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At least 1,711 records · Page 95Linked to original sources
PubMed2000

Exacerbation of noise-induced hearing loss in mice lacking the glutamate transporter GLAST.

Acoustic overstimulation is one of the major causes of hearing loss. Glutamate is the most likely candidate neurotransmitter for afferent synapses in the peripheral auditory system, so it was proposed that glutamate excitotoxicity may be involved in noise trauma. However, there has been no direct evidence that noise trauma is caused by excessive release of glutamate from the inner hair cells (IHCs) during sound exposure because studies have been hampered by powerful glutamate uptake systems in the cochlea. GLAST is a glutamate transporter highly expressed in the cochlea. Here we show that after acoustic overstimulation, GLAST-deficient mice show increased accumulation of glutamate in perilymphs, resulting in exacerbation of hearing loss. These results suggest that GLAST plays an important role in keeping the concentration of glutamate in the perilymph at a nontoxic level during acoustic overstimulation. These findings also provide further support for the hypothesis that IHCs use glutamate as a neurotransmitter.

ATP-Binding Cassette Transporters↗
PubMed2002

Asymmetry in event-related potentials to simulated auditory motion in children, young adults, and seniors.

We studied auditory evoked responses to the apparent movement of a burst of noise in the horizontal plane. Event-related potentials (ERPs) were measured in three groups of participants: children in the age range from 9 to 12 years, young adults in the age range from 18 to 34 years, and seniors in the age range from 65 to 80 years. The topographic distribution of grand-averaged ERP activity was substantially greater over the right hemisphere in children and seniors but slightly greater over the left hemisphere in young adults. This finding may be related to age-related differences in the extent to which judgments of sound movement are based on displacement versus velocity information.

Adolescent↗
PubMed1992

Postoperative hearing recovery in a case of delayed hearing loss after acoustic neurinoma removal.

Delayed postoperative hearing loss after acoustic neurinoma removal is seldom observed. The presented case illustrates the phenomenon of delayed postoperative hearing loss which was observed 4 days after removal of a large acoustic neurinoma. Intraoperative brainstem auditory evoked potentials (BAEP) revealed a gradual loss of wave V with preservation of wave I. In animal experiments a dissociated loss of BAEP has been associated with impairment of microcirculation due to secondary edema. Vasoactive treatment was initiated and after 11 days a partial hearing recovery could be documented. Transient disturbance in microcirculation of vasa nervorum of the cochlear nerve is assumed to be responsible for postoperative hearing fluctuation.

Audiometry, Pure-Tone↗
PubMed1992

[Resection of the semicircular canal system with preserved hearing--an animal experiment study].

In a previous investigation we selectively resected the lateral semicircular canal of the rabbit, preserving the hearing in 67% of the animals. We now report an attempt to remove all three canals in one step with a microsurgical technique using fibrin glue and bone chips. Brain-stem auditory potentials were recorded at intervals up to 3 months after operation. Residual hearing could be recorded in 50% of rabbits. These animals regularly showed a 30-40 dB deterioration of hearing.

Animals↗
PubMed2005

Specific findings in distortion product otoacoustic emissions and growth functions with chronic tinnitus.

Chronic tinnitus has a very high prevalence in industrialized countries. Latest studies found chronic tinnitus in 4% of the German population, with almost 2% suffering severely in their daily life. Because no curative therapeutic approach is available--neither pharmacological nor surgical--the main focus lies in treatments that enhance the habituation of tinnitus. Habituation occurs in almost 50% of affected patients as a normal process, leading to a complete compensation. This finding is based on the ability of the auditory perception to habituate random noise and focus on important acoustic information. According to our audiological data, 90% of tinnitus patients have deficits in inner-ear function as a generator of tinnitus, mainly in the outer hair cells. This occurrence can be verified by registration of distortion products of otoacoustic emissions. Thus, the main origin of tinnitus is peripheral, and most patients suffer from accompanying hearing loss, even though it is sometimes mild or subjectively not even noticed. In almost 50% of our patients, we find hyperfunction of outer hair cells, again recorded via distortion products of otoacoustic emissions and their growth functions. Normal efferent reduction of distortion products through contralateral acoustic stimulation does not take place in most tinnitus patients. This finding shows that central auditory functions are also disturbed in chronic tinnitus patients, leading to reduced efferent effects on the hair cells and thus impeding habituation. Tests to verify these more central pathological findings have yet to be developed. We have data on diminished ability to distinguish stimuli from random noise by bilateral sound processing: The so-called bilateral masking difference test results are pathological in almost 30% of patients suffering from chronic tinnitus. We concluded from our audiological data that chronic tinnitus is primarily a cochlear dysfunction, but habituation is impeded by accompanying or consecutive deficits of the central auditory pathway. Regarding therapeutic approaches, these central functions can be trained by hearing therapy, as we know from patients' rehabilitation.

Adolescent↗
PubMed1991

Age-related changes in binaural processing: I. Evoked potential findings.

Possible age-related effects of speech competition in one ear on the late auditory (LAEP) and P300 event-related potentials recorded at the other ear were investigated with female volunteers. In each of the age categories of 20 to 34, 35 to 49, 50 to 64, and 65 to 80 years, 10 subjects were tested. While contralateral speech competition produced no significant amplitude or latency changes in the earlier auditory brainstem or middle latency responses, several age- and competition-related effects were observed with the later-occurring LAEP and P300 responses. With contralateral competition, the two oldest groups exhibited significantly larger reductions in the N1-P2 peak-to-peak amplitude of the LAEP than did the two youngest groups. While significant decreases in P300 amplitude also occurred with the competition, the magnitude of this effect was not age-related. In addition, small but statistically significant increases in the latency of all three major components, N1 and P2 of the LAEP, and P300, occurred in the presence of contralateral competition. These effects also did not differ among the four age groups. Thus, the LAEP appears to be sensitive to some form of age-related change in binaural processing or attention, although the P300, while sensitive to contralateral competition, did not reflect an age-related component in this effect.

Adult↗
PubMed1991

[Selective resection of the lateral semicircular canal with hearing preservation--an animal experiment study].

The goal of our investigation was to develop a method for removing parts of the vestibular labyrinth by surgery without inducing a loss of auditory function. Three different surgical lesions were created in the lateral semicircular canal of the rabbit: (1) fenestration; (2) fibrin glue perfusion of the canal following fenestration; and (3) destruction of the semicircular canal by drilling after fenestration and fibrin glue perfusion. Brain-stem auditory potentials were recorded repeatedly up to 3 months after operation. They demonstrated preservation of hearing in all rabbits in the first group, in 78% of the second and 67% of the third group. In the last group a 20 dB deterioration of hearing was regularly noticed. Histological study revealed the utmost importance of the fibrin glue perfusion of the perilymph space of the semicircular canal inducing an interruption of the peri- and endolymph flow. A precise microsurgical technique was crucial for hearing preservation.

Animals↗
PubMed1990

[Objective topographic diagnosis of damage of the organ of hearing].

An analysis of the results of electrophysiologic examinations of hearing (impedance audiometry, BSER, MLR, SP) in 50 patients aged between 1 and 9 years perceptive bilateral hypoacusis reveals that the system of objective methods makes it possible not only the differentiation of cochlear and retrocochlear lesions, but also to demonstrate changes in upper part of the hearing tract. Electrophysiologic examinations of hearing help us to reveal the causes of failure in rehabilitation of speech and hearing and make possible to objectively study the conditions of hearing. In can be assumed that in the future combination of electrophysiologic methods with modern ways of imaging, changes in the nervous system will allow us to interpret by topographic diagnosis the results of EA examinations more deeply.

Acoustic Impedance Tests↗
PubMed1990

The masking-level difference in children.

The masking-level difference (MLD) was investigated in children aged 3.9 to 9.5 years and in an adult control group in order to examine the development of the MLD with age. A three-alternative forced-choice adaptive tracking procedure was used for all listeners. MLDs were determined for a 500-Hz pure-tone signal presented in a 300-Hz-wide masking noise centered on 500 Hz, where both interaural time and amplitude cues were present, and in 40-Hz-wide maskers centered on 500 Hz, where either amplitude (MLD delta a) or time (MLD delta t) cues were present. The masking noise level was fixed at 60 dB/Hz SPL. For the 300-Hz-wide masker, the MLDs of the children increased in magnitude up until the age of 5 or 6 years. For the 40-Hz-wide maskers, the MLDs of the 5- and 6-year-old children were still somewhat below adult values. It is possible that these differences between adults and children are related to the development of the peripheral/brainstem auditory system. By this interpretation, the MLD might be small in young listeners because the interaural time and amplitude cues underlying the MLD are coded with relatively poor precision. However, it is perhaps more likely that these differences are coded precisely in the peripheral auditory system, but that more central auditory processes are relatively inefficient in extracting the interaural information.

Acoustic Stimulation↗
PubMed1987

Auditory brainstem responses in young adults with Down syndrome.

Auditory brainstem response (ABR) wave V detection levels, latency, and amplitude were studied in a group of 15 young adults with Down syndrome for whom behavioral measures of hearing sensitivity were also obtained. Comparisons were made to a group of nonretarded control subjects matched by age and sex. Auditory brainstem response detection levels were elevated, response amplitude was reduced, and latency-intensity functions were significantly steeper for the subjects with Down syndrome than for the control group. These findings were associated with a high frequency (8000 Hz) hearing loss prevalent in the otherwise normal-hearing experimental group.

Adolescent↗
PubMed1987

Effects of click polarity on ABR peak latency and morphology in a clinical population.

Magnitude and direction of click phase-related shifts for ABR peaks I through V and the major interpeak intervals were measured for normal ears and ears with varying degrees of high frequency (HF) hearing loss. Latencies of Waves I and V were relatively stable with inversion of stimulus phase in ears with normal hearing and mild degrees of HF hearing loss, but the incidence of substantial phase-induced latency shifts increased in proportion to pure tone deficits. Waves II and IV demonstrated the greatest shifts in all hearing loss categories. Summation of dissimilar responses obtained with opposite acoustic polarities may result in response degradation. A number of phase-specific ABR abnormalities are discussed. In the greater proportion of ears, rarefaction clicks were the more productive stimulus in eliciting the full complement of response peaks.

Acoustic Stimulation↗
PubMed1986

Cochlear echoes, spontaneous emissions, and some other recent advances in auditory science.

This is the second of two tutorials designed as an update on recent advances in auditory science for audiologists, otolaryngologists, and others studying or working in the area of hearing and deafness. This article spans diverse areas from psychophysical measures of audiogram fine structure to physical measurements of the motion of the basilar membrane and to so-called cochlear echoes and acoustic emissions. The review is not comprehensive but it gives an overview of salient points of interest as well as an indication of the current state of knowledge in these areas.

Acoustic Stimulation↗
PubMed1985

[Experimental study of the ototoxicity of cisplatinum].

Cisplatinum, used in numerous multiple chemotherapy regimens, provokes cochleovestibular toxicity. Two series of rats were treated with single or increasing fractionated doses, and audiometric consequences evaluated from modifications in auditory evoked potentials from brain stem and from electrocochleographic recordings. The ototoxic effect was found to be dose related with a cumulative effect. Fractionated doses were less ototoxic than single doses. The mechanism of production of this ototoxicity has not been determined but is probably similar to that of the aminoglycosides.

Animals↗