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PubMed1979

Auditory arousal thresholds of good sleepers and poor sleepers with and without flurazepam.

Auditory arousal thresholds of good (N = 12) and poor (N = 12) sleepers (sleep onset insomniacs) were obtained during stage 2, stage 4, and REM sleep at various times of the night. Despite claims of being "light" sleepers who are easily awakened by noise, poor sleeper auditory arousal thresholds were the same as those of good sleepers. Flurazepam (30 mg) increased the auditory arousal thresholds of poor sleepers (N = 6), but the increase was statistically significant only during the period of peak effect which occurred 1--2 hr after ingestion. Consistent with poor sleeper complaints of trouble falling asleep, the return to sleep (i.e., sleep latency) was significantly longer for poor than for good sleepers following stimulus arousals during the first stage 2 and first stage 4 periods of the night. Sleep latencies for good and poor sleepers did not differ significantly following subsequent arousals. The sleep latency following the first stage 2 stimulus arousal was significantly reduced in poor sleepers during flurazepam-induced sleep.

Acoustic Stimulation↗
PubMed1984

Dissociation of visual and auditory order thresholds after cerebral injury in man.

Visual and auditory order thresholds were measured with aphasic patients suffering from lesions of the left hemisphere, non-aphasic patients with lesions of the right hemisphere, and a control-group of normals. The aphasic patients showed the highest auditory order thresholds. Visual order thresholds were equal for both groups of patients, but significantly increased compared to those of the control-group. It seems that a lesion of the left hemisphere has consequences for temporal signal processing. The impairment affects primarily the auditory modality. This finding perhaps explains certain difficulties of aphasic patients on the phonetic level.

Acoustic Stimulation↗
PubMed1993

The influence of military low-altitude flight noise on the inner ear of the guinea pig. Part I: Hearing threshold measurements.

The auditory thresholds of about 60 anaesthetized guinea pigs were determined at 3 or 4 frequencies between 2 and 20 kHz using the acoustically evoked brain stem potentials. The animals were then exposed to electro-acoustically reproduced MLAF noise with peak levels between 120 and 130 dB(A). The exposure occurred either once or else four times within either 3 or 60 minutes. The level of noise increased at 7.5 and 75 dB/s (slow and fast increase). TTS was then determined. PTS was measured one week later. In over half the animals, exposure to rapidly increasing noise level with a peak of 126 dB(A) induced PTS > or = 30 dB for at least one frequency. Exposure to a slowly increasing noise level with the same peak provoked significantly smaller PTS. 4 exposures to a rapidly rising noise level within 3 minutes induced significantly smaller PTS than the same dosage within 60 minutes. Only in the latter case was PTS greater than TTS.

Aerospace Medicine↗
PubMed1990

Experimental endolymphatic hydrops: are cochlear and vestibular symptoms caused by increased endolymphatic pressure?

The correlation between inner ear pressure and cochlear function was investigated in guinea pigs with unilaterally obliterated endolymphatic sacs and ducts. In 11 animals that developed endolymphatic hydrops, auditory thresholds as monitored by auditory evoked action potentials had increased with recruitment. Most of these animals also experienced episodes of spontaneous nystagmus. In control ears endolymphatic pressure did not differ more than 0.5 cm H2O from perilymphatic pressure. In six of 11 hydropic ears, endolymphatic pressure was more than 0.5 cm H2O higher than perilympathic pressure; auditory thresholds in all these ears had deteriorated within 2 weeks before pressure recording. No further hearing deterioration within this period was noted in five hydropic ears with endolymphatic pressure equal to or lower than perilymphatic pressure. Endolympathic-perilymphatic pressure gradients may contribute to auditory threshold increase in endolymphatic hydrops, but are not its only cause.

Animals↗
PubMed2001

The relative impact of generic head-related transfer functions on auditory speech thresholds: implications for the design of three-dimensional audio displays.

BACKGROUND: Auditory speech thresholds were measured in this study. METHODS: Subjects were required to discriminate a female voice recording of three-digit numbers in the presence of diotic speech babble. The voice stimulus was spatialized at 11 static azimuth positions on the horizontal plane using three different head-related transfer functions (HRTFs) measured on individuals who did not participate in this study. The diotic presentation of the voice stimulus served as the control condition. RESULTS: The results showed that two of the HRTFS performed similarly and had significantly lower auditory speech thresholds than the third HRTF. All three HRTFs yielded significantly lower auditory speech thresholds compared with the diotic presentation of the voice stimulus, with the largest difference at 60 degrees azimuth. CONCLUSION: The practical implications of these results suggest that lower headphone levels of the communication system in military aircraft can be achieved without sacrificing intelligibility, thereby lessening the risk of hearing loss.

Acoustics↗
PubMed1984

The effect of calibration tolerance values on obtained audiometric threshold: a hearing conservation perspective.

Auditory threshold was assessed at six commonly used audiometric test frequencies and for frequencies just within calibration tolerances for frequencies above and below these. Results indicate that differences of up to 23 dB in obtained auditory threshold values result from variation in frequency within tolerances. These findings are discussed in terms of their importance in industrial hearing conservation.

Audiometry↗
PubMed2006

Reply to comment on "Auditory-nerve first-spike latency and auditory absolute threshold: a computer model".

Krisha [J. Acoust. Soc. Am., in press (2006)] has commented that an explanation based on presynaptic calcium accumulation at the inner hair cell is an incorrect explanation for the success of a model of the auditory periphery [Meddis, R., J. Acoustic. Soc. Am. 119, 406-417 (2006)] in explaining data on first-spike auditory nerve latency. This reply accepts the criticism and accepts the strength of an alternative explanation based on expected latencies in random sequences of low-probability events. This reply also goes on briefly to explore the application of this argument to other phenomena, including the dependence of absolute auditory threshold on the duration of the stimulus. This has wide-ranging implications for the concept of "temporal integration" in psychophysics.

Action Potentials↗
PubMed1982

Auditory brainstem responses (ABR) in the aged.

86 male subjects, aged between 60 and 86 years (M = 69.5), underwent pure-tone audiometry, impedance tests and brainstem response audiometry (BRA). Subjects have been classified into four age-related groups: 1) 34 subjects, aged between 60 and 65; 2) 22, aged between 66 and 70; 3) 22 aged between 71 and 75; 4) 8, aged between 76 and 86. They have also been classified into four groups on the basis of their mean auditory threshold at 0.5, 1, 2, 4 and 8 kHz: 1) 14 subjects with mean auditory threshold less than or equal to 30 dB HL; 2) 16, between 31 and 40; 3) 24, between 41 and 50; 4) 32, with mean auditory threshold greater than or equal to 51 dB HL. 19 normally hearing adults, aged between 28 and 42, were chosen as controls. Statistically significant correlations have been found between age and mean auditory threshold (P less than or equal to 0.001), between wave latency V and age (P less than or equal to 0.001), between wave latency V and the mean pure-tone auditory threshold at 0.5, 1, 2, 4 and 8 kHz (P less than or equal to 0.001) and between the V-I interval and age (P less than or equal to 0.001). The discrepancy between the mean auditory threshold and the ABR waveform, the overall amplitude's reduction of ABR waves and the progressive lengthening of V-I interval values, seem to indicate that age-related changes involve not only the end organ but also the brainstem auditory structures.

Age Factors↗
PubMed2000

Electrical cochlear stimulation in the deaf cat: comparisons between psychophysical and central auditory neuronal thresholds.

Cochlear prostheses for electrical stimulation of the auditory nerve ("electrical hearing") can provide auditory capacity for profoundly deaf adults and children, including in many cases a restored ability to perceive speech without visual cues. A fundamental challenge in auditory neuroscience is to understand the neural and perceptual mechanisms that make rehabilitation of hearing possible in these deaf humans. We have developed a feline behavioral model that allows us to study behavioral and physiological variables in the same deaf animals. Cats deafened by injection of ototoxic antibiotics were implanted with either a monopolar round window electrode or a multichannel scala tympani electrode array. To evaluate the effects of perceptually significant electrical stimulation of the auditory nerve on the central auditory system, an animal was trained to avoid a mild electrocutaneous shock when biphasic current pulses (0.2 ms/phase) were delivered to its implanted cochlea. Psychophysical detection thresholds and electrical auditory brain stem response (EABR) thresholds were estimated in each cat. At the conclusion of behavioral testing, acute physiological experiments were conducted, and threshold responses were recorded for single neurons and multineuronal clusters in the central nucleus of the inferior colliculus (ICC) and the primary auditory cortex (A1). Behavioral and neurophysiological thresholds were evaluated with reference to cochlear histopathology in the same deaf cats. The results of the present study include: 1) in the cats implanted with a scala tympani electrode array, the lowest ICC and A1 neural thresholds were virtually identical to the behavioral thresholds for intracochlear bipolar stimulation; 2) behavioral thresholds were lower than ICC and A1 neural thresholds in each of the cats implanted with a monopolar round window electrode; 3) EABR thresholds were higher than behavioral thresholds in all of the cats (mean difference = 6.5 dB); and 4) the cumulative number of action potentials for a sample of ICC neurons increased monotonically as a function of the amplitude and the number of stimulating biphasic pulses. This physiological result suggests that the output from the ICC may be integrated spatially across neurons and temporally integrated across pulses when the auditory nerve array is stimulated with a train of biphasic current pulses. Because behavioral thresholds were lower and reaction times were faster at a pulse rate of 30 pps compared with a pulse rate of 2 pps, spatial-temporal integration in the central auditory system was presumably reflected in psychophysical performance.

Age Factors↗
PubMedDate not supplied

The approximation of audiometric thresholds by auditory brain stem responses.

Auditory brain stem response (ABR) thresholds for tone pip stimuli were compared with audiometric thresholds for 63 ears to assess the feasibility of deriving audiograms with ABR techniques. Correlations between the two measures were highly significant, indicating a high degree of accuracy in assessing degree and configuration of hearing loss with ABR. Patients with conductive losses showed a simple one-to-one relationship between ABR and audiometric thresholds, while patients with cochlear losses did not. Possibly this is due to the effects of abnormal temporal integration or poor frequency selectivity in this latter group.

Adolescent↗
PubMed1997

alpha-difluoromethylornithine ototoxicity. Chemoprevention clinical trial results.

OBJECTIVES: To determine the effects of low-dose oral eflornithine hydrochloride (difluoromethylornithine [DFMO]) administration on hearing and to identify factors that influence those effects. DESIGN: Combined data from 2 studies: a prospective, randomized phase 1 clinical trial of eflornithine (n = 26 subjects) and a prospective, randomized, placebo-controlled phase 2 clinical trial of eflornithine (n = 40 subjects). SETTING: Ambulatory academic tertiary care referral center. PARTICIPANTS: Sixty-six volunteer subjects who had previously treated bladder, prostate, or colon cancer with no current evidence of neoplastic disease, or who were healthy individuals at increased risk for colon cancer, all without need of hearing amplification. INTERVENTIONS: Subjects were randomized to receive oral eflornithine at daily doses between 0.5 and 3 g per square meter of body surface area (g/m2) for 6 to 12 months (phase 1 study) or randomized to receive placebo or eflornithine, 0.5 g/m2 for 12 months (phase 2 study). OUTCOME MEASURES: Auditory thresholds were measured before, during, and after eflornithine administration. Auditory thresholds and threshold shifts were evaluated with regard to eflornithine dose, serologic variables, and demographic factors. RESULTS: Predictable shifts in auditory thresholds occurred following administration of eflornithine. As the daily dose of eflornithine increased, the magnitude and incidence of threshold shift increased, and the time until onset of threshold shift decreased. Threshold changes were greater in the lower frequencies than in the higher frequencies. Subjects' sex, age, and renal function had no effect on eflornithine-associated threshold shifts. Threshold shifts were reversible after eflornithine treatment was discontinued. CONCLUSIONS: Administration of eflornithine is associated with a predictable shift in auditory thresholds. The magnitude and incidence of threshold shift correlate with the daily eflornithine dose.

Anticarcinogenic Agents↗
PubMed1993

[The discomfort threshold studied in operators at the control consoles in automated production with a view to its use in job selection].

The results from the investigation of the threshold of discomfort in 385 operators from firm "Kremikovtsi" are discussed. The most expressed changes are found in operators with increased tonal auditory threshold up to 45 and above 50 dB, in high confidential probability. The observed changes in the threshold of discomfort are classified into 3 groups: 1). Raised tonal auditory threshold (up to 30 dB) without decrease in the threshold of discomfort; 2). Decreased threshold of discomfort (with about 15-20 dB) in raised tonal auditory threshold (up to 45 dB); 3). Decreased threshold of discomfort on the background of raised (above 50 dB) tonal auditory threshold. On 4 figures are represented audiograms, illustrating the state of tonal auditory threshold, the field of hearing and the threshold of discomfort. The field of hearing of the operators from the III and IV groups is narrowed, and in the latter also deformed. The explanation of this pathophysiological phenomenon is related to the increased effect of the sound irritation and the presence of recruitment phenomenon with possible engagement of the central end of the auditory analyser. It is underlined, that the threshold of discomfort is sensitive index for the state of the individual norms of each operator for the speech-sound-noise discomfort.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Effect of 10 yr of the iodine supplementation on the hearing threshold of iodine deficient schoolchildren.

OBJECTIVE: Auditory disturbances may be present in iodine deficient children. The aim of this study was to determine the effect of long-term iodine supplementation on auditory thresholds in iodine deficient children. DESIGN AND METHODS: 70, 70 and 72 schoolchildren of an area of severe iodine deficiency were studied before intervention (1989), 3 yr after injection of 480 mg iodized oil (1992) and 7 yr after consumption of iodized salt (1999), respectively. Goiter was graded and serum T4, T3, TSH and thyroglobulin concentrations and urinary iodine levels were measured. Audiometry was performed with a pure tone audiometer. RESULTS: There was significant decrease in the prevalence and severity of goiter and serum TSH and thyroglobulin concentrations, and significant rise in serum T4 in 1992 and 1999, as compared to 1989. Before iodine supplementation, hearing was abnormal in 44% of schoolchildren, mean hearing threshold was 15.8 +/- 5.9 and in all children was >10 dB. Mean hearing threshold decreased to 10.2 +/- 4.6 and 10.0 +/- 5.9, 3 and 10 yr after intervention (p < 0.001). Forty seven and 62% of children had thresholds < 10 dB in 1992 and 1999, respectively. Hearing thresholds > 15 dB were detected in 46, 11 and 10% of schoolchildren in 1989, 1992 and 1999, respectively (p < 0.001). CONCLUSION: Continuous iodine supplementation permanantly improves the auditory thresholds of iodine deficient children.

Adolescent↗
PubMed1985

[Measurement of an auditory impairment induced by aminoglycosides using a shuttle box method in newborn rats].

To investigate the auditory impairment induced by the administration of aminoglycosides in the newborn, the shuttle box method was employed to measure the auditory threshold of rats. Five groups of newborn rats were administered kanamycin sulfate, 250 and 500 mg/kg, streptomycin sulfate, 250 and 500 mg/kg, or 1 ml/kg saline, subcutaneously, from the 10th to the 15th day of birth. The auditory threshold of the control group could be measured by the shuttle box method at the age of 100 days. The auditory threshold of the control group was 52.1 +/- 1.0 dB (N = 14). The auditory thresholds of the animals treated with kanamycin 250 mg/kg and streptomycin 250 mg/kg groups were measured in only 1 (61.0 dB) and 4 (64.8 +/- 4.6 dB), respectively, since the auditory toxicity of these drugs in newborn rats was stronger than adult rats. Auditory threshold of the 250 mg/kg streptomycin group was significantly higher than that of the control group. The animals which could not be measured for the auditory threshold had the ability to acquire conditioned avoidance response when both conditioned stimuli (tone and light) were presented. However, after differentiation of the stimuli, the percent avoidance to tone in these animals was significantly decreased and did not recover by the following trainings, while the percent avoidance to light was similar to that before the differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Cochlear nucleus, inferior colliculus, and medial geniculate responses during the behavioral detection of threshold-level auditory stimuli in the rabbit.

Rabbits were conditioned to respond behaviorally to auditory stimuli by pairing a white-noise conditioned stimulus (CS) with a corneal airpuff unconditioned stimulus (US). The conditioned response (CR) was movement of the nictitating membrane (NM). After the subjects were responding at better than the 90% correct level, the intensity of the auditory stimulus was reduced to behavioral threshold using a staircase procedure. Simultaneous measurements of neural unit activity and behavioral NM responses were then made in rabbits performing at behavioral threshold. After the experiment was completed neural unit responses during behavioral detection trials were compared to neural responses made during nondetection trials. Neural unit responses to a constant intensity, white-noise stimulus at behavioral threshold were well defined and essentially identical on behavioral detection and nondetection trials in the ventral cochlear nucleus, the ventrolateral division of the central nucleus of the inferior colliculus, and the ventral division of the medial geniculate body. This suggests that an auditory stimulus can be neuronally "detected" without being behaviorally detected, and that the neural "decision" to respond behaviorally is not made in these nuclei. Responses recorded from the dorsomedial division of the central nucleus of the inferior colliculus, the pericentral nucleus of the inferior colliculus, and less commonly in the medial division of the medial geniculate body were also clearly present and nearly identical during the onset of the auditory stimulus, but were sometimes consistently different for detection and nondetection conditions during the latter part of the auditory stimulus. These brain regions appear to receive both auditory and nonauditory inputs, and show responses which are more highly correlated with detection behavior.

Acoustic Stimulation↗
PubMed2002

The effects of noise on the auditory sensitivity of the bluegill sunfish, Lepomis macrochirus.

As concerns about the effects of underwater anthropogenic noises on the auditory function of organisms increases, it is imperative to assess if all organisms are equally affected by the same noise source. Consequently, auditory capabilities of an organism need to be evaluated and compared interspecifically. Teleost fishes provide excellent models to examine these issues due to their diversity of hearing capabilities. Broadly, fishes can be categorized as hearing specialists (broad hearing frequency range with low auditory thresholds) or hearing generalists (narrower frequency range with higher auditory thresholds). The goal of this study was to examine the immediate effects of white noise exposure (0.3-2.0 kHz, 142 dB re: 1 microPa) and recovery after exposure (1-6 days) on a hearing generalist fish, bluegill sunfish (Lepomis macrochirus). Noise exposure resulted in only a slight, but not statistically significant, elevation in auditory threshold compared to fish not exposed to noise. In combination with results from our previous studies examining effects of noise on a hearing specialist fish, the fathead minnow (Pimephales promelas), this study provides evidence supporting the hypothesis that fish's auditory thresholds can be differentially affected by noise exposure.

Animals↗