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Results for “Auditory Threshold”

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At least 649 records · Page 36Linked to original sources

PubMed1975

Auditory evoked frequency following responses in man.

A sound-evoked sinusoidal response was recorded from the temporal scalp area in six humans. This evoked signal is similar in its characteristics to (and may correspond with) the "frequency-following response" of Worden and Marsh recorded on the scalp in man by Moushegian and colleagues. The site of origin of the response recorded in these subjects is not known, but it is of interest that the aspect of the scalp, and that the influence of arousal state on response amplitude paralleled the described effects of changes in arousal state on the primary auditory cortical evoked response. This technique may allow for the direct measurement of auditory thresholds across the frequency domain. This is possible because measured responses can be obtained at sound levels of the order of 15 to 20 dB across the frequency range from 300 to 2,500 Hz.

Acoustic Stimulation↗

PubMed1997

Sound-power collection by the auditory periphery of the Mongolian gerbil Meriones unguiculatus: III. Effect of variations in middle-ear volume.

The effects of variations in middle-ear cavity size on hearing sensitivity in the Mongolian gerbil are predicted by computing the effect on acoustic power input to the middle ear. Acoustic power collection from a diffuse sound field was computed from measurements of the middle-ear input impedance and external-ear radiation impedance and mathematical models of the middle and external ear presented in the first two papers of this series [J. Acoust. Soc. Am. 92, 157-177 (1992); J. Acoust. Soc. Am. 99, 3044-3063 (1996)]. A reduction in middle-ear cavity volume to 1/4 its normal value is predicted to cause a frequency-selective elevation in auditory threshold of as much as 12 dB, with the largest elevation occurring in the 1-2 kHz range. Greater reductions produce larger threshold elevations. Increases in cavity volume cause decreases in the predicted threshold of at most 12 dB. Threshold predictions for volumes equal to those of the smaller hamster and the larger kangaroo-rat middle-ear cavity volumes resemble threshold functions measured in those animals. Results are consistent with the idea that large middle-ear cavities evolved in gerbil to improve hearing sensitivity below 3 kHz and thereby improve the animal's chances for survival.

Animals↗

PubMedDate not supplied

[Relationship between perception of low-frequency amplitude modulation, age and training in man].

As it was shown earlier, normal hearing in man is characterized by selective sensitivity to amplitude modulation (AM) of sound within the frequency region of 4--8 cps, which corresponds to the most probably AM frequency of the speech signal. Since this phenomenon is presumably due to a constant training for speech perception, it has been investigated in ontogenesis, i.e. starting from 7--8-year children, in whom the process of speech learning is especially intensive. The results obtained indicate that the auditory threshold in children at the age of 7--8, 9--10 and 13--14 years exhibits evident preferable sensitivity in the region of 4--8 cps. Besides, it was found that although the thresholds to 1--2 and 32--64 cps frequencies decrease with ageing, no decrease of the sensitivity takes place within the region of 4--8 cps. Similar data were obtained during special or professional (musical) training of the subjects.

Adolescent↗

PubMed2002

Loudness changes associated with the perception of an auditory after-image.

The Zwicker tone (ZT) is an auditory sensation that occurs following the presentation of broadband noise containing a spectral notch. The present study aimed to test whether the changes in auditory thresholds that have been shown to follow the presentation of the ZT inducer are accompanied by suprathreshold effects. Using an interaural loudness-balance procedure, the loudness of probe tones presented after notched and after flat noise was compared. The results revealed small differences in the influence of the two types of noise on loudness at low intensities only. This suggests that the influence of notched noise stimulation on the auditory system is mediated by changes in the internal noise in auditory centres.

Adult↗

PubMed1981

[A factor analysis of cochleovestibular findings. (author's transl)].

Using the variables auditory threshold, speech audiometry, SISI, ABLB, stapedius reflex, Carhart-test, Békésy audiometry and calorization three factors could be extracted: 1. The quality of peripheral speech-coding in combination with central processing; 2. the degree of damage of the inner ear (threshold, distance between hearing-threshold and reflex-threshold, SISI and calorization); 3. a retrocochlear factor. SISI and ABLB are both tests concerning the inner ear, but must be regarded separately as it is to be supposed that these two findings are caused be two different pathologic processes.

Audiometry↗

PubMed1992

Behavioral development following daily episodes of mother-infant separation in the rat.

Use of dermal or inhalation routes of maternal exposure during the postnatal period in rodent developmental neurotoxicity evaluations would be most practical if dams could be separated from their pups during the exposure period. However, this procedure raises questions concerning the effects of mother-infant separation itself on neurotoxicity endpoints. In the present study, Sprague-Dawley rat pups were either maternally deprived in warm incubators for 6 hr each day (7:00 AM-1:00 PM) or left with their dams (control), from Postnatal Day 4-20 (PND4-20), and were tested on a range of endpoints commonly used in developmental neurotoxicology. These included motor activity (PND13, 17, 19, 21, 29, 60), olfactory learning (PND18) and retention (PND25), T-maze delayed alternation (PND23, 24), acoustic startle response (PND23, 62), and auditory thresholds (PND62). None of the behavioral measures were affected by daily separation. Apparently, interrupting the mother-infant interaction for 6 hr/day has little or no effect by itself on behavioral development, as assessed by these measures.

Aging↗

PubMed1996

Hearing in the FM-bat Phyllostomus discolor: a behavioral audiogram.

Absolute auditory thresholds of six adult lesser spear-nosed bats Phyllostomus discolor (Chiroptera, Phyllostomidae) were determined in a two-alternative forced-choice procedure. Behavioral response to pure tone stimuli could be elicited throughout the tested frequency range of 5-142 kHz. The shape of the average audiogram is characterized by two sensitivity peaks and a pronounced increase of thresholds around 55 kHz, and towards the limits of the tested frequency range. The spectral extent of both sensitivity peaks shows a close relation to the bandwidth of two types of species-specific vocalizations. The first low threshold area (> 10 and < 55 kHz) of the audiogram seems perfectly adapted to the directive call used for intraspecifc communication, whereas the second sensitivity peak, centered around 85 kHz, covers most of the bandwidth of the species' echolocation calls.

Acoustic Stimulation↗

PubMed1988

Schizoid personality, inter-hemispheric transfer, and left hemisphere over-activation.

This study assesses the external validity of schizoid personality against multiple measures of cerebral laterality designed to distinguish between left hemisphere (LH) over-activation, LH damage and inter-hemisphere transfer deficit interpretations of schizotypy. Questionnaire measures of schizoid personality were assessed in an undergraduate population and related to laterality measures of both verbal and nonverbal dichotic listening, haptic inter- and intra-manual matching, employment of left and right hemisphere strategies during the haptic task, lateral eye-movements, and left and right ear auditory thresholds. A high score on a composite index of schizoid personality was significantly related to greater asymmetry (right ear advantage) in verbal dichotic listening, the use of LH strategies, and lower right ear thresholds, an overall pattern of results indicating LH over-activation in schizoids. It is suggested that studies comparing schizophrenic patients with normal controls minimize the likelihood of obtaining group differences if they fail to take into account schizoid personality in the controls.

Adult↗

PubMed1989

Progressive hearing loss in Usher's syndrome.

In 18 patients with Usher's syndrome, progressive hearing loss was verified audiologically in eight cases. Despite poor auditory threshold values and low speech discrimination scores, there was only one patient who could not communicate with speech. The possibility of hearing impairment being mainly progressive in Usher's syndrome is discussed.

Adolescent↗

PubMed1979

Microprocessor versus self-recording audiometry in industry.

Auditory thresholds of 46 industrial workers tested on both a self-recording audiometer and a microprocessor audiometer showed significant differences at 2, 3, 6, and 8 kc/s with the self-recording instrument measuring lower thresholds by from 2.3 to 6.7 db. Differences appear to be the result of the psychophysical methods used and the use of pulsing versus steady tones. The differences, though significant, should be of little consequence in a carefully administered industrial hearing conservation program.

Adult↗

PubMed1994

Trimethyltin disrupts N1 sensitivity, but has limited effects on the summating potential and cochlear microphonic.

Trimethyltin (TMT), a model neurotoxicant, has previously been demonstrated to disrupt auditory thresholds in laboratory subjects. In this experiment we characterized the potency of this ototoxicant by means of a dose response study and then evaluated the functional effects of TMT administration when tone-bursts were presented at supra-threshold levels. Guinea pigs were anaesthetized and prepared for electrophysiological measurement of the compound action potential (CAP) and cochlear microphonic (CM). Subsequently averaged wave forms generated by tone-bursts of 0-80 dB SPL were evaluated in order to calculate both a N1 and a summating potential (SP) input-output function. We show that TMT at doses as low as 0.2 mg/kg produce elevations in N1, but not in the CM isopotential curve. Using exposures to 0.5 mg/kg TMT we show a profound reduction in the slope of the N1 input-output curve, but no shift in the SP. The results are consistent with the hypothesis that TMT disrupts function at the synapse between the inner hair cell and the Type 1 spiral ganglion cell.

Acoustic Stimulation↗

PubMed1992

Upper airway anesthesia delays arousal from airway occlusion induced during human NREM sleep.

Six healthy subjects (5 males and 1 female, 26-40 yr old) were studied during non-rapid-eye-movement (NREM) sleep to assess the role of upper airway (UA) afferents in the arousal response to induced airway occlusion. Subjects wore an airtight face mask attached to a low-resistance one-way valve. A valve in the inspiratory circuit allowed instantaneous inspiratory airway occlusion and release; the expiratory circuit remained unoccluded at all times. Each subject was studied during two nights. On one night, occlusions were created during stable stage 2 NREM sleep before and after application of 4% lidocaine to the oral and nasal mucosa. On the other night, the protocol was duplicated with saline ("sham anesthesia") rather than lidocaine. The order of nights was randomized. Occlusions were sustained until electroencephalographic arousal. Three to 12 occlusions were performed in each subject for each of the four parts of the protocol (pre- and post-lidocaine, pre- and post-saline). The auditory threshold for arousal (1,500-Hz tone beginning at 30 dB) was also tested before and after UA lidocaine. For the group, arousal time after UA anesthesia was prolonged compared with preanesthesia arousal time (P less than 0.001); arousal time after sham anesthesia did not significantly increase from before sham anesthesia (P = 0.9). The increase in arousal time with UA anesthesia was greater than the increase with sham anesthesia (P less than 0.001). The auditory arousal threshold did not increase after UA anesthesia. Inspiratory mask pressure, arterial O2 saturation of hemoglobin, and end-tidal PCO2 during occlusions were similar before and after UA anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1999

Steroid treatment improves cochlear function in the MRL.MpJ-Fas(lpr) autoimmune mouse.

Corticosteroid therapy is used to reverse autoimmune sensorineural hearing loss, although little is known of the mechanism by which this occurs. This has been due to the lack of a suitable animal model with spontaneous hearing loss that is steroid responsive. The present study examined the effects of prednisolone treatment on auditory thresholds in the MRL.MpJ-Fas(lpr) autoimmune mouse to determine its suitability as such a model. Autoimmune mice at 3.5-4. 5 months of age were evaluated by pure-tone auditory brainstem response (ABR) to establish threshold elevations due to the disease. The steroid treatment group was then given prednisolone in their drinking water for 2.5 months, while untreated controls were given tap water. Significantly more steroid treated mice survived to the time of post-treatment ABR evaluation. Half of the steroid treated ears demonstrated either improvement or no change in cochlear function compared to only 25% in the untreated controls. Overall, cochlear thresholds in the untreated controls increased by 14.7 dB, whereas no significant threshold increase was seen in the steroid treated group (4.3 dB) over the treatment period. No qualitative anatomical differences were seen in the ears of those mice surviving to the end of the study. These findings establish the autoimmune mouse as a model for studies of steroid responsive mechanisms within the ear. This could apply to autoimmune sensorineural hearing loss, as well as any hearing disorder for which steroid therapy is recommended.

Administration, Oral↗

PubMed1996

Decreased auditory function in the C3H/lpr autoimmune disease mouse.

To better understand autoimmune-related inner ear disease, cochlear structure and function were evaluated in the C3H/lpr autoimmune strain mouse, a model for systemic lupus erythematosus. C3H/lpr mice were examined at ages from 2 to 12 months along with age-matched C3H/HeJ controls. Autoimmune disease onset occurred at 3-4 months of age as serum immune complexes, antinuclear antibodies, and spleen weights were significantly elevated. Auditory brainstem response (ABR) audiometry showed normal auditory thresholds in C3H/lpr mice at 4 months of age, but elevated thresholds by 6 months, particularly in the high frequencies. Examination of the cochleas revealed no apparent loss of hair cells or spiral ganglion neurons, even in those mice with 50 dB SPL threshold shifts. However, changes were observed in the stria vascularis, including edematous spaces, enlarged capillaries, and thickened vessel linings. These findings imply that cochlear dysfunction in the autoimmune disease mice is the result of stria vascularis pathology.

Analysis of Variance↗

PubMed1985

Tinnitus and/or hearing loss elicited by facial mimetic movement.

Temporary tinnitus and/or hearing loss elicited by contraction of facial mimetic muscles are often observed on the affected side in patients recovering from facial nerve paralysis and in those with facial spasm. In order to clarify the mechanism of this phenomenon, changes in auditory threshold and middle ear compliance during voluntary contraction of mimetic muscles were investigated. The results suggest that this type of tinnitus and/or hearing loss is due to nonacoustic contraction of the stapedial muscle synchronous with contraction of mimetic muscles.

Acoustic Impedance Tests↗

PubMed1975

Human auditory evoked responses during hangover.

Auditory evoked responses (AER) to trains of 6 click stimuli (1 click/sec) were studied in 9 subjects under hangover, tired control, and normal control conditions in order to find out whether the symptoms of hyperexcitability during hangover have a correlate in the characteristics of the AER. In addition, the audiograms were measured. AERs to the first click in a stimulus train were markedly smaller during hangover than in the other 2 states. The amplitude levels of the AERs during the repetition of the click stimulus were, however, similar under all three conditions. The audiograms obtained in the three states were similar except for a very slight decrease of auditory threshold sensitivity during hangover as compared with the tired control condition. The results show that the effects of hangover on AERs resemble those of alcohol intoxication. The symptoms of hyperexcitability during hangover cannot be explained in terms of increased peripheral sensitivity.

Acoustic Stimulation↗

PubMed1986

Identification of polyamines in the cochlea of the rat and their potential role in hearing.

The occurrence of reversible hearing loss in patients treated with the polyamine biosynthesis inhibitor, alpha-difluoromethylornithine (DFMO), led to the hypothesis that this functional hearing deficit might be due to polyamine depletion in the cochlea. To test this hypothesis the polyamine content (putrescine, spermidine and spermine) of the cochleas of normal rats was measured and compared to that of DFMO-treated rats. For the first time, it was demonstrated that in the cochleas of normal rats there were substantial amounts of spermidine and spermine but no detectable putrescine. There was also no measurable ornithine decarboxylase. The DFMO treatments employed in this study were not effective, however, in depleting the cochlear polyamines to levels generally considered critical for disrupting polyamine-dependent processes in other systems. Thus, it is not surprising that auditory thresholds, which were evaluated using brainstem evoked potentials, remained unaltered in the DFMO-treated rats. Demonstration of a role for polyamines in hearing awaits further investigation with the use of more potent inhibitors or other model systems for hearing.

Animals↗

PubMed1983

Temporal integration of pure tones in the cat.

A behavioral method for assessing auditory threshold in cats using food reward conditioning is described. The method requires that the cat press its nose against a touch panel in order to receive a stimulus and that it remove its nose when the stimulus is detected. Behavioral thresholds for pure tone stimuli of various durations are described for three laboratory-raised cats. For all frequencies tested, detection threshold varies as an exponential function of stimulus duration. For frequencies from 125 Hz to 8 kHz, integration time constant and stimulus frequency are inversely related. Response latencies are also affected by the duration of the stimulus. Results are considered in the light of similar measures obtained from human subjects.

Animals↗