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PubMedDate not supplied

Effects of acute styrene and simultaneous noise exposure on auditory function in the guinea pig.

Although styrene has been demonstrated to disrupt vestibular function acutely, parallel studies have not been conducted in the auditory system. This article presents data on the effects of acute styrene administration by injection and inhalation on cochlear function. No deleterious effect of the maximally tolerated styrene dose on hearing was identified when cochlear function was assessed using a within-subjects design. When guinea pigs were administered styrene by inhalation during a single 7-h period, normal auditory function was observed both 1 and 7 days later as compared to chamber controls which did not receive styrene. In some instances, the interactive effects of noise and simultaneous styrene inhalation were studied to determine whether chemical exposure might enhance the disruptive effects of noise on hearing. While a persistent noise-induced hearing loss was observed 1 day following exposure, subjects administered styrene simultaneously did not show a greater hearing loss than those receiving noise alone. Finally, when a 7-day recovery period for noise-induced hearing loss was interposed before audiometric testing, the combined exposure to styrene and noise was not more potent than noise alone in elevating auditory thresholds. Although auditory dysfunction has been reported following subchronic styrene administration, the current results do not support an ototoxic effect of styrene at the level of the cochlea with short-term exposure.

Action Potentials↗
PubMed1986

Auditory arousal thresholds of normal and near-miss SIDS infants.

The sleep characteristics and auditory arousal thresholds of 20 near-miss sudden infant death syndrome (SIDS) infants and 97 age- and sex-matched normal infants were studied. It was observed that spontaneous arousals occurred significantly less frequently in the near-miss SIDS infants. In both groups, induced arousals occurred at comparable stimulation intensities, and arousal thresholds decreased significantly from the 44th to the 52nd postconceptional week. This supports the notion that both groups present a similar maturational process within the auditory pathways and brainstem, and that arousal is not related to differences in behavioural response to ambient noise during sleep.

Acoustic Stimulation↗
PubMed1991

Auditory function in young patients with type 1 diabetes mellitus.

Comprehension of the effect of diabetes mellitus on auditory function has been hindered by the fact that previous studies have evaluated hearing function in heterogeneous groups of patients with diabetes mellitus, thus giving conflicting results. We have performed audiometric studies in 46 consecutive patients. 13 with newly diagnosed type 1 diabetes mellitus (group 1) and 33 with type 1 diabetes mellitus of more than 3 years of duration (group 2), of 14 to 40 years of age. The results were compared to an age-matched control group. Pure-tone auditory thresholds were significantly higher in all frequencies 250-8,000 Hz in both groups when compared to the control subjects. Ten patients, all of which belonged to group 2, had auditory thresholds above 30 dB in at least one frequency, showing a conversational hearing loss that ranged between 11 and 44%. However, none of them referred subjective hypoacusia. Univariate analysis revealed significant associations between auditory thresholds and age, duration of disease as well as retinopathy, but not with neuropathy, HbA1c or hypoglycaemic episodes. Only age and duration of disease independently correlated with an auditory threshold using multiple regression. We conclude that type 1 diabetes mellitus can cause mild sensorineural hearing impairment which correlates with age and duration of disease.

Adult↗
PubMed1999

Using electrically evoked auditory reflex thresholds to fit the CLARION cochlear implant.

This paper describes a method for measuring electrically elicited auditory reflex thresholds (EARTs) in young children who use the CLARION Multi-Strategy Cochlear Implant. The EART is an objective measure that can guide the fitting of a cochlear implant in individuals who are unable to perform behavioral tasks required to program the device. Reflexes were obtained in 11 of 17 pediatric Clarion users. The EART current level indicated a point at which an auditory percept was present and the sound was loud, but not uncomfortable. The EART then was used as a basis for conditioning behavioral responses, and as a guideline for setting most comfortable loudness levels.

Cochlear Implantation↗
PubMed1993

The effects of long-term cochlear hearing loss on the functional organization of central auditory pathways.

We have developed an animal model of neonatal high-frequency cochlear hearing loss to investigate the long-term effects on the central auditory pathways. Specifically, we have induced basal cochlear lesions in newborn kittens using the ototoxic aminoglycoside, amikacin. We have monitored the consequent auditory threshold elevations using auditory brainstem evoked responses (ABR) to tone pip stimuli. In the mature animal we have mapped tonotopic (cochleotopic) representation in primary auditory cortex (AI) using standard micro-electrode recording techniques, and we show that this map becomes massively re-organized. In particular, one frequency area that corresponds to the high frequency cut-off slope of the subject's audiogram appears to become greatly expanded, in some cases to take up 75% of AI surface. In general, the development of normal cochleotopic or tonotopic representation in cortex appears to depend upon the integrity of ascending sensory input from the cochlea particularly during early stages of development. With the clinician in mind, we discuss our findings in relation to practical issues.

Acoustic Stimulation↗
PubMedDate not supplied

Audiograms estimated from brainstem tone-evoked potentials in dogs from 10 days to 1.5 months of age.

The objective of this study was to build audiograms from thresholds of brainstem tone-evoked potentials in dogs and to evaluate age-related change of the audiogram in puppies. Results were obtained from 9 Beagle puppies 10-47 days of age. Vertex to mastoid brainstem auditory-evoked potentials in response to 5.1-millisecond Hanning-gated sine waves with frequencies octave-spaced from 0.5 to 32 kHz were recorded. Three dogs were examined at 10, 13, 19, 25, and 45 days. Four other dogs were examined at 16 days. Data from 7 dogs between 42 and 47 days of age were pooled to obtain audiogram reference values in 1.5-month-old puppies. The best auditory threshold lowered from above 60 dB sound pressure level (SPL) to values close to 0 dB SPL between 13 and 25 days of age and then stabilized. The audible frequency range widened, including 32 kHz in all tested dogs from the 19th day. In the 7 1.5-month-old puppies, the mean auditory threshold decreased by 11 dB per octave from 0.5 to 2 kHz. The auditory threshold was lowest and held the same value from 2 to 8 kHz. The mean auditory threshold increased by 20 dB per octave from 8 to 32 kHz. Near threshold, click-evoked potentials test only a small part of the audible frequency range in dogs. Use of tone-evoked potentials may become a powerful tool in investigating dogs with possible partial hearing loss, including during the auditory system maturation period.

Age Factors↗
PubMed1985

Development of absolute thresholds in chickens.

Absolute auditory thresholds were estimated in chickens at 0 and 4 days after hatching. Momentary suppressions of the chicks' regular peeping, following the onset of a tone, were used as indications of stimulus detection. In the first experiment a staircase procedure was used to estimate thresholds. The absolute thresholds of both ages were the same at low frequencies (250-500 Hz), but at higher frequencies (1-2 kHz) 4-day-old chicks had lower thresholds than the 0-day-old chicks. The estimates of thresholds at 1 kHz were corroborated in the second experiment with a method of constant stimuli. A more efficient modified method of limits was used to replicate the age by frequency interaction in the third experiment. These changing thresholds are likely to reflect a developmental process somewhere in the auditory system and not some nonsensory artifact for two reasons: similar thresholds at low frequencies show that developmental differences are not due to differences in the sensitivity of the testing procedure at the two ages and thresholds obtained from the 4-day-old birds are similar to estimates from mature birds. In conclusion, responsiveness to low frequencies develops before responsiveness to higher frequencies, showing that the development of absolute thresholds is correlated with other measures of functional maturation in the auditory system.

Aging↗
PubMedDate not supplied

[Stable auditory evoked potentials in the study of two patients with auditory neuropathy].

INTRODUCTION: We described the results of the auditory multiple steady state response (MSSR) technique in the assessment of two patients with auditory neuropathy (AN). The aim of this study was to corroborate the correspondence between the MSSR generators elicited by amplitude modulated tones ranging between 80-100 Hz, with the generators of auditory brain stem response (ABR). Moreover, we would also try to demonstrate the validity of the MSSR in the diagnosis of AN in children. MATERIAL AND METHODS: Two children diagnosed of hyperbilirrubinemia, aged, 18 months and 10 years have been studied with MSSR (500, 1000, 2000 and 4000Hz); ABR with clicks; OAE; behavioural audiometry; MRI and acoustic reflexes. RESULTS: A difference between electrophysiological and behavioural audiogram in both cases diagnosed with auditory neuropathy have been found. The auditory thresholds were similar using the two types of evoked potentials (MSSR and ABR). Both techniques showed an increment of auditory threshold congruous with a severe auditory impairment, while behavioural audiometry showed only a mild elevation of auditory threshold. We can also see how the threshold differed between frequencies using behavioral audiometry and MSSR. CONCLUSION: It is concluded that our findings are in agreement with previous studies and they sustain the theory about the coincidence of MSSR at fast rate (80-110 Hz) and ABR generators. Also, we demonstrate the usefulness of the MSSR as an objective [corrected] electroaudiometric tool in patients with auditory neuropathy as ABR. This technique is thus a recommendable test to complete the audiological study in infants with AN, to establish a more precise treatment.

Cerebellopontine Angle↗
PubMed1980

The acoustic reflex pattern studied by the averaging technique.

The acoustic reflex threshold and its pattern in response to stimuli of different intensities, were investigated by means of the signal-averaging technique in 20 normal, 20 sensorineural-impaired and 10 successfully stapedectomized ears. Trains of tone bursts between 110 and 0 dB HL were used. The frequencies tested were 500, 1 000, 2 000 and 4 000 Hz. In all normal subjects, the pattern of the acoustic reflex for stimuli between 110 and 100 dB HL was biphasic with an initial positive plateau followed by a longer negative one. For stimuli below 80 dB HL, the pattern of the reflex was monophasic with a single positive peak. In the sensorineural-impaired ears, the same double pattern of the waveform was obtained. In the stapedectomized ears, no compliance changes were observed for any sound stimuli. By the averaging technique, the difference between the acoustic reflex threshold and the auditory threshold was found to be between 7.5 and 32.5 dB, in normal and sensorineural-impaired ears.

Acoustic Impedance Tests↗
PubMed1980

Hearing threshold shifts from prolonged exposure to noise in guinea pigs.

Auditory thresholds were assessed in three guinea pigs with a conditioning procedure based on the positive reinforcement paradigm. Thereafter, the guinea pigs were exposed for 5 days to third octave band noise centred at 2 kHz at 100 dB SPL. Thresholds at 0.5, 2 and 4 kHz were controlled during the exposure and up to 120 days after exposure. After 6 h of exposure, the threshold shift at 4 kHz reached 40 dB and increased slowly to 45 dB by the fifth day. The quasi-asymptotic shift was less expressed at 2 kHz, where the initial threshold shift amounted to 20 dB and rose to 40 dB by the fifth day. Thresholds recovered in the time course of 5 days after exposure and a significant permanent threshold shift was present 120 days after exposure. It amounted to 35 dB at 4 kHz and to 20 dB at 2 kHz. Auditory thresholds were dependent upon the duration of the stimulus: the decrease in duration of a tone from 200 ms to 2 ms caused a rise in threshold of about 10 dB before as well as after the exposure. The effects of prolonged noise exposure upon guinea pigs are similar to those found in chinchillas with the exception of the permanent threshold shift, which is more marked in guinea pigs.

Acoustic Stimulation↗
PubMed1999

Auditory arousal thresholds after selective slow-wave sleep deprivation.

OBJECTIVES: The aim of this study is to assess Auditory Arousal Thresholds (AATs) three times during an undisturbed baseline night and to compare them to AATs during the recovery night that follows two consecutive nights of selective SWS deprivation. The presence of a time-of-night effect on AATs will also be assessed. METHODS: Ten male Ss slept in the laboratory for 6 consecutive nights. The first two nights were undisturbed. The 3rd night was considered as baseline. During the 4th and 5th nights, selective SWS deprivation was obtained by means of acoustic stimulation. The 6th night was a recovery. In the last 4 nights Ss were awakened three times, after 2, 5 and 7.5 h of sleep, respectively. All the awakenings were carried out from stage 2 (after at least 5 consecutive min of stage 2), by means of 1000 Hz ascending tone series. The AAT determination was based on EEG-EMG criteria: at least 10-s of clear alpha rhythm and/or a 10 s movement arousal. RESULTS: During both deprivation nights, SWS amount was close to zero. In the ensuing recovery night a significant SWS rebound was found, accompanied by a significant increase of AATs with respect to the baseline. Furthermore, there was a significant linear decrease of AATs during the night. Finally, the individual correlations between AATs and SWS amount were significant in 4 out of 10 Ss. CONCLUSIONS: These results confirm that AATs are a reliable index of sleep depth by showing that the SWS rebound following selective SWS deprivation is paralleled by a significant AAT enhancement. The experimental paradigm also allows us to claim that AATs show a decreasing linear trend during the night, having excluded any procedural bias. Finally, AATs can be directly related to SWS amount that preceded the awakening, although the individual correlations between AATs and SWS have to be considered with caution, given the high inter-subject variability and the small number of observations.

Acoustic Stimulation↗
PubMed2003

Auditory temporal order discrimination and backward recognition masking in adults with dyslexia.

The ability of 20 adult dyslexic readers to extract frequency information from successive tone pairs was compared with that of IQ-matched controls using temporal order discrimination and auditory backward recognition masking (ABRM) tasks. In both paradigms, the interstimulus interval (ISI) between tones in a pair was either short (20 ms) or long (200 ms). Temporal order discrimination was better for both groups of listeners at long than at short ISIs, but no group differences in performance were observed at either ISI. Performance on the ABRM task was also better at long than at short ISIs and was influenced by variability in masker frequency and by the spectral proximity of target and masker. The only significant group difference was found in one condition of the ABRM task when the target-masker interval was 200 ms, but this difference was not reliable when the measure was of optimal performance. Moderate correlations were observed between auditory thresholds and phonological skill for the sample as a whole and within the dyslexic and control groups. However, although a small subgroup of dyslexic listeners with poor phonology was characterized by elevated thresholds across the auditory tasks, evidence for an association between auditory and phonological processing skills was weakened by the finding of a subgroup of control listeners with poor auditory processing and normal phonological processing skills.

Adult↗
PubMed1992

Circadian modulation of the rat acoustic startle response.

The acoustic startle response (ASR) of male rats was measured during several sessions over a 24-hr period in both a light-dark cycle and a constant-dark condition. Each session consisted of 10 trials each at 80, 90, 100, 110, and 120 dB white noise. The results indicate robust daily and circadian modulation of ASR amplitude that consist of an approximately twofold nocturnal increase at eliciting-stimuli intensities above 80 dB. Similar results were observed in female rats in constant-dark conditions. To determine whether daily changes in auditory thresholds were responsible for the observed modulation, ASR reflex modification procedures were used. These procedures were designed to measure auditory thresholds at frequencies of 10 and 40 kHz at several times of day. The results suggest a lack of significant circadian differences in auditory thresholds at these frequencies. This study demonstrates a novel role of the rat circadian system in the modulation of ASR amplitude.

Acoustic Stimulation↗
PubMed1999

[Observation of distortion product otoacoustic emissions in recovery course of sudden deafness].

OBJECTIVE: To realize the DPOAE resulting in sudden deafness and to investigate the changes of OAE in the recovery course of sudden deafness. METHOD: The basic characters of distortion product OAE (DPOAE) were studied in 60 ears of 30 cases with sudden deafness. The treatment and following-up were carried on too. RESULT: The incidence and amplitude of OAEs in the affected ears were lower than that of normal ears and normal group, and the threshold of DPOAE was higher too. In the recovery course the amplitude and threshold of DPOAE were improved with the restoration of auditory threshold, but the restoring rate (RR) of auditory threshold was higher. CONCLUSION: The DPOAE in sudden deafness implies a serious sensorineural hearing loss. In the recovery course, the amplitude and threshold of DPOAE is later than that of the pure-tone behavioral threshold, which implies that DPOAE is a sensitive and direct way in reflecting the function of cochlea.

Adult↗
PubMed1978

Effects of long rise time stimuli on the latencies of the slow V potentials.

Tone bursts with 5, 250 and 500 msec rise time and 70 dB HL (ISO) intensity at the plateau were used to evoke the slow V potentials in ten adults. The mean prolongations of the latencies have been determined and correlated with the subjective auditory thresholds, obtained before each test by conventional push-button audiometry. In normal-hearing subjects our results show a prolongation of the latencies of the slow V potentials when stimuli with longer rise time were used. In subjects with elevated auditory thresholds an almost linear correlation was found between the prolongations of the latencies and the subjective auditory thresholds.

Acoustic Stimulation↗
PubMed1986

Auditory processing in spinal cord injury: a preliminary investigation from a sensory deprivation perspective.

Research on sensory deprivation suggests that the loss of somatosensory input to the central nervous system may have an impact on cortical reactivity and subsequent cognitive task efficiency. Individuals with spinal cord injury have a permanent loss of such input to varying degrees. However, there have been few investigations of cognitive processing in spinal cord injury. In this study, six outpatients with quadriplegia and 12 able-bodied controls were administered a dichotic listening task while auditory evoked response data and auditory threshold data were recorded. There were no differences between groups in terms of auditory threshold or auditory evoked responses. However, the outpatient quadriplegic group was more successful than the able-bodied controls in performing the dichotic listening task at one but not all levels of complexity. Results suggest that differences in cognitive processing ability between spinal cord injured and able-bodied individuals may reflect higher level motivational attention-concentration differences rather than more basic auditory and neurophysiologic processing differences.

Analysis of Variance↗
PubMed1984

Frequency and age-dependent auditory evoked potential thresholds in infants.

Auditory evoked-potential thresholds to 0.5, 4.0 and 10.0 kHz tone pips were measured in 40 normal infants 2-28 wks old and 14 normal hearing adults. Thresholds to 500 Hz tone pips were based upon the steady-state, 40 Hz evoked potential. Thresholds to 4.0 and 10.0 kHz tone pips were based upon the brainstem response. Stimulus intensity was varied in 5-dB steps for threshold search. The greatest difference between infant and adult thresholds occurred at 4.0 kHz. The magnitude of this difference decreased with age; however, differences were still significant up to 28 wks of age. No significant differences were seen at 500 Hz. To the 10.0 kHz stimulus only the youngest (2-4 wk) infants had thresholds that were significantly higher than adults. The reasons proposed to explain these results are complex interactions between immaturity of the conductive mechanism, brainstem pathways, and possibly the cochlea.

Acoustic Stimulation↗