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At least 307 records · Page 17Linked to original sources
PubMedDate not supplied

Auditory brainstem and middle latency evoked response sensitivity near threshold.

Auditory brainstem response (ABR) and middle latency evoked response (MLER) testing have been used successfully for assessing hearing sensitivity electrophysiologically. Though both procedures have their proponents, ABR seems to be the more popular of the two. However, this study shows that overall, MLER waves occur with greater frequency at low sensation level than ABR waves. Specifically, MLER wave Pa was the most sensitive wave, followed by ABR wave V, MLER wave Pb, ABR wave III, MLER wave Pc, and ABR wave I. Latencies were more consistent and predictable for ABR than MLER. However, as expected, amplitudes for MLER wave were greater than those for ABR. Given these results, those involved in measuring hearing sensitivity electrophysiologically are encouraged to consider the potential of the MLER measure and not limit their scope of assessment to ABR.

Acoustic Stimulation↗
PubMed1998

Early post-laser stapedotomy hearing thresholds.

OBJECTIVE: Auditory testing is not routinely performed within 4-6 weeks after stapedotomy, because hearing acuity is thought to be transiently depressed. In rare circumstances, postsurgical auditory and vestibular complaints may lead one to test hearing soon after stapedotomy. The early postoperative effects of carbon dioxide (CO2) and potassium titanyl phosphate (KTP) lasers, which now are routinely used to perform stapedotomies, have not been reported. The purpose of this report is to present normative data for auditory thresholds measured within 2 weeks of laser stapedotomy. STUDY DESIGN: The study design was a prospective, unblinded study. SETTING: The study was conducted at three academic medical centers. PATIENTS: Thirty-six subjects undergoing 38 stapedotomies for otosclerosis by 5 surgeons participated. MAIN OUTCOME MEASURES: Behavioral audiometry was performed using standard techniques beginning before surgery and continuing through > 1 year after surgery. RESULTS: The CO2 laser was used in 26 stapedotomies and the KTP laser was used in 12. Nine cases were revision procedures. Bone conduction pure-tone averages and speech discrimination scores did not worsen during the early postoperative period. Bone conduction at 250 and 4,000 Hz dropped slightly within the first 2 weeks (-4.3 and -6.7 dB) but recovered thereafter. Bone conduction at 1,000 Hz actually improved within the first week after surgery (+6.2 dB, p = 0.021). Significant improvements in air conduction thresholds (and air-bone gap) were seen at the second week and late audiometry. The results for CO2 and KTP laser-treated groups were not significantly different. CONCLUSIONS: Cochlear function is not significantly depressed in the early postoperative period after laser (CO2 or KTP) stapedotomy.

Audiometry, Pure-Tone↗
PubMed2006

Auditory-nerve first-spike latency and auditory absolute threshold: a computer model.

A computer model of the auditory periphery was used to address the question of what constitutes the physiological substrate of absolute auditory threshold. The model was first evaluated to show that it is consistent with experimental findings that auditory-nerve fiber spikes can be predicted to occur when the running integral of stimulus pressure reaches some critical value [P. Heil and H. Neubauer, J. Neurosci. 15, 7404-7415 (2001)]. It was then modified to examine two ways in which the accumulation and clearance of receptor presynaptic calcium might explain this effect. Both methods gave results that matched the animal data. It was also shown how the rate of clearance of presynaptic calcium could be used to explain the origin of differences between low and high spontaneous-rate fiber types. When spiking activity is aggregated across a number of similar high spontaneous-rate fibers and used as the input to a model of a cochlear nucleus coincidence neuron, its response can be used to judge whether or not a stimulus is present. A simulated psychophysical experiment then demonstrated that this simple decision procedure can reproduce measurements of absolute auditory threshold for tones in quiet where the threshold is a joint function of both time and level.

Acoustic Stimulation↗
PubMed1996

Hearing threshold as measured by auditory brain stem response in human neonates.

OBJECTIVES: This article evaluates the concept of auditory threshold and discusses the limitations of assessing threshold in human neonates. The advantages and limitations of assessing neonatal threshold by means of auditory brain stem response (ABR) are discussed, and data from several studies of newborn ABR threshold are compared. The authors report data from their own study designed to compare adult and neonatal ABR threshold using tonal stimuli. EXPERIMENTAL DESIGN: Several studies are compared. Data from the authors are ABR thresholds for tone bursts of 0.5, 1.5, 4, and 8 kHz, determined from 2-channel recordings in full-term neonates and adults. Stimuli were calibrated in SPL by means of a probe microphone inserted into the ear canal along with the insert transducer of each subject. RESULTS: All studies find a degree of threshold elevation in neonates relative to adult threshold. Neonatal ABR thresholds from our laboratory for stimuli from 500 through 8000 Hz are elevated relative to adult thresholds by 5 to 25 dB. Threshold elevation in our data and in other studies has found that neonatal ABR thresholds to high-frequency stimuli show the largest elevation relative to adults and low-frequency stimuli the most mature. CONCLUSIONS: Thresholds of neonates, as measured by the ABR, are immature especially for high-frequency stimuli. Proper stimulus calibrations, which removes the influence of ear canal resonance, are important for comparisons of data across age groups. Developmental differences in the conductive mechanism and neural immaturity are the most harmonious explanations for elevation of neonatal ABR thresholds.

Adult↗
PubMedDate not supplied

Tone decay at threshold with auditory electrical stimulation in digisonic cochlear implantees.

The present study aims to evaluate tone decay (auditory adaptation) in Digisonic cochlear implant patients, and to compare tone decay results with speech recognition performance. The following criteria are evaluated: tone decay occurrence, place effect, pulse rate effect, and correlation with speech recognition. A great variability in tone decay was found among the subjects. The amount of tone decay, measured as a percentage of the electrical dynamic range, depends to some extent on electrode location, which may be linked with the frequency dependence of acoustical tone decay. However, it is likely that acoustically and electrically evoked adaptation does not involve the same process. Also, an effect of pulse rate was found. However, no relationship between the amount of tone decay and speech recognition abilities was observed. Evaluation of tone decay in cochlear implant patients might not only allow further evaluation of the condition of their auditory system, but also provide a means to determine preoperatively the specific characteristics of a subject's residual auditory capacities.

Adaptation, Physiological↗
PubMed1985

Sleep stages, auditory arousal threshold, and body temperature as predictors of behavior upon awakening.

Attempts to demonstrate sleep stage effects on waking behavior have been equivocal at best. The present study provided a more sensitive approach to this problem by assessing performance and subjective alertness at repeated awakenings across baseline sleep and across recovery sleep following 40 and 64 hours of sleep deprivation. These behaviors were then compared to changes in EEG sleep, body temperature, and auditory threshold within these nights. Comparison of means between baseline and recovery sleep indicated that the behavioral variables were generally more sensitive than sleep stages to different amounts of prior wakefulness. Multiple regression analyses revealed no consistent covariation between behavior and any sleep stage which was independent of the correlations among the sleep stages themselves. Thus, distinct functions for specific sleep stages were not apparent from the comparison of means or the regression analyses. However, significant positive covariations were obtained between body temperature and performance, and auditory threshold and sleepiness. Significant negative covariations were obtained between body temperature and sleepiness, and auditory threshold and performance. From these results it was concluded that the most reliable predictors of behavior upon awakening were: the amount of wakefulness prior to sleep, the total amount of accrued sleep, circadian time as indexed by body temperature, and depth of sleep.

Adolescent↗
PubMed2004

Auditory steady-state responses reveal amplitude modulation gap detection thresholds.

Auditory evoked magnetic fields were recorded from the left hemisphere of healthy subjects using a 37-channel magnetometer while stimulating the right ear with 40-Hz amplitude modulated (AM) tone-bursts with 500-Hz carrier frequency in order to study the time-courses of amplitude and phase of auditory steady-state responses (ASSRs). The stimulus duration of 300 ms and the duration of the silent periods (3-300 ms) between succeeding stimuli were chosen to address the question whether the time-course of the ASSR can reflect both temporal integration and temporal resolution in the central auditory processing. Long lasting perturbations of the ASSR were found after gaps in the AM sound, even for gaps of short duration. These were interpreted as evidences for an auditory reset mechanism. Concomitant psycho-acoustical tests corroborated that gap durations perturbing the ASSR were in the same range as the threshold for AM gap detection. Magnetic source localizations estimated the ASSR sources in the primary auditory cortex, suggesting that the processing of temporal structures in the sound is performed at or below the cortical level.

Acoustic Stimulation↗
PubMed2006

[Analysis of auditory function on normal growth children in city and rural areas].

OBJECTIVE: To study the auditory function of Chinese normal growth children, and to get a first hand data for protecting children's hearing. METHOD: The normal growth children (6 to 12 years old) in Qinling mountain area, pasturing area around Qinghai Lake and Nanjing city were included in the study, and their whole frequency auditory thresholds were examined on the spot. The auditory thresholds were analyzed. RESULT: There was significant difference between the boys' and girls' auditory thresholds among nearly the whole frequency in Qinling mountain. And there was significant difference between the boys' and girls' auditory thresholds among high frequency and super high frequency in pasturing area around Qinghai Lake, while the girls' auditory function was better than the boys'. In contrast, in Nanjing city no difference was found between the boys' and girls' auditory thresholds. The auditory thresholds in high frequency and super high frequency of the boys in Nanjing city were lower than those of the boys in mountain area and plateau pasturing area, while there was no difference between the girls except for low frequency. CONCLUSION: Worse auditory function was found in Chinese rural areas, especially among the boys. According to the local residents' living condition, the children in remote area nearly had no chance to receive the modern industrial noise and other strong noise. So the firecrackers' noise perhaps made this situation. And the education to avoid the firecrackers' noise must be put into practice in Chinese rural area since childhood.

Audiometry, Pure-Tone↗
PubMed1994

Ontogenetic variations in auditory arousal threshold during sleep.

Developmental variations in auditory arousal thresholds during sleep were investigated in four groups of normal male subjects--children, preadolescents, adolescents, and young adults. Arousal thresholds were determined during NREM and REM sleep for tones presented via earphone insert on a single night following two adaptation nights of undisturbed sleep. Age-related relationships were observed for both awakening frequency and stimulus intensity required to effect awakening, with awakenings occurring more frequently in response to lower stimulus intensities with increasing age. Although stimulus intensities required for awakening were high and statistically equivalent across sleep stages in nonadults, higher intensity stimuli were required in Stage 4 relative to Stage 2 and REM sleep in adults. These results confirm previous observations of marked resistance to awakening during sleep in preadolescent children and suggest that processes underlying awakening from sleep undergo systematic modification during ontogenetic development.

Adolescent↗
PubMed1985

Auditory arousal thresholds during sleep in hyperkinetic children.

Auditory arousal thresholds were determined throughout sleep (4-night protocol) in prepubertal nonmedicated and medicated hyperkinetic and normal control male children. The most striking result was the general inability to arouse children of all groups to behavioral response even at intensities up to 123 dB sound pressure level. Of total awakening attempts, 52.5% resulted in non-arousal, 13% resulted in partial, nonsustained physiological arousal responses, and 34.3% were associated with complete awakenings. A significant increase in proportion of awakenings and decrease in the frequency of nonarousals occurred across the night. The groups did not differ with respect to the number of arousal responses. Although nonmedicated hyperkinetic children tended to have lower arousal thresholds relative to children in both comparison groups, the only significant group difference was a lower threshold response in nonmedicated, relative to medicated, hyperkinetic subjects during stage 2 sleep. Arousal thresholds in hyperkinetic children receiving stimulant medication approximated those of normal control children. The enhanced sensitivity of nonmedicated hyperkinetic subjects to auditory stimuli during sleep is interpreted as indicating that processes responsible for elevating arousal threshold at this time are less effective in these children.

Arousal↗
PubMed1995

Influence of myelography on the developmental curve of auditory brainstem responses and hearing loss.

Auditory threshold and auditory brainstem response studies were conducted in 50 patients before and after myelography. Analysis of amplitudes and latencies of auditory brainstem measurements demonstrated significant disorders of function of the cochlea and auditory pathway. The Jewett I wave showed a prolongation of latency from 1.92 to 1.98 ms using an average of all repetition rates. The Jewett III wave showed prolongation from 4.01 to 4.14 ms and the Jewett V wave prolongation from 6.01 to 6.16 ms. At the same time average amplitudes for Jewett III and V decreased. In most of the patients these disorders of function were found to be subclinical. However, 12 patients had changes ranging from a subjectively slight hearing loss to an audiometrically defined acute hearing loss. The reasons for these disorders could not be clarified. An open cochlear aqueduct through which perilymph can enter the subarachnoid space, leading to secondary endolymphatic hydrops, was suggested as the cause for the losses found. Changes in brainstem audiometry were also explained by changes in osmolality of inner ear fluids, leading to the development of an endolymphatic hydrops.

Adult↗
PubMed1997

Auditory behavioral thresholds for Japanese macaques using insert earphones.

The goal of this study was to measure behavioral auditory thresholds in four Japanese macaques. Animals were trained using food as a reward in an operant reinforcement paradigm. Stimuli were 1-s sinusoids with 10-ms rise/fall times delivered through insert earphones (Etymotic ER-1) having expandable foam eartips. The animals generally produced threshold contours similar in shape to those reported for other macaques species, except that the low-frequency thresholds may have been slightly higher in the present studies. At middle and high frequencies, thresholds fell at the lower extreme of the range previously reported in other macaque species. The possible difference in low-frequency thresholds may have been a result of either transducer and calibration differences between studies or true species variations, or both. Though somewhat limited at high frequencies, the insert earphones used in these studies offer more reliable calibrations, less susceptibility to changes in positioning with movement of the animal, and greater interaural attenuation.

Animals↗
PubMed1989

[Activities of single cochlear nerve fibers in rats].

Activities of 325 single cochlear nerve fibers in response to pure tones at various frequencies including ultrasonic sounds were observed in rats. The stimulus sounds were measured with a probe tube inserted into an ear canal and a microphone and expressed in dB SPL. The best frequency (BF, characteristic frequency) and the threshold at BF were determined in every fiber. The measured BF ranged from 0.58 kHz to 62.6 kHz. BF and the threshold at BF of a fiber with the lowest BF-threshold were 27.49kHz and 6dB SPL respectively. The highest sensitivity was found in fibers with BF from 20 to 50 kHz. The tuning curve rose from BF and its slope was steeper for the high side than the low one as observed in other animals. The sharpness of the tuning curve was expressed by QN values, where QN is the ratio of BF to the band width at N dB above the BF threshold. Mean and the variance of Q10dB, Q20dB, Q30dB, Q40dB, Q50dB, all increased as the BF did. Almost all fibers had spontaneous discharge. The discharge rate increased with the increase in sound intensity and saturated at about 30 dB above the threshold. The auditory threshold curve obtained from distribution of the lowest BF-threshold of 325 fibers was consistent with the audiograms determined behaviorally.

Acoustic Stimulation↗
PubMed1979

Trialwise tracking method for measuring drug-affected sensory threshold changes in animals.

Rats and rhesus monkeys were trained under a multiple schedule, the components of which were random ratio schedules for food presentation and for shock presentation. The discriminative stimulus for the shock presentation component was a pure tone for the rats and a light for the rhesus monkeys. In the test session under the extinction condition for the shock presentation component, the intensity of the discriminative stimulus was successively either decreased by fixed units when the conditioned suppression was observed or increased when the conditioned suppression was not observed. The levels finally oscillated within a narrow range around the threshold. The auditory thresholds of rats were increased by intramuscular administration of quinidine at 20 mg/kg and also by repeated intramuscular administration of kanamycin at 250 and 500 mg/kg/day. In rhesus monkeys, visual thresholds were raised by application of pilocarpine at 0.02-0.16 mg/kg to the eyes and also by subcutaneous administration of LSD-25 at 4-8 micrograms/kg in one monkey and at 20-30 micrograms/kg in another. The method used for tracking the animals' sensory thresholds was sensitive enough to test the selective effect of the drugs and was also a relatively easy way to obtain a stable behavioral baseline for experimental purposes.

Animals↗
PubMed2005

Hearing impairment in TRPV4 knockout mice.

Transient receptor potential channel vanilloid subfamily 4 (TRPV4), a member of TRP family, is a mechanosensitive non-selective cation channel. To investigate the role of TRPV4 in the cochlea, the hearing thresholds and effects of acoustic overexposure on the cochlea were examined in TRPV4 knockout mice. TRPV4 knockout mice at age 8 weeks exhibited normal, but those at 24 weeks revealed significantly higher thresholds by auditory brainstem response. The auditory threshold shift was significantly larger in the TRPV4 knockout than in the TRPV4+/+ mice 1 week after the acoustic overexposure of 128dB SPL. The present findings suggest that disruption of TRPV4 causes delayed-onset hearing loss and makes the cochlea vulnerable to acoustic injury.

Acoustic Stimulation↗