Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cochlear Microphonic Potentials”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1985

Evoked acoustic emissions and cochlear microphonics in the mustache bat, Pteronotus parnellii.

In the echolocating bat, Pteronotus parnellii, otoacoustic responses at a frequency of 62 kHz are measurable in the external ear canal during continuous and after transient acoustic stimulation. These responses are interpreted to represent emissions from the cochlea. They can reach an amplitude as large as 70 dB SPL and occur in the frequency range most important for echolocation, namely on the average about 700 Hz above the constant frequency component of the orientation calls. A sharp maximum of the amplitude of cochlear microphonic potentials at about 62 kHz could be correlated with the emission frequency. In one bat an evoked otoacoustic response changed to a spontaneous otoacoustic emission. The frequency and amplitude of the evoked otoacoustic responses reversibly decreased after exposure for 1 min to continuous sounds of more than 85 dB SPL with frequencies of about 2.5-7.5 kHz above the emission frequency. Similar effects occurred during anaesthesia or cooling. A possible relation between the existence of otoacoustic emissions and morphological specializations of the cochlea is discussed.

Acoustic Impedance Tests↗
PubMed1992

Coherence of frequency modulation is encoded by cochlear-generated distortion.

Nonlinearities of the peripheral auditory system generate distortion products which present to the central auditory system as apparent acoustic stimuli. The frequency and amplitude of distortion products reflect the frequency, phase and amplitude relationship of the components of a complex stimulus. When the stimulus consists of harmonically-related primaries, the amplitudes of the major distortion products are a function of the relative phase of the presented (primary) tones. We have previously shown (McAnally and Calford, 1990) that the variation of amplitude of the distortion as a function of the relative phase of a pair of harmonically-related primaries is well modelled as a function of the interaction of the multiple modes of distortion which fall at the same frequency (e.g. difference frequency and cubic difference frequency). A possibility raised by this result is that coherence of frequency modulation (that which maintains harmonicity) could be encoded in the amplitude of distortion. This was examined in measurements of both the cochlear microphonic potential (CM) and the responses of auditory nerve fibres in anaesthetized cats. Very small deviations from coherence of frequency modulation produced changes in the amplitude of the CM potential at the frequency of distortion. Also the discharges of auditory nerve fibres tuned to the frequency of distortion were found to be modulated at the same frequency as the amplitude changes observed in the CM. There was no variation in distortion amplitude in the CM and no modulation of auditory nerve discharges when primaries were frequency modulated coherently. It is suggested that amplitude modulation of distortion gives the auditory system its demonstrated sensitivity to minor departures from coherence of frequency-modulated, harmonically-related tones.

Acoustic Stimulation↗
PubMed1988

Contributions of the middle ear to the development of function in the cochlea.

The contribution of middle ear immaturities to the development of cochlear microphonic potential (CM) responses was studied throughout the ontogeny of auditory function in the Mongolian gerbil. CM produced by direct mechanical stimulation of the stapes was compared with CM generated by acoustic stimulation of the intact ear at various postnatal ages. The results indicated that during development acoustically generated CM reflects middle ear as well as inner ear maturational factors. With direct stapes driving, CM was first elicited at 10 days after birth (DAB), two days earlier than with acoustic stimulation. Controlling for the contributions of middle ear immaturity, maturation of the inner ear accounted for approximately a 75 dB improvement in CM thresholds between 10 and 18 DAB. Comparisons between the results obtained with the acoustic and stapes driving stimulation protocols suggested that the major maturational changes in the middle ear conduction apparatus occurred between 14 and 16 DAB. This period was associated with the final stages of resorption of middle ear mesenchyme and ossicular ossification. Before 16 DAB, acoustically evoked CM thresholds reflect approximately a 25 dB loss in sensitivity due to middle ear immaturity.

Acoustic Stimulation↗
PubMed1982

Influence of argon laser stapedotomy on cochlear potentials. I: Alteration of cochlear microphonics (CM).

In guinea pigs the cochlea microphonics (CM) were recorded during and after argon laser stapedotomy. Short termed drastic depression of CM was observed. This effect involved the entire frequency range of the cochlea. The recovery was mostly complete and often started already during laser irradiation or at the end of the laser exposure. A marked sensitivity loss of the cochlea only occurred with large stapedotomy holes followed by massive perilymph leakage. A momentary heat related instability of the entire stapes is suggested to cause the CM depression. In addition we observed a thermoacoustic effect on the CM. This laser evoked response seems to cause no harm to the cochlea.

Animals↗
PubMed1987

Genetic and functional analysis of the otosclerosis-like condition of the LP/J mouse.

The LP/J mouse is the only available genetic model for otosclerosis. The otosclerosis-like condition of the LP/J mouse resembles the human condition in several ways, although there are differences in the two species in the most common locus of the dysplastic otic lesions. The mouse model would be more useful if its auditory dysfunction and genetic inheritance could also be compared with the human disease. Matings of the otosclerosis-like LP/J and the normal CBA/J inbred mice were used to generate F1 and backcross generations. The F1 showed neither functional (electrocochleographic) nor anatomical abnormalities, indicating a recessive nature of the mouse genetic disease. This is in contrast to some reports of dominance (with incomplete penetrance) of otosclerosis in humans. No evidence of X-chromosome-linked genetic influence was found in the mouse, in agreement with the human condition. These interpretations were confirmed in tests of the backcross of the F1 to the CBA/J parental genotype (BC). The anatomical and functional abnormalities were present in some of the backcrosses of the F1 to the LP/J parental genotype (BL). A comparison of bone-conducted and air-conducted electrocochleographic responses provided evidence for both conductive and sensorineural losses in the LP/J and BL mice.

Action Potentials↗
PubMed1989

Detuning of cochlear action potential tuning curves at high sound pressure levels: influence of temporal, spectral and intensity variables.

Action potential (AP) tuning curves (TCs), generated by probe stimuli of 60-65 dB SPL with short rise and decay (r&d) times, are less sensitive (have elevated tip thresholds) and are detuned (the frequency is shifted away from that of the probe stimulus, towards a middle frequency of the audiogram). These effects are more pronounced with forward than with simultaneous masking. TCs generated by masking tonal and narrow band noise stimuli are nearly identical, even though the spectrum is much wider for the noise stimulus. Decreasing r&d time has the same effect on TCs generated from both noise and tonal stimuli, even when it only measurably increases the acoustic splatter of the latter. Detuning appears to be related to a temporal-intensity interaction.

Action Potentials↗
PubMed1986

Comparative actions of quisqualate and N-methyl-D-aspartate, excitatory amino acid agonists, on guinea-pig cochlear potentials.

We examined dose-dependent changes in the amplitude of guinea-pig cochlear microphonic potentials (CM), summating potentials (SP) and compound auditory nerve action potentials (CAP) produced after perfusing perilymphatic scalae with artificial perilymph containing either the transmitter candidate, L-glutamate; one of the excitatory amino acid agonists, quisqualate, kainate, N-methyl-D-aspartate (NMDA) or D-glutamate; or the control, alpha-ketoglutarate. None of these compounds significantly altered CM or SP. Kainate abolished CAP, but only partial suppression occurred using maximal effective doses of quisqualate (67%) or L-glutamate (82%). The remaining compounds had only marginal effects on CAP. The potency of quisqualate (EC50 = 14.8 microM) exceeded that of both kainate (EC50 = 66.9 microM) and L-glutamate (EC50 = 1.41 mM). These data suggest the presence of neuronal, possibly postsynaptic, excitatory amino acid receptor subpopulations which are preferentially sensitive to quisqualate and to kainate, but not to NMDA. These findings are discussed in the framework of our hypothesis that the proposed quisqualate and kainate receptors are normally activated by an endogenous excitatory amino acid such as L-glutamate which the hair cells release as a neurotransmitter.

Action Potentials↗
PubMedDate not supplied

Transtympanic electrocochleography in patients with syphilis and hearing loss.

Transtympanic electrocochleography was carried out on 18 syphilitic patients (30 ears were tested) most of whom were suffering from the late onset congenital form of the disease. A diphasic action potential with a large negative summating potential on the descending limb was found in 77.7% of ears; the cochlear microphonic potential was always of small amplitude. While these findings are not pathognomonic of syphilis, they are characteristic and may be explained on pathological grounds.

Action Potentials↗
PubMed1977

Identification and separation of acoustic frequency following responses (FFRS) in man.

Frequency following responses (FFRs) to monaural tone bursts were recorded in normal and hearing impaired subjects as the potential difference between an ipsilateral earlobe electrode and a scalp vertex electrode. Whenn the rubber tube coupler between the earphone and the subject's ear was clamped, a stimulus artefact FFR was occasionally recorded. The "biological" FFR had a latency of about 1 msec and an irregular wave form which was made more sinusoidal by the addition of white noise. When the responses to tone bursts of opposite onset phases were added together, a "double frequency" FFR was obtained which had a latency of about 6 msec and whose amplitude was appreciably reduced by white noise. In some hearing impaired subjects (with no neural responses to clicks), this longer latency double frequency component could not be recorded, while in those cases in which the cochlear microphonic potential could be recorded, the shorter latency FFR was also present. It is concluded that the FFR in normally hearing subjects is made up of a short latency cochlear microphonic component and a longer latency neural component.

Adolescent↗
PubMed1977

Usher's syndrome: electrophysiological tests of the visual and auditory systems.

The symptoms of Usher's syndrome - congenital hearing impairment and tapetoretinal dystrophy - are difficult to detect in young children. The electroretinogram (ERG), visual evoked potential (VEP), auditory nerve and brain-stem responses as well as the cochlear microphonic potentials were used to evaluate the defects of the visual and auditory systems in 20 patients, 3-45 years of age. This study demonstrates the usefulness, reliability and convenience of the electrophysiological tests for early diagnosis and functional evaluation of Usher's syndrome.

Adolescent↗
PubMed1985

[Electrophysiologic studies on the course of the adaptation phase following noise stress].

It was the aim of this study to settle the problem whether the post-stimulatory pattern of the extent of excitation (amplitude, latency) registered with the cortical evoked potentials can be verified in the recovery phase via leads from the brain stem region and cochlea. In this context electrophysiological measurements with human and animal material were performed. After a five-minute stimulation with a wide-band noise of various intensity we examined in the post-stimulation phase the specific stimulus pattern of the evoked potentials during an interval of 5 minutes with a resolution of 5 sec. We determined the change in response patterns of evoked potentials. Finally, the relevance of the results with regard to various nuclei of the auditory pathway is compared with corresponding electrophysiological measurements of the cochlear microphonics potentials, the VIII nerve compound action potential, and evoked potentials of different units of the brain stem and brain.

Animals↗
PubMedDate not supplied

Bioelectric phenomena in the ototoxicity of nitrogen mustard.

The effects of nitrogen mustard on the electrical potentials of the inner ear were studied, and the results were correlated with the histopathologic findings which have been reported in nitrogen mustard ototoxicity. The endocochlear DC potential (EP) decreased rapidly after an injection of nitrogen mustard (NM). The amplitude of the cochlear microphonics potential (CM) diminished rapidly, and no substantial recoveries were observed. No significant changes in the magnitude of the negative potential of organ of Corti (NPOC) were observed. A large negative summating potential (SP) was recorded even when the amplitude of the CM had diminished.

Acoustic Stimulation↗
PubMed1986

Development of mammalian endocochlear potential: normal ontogeny and effects of anoxia.

The development of the positive endocochlear potential (EP), the negative anoxic EP, and the organ of Corti potential were measured at various postnatal ages in the Mongolian gerbil, beginning at 8 days after birth (DAB). The organ of Corti potential (OCP) was present at 8 DAB but averaged 21% less than the adult value. OCP increased regularly with age, reaching adult values of -90 mV by 14 DAB. The positive EP was first observed at 10 DAB, at which age it averaged only 2-3 mV. This potential increased monotonically between 10 and 20 DAB, by which time it had reached the adult value of 75 mV. Anoxia did not result in a negative EP until 12 DAB, at which age this potential averaged -7 mV. The negative anoxic EP matured more rapidly than the positive EP, achieving the adult value of 40 mV by 18 DAB. During development the positive EP appeared to closely parallel the maturation of glucose metabolism in the stria vascularis. The negative anoxic EP was more closely related temporally to the development of cochlear microphonic potential (CM) thresholds. It is hypothesized that changes which occur between 10 and 16 DAB in the apical membranes of the cochlear hair cells contribute to the maturation of both CM and the negative anoxic EP.

Animals↗
PubMed1986

Vestibular microphonic potentials in pigeons.

Electrical responses to acoustic stimuli were measured by placing thin wire electrodes in the vestibular system of a pigeon model. Responses were measured after extirpation of the cochlea and the application of tetrodotoxin to the perilymphatic space. Responses seen were comparable to those of known cochlear microphonic potentials. These findings indicate that acoustic stimuli can evoke microphonic potentials in the vestibular system of the pigeon. We also found that vibrational amplitudes of less than 1 nm were sufficient to evoke a vestibular microphonic potential.

Acoustic Stimulation↗
PubMed1976

Changes in cochlear microphonic sensitivity after priming C57BL/6j mice at various ages for audiogenic seizures.

Groups of mice were briefly exposed to a one-octave band of noise at 14, 18, 28, 38, or 58 days of age. Five days later the groups were divided, and some mice were behaviorally tested for audiogenic seizures by reexposing them to the same sound. The round window cochlear microphonic potential was measured in the remaining animals and compared with that observed in unprimed control subjects. Seizure behavior occurred in all animals primed on Day 18 but rarely for subjects in the other age groups. Cochlear microphonic threshold curves in mice primed on Day 18 showed a 30-dB loss in sensitivity, while all other primed groups showed little change. These data were discussed in terms of the "disuse-supersensitivity" hypothesis previously proposed to account for the physiological effects of priming in mice.

Acoustic Stimulation↗
PubMedDate not supplied

Comparison of hearing threshold determined by auditory pathway electric responses and by behavioural responses.

In order to evaluate their reliability for determing the hearing threshold, the cochlear microphonic potentials, the auditory nerve and brain stem neural evoked responses as well as the cortical evoked responses were compared with the behavioural hearing thresholds of the same subjects in the same session. The threshold for recording the cochlear microphonic potnetial was found to be appreciably higher than the behavioral threshold. The threshold for recording the auditory nerve and brain stem responses was within a few decibels of the behavioural threshold. The thresold of the cortical evoked response was several decibels higher. It is concluded that (1) the auditory nerve and brain stem neural evoked responses are the best indicators of hearing threshold; (2) the cortical evoked responses are usually comparable, and (3) all types of evoked responses are indispensable aids in the evaluation of hearing and the determination of site of lesion in the auditory system.

Audiometry↗
PubMed1986

Trimethyltin ototoxicity: evidence for a cochlear site of injury.

The environmental contaminant, trimethyltin (TMT), produces a profound elevation in tone intensity necessary to inhibit the acoustic startle reflex in laboratory animals which recovers over a prolonged period except at very high frequencies. The recovery that is observed does not begin until 3 to 5 weeks after a single acute administration depending upon dosage. As opposed to the very temporary threshold shifts by the salicylates and loop diuretics or the permanent and progressive ototoxicity resulting from aminoglycoside antibiotics the time course for recovery of acoustic startle reflex inhibition after TMT appears to be an anomaly for a chemical ototoxicant. In terms of the duration of loss only, this pattern appears similar to that sometimes observed after noise exposure. The current investigation replicates the finding that recovery of acoustic startle reflex inhibition after TMT is frequency related in that only the highest frequency impairment appears to be permanent. While this frequency dependence suggests a cochlear locus of injury, both the known neurotoxic effects of TMT and the time course of the behavioral impairment suggest a more central locus of injury. Compound action potential and cochlear microphonic recordings made from the round window in the current study confirm a preferential high frequency effect of TMT and demonstrate a significant cochlear component to the ototoxic effects of this agent.

Action Potentials↗
PubMed1987

Modulation of the masking phenomenon by the crossed part of the medial olivocochlear bundle.

The masking phenomenon is used in clinical investigation of the inner ear to determine the frequency selectivity properties of the auditory system. Sectioning of the crossed part of the medial efferent bundle in a guinea pig model decreases the simultaneous masking phenomenon. The efferent effect seen in the forward masking varied with the masking paradigm used. When the masker onset precedes the maskee onset by more than 40 ms, masking diminishes after sectioning the crossed part of the medial efferent bundle. When this duration was shortest (30 ms), no effect was observed. This phenomenon could be explained by the time necessary to stimulate the medial efferent loop. Our results could explain some differences observed in the compound action potential masking curves with different masking paradigms.

Acoustic Stimulation↗