PubMed Health⌕ Search

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 955 records · Page 53Linked to original sources
PubMedDate not supplied

Thresholds of intracranially recorded auditory field potentials in the pigeon compared with compound action potential thresholds.

The compound action potential (CAP) thresholds provide a reliable indicator for cochlear functional integrity during experimentation in birds as well as in mammals. However, if experimental manipulations are necessary in the middle ear/inner ear spaces, the round window electrodes are often inconvenient. In search for an alternative for CAP recordings, intracranial recordings of acoustically evoked field potentials from the nucleus angularis/magnocellularis were made in pigeons using stereotactically placed electrodes. The responses were compared with those recorded from intracranial surface electrodes placed on the dura mater and compared with CAP responses recorded from the round window. The field potentials recorded from the nucleus angularis/magnocellularis contain a significant contribution from the auditory nerve, as large in amplitude as the CAP recorded at the round window. The recordings from the intracranial surface electrodes were noisier and the contribution from the auditory nerve was too small to be used as a fast monitor of the condition of the inner ear. Threshold curves as a function of frequency could be determined with an automated method from the nucleus angularis/magnocellularis with the same sensitivity and accuracy as from the round window CAP within a few minutes. These results demonstrate that stereotactic recordings of field potentials from the nucleus magnocellularis/angularis region are a suitable alternative to reliably monitor the condition of the inner ear when round window electrodes cannot be used.

Animals↗
PubMed1994

Behavioral and electrophysiological responses to electrical stimulation in the cat. I. Absolute thresholds.

Estimates of electrical auditory brainstem response (EABR) thresholds are compared with behavioral thresholds for electrical stimulation in the same subject using identical stimuli and electrode configurations. Four cats were behaviorally trained to measure acoustic auditory thresholds using food as a reward in an operant reinforcement paradigm. One of the animals was then implanted, in an otherwise normal ear, with a scaled-UCSF multi-contact electrode array containing four intracochlear electrodes. Three animals were implanted with an electrode array containing eight intracochlear contacts and one extracochlear contact under the temporalis muscle following unilateral cochlear perfusion with 10% neomycin solution. Stimuli for the behavioral studies were single presentations of 200 us/phase biphasic current pulses. For the EABR studies, the same stimulus was presented at a rate of 32/s. In general, for the animal with the four-contact array and two of the three subjects with the eight-contact implant, changes in electrode configuration produced well-differentiated changes in threshold. For these three subjects, comparisons of behavioral and EABR thresholds for the majority of monopolar and bipolar electrode configurations tested showed excellent agreement (r2 = 0.88). Correlations between behavioral and EABR measures in these animals were comparable for bipolar and monopolar arrangements (r2 = 0.88 for bipolar and 0.87 for monopolar). For one subject with the eight-contact electrode, who showed similar monopolar and bipolar electrode behavioral thresholds for all tested electrode spacings or configurations, most EABR thresholds were substantially higher than, and poorly correlated with, behavioral thresholds (r2 = 0.15; r2 = 0.28 for monopolar arrangements, and r2 = 0.12 for bipolar arrangements).

Animals↗
PubMed1991

The effects of rate and forward masking on human adult and newborn auditory evoked brainstem response thresholds.

Several investigators have reported that human newborn auditory brainstem evoked response (ABR) thresholds to clicks are about 10-20 dB higher than human adult thresholds to the same stimuli (Galambos & Hecox, 1978; Shulman-Galambos & Galambos, 1979; Lasky, Rupert, & Waller, 1987). The present study replicated these results, but, in addition, addressed developmental differences in ABR thresholds due to forward masking and changes in stimulus repetition rate. Eight human newborns and seven human adults served as subjects. Newborn ABR thresholds to a 100 microseconds click which followed a 82 db(A) SPL 50 ms broadband forward masker by 10 ms were significantly more elevated relative to their unmasked ABR thresholds than were those of the adults. Relatively loud sounds seem to have a greater effect on the newborn's ability to process subsequently presented soft sounds than they do on adult processing. In contrast, changes in repetition rate of 100 microseconds clicks from 10/s to 50/s had no greater effect on newborn than adult ABR thresholds. At near threshold stimulus levels, rate effects on the ABR are not apparent in newborns nor adults.

Adult↗
PubMed1997

Effects of selective inner hair cell loss on auditory nerve fiber threshold, tuning and spontaneous and driven discharge rate.

Current theories assume that the outer hair cells (OHC) are responsible for the sharp tuning and exquisite sensitivity of the ear whereas inner hair cells (IHC) are mainly responsible for transmitting acoustic information to the central nervous system. To further evaluate this model, we used a single (38 mg/kg) or double dose (38 mg/kg, 2 times) of carboplatin to produce a moderate (20-28%) or severe (60-95%) IHC loss while sparing a large proportion of the OHCs. The surviving OHCs were functionally intact as indicated by normal cochlear microphonic (CM) potentials and distortion product otoacoustic emissions (DPOAE). Single-unit responses were recorded from auditory nerve fibers to determine the effects of the moderate or severe IHC loss on the output of the surviving IHCs. Most neurons that responded to sound in the single-dose group had normal or near-normal thresholds and normal tuning. Relatively few neurons in the double-dose group responded to sound because of the severe IHC loss. The neurons that did respond to sound had narrow tuning curves. Some neurons in the double-dose group also had thresholds that were within the normal range, but most had thresholds that were elevated a mild-to-moderate degree. These results indicate that intact IHCs can retain relatively normal sensitivity and tuning despite massive IHC loss in surrounding regions of the cochlea. However, the spontaneous and driven discharge rates of neurons in the carboplatin-treated animals were significantly lower than normal. These changes could conceivably be due to sublethal damage to surviving IHCs or to postsynaptic dysfunction in the auditory nerve.

Action Potentials↗
PubMed2002

Prediction of hearing threshold in infants using auditory steady-state evoked potentials.

This retrospective study examines the relationship between auditory steady-state evoked potential (ASSEP) thresholds determined in infancy and subsequently obtained behavioral hearing levels in children with normal hearing or varying degrees of sensorineural hearing loss. Overall, the results from 211 subjects showed that the two test techniques were highly correlated, with Pearson r values exceeding .95 at each of the audiometric test frequencies between 500 and 4000 Hz. Analysis of the findings for babies with significant hearing loss (moderate to profound levels) showed similar threshold relationships to those obtained in previous studies involving adults and older children. The results for infants with normal or near-normal hearing did, however, differ from those reported for older subjects, with behavioral thresholds typically 10 to 15 dB better than would have been predicted from their ASSEP levels.

Acoustic Impedance Tests↗
PubMed1995

Audiogram construction using frequency-specific auditory brainstem response (ABR) thresholds.

Brainstem evoked response audiometry (ABR) permits auditory pathway assessment without the need for voluntary response. Brainstem responses are unaffected by attention, drugs, and most other confounding conditions. Consequently, if ABR could be used to determine hearing threshold in the speech frequencies, it would have great value for patients who are unable or unwilling to respond accurately during behavioral audiometric testing. Utilizing broad band clicks, one can only estimate hearing sensitivity in the frequency range of 2,000 to 4,000 Hz. This is inadequate for medical or legal purposes in which hearing in the speech frequencies must be assessed. Consequently, we have developed a modified ABR technique that permits a more accurate determination of hearing threshold at 500, 1,000, 2,000 and 3,000 Hz, as illustrated in tests on 27 normal ears. This technique has great potential value for neonatal and mentally handicapped populations, as well as for individuals involved in hearing loss litigation.

Adult↗
PubMed2006

A comparison of 40 Hz auditory steady-state response (ASSR) and cortical auditory evoked potential (CAEP) thresholds in awake adult subjects.

Evoked potential thresholds using the 40 Hz auditory steady-state response (ASSR) and cortical auditory evoked potential (CAEP) were recorded at 500 Hz and 4000 Hz test frequencies in 36 subjects with normal acuity, and 30 subjects with sensorineural hearing loss. ASSR threshold sensation levels (SLs) were lower in ears with greater degrees of hearing loss, and for the 500 Hz stimulus. Mean SLs (maximum duration of a single recording: 89 seconds) were as follows at 500 Hz and 4000 Hz respectively: normal hearing group, 16.9+/-10.3 dB and 42.4+/-14.4 dB; mild-moderate group, 10.6+/-8.8 dB and 23.8+/-8.1 dB; severe-profound group, 10.0+/-13.2 dB and 21.5+/-18.9 dB. CAEP SLs showed no change with hearing level and CAEP/behavioural differences were similar at each test frequency. Mean SLs for CAEP threshold (single recording duration: 84 seconds) at 500 Hz and 4000 Hz respectively were: normal hearing group, 10.3+/-6.4 dB and 11.5+/-3.8 dB; mild-moderate group, 8.4+/-7.4 dB and 13.2+/-12.4 dB; severe-profound group, 11.0+/-6.6 dB and 15.9+/-16.4 dB. The results of this study suggest that while both 40 Hz ASSR and CAEP can reflect the behavioural audiogram, CAEPs may provide a more reliable estimate of hearing in awake adults.

Acoustic Stimulation↗
PubMed1988

Perinatal hypoxia and auditory brainstem response thresholds: no evidence of permanent hearing loss.

It has been suggested that pre-natal and or peri-natal hypoxia can cause permanent hearing loss as a result of interference with the generation of the endocochlear potential, especially if this interference occurs during the critical period of endocochlear potential development. This hypothesis was tested in 4 series of experiments: in neonatal rats exposed to pure nitrogen for several minutes; in neonatal and adult cats respirated with hypoxic gas mixture for an hour; in neonatal rats and cats breathing hypoxic gas mixture for several hours; and in neonatal rats in hypobaric chamber for several days. In each experiment, the auditory nerve-brainstem evoked response threshold was elevated during hypoxia in those animals in which it could be measured but was normal when determined several hours to days later. This is evidence for a remarkable ability of the auditory system to recover from periods of hypoxia even during the critical period of endocochlear potential development.

Animals↗
PubMed1981

Threshold sensitivity of the auditory pathway: effects of worsening signal-to-noise ratio in the auditory nerve.

Perfusions of scala tympani with high potassium solutions increase spontaneous activity of auditory nerve fibres without affecting their threshold sensitivity. In these circumstances, however, the signal-to-noise ratio of the auditory nerve response to a given stimuli is worsened. Recordings from cochlear nucleus neurones during such perfusions indicate that this worsening is critical for threshold sensitivity at higher levels in the auditory pathway.

Acoustic Stimulation↗
PubMed1989

[Cross correlation function of BAEP for objective assessment of hearing threshold].

Brainstem auditory evoked potentials (BAEP) recorded were equally divided into two subensembles and a cross correlation function R (lambda) was calculated for them. The average amplitude of R (lambda) around lambda = 0 was chosen as the criterion for hearing threshold measurement. A linear regression equation which represented the relationship between the criterion and stimulus intensity above threshold was obtained on 21 normal and abnormal ears and thus a equation for assessment of hearing threshold was derived. When the equation was applied to ears to be evaluated, the criteria obtained at three different stimulus intensities above threshold were put into the equation and the mean value was calculated for assessment of hearing threshold. The results from 8 ears with different degrees of hearing loss demonstrated that the differences between estimated thresholds and corresponding subjective thresholds are 4.6 dB on the average.

Auditory Threshold↗
PubMedDate not supplied

[Correlation of auditory brainstem evoked potentials and pure tone audiometric thresholds].

This work is on relation existing between the objective threshold of auditory brainstem responses in adults and those existing in the different frequencies of audiometry pure-tone, in order to make the audiometry from the objective threshold of the ABR, from the subjective threshold to the click, and the type of hearing loss in question. Such results can be transferred to children, and starting from the ABR in children we could guess their probable audiometric profiles. On that purpose we have studied the auditory brainstem responses and the pure-tone audiometry in 168 ears suffering from hearing-loss, both conductive and sensory neurals with and without recruitment, with different degrees of hearing losses and audiometric profiles. The results have confirmed the relation existing between the threshold of evoked brainstem responses and those of high frequencies, 2,000, 4,000 and 8,000 herzs. We have also proved that the threshold ABR has a predicting value on the audiometry of patients, and that the difference between the objective threshold ABR and the subjective one represents the inclination degree of the pure tone audiometry, which considerably reduces the great variability presented by the prediction of thresholds of low tones starting from ABR.

Adolescent↗
PubMedDate not supplied

Age-related auditory brainstem response (ABR) threshold changes in the dancer mouse mutant.

An age-related analysis of auditory brainstem response (ABR) thresholds in 42 heterozygotic dancer mouse mutants (1-13 months old) showed an impairment of ABR thresholds with increasing age, though individual threshold curves could vary considerably. As compared with normal CBA/CBA mice, a progressive deterioration of ABR thresholds occurred from the 2nd postnatal month onwards. The dancer mutant has an inner ear with a morphogenetic type of defect, caused by a semidominant gene which is located in chromosome 19.

Aging↗
PubMed2000

The influence of a pacifier on infants' arousals from sleep.

OBJECTIVE: The risk of sudden infant death during sleep was postulated to decrease with the use of a pacifier and by conditions facilitating arousals from sleep. We evaluated the influence of a pacifier on arousal from sleep in healthy infants. STUDY DESIGN: Fifty-six healthy infants were studied with polygraphy during 1 night; 36 infants used a pacifier regularly during sleep, and 20 never used a pacifier. Thumb users or occasional pacifier users were not included in the study. The infants were recorded at a median age of 10 weeks (range 6 to 19 weeks). To evaluate auditory arousal thresholds, the infants were exposed to white noise of increasing intensity during rapid eye movement sleep. RESULTS: Polygraphic arousals occurred at significantly lower auditory stimuli in pacifier users than in nonusers (P =.010). Compared with nonusers, pacifier users were more frequently bottle-fed than breast-fed (P =. 036). Among infants sleeping without a pacifier, breast-fed infants had lower auditory thresholds than bottle-fed infants (P =.049). CONCLUSIONS: Infants using pacifiers during sleep had lower auditory arousal thresholds than those who did not use a pacifier during sleep. Breast-feeding could be a further factor contributing to lower arousal thresholds. These findings could be relevant to the occurrence of sudden infant deaths during sleep.

Arousal↗
PubMed1989

Auditory acuity in adrenocorticoid insufficiency.

Studies in man have proposed that individuals with adrenocorticoid insufficiency show a heightened auditory detection threshold. This hyperacuity was shown to be specific for deficits in carbohydrate-active steroids, with threshold levels improved at least 13 dB between 1,000 Hz and 4,000 Hz. These reversible changes in auditory detection have been related to specific influences of glucocorticoids on the metabolism of neural tissue. The present study was designed to examine the hypothesis that glucocorticoid deficiencies cause decreased electrocochleographically measured auditory thresholds with interference in the central conduction of these impulses. A rat model was employed in an attempt to demonstrate the mechanism for a state of increased neural excitability in the absence of carbohydrate-active steroid influence. Electrocochleographic and auditory brain-stem evoked response threshold and latency determinations were made in eight experimental rats. Adrenalectomies were then performed in all animals with postoperative electrocochleographic and auditory brain stem responses being made at 3, 7, and 21 days. Threshold recordings for all experimental animals showed no significant changes following the cessation of glucocorticoid production. Latency measurements revealed impaired central neural transmission of the first and second order neurons. The possible mechanisms for these findings are discussed.

Adrenalectomy↗
PubMedDate not supplied

Evoked responses from inferior colliculus as an index of hearing thresholds in guinea pigs.

Bipolar electrodes were implanted in the inferior colliculus of 10 healthy guinea pigs, and visual detection level thresholds of auditory evoked responses were obtained at 17 frequencies between 0.5 and 20.0 kHz. One microvolt isopotential curves from the round window for the same test frequencies were obtained in these animals. A comparison between the evoked response threshold curves and previous reports of the behavioral audiogram reveals a favorable correlation. The cochlear potential curve, however, appears to be a less efficient predictor of the audibility curve than the evoked response thresholds. The utility of evoked response audiometry from the inferior colliculus for quickly assessing auditory thresholds in the guinea pig is discussed.

Acoustic Stimulation↗
PubMed2002

Enhancement of signal-to-noise ratio and phase locking for small inputs by a low-threshold outward current in auditory neurons.

Neurons possess multiple voltage-dependent conductances specific for their function. To investigate how low-threshold outward currents improve the detection of small signals in a noisy background, we recorded from gerbil medial superior olivary (MSO) neurons in vitro. MSO neurons responded phasically, with a single spike to a step current injection. When bathed in dendrotoxin (DTX), most cells switched to tonic firing, suggesting that low-threshold potassium currents (I(KLT)) participated in shaping these phasic responses. Neurons were stimulated with a computer-generated steady barrage of random inputs, mimicking weak synaptic conductance transients (the "noise"), together with a larger but still subthreshold postsynaptic conductance, EPSG (the "signal"). DTX reduced the signal-to-noise ratio (SNR), defined as the ratio of probability to fire in response to the EPSG and the probability to fire spontaneously in response to noise. The reduction was mainly attributable to the increase of spontaneous firing in DTX. The spike-triggered reverse correlation indicated that, for spike generation, the neuron with I(KLT) required faster inward current transients. This narrow temporal integration window contributed to superior phase locking of firing to periodic stimuli before application of DTX. A computer model including Hodgkin-Huxley type conductances for spike generation and for I(KLT) (Rathouz and Trussell, 1998) showed similar response statistics. The dynamic low-threshold outward current increased SNR and the temporal precision of integration of weak subthreshold signals in auditory neurons by suppressing false positives.

Animals↗