. These associations seem to implicate the phenomena underlying the increased 8000-Hz thresholds in the speech recognition problems of the elderly, and appear to support the concept of peripheral auditory deterioration with aging even among those with essentially normal hearing.

Adult↗

PubMed1988

Potentiation of noise induced threshold shifts and hair cell loss by carbon monoxide.

Previous studies have determined that severe systemic hypoxia disrupts cochlear function acutely, but have suggested that augmentation of cochlear perfusion may successfully protect cochlear function under all but the most profound hypoxic treatments. In the current study we report on the chronic effects of simultaneous exposures to noise and carbon monoxide on pure tone thresholds and hair cell survival in rats. Following initial threshold determination, rats received acute exposure to carbon monoxide, noise, or both agents concurrently. Thresholds were evaluated 2-4 and 6-8 weeks later. The data show that carbon monoxide alone does not affect either auditory thresholds or compromise hair cells at the light microscopic level. The noise exposure alone produced variable, but quite limited permanent threshold shifts which were related to the power spectrum of the broad band noise that was employed. Hair cell loss was restricted to the basal turn of the cochlea. Simultaneous exposure to carbon monoxide and noise induced large threshold shifts at all frequencies studied, but the effect was greatest at the highest test frequency; an effect not consistent with the noise power spectrum. Widespread hair cell loss persisted over fully half of the basilar membrane in the most severely affected rat. Outer hair cells appear to be particularly vulnerable. Carbon monoxide plus noise did not appear to preferentially disrupt a particular row of outer hair cells. These data complement existing evidence that hyperoxia can mitigate against noise induced injury and reinforce the view that some types of noise induced damage may result from metabolic insufficiencies.

Acoustic Stimulation↗

PubMedDate not supplied

Changes of hair cell stereocilia and threshold shift after acoustic trauma in guinea pigs: comparison between inner and outer hair cells.

The vulnerability of inner hair cells (IHCs) and outer hair cells (OHCs) to acoustic overstimulation is still controversially discussed. The present study was undertaken to investigate the vulnerability of IHCs and OHCs and the relation between chronological changes of auditory threshold shifts and stereocilia damages on IHCs and OHCs in guinea pigs after moderate acoustic trauma, caused by a single continuous exposure to pink noise (20 Hz to 20 kHz) of around 106 +/- 2 dB SPL for 44 h. Stereocilia changes and threshold shifts of auditory brainstem responses (ABR) were assessed at regular intervals after noise exposure for 9 weeks. Scanning electron microscopy demonstrated the morphological changes of stereocilia as early as 1 day after noise exposure. The morphological changes included fused, bent, collapsed, and even missing stereocilia. These damages were more prominent on IHCs than on OHCs. The shift of ABR threshold was not parallel to the chronological change of the stereocilia on IHCs as well as OHCs. The elevation of the ABR threshold (40-60 dB SPL) was greatest on the 1st day after noise exposure, whereas the stereocilia showed the most damage 7 days after noise exposure. Combined with the results from previous studies, we conclude that moderate-level (around 105-110 dB) noise tends to induce more damage to the stereocilia of IHCs than of OHCs. Other damage (e.g., metabolic disturbance) than morphological damage of hair cell stereocilia may contribute partially to the hearing threshold shift induced by moderate acoustic overstimulation.

Animals↗

PubMed1998

Current evaluation of pseudohypacusis: strategies and classification.

Some cases of pseudohypacusis may involve medicolegal aspects and require a confirmed and quantitative diagnosis. These challenging cases must be identified, and then evaluated with basic audiologic and sophisticated electrophysiologic tests. Data on 64 patients with pseudohypacusis collected over a 4-year period are reported. A classification system was developed from an analysis of these cases and is presented for clinical evaluation and diagnosis. In many cases, conventional audiologic evaluation involving pure tone and speech audiometry may be adequate and sufficient for diagnosis. In more complex cases, evoked otoacoustic emissions (EOAEs) and auditory brain stem responses (ABRs) are needed for confirmation of peripheral auditory sensitivity. We found that EOAEs were the most rapid economical, and objective method, and confirmed the diagnosis of hearing loss in 78.1% of cases. Fifteen percent of subjects required ABRs to substantiate the diagnosis. The reliability of basic audiologic tests based on previous clinical investigations and data from the literature are discussed. We conclude that a thorough knowledge and understanding of pseudohypacusis is essential to verify the existence of pseudohypacusis, to determine its type, and to quantify the auditory thresholds.

Acoustic Stimulation↗

PubMed1989

Rapid changes in cochlear nucleus cell size following blockade of auditory nerve electrical activity in gerbils.

Large spherical cells of the mammalian anteroventral cochlear nucleus (AVCN) receive direct excitatory input from auditory nerve axons. Trans-synaptic regulation of neuronal cell size and cell number after cochlear ablation has been previously demonstrated in neonates of several vertebrate species, including the gerbil. Such changes may be related to loss of spontaneous or evoked auditory nerve electrical activity or to loss of activity-independent factors. We have developed a method to chronically, yet reversibly, block auditory nerve electrical activity without violating the integrity of the inner ear. Tetrodotoxin (TTX) was embedded in an ethylene-vinyl acetate copolymer resin (Elvax). A small piece of Elvax containing TTX was placed next to the round window membrane, which allowed TTX to diffuse into the inner ear. As a measure of the effectiveness of manipulation, the onset, duration, and magnitude of the auditory threshold shift were measured by the auditory brainstem response. The sound-evoked response was abolished within 10 minutes of placement of TTX on the round window membrane. The duration of threshold shift was dose-dependent and lasted 24-46 hours. Implants of Elvax without TTX did not produce a significant threshold shift. TTX, which blocks voltage-gated sodium channels, did not abolish the potassium-based cochlear microphonic response. The consequence of blocking afferent electrical activity on gerbil AVCN large spherical cells was examined by measuring their cross-sectional area after each of four manipulations: unilateral auditory nerve action potential blockade with TTX; unilateral surgical cochlear ablation; ipsilateral TTX exposure/contralateral cochlear ablation; and unilateral sham operation (Elvax without TTX).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗