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PubMed1994

Effect of component-relative-entropy on the discrimination of simultaneous tone complexes.

Results are reported from a number of experiments investigating the effects of stimulus uncertainty on the discrimination of simultaneous multitone complexes. With few exceptions the data were well described by a model in which average threshold for the detection of a change in one or more components varies with the components' relative entropy (CoRE) in the complex [R.A. Lutfi, J. Acoust. Soc. Am. 94, 748-758 (1993)]. In different experiments, thresholds for the detection of a change in target level were found to be linearly related to CoRE for manipulations in the number of targets, the number of context tones, and the relative degree of level perturbation on tones from trial to trial. The slopes of the functions did not change with measures taken at different points on the psychometric function, and in most cases were close to the theoretical value of b = -1.0, as predicted by strict application of the model. Also as predicted (but for the exception of one listener) increasing the level of the target beyond that of the context had little or no effect on threshold. A correlational analysis of the trial-by-trial data revealed a tendency of listeners to give negative weight to frequencies immediately above the target, and to adjust weights in response to changes in the relative degree of level perturbation. Though inconsistent with the basic premise of the model, the variation in weights was not so great as to materially affect the predictions for mean thresholds.

Adult↗
PubMedDate not supplied

Recovery of vestibular-evoked myogenic potential: relationship to other neural disorders in two patients with acute sensorineural hearing loss.

We report the recovery of the inferior vestibular neural system disorder by monitoring the vestibular-evoked myogenic potential (VEMP) in two patients suffering from acute sensorineural hearing loss with vertigo. Patients presented absent VEMP, canal paresis, and severe hearing disorder. After 10 months, the function of the inferior vestibular neural system was recovered in both cases while that of the superior vestibular neural system was recovered in one case and partially recovered in the other. In addition, the hearing sensitivity was only partially recovered in both cases. The recovery of the inferior vestibular neural system was confirmed by our current results. These results suggested that time course of recoveries of the superior and inferior vestibular neural systems, and of the cochlear neural system, were somewhat different in the two cases.

Acute Disease↗
PubMed1992

Cochlear and renal pathology in the autoimmune strain mouse.

This study was designed to investigate the role of immunologic mechanisms in sensorineural hearing disorders and the relationship between inner ear and renal disorders. Autoimmune strain (NZB/kl) mice, in which autoimmune disease can be spontaneously induced, were used in this study. The mice were tested for acoustic brain stem responses, cochlear and renal disorders, and circulating immune complex serology by means of enzyme immunoassay. Pathologic studies consisted of observation of tissue changes following hematoxylin and eosin staining and indirect immunofluorescence staining under light microscopy. Compared to controls, the hearing was impaired in NZB/kl mice. Indirect fluorescence staining showed immunoglobulin G deposits in the stria vascularis. There was a correlation between the degree of hearing impairment and the severity of stria vascularis lesions. The NZB/kl mouse can provide a model for sensorineural hearing disorders secondary to immunologic disorders.

Animals↗
PubMed2005

Mechanism of cochlear excitation at low intensities.

In order to assess the mechanisms of cochlear activation, the cochlear fluids of one cochlea of a guinea-pig (I) were coupled to those of a cochlea of a second guinea-pig (II) by means of a saline-filled narrow bore tube, the ends of which were placed in the fluids around the opened round windows of both cochleae, thus joining the two cochleae from two different animals into a single, larger, unsealed fluid system. In response to air-conducted sound stimulation of cochlea I, auditory nerve-brainstem evoked responses could be recorded in animal II, not only when the coupling tube was filled with saline, but also when it was filled with ultrasound gel (viscosity 100,000 greater than that of water), when there was a very large hole encompassing a relatively large expanse of the cochlear shell of animal I, and even when animal I was no longer alive. The necessary control experiments were performed. Therefore, it is suggested that at low stimulus intensities, the passive, incoming basilar membrane traveling wave may not activate the cochlea. Instead the fluid pressures (condensation/rarefactions) induced in the cochlear fluids by vibrations of the stapes footplate may be adequate to directly activate the outer hair cells, which then generate an active component of basilar membrane displacement.

Acoustic Stimulation↗
PubMed1985

Evoked potentials as indicators of auditory maturation.

Evoked potentials are used widely to quantify the state of maturation of the auditory nervous system both in humans and animals. In animals a comparison between the rate of maturation obtained with evoked potential recording and with single unit recording can be made. In addition comparison with results from behavioural studies is possible. The presently available material suggests qualitatively similar time courses for single unit, evoked potential and behavioural data in the cat. However, quantitatively there are quite sizeable differences. Applications in humans only allow comparison with behavioural data, the amount and reliability of which at the moment are small. On the basis of the animal results an optimistic view point may be taken but diversity between some large studies on maturation of the human auditory evoked potentials do not substantiate this at the moment.

Animals↗
PubMedDate not supplied

Sequence of exposure to noise and toluene can determine loss of auditory sensitivity in the rat.

Rats were exposed to noise (100 dB Leq, 10 h/d, 7 d/w, 4 w), or to toluene (1,000 ppm, 16 h/d, 7 d/w, 2 w), or to noise followed by toluene. Auditory sensitivity was tested before exposure, and 1 to 4 weeks after exposure, by brainstem audiometry using a 1/3-octave filtered sine wave stimulus at the frequencies 1.6, 3.15, 6.3, 12.5 and 20.0 kHz. Some auditory impairment was observed after all exposures. The sensitivity loss after exposure to noise followed by toluene was greater than that recorded after exposure to noise alone or toluene alone, but did not exceed the summated loss caused by noise alone and toluene alone at any frequency. This result contrasts with the earlier reported effect of the same exposures in the reversed order. It is concluded that the exposure sequence can determine the extent of auditory impairment.

Animals↗
PubMed1991

Hearing fluctuation during migraine attacks. Activity of propranolol-HCl in rats.

Transitory hearing impairment has been well documented in humans during basilar migraine attacks. Ischemia induced by activation of central nervous system adrenoreceptors by cAMP is one of the mechanisms that has been implicated, as well as calcium metabolism alterations. Propranolol-HCl has proven to be an effective treatment. Massive local adrenaline release is regarded as the primum movens mechanism triggering the liberation of other beta-receptor activators resulting in sterile edema and exudate. This exudate can be visualized (via ophthalmoscope) and is viewed as pathognomonic of a migraine attack. We investigated both the action of adrenaline and Propranolol-HCl on brainstem auditory potentials in 3 groups of young rats. The first group was perfused intra-arterially with adrenaline. The second group received the same treatment plus a prophylactic daily dose of Propranolol-HCl. The third group served as the control and received Propranolol-HCl, but was perfused with a Ringer solution. Alterations in blood flow and hearing sensitivity (BERA) following perfusion occurred in the first group only. Propranolol seems to exhibit a protective action during experimental attempts to induce migraine-like attacks in rats.

Animals↗
PubMed1993

The role of summating potential in the diagnosis and management of Menière's disease.

To assess the role of a negative summating potential (-SP) in the clinical diagnosis and management of Menière's disease, the relationship of -SP abnormality to clinical symptoms, hearing level and caloric test results was examined in 70 patients with unilateral Meniere's disease. The click-induced -SP and action potential (AP) were recorded by extratympanic electrocochleography. When SP/AP ratio exceeded 0.43, the -SP was considered to be abnormal. No significant relationship was found between abnormal -SP and clinical symptoms (the duration of cochlear and vestibular symptoms, recent hearing fluctuation and recent vertigo attack). Ears with abnormal -SP had a significantly worse hearing loss at high frequencies (2-8 kHz) than ears with normal -SP, whereas there was no significant difference in hearing loss at low frequencies (0.25-1 kHz) between both ears. No significant relation was found between abnormal -SP and abnormal unilateral weakness in caloric test. The results indicate that the click-induced -SP reflects the pathophysiology of Menière's disease basically in the cochlear partition at high frequencies.

Action Potentials↗
PubMed1994

Effects of olivocochlear bundle section on otoacoustic emissions in humans: efferent effects in comparison with control subjects.

The effects of contralateral acoustic stimulation on evoked otoacoustic emissions (OAE) were examined in three subject groups in order that the impact of efferent olivocochlear bundle section (as a consequence of vestibular neurectomy) could be compared with normal findings, and with a control surgical population. Results demonstrated that the inhibitory effect of contralateral noise on OAE amplitude was absent from the cochlea with severed efferent fibers. These findings appear to be independent of acoustic reflex activity, as suppression was absent despite normal reflexes. Inter-aural suppression of emissions recorded from the patients' intact cochleae act as a control and show a clear reduction in amplitude during contralateral stimulation in a frequency specific pattern consistent with normal findings. Patients who had undergone a similar surgical approach for vascular decompression of the VIIIth nerve without vestibular nerve section, were studied in order to assess the impact of retrolabyrinthine surgery on inter-aural suppression. Inhibition of OAE amplitude was maintained in all control cases in both the operated and intact sides, and was consistent with suppression observed in normal subjects, suggesting that the surgical procedures had not disturbed inter-aural suppression of otoacoustic emissions. It is concluded that the olivocochlear efferent system, when activated by low level contralateral acoustic stimulation, has an inhibitory role in controlling the cellular mechanisms responsible for the generation of otoacoustic emissions in humans. OAE techniques in conjunction with contralateral acoustic stimulation may thus prove to be of value in providing a rapid and non-invasive clinical test of efferent function and offer a means of investigating the functional significance of the efferent auditory system in humans.

Acoustic Stimulation↗
PubMed1984

Simultaneous recording of auditory evoked potentials. Relationships among the fast, middle and long latency components.

The whole pattern of the fast, middle and long latency auditory evoked potentials (AEP) was recorded simultaneously from the scalp surface of 13 normal-hearing adults. The individual responses were displayed on a nonlinear time axis in order to improve identification of the components. Stimulation consisted of 2048 unfiltered clicks, delivered monaurally at 80, 60, 40 dB HL with an ISI of 750 ms. Changes in mean latency and amplitude of each AEP component were statistically evaluated in relation to intensity and electrode montage (vertex-mastoid ipsi- and contralateral to the stimulated ear). The latencies of fast components I-VI and the slow P1 increase significantly with declining stimulus intensity. The amplitudes of the fast, I, II, III, V and the slow P1-N1, P2-N2 decrease significantly with intensity. As regards differences due to the electrode montage the contralateral recording causes significant changes in latency of the fast potentials up to wave IV, and changes in amplitude of the fast up to wave V, and of the slow P1-N1 and P2-N2. Therefore, as their latency and amplitude seem to be less closely related to the stimulus and electrode placement, the middle components behave differently, compared with the preceding and following components. Based on parametric comparisons of potentials ranging widely in latency, but each one evoked by an equal sensory input, this kind of AEP evaluation may be useful both for neurophysiological and clinical studies of the whole auditory pathway function.

Adult↗
PubMed1987

Effects of age and sex on auditory brain stem response. A new aspect.

The age and sex dependence of the latencies and interpeak intervals (IPI) of the auditory brain stem response (ABR) was investigated in 86 males and 69 females. The latencies of the waves I, III and V as well as the IPI I-V and III-V are significantly shorter in females than in males. A correlative linear dependence on age could be shown for the latencies of waves I, III and V in males and for the wave V latency in females. The slopes of the regression lines calculated for the dependence of ABR latencies I, III and V on age tend to be steeper in males than in females. The slope increases from wave I to wave V. The male and female regression lines intersect the latency axis at about the same point (at the same latency value at age A = O). On the basis of these results, the hypothesis is established, that age and sex dependence is not caused by different mechanisms. The ABR latency differences between males and females are in the main the result of the ABR age dependence being less pronounced in females than in males.

Aging↗
PubMed1997

The effect of head size on the auditory brainstem response for two breeds of dog.

Many studies have shown that the auditory brainstem response (ABR) is influenced by the sex of the subject. The explanation offered most often for this sex difference is the smaller head size and brain dimensions in the female. Since breeds of dog have different head sizes, this makes them useful subjects to test the hypothesis that ABR latency covaries with head size. Subjects comprised 20 Dalmatians and 20 Jack Russell terriers. The maximum width of the head was 123 +/- 8 mm in the Dalmatian and 88 +/- 5 mm in the Jack Russell. An auditory brainstem response was carried out using a click stimulus at 75 dB nHL. The latency of wave V and the I-V interval was longer (0.3 and 0.17 ms respectively) in the Dalmatian, although the correlation of these measurements with head size (which ranged from -0.2 to +0.3) was not statistically significant. These findings do not support the theory that differences in ABR latency are due to differences in head size per se. Correlation of latency with body temperature and with age was also weak and not statistically significant.

Animals↗
PubMed1993

Feature processing during high-rate auditory selective attention.

Auditory event-related brain potentials (ERPs) and reaction times were analyzed in a selective attention task in which subjects attended to tone pips presented at high rates (interstimulus intervals [ISIs] of 40-200 msec). Subjects responded to infrequent target tones of a specified frequency (250 or 4000 Hz) and location (left or right ear) that were louder than otherwise identical tones presented randomly to the left and right ears. Negative difference (Nd) waves were isolated by subtracting ERPs to tones with no target features from ERPs to the same tones when they shared target location, frequency, or both frequency and location cues. Nd waves began 60-70 msec after tone onset and lasted until 250-350 msec after tone onset, even for tones with single attended cues. The duration of Nd waves exceeded the ISIs between successive tones, implying that several stimuli underwent concurrent analysis. Nd waves associated with frequency processing had scalp distributions different from those associated with location processing, implying that the features were analyzed in distinct cortical areas. Nd waves specific to auditory feature conjunction were isolated. These began at latencies of 110-120 msec, some 30-40 msec after the Nds to single features. The relative timing of the different Nd waves suggests that auditory feature conjunction begins after a brief parallel analysis of individual features but before feature analysis is complete.

Acoustic Stimulation↗
PubMed1997

[Scanning and transmission electron microscopic observations of the inner ear of hamsters with hyperlipidemia].

The relationship between hyperlipoproteinemia and sensorineural hearing loss has been studied by means of guinea pig models with hypercholesterolemia. However, these observations of the inner ear using guinea pig models have been limited to a short time. By using a golden hamster model with hypercholes terolemia, I was able to observe the inner ear for a long time. Two-month-old hamsters were fed a hyperlipid diet consisting of standard chow supplemented with 3% cholesterol and 15% cattle fat for 30, 60, 90, 120, and over 150 days. Six-month-old hamsters were fed the hyperlipid diet for 30 days. Then the animals were examined for auditory dysfunction and morphological changes in the cochlea. Biochemical findings in the serum showed hyperlipoproteinemia, especially hypercholesterolemia. Regarding auditory dysfunction, the threshold change in the auditory brainstem response (ABR) was mild. Scanning and transmission electron microscopic revealed many protrusions toward the endolymphatic space on the surface of the marginal cells of the stria vascularis. Vascular degeneration of the marginal cells and intermediate cells of the stria vascularis was also observed. In addition, protrusions containing a lysozome structure consisting of outer piller cells were observed on the organ of Corti. These results with experimental hamsters fed a hyperlipid diet indicate that such a diet may induce functional changes in the cochlea such as auditory dysfunction with the occurrence in hypercholesterolemia.

Animals↗
PubMed2000

Predicting vulnerability to acoustic injury with a noninvasive assay of olivocochlear reflex strength.

Permanent noise-induced damage to the inner ear is a major cause of hearing impairment, arising from exposures occurring during both work- and pleasure-related activities. Vulnerability to noise-induced hearing loss is highly variable: some have tough, whereas others have tender ears. This report documents, in an animal model, the efficacy of a simple nontraumatic assay of normal ear function in predicting vulnerability to acoustic injury. The assay measures the strength of a sound-evoked neuronal feedback pathway to the inner ear, the olivocochlear efferents, by examining otoacoustic emissions created by the normal ear, which can be measured with a microphone in the external ear. Reflex strength was inversely correlated with the degree of hearing loss after subsequent noise exposure. These data suggest that one function of the olivocochlear efferent system is to protect the ear from acoustic injury. This assay, or a simple modification of it, could be applied to human populations to screen for individuals most at risk in noisy environments.

Acoustic Stimulation↗