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PubMedDate not supplied

[Communication and auditory behavior obtained by auditory evoked potentials in mammals, birds, amphibians, and reptiles].

METHODS ANIMALS: amphibians, Frog catesbiana (frog bull, 30 animals); reptiles, Sceloporus torcuatus (common small lizard, 22 animals); birds: Columba livia (common dove, 20 animals), and mammals, Cavia porcellus, (guinea pig, 20 animals). With regard to lodging, all animals were maintained at the Institute of Human Communication Disorders, were fed with special food for each species, and had water available ad libitum. Regarding procedure, for carrying out analysis of auditory evoked potentials of brain stem SPL amphibians, birds, and mammals were anesthetized with ketamine 20, 25, and 50 mg/kg, by injection. Reptiles were anesthetized by freezing (6 degrees C). Study subjects had needle electrodes placed in an imaginary line on the half sagittal line between both ears and eyes, behind right ear, and behind left ear. Stimulation was carried out inside a no noise site by means of a horn in free field. The sign was filtered at between 100 and 3,000 Hz and analyzed in a computer for provoked potentials (Racia APE 78). RESULTS: In data shown by amphibians, wave-evoked responses showed greater latency than those of the other species. In reptiles, latency was observed as reduced in comparison with amphibians. In the case of birds, lesser latency values were observed, while in the case of guinea pigs latencies were greater than those of doves but they were stimulated by 10 dB, which demonstrated best auditory threshold in the four studied species. Last, it was corroborated that as the auditory threshold of each species it descends conforms to it advances in the phylogenetic scale. CONCLUSIONS: Beginning with these registrations, we care able to say that response for evoked brain stem potential showed to be more complex and lesser values of absolute latency as we advance along the phylogenetic scale; thus, the opposing auditory threshold is better agreement with regard to the phylogenetic scale among studied species. These data indicated to us that seeking of auditory information is more complex in more evolved species.

Amphibians↗
PubMedDate not supplied

Asymptotic noise-induced temporary threshold shift in chinchilla measured by the auditory evoked response.

Monaural chinchillas were exposed to octave band (4 kHz center frequency) noise at 80 dB SPL for 96 h. Auditory threshold at frequencies of 1, 2, 4, and 8 kHz was estimated by the auditory evoked response (AER) technique prior to noise exposure, and on a fixed schedule, both during exposure and following removal from the noise. Results were analyzed in terms of both threshold and threshold shift. Results indicate that the AER is adequate measure of asymptotic noise-induced temporary threshold shift. Advantages of the use of AER as opposed to behavioral means of threshold determination are discussed. Threshold during this long-term noise exposure was found to be determined by the spectral and intensity components of the noise independent of pre-exposure threshold. Implications for future research in long-term noise exposure are discussed.

Acoustic Stimulation↗
PubMed1999

The fine structure of the recovering auditory detection threshold.

Detection thresholds were gathered for a 2 kHz Gaussian-shaped probe (standard deviation = 0.5 ms), centered at intervals of as little as half a millisecond over 0-30 ms following a 200 ms, 97 dB SPL, 2 kHz tone. Surprisingly, there were small, sudden rises and falls superimposed on each subject's generally smooth recovery. Even more obvious were nonmonotonicities in the standard deviation of the cumulative normal fitted to each threshold's psychometric function.

Adult↗
PubMed2006

Comment on "Auditory-nerve first-spike latency and auditory absolute threshold: a computer model" [J. Acoust. Soc. Am. 119, 406-417 (2006)].

A recent paper by Meddis [J. Acoust. Soc. Am. 119, 406-417 (2006)] shows that an existing model of the auditory nerve [Meddis and O'Mard, J. Acoust. Soc. Am. 117, 3787-3798 (2005)] is consistent with experimentally-measured first-spike latencies in the auditory nerve [Heil and Neubauer, J. Neurosci. 21, 7404-7415 (2001)]. The paper states that this consistency emerges because in the model, the calcium concentration inside the inner hair cell builds up over long periods of time (up to at least 200 ms) during tone presentation. It further states that integration over long time-scales happens despite the very short time constants (< 1 ms) used for the calcium dynamics. This letter demonstrates that these statements are incorrect. It is shown by simulation that calcium concentration inside the hair cell stage of the Meddis model rapidly reaches a steady state within a few milliseconds of a stimulus onset, exactly as expected from the short time-constant in the simple first-order differential equation used to model the calcium concentration. The success of the Meddis model in fitting experimental data actually confirms earlier results [Krishna, J. Comput. Neurosci. 13, 71-91 (2002a)] that show that the experimental data are a natural result of stochasticity in the synaptic events leading up to spike-generation in the auditory nerve; integration over long time scales is not necessary to model the experimental data.

Action Potentials↗
PubMed1997

Age-related and gender-related changes in monaural speech recognition.

Previous studies of older listeners suggest age-related declines in speech recognition. However, the interpretation of these results is not straightforward because auditory thresholds, which account for the largest proportion of the variance in speech-recognition scores, also vary considerably with age. Here, effects of age, gender, and auditory thresholds on several measures of speech recognition were assessed for a large sample of individuals enrolled in a longitudinal study of age-related hearing loss. Participants ranged in age from 55-84 years. They were evaluated with a battery of conventional audiometric measures and speech-recognition materials, including NU-6 monosyllabic words, Synthetic Sentence Identification sentences, and high-context and low-context sentences from the Speech Perception in Noise test. Two analyses were conducted to assure that changes in speech-recognition scores with age were examined independently of age-related changes in auditory thresholds. In the first analysis, no significant differences in speech recognition were observed for individuals in three age groups (55-64, 65-74, 75-84 years) who were selected so that average puretone thresholds for the groups were within 5 dB. In the second analysis, using partial correlations to adjust both score and age for their association with average thresholds, significant declines with age were observed for males in maximum word recognition, maximum synthetic sentence identification, and keyword recognition in high-context sentences. For females, no significant changes in speech recognition with age were observed for any test.

Age Factors↗
PubMed2005

Underwater temporary threshold shift in pinnipeds: effects of noise level and duration.

Behavioral psychophysical techniques were used to evaluate the residual effects of underwater noise on the hearing sensitivity of three pinnipeds: a California sea lion (Zalophus californianus), a harbor seal (Phoca vitulina), and a northern elephant seal (Mirounga angustirostris). Temporary threshold shift (TTS), defined as the difference between auditory thresholds obtained before and after noise exposure, was assessed. The subjects were exposed to octave-band noise centered at 2500 Hz at two sound pressure levels: 80 and 95 dB SL (re: auditory threshold at 2500 Hz). Noise exposure durations were 22, 25, and 50 min. Threshold shifts were assessed at 2500 and 3530 Hz. Mean threshold shifts ranged from 2.9-12.2 dB. Full recovery of auditory sensitivity occurred within 24 h of noise exposure. Control sequences, comprising sham noise exposures, did not result in significant mean threshold shifts for any subject. Threshold shift magnitudes increased with increasing noise sound exposure level (SEL) for two of the three subjects. The results underscore the importance of including sound exposure metrics (incorporating sound pressure level and exposure duration) in order to fully assess the effects of noise on marine mammal hearing.

Animals↗
PubMed1995

Thresholds for auditory brain stem responses to tones in notched noise from infants and young children with normal hearing or sensorineural hearing loss.

OBJECTIVE: To assess the accuracy of threshold estimates determined using the auditory brain stem responses (ABRs) to brief tones presented in notched noise in a group of infants and young children with normal hearing or sensorineural hearing loss (SNHL). DESIGN: The thresholds for ABRs to brief duration 500, 2000, and 4000 Hz tones presented in notched-noise masking were evaluated in infants and young children with normal hearing (N = 34) or SNHL (N = 54). Tone-evoked ABR thresholds were compared with behavioral thresholds obtained at follow-up audiologic assessments, for a total of 220 comparisons. RESULTS: ABR thresholds for the infants with bilateral normal hearing were 23.6, 12.9, and 12.6 dB nHL for 500, 2000 and 4000 Hz, respectively. Most (92 to 100%) infants with normal hearing showed ABRs to 30 dB nHL tones. Across all subjects (i.e., those with normal hearing and those with impaired hearing), high ( > or = 0.94) correlations were found between the ABR and behavioral thresholds. The mean differences between ABR (dB nHL) and behavioral (dB HL) thresholds across all subjects were 8.6, -0.4, and -4.3 dB for 500, 2000, and 4000 Hz, respectively. Overall, 98% of the ABR thresholds were within 30 dB of the behavioral thresholds, 93% were within 20 dB, and 80% were within 15 dB. CONCLUSIONS: These threshold results for the ABR to brief tones in notched noise obtained for infants and young children are similar to those obtained in similar studies of adults. The technique may be used clinically with reasonable accuracy to estimate pure-tone behavioral thresholds in infants and young children who are referred for diagnostic threshold ABR testing.

Audiometry, Pure-Tone↗
PubMed2000

Release from masking in virtual auditory space during sustained positive acceleration.

BACKGROUND: The use of a three-dimensional (3-D) auditory display to significantly lower subject detection level while maintaining comprehension under sustained positive G-stress was explored in this study. METHODS: Auditory threshold levels were measured for detecting a band limited pulsed signal in the presence of a broadband diotic masker at both + 1 Gz (rest position) and under sustained +3 Gz. The pulsed signal was presented diotically and was spatialized at one of four static azimuth positions on the horizontal plane. RESULTS: Results showed that auditory thresholds were not significantly affected by sustained +3 Gz stress. Compared with a diotic presentation, subjects reached an average of 6.8 dB lower auditory threshold at +1 Gz and under sustained +3 Gz when the pulsed signal was spatialized at a static position of 90 degrees azimuth on the horizontal plane. CONCLUSION: The implication of these results and suggestions for further research are discussed.

Adult↗
PubMed1996

Auditory awakening thresholds in sleepy and alert individuals.

Twenty-seven healthy men and women with regular sleep-wake habits (and no habitual napping) participated in a study to determine the relation between auditory awakening thresholds (AAT) and multiple sleep latency test (MSLT) scores. Subjects were free of any sleep complaints and were screened polysomnographically. Nine subjects had a screening MSLT of < or = 5 minutes (sleepy group), and 18 subjects had an MSLT of > or = 10 minutes. Subjects were assigned to three groups: a sleepy group, alert group and an alert sleep-deprived group. Subjects underwent 2 nights of AAT testing with at least 5 days in between each study night. AATs were determined at 0100, 0300, 0500 and 0730 hours. There were a total of 209 available AAT determinations, with a comparable number of trials across the groups. Because 68% of AAT determinations were done out of stage 2 non-rapid eye movement (NREM) sleep, the thrust of the analysis was based on the results of this stage of sleep. The AATs were averaged across the two experimental nights. Trials 1 and 2 (first half of the night) and 3 and 4 (second half of the night) were averaged for each subject. There was no main effect of group on AATs. However, there was a significant main effect of time and a significant group by time interaction. The former indicated an overall decline in AATs across the night. More importantly, the three groups had comparable AAT levels during the first half of the night:. Sleepy and alert-deprived subjects, however, failed to show a decline in AATs, whereas the alert group showed a significant decline in the second half of the night. This differential rate of decline in AATs is suggested to be related to the differences in sleep homeostasis among alert and sleepy individuals.

Acoustic Stimulation↗
PubMedDate not supplied

Two-year decline in vision but not hearing is associated with memory decline in very old adults in a population-based sample.

BACKGROUND: Recent cross-sectional research in cognitive aging has demonstrated a robust association between visual acuity, auditory thresholds and cognitive performance in old age. However, the nature of the association is still unclear, particularly with respect to whether sensory and cognitive function are causally related. OBJECTIVE: This study aimed to determine whether marked declines in performance on screening measures of either visual acuity or auditory thresholds have an effect on cognitive decline over 2 years. METHODS: The sample from the Australian Longitudinal Study of Ageing (n = 2,087) were assessed in 1992 and 1994 on measures of sensory and cognitive function as part of a larger clinical assessment. A quasi-experimental design involving comparison of extreme groups using repeated measures MANCOVA with age as a covariate was used. RESULTS: Group performance on measures of hearing, memory, verbal ability and processing speed declined significantly. Decline in visual acuity had a significant effect on memory decline, but not on decline in verbal ability or processing speed. Decline in hearing was not associated with decline in any cognitive domain. CONCLUSION: The common association between visual acuity, auditory thresholds and cognitive function observed in cross-sectional studies appears to be disassociated in longitudinal studies.

Aged↗
PubMedDate not supplied

Evaluation of risk factors for hearing impairment in at risk neonates by brainstem evoked response audiometry (BERA).

Thirteen (19.2%) of 68 at risk neonates in an intensive care nursery with one or more adverse perinatal clinical factors viz; prematurity (less than 37 wks), low birth weight (less than 2000 gm), hyperbilirubinemia requiring active intervention, birth anoxia, neonatal seizures, infections, aminoglycoside administration, and craniofacial malformations; were diagnosed to have hearing impairment (elevated auditory threshold) by BERA testing performed within the first six weeks of life at a mean conceptional (gestational age + age after birth) age of 40.2 +/- 0.6 wks. As against this, 20 healthy term neonates who were examined at a mean conceptional age of 40.4 +/- 0.8 weeks had a normal hearing threshold of 30 db nHL. Elevated auditory threshold was found more frequently in neonates with multiple clinical adverse factors than in those having single risk factor (6/13 Vs 7/55, p less than 0.001). On multiple logistic regression analysis, however, only 2 factors viz; hyperbilirubinemia at level exceeding indication for exchange transfusion and birth weight less than 1500 gm, were found to be significantly correlated with the hearing impairment in the affected neonates and in that order of importance. Prematurity, birth asphyxia, neonatal seizures, infections and aminoglycoside administration had no significant correlation with hearing impairment. Since most of the neonates admitted to the neonatal ICU have one or more identified adverse risk factors, their hearing screening by BERA at the time of discharge seems justified.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1978

Pure tone thresholds for the rhesus monkey.

Auditory thresholds were measured for 18 ears from 13 rhesus monkeys using a simple reaction-time procedure. The threshold contour was a smooth W-shaped function with rises at the extreme frequencies and around 4 kHz and was comparable in shape with previously reported thresholds for this animal. Standard deviations averaged 5.3 dB.

Animals↗
PubMed1997

[Preliminary studies of auditory fusion frequency in noise effects].

Auditory fusion frequency (AFF) of impulse sound and paired pitch in 80 workers exposed to noise and 60 non-exposed ones were measured to study the relationship between AFF and auditory fatigue. AFF test software was made by the authors themselves, and a stimulating sound signal was evoked in a personal computer. Relationship between AFF in non-exposed workers and their ages was explored, and AFF in exposed ones before and after their exposure was compared. Results showed that no relationship between AFF and their sex and ears in non-exposed group was found. There was a significant difference in AFF between groups of 50-59-year and less than or equal to 49-year. Stimulating sound was more sensitive in its carrier wave or center frequency of 1,000 Hz, and paired pitch has higher value in screening for subjects with auditory threshold shift at about 1/40 octave band. There was significant consistency in transient auditory threshold shift, an important indicator of AFF and auditory fatigue. Measurement of AFF is more stable, repeatable and less deviated, and needs only simple acoustic conditions. Hence, it is a practical superthreshold audiometry.

Adult↗