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Results for “Cochlear Microphonic Potentials”

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At least 1,081 records · Page 60Linked to original sources
PubMed1986

[Oto-acoustic emissions and their significance for inner ear research].

In contrast to the formerly held opinion it is now clear that the spontaneous oto-acoustic emissions (OAEs) are pure sinus tones. Frequency shifting (small oscillations and a drifting in one of the two directions) causes broadening of the image in Fourier's transformation, especially when being averaged. These spontaneous OAEs can be observed in ears with minimal disturbance--often not yet detectable by means of pure tone threshold. In such ears the synchronisation of the hair-cells is out of order and this leads to the spontaneous OAEs. With increasing sensitivity of the microphones OAEs can be found in more and more ears. A connection between spontaneous and evoked OAEs can be shown when calculating a FFT from the image of an evoked emission: the spectrum is similar to that of spontaneous OAEs from the same ear. TTS situations in spontaneous OAEs: the reduction of the ability of synchronisation cancels the emission, which will reappear after some time (shifted in frequency). To explain the frequency resolution in the cochlea an active filter has been postulated and the OAEs are claimed to be a reflection of the same; in fact, they are one of the proverbial keyholes through which we might gain a glimpse of what is taking place in the cochlea.

Animals↗
PubMed1988

[Organogenesis of hearing. Development of the ear].

From a review of the literature, the authors describe the development of the auditory organ, from embryogenesis to function, explaining the hearing abilities of the newborn as well as the possibilities of hearing in utero.

Animals↗
PubMed1987

A study of hearing in the elderly using non-invasive electrocochleography and auditory brainstem responses.

The auditory brainstem responses exhibited normal interpeak intervals of waves I-III and I-V in a group of 31 elderly people (mean age 82 years), indicating normal conduction through the brainstem. The amplitudes of the waves I, III and V were significantly reduced and the peaks I, III and V showed a delay in latency, reflecting a predominantly lower level of activity in the elderly cochlea. Extratympanic electrocochleography yielded significantly reduced amplitudes of the N1 component of the action potential, summating potential and cochlear microphonics in the elderly compared to the young controls. A heterogeneity of patterns of input/output functions was observed and interpreted as either an absence of recruitment, as partial or as complete recruitment. The findings are in keeping with pathological evidence of severe damage to outer hair cells and complete atrophy of part of the basal coil.

Adult↗
PubMed1988

[Contribution of cochlear acoustic emissions in pediatric audiology].

A new method is described for pediatric otologic exploration : cochlear acoustic emissions (CAE), and results reported of CAE recordings in 15 children with normal hearing and 31 infants at otoneurologic risk, suspected of having moderate or severe hypoacusia on conventional audiometry. Results were compared with those obtained by study of V wave threshold of AEP. The incidence of CAE in children and infants with normal hearing was 100%, the absence of CAE being related to a V ware threshold of AEP of 30 dB nHL or more. The CAE threshold is closely related to that of the V wave of AEP. The use of CAE, a rapid, non-invasive, objective audiometric method, could be a first line screening technic allowing separation, within several minutes, of a normal hearing population from one with a lesion of transmission or endocochlear apparatus with CAE V wave threshold of over 30 dB nHL. In addition, in children with a flat AEP the CAE allows study of the cochlear independently of auditory pathways.

Adolescent↗
PubMed1986

Binaural acoustic reflex activity following monaural noise exposure in decerebrate chinchillas.

Acoustic reflex thresholds, latencies and magnitudes were recorded binaurally in decerebrate chinchillas suffering monaural, temporary noise trauma. Simultaneous recordings of cochlear microphonics from both cochleae during monaural reflex stimulation served as an index for acoustic reflex dynamics. Baseline values of threshold, latency and magnitude were recorded from ipsilateral and contralateral ears prior to a monaural 2-hour exposure to a 0.5-kHz octave-band noise at 100 dB SPL. Reflex dynamics were measured immediately after exposure and again following 1 h of recovery. Cochlear microphonic input-output functions for the exposed ear were completed prior to and after cessation of the noise and after 1 h of recovery. Acoustic reflex threshold and magnitude increased and latency decreased following exposure to noise for both the ipsilateral and contralateral recording conditions. Reflex activity in the nonexposed ear was unaffected. Reflex properties returned to pre-exposure values following recovery. These responses followed the same time course as changes in cochlear sensitivity. Alterations in reflex response following noise exposure is caused by changes at purely peripheral sites.

Animals↗
PubMed1987

[Oto-acoustic emissions. I. Evoked oto-emissions: a new technic of functional study of the cochlea].

Otoacoustic emissions (OAE) are sounds emitted by the cochlea and recordable in the external ear canal by a miniature microphone. These OAE reflect the existence of an active mechanism within the cochlea, probably based upon outer hair cells (OHC). Recordings of OAE are easy, noninvasive, objective and permit the exploration of an essential property of the cochlea which was impossible to study by the usual electrophysiological techniques. Clinical applications are discussed in this paper.

Adolescent↗
PubMed1987

[Oto-acoustic emissions. II. Spontaneous oto-emissions: results in normal subjects or patients with tinnitus].

Sounds can be emitted by the cochlea in the absence of any stimulation. This phenomenon is called spontaneous oto-acoustic emissions (SOAEs) and they can be recorded in the external auditory canal using a sensitive microphone. This phenomenon seems to be due to an abnormality of the active cochlear mechanisms. SOAEs have been studied in 140 human subjects, 140 of them suffering with tinnitus, while 80 were used as the control group. SOAEs have been studied as a function of age, and of the audiometric state. Possible relationships between SOAEs and tinnitus have also been studied. This study shows the interest of recording SOAEs for an early diagnosis of cochlear dysfunction. It also shows that there is no clear correlation between tinnitus and SOAEs.

Adolescent↗
PubMed1986

[Cochlear implants].

Since the middle of 1984, the HNO-Klinik der Medizinischen Hochschule Hannover has provided deaf adults with a 22-channel cochlear implant (CI) device of Clark-NUCLEUS. The digital working system consists of an implantable stimulator/receiver and an externally worn speech processor. Energy and signals are transmitted transcutaneously via a transmitter coil. During the prevailing 26 operations (April 1986) the electrode array could be inserted at least 17 mm into the cochlea. The threshold and comfort levels of all patients were adjusted very quickly; the dynamic range usually grows during the first postoperative weeks. The individual rehabilitation results vary greatly, but all patients show a significant increase of vowel and consonant comprehension while using the speech processor and an improvement of words understood per minute in speech tracking from lip-reading alone to lip-reading with speech processor. Four months after surgery seven of 17 patients (group I) are able to understand on average 42.7 words per minute by speech tracking without lip-reading. Six patients (group II) recognise 69.2% of vowels and 42.5% of consonants by speech processor alone. Four patients (group III) can correctly repeat only vowels (52.3%) without lip-reading, but using the speech processor together with lip reading they have an improvement in consonant understanding of 37.9% and under freefield conditions they are able to understand up to 17.8% numbers of the Freiburg speech test.

Cochlear Implants↗
PubMed1985

[Early and late reaction of the guinea pig cochlea to impulse noise].

Guinea pigs (GP) were exposed to 10 impulses of 164 dB (SPL). Measuring of cochlear microphonics (CM) at frequencies between 0.5 and 10 kHz and morphological examination of the cochlea by the surface preparation technique followed 2 hours, 2 and 6 weeks after exposure to impulse noise. During the 2 hours following noise exposure the amplitudes of CM decreased in all tested frequencies, while recovery of CM never could be observed at this time. Subsequent morphological changes in the structure of the organ of Corti could be found. They varied considerably between the tested animals. 2 and 6 weeks after exposure to 10 impulses all GP had irreversible defects in the cochlea in an extent from an incomplete pattern of outer hair cells up to a total lack of areas of the organ of Corti. Only in GP with morphological damages in a small extent CM were recordable again. A good agreement of functional and morphological results was established. It can be concluded that exposure to few single impulses with peaks of sound pressure of sufficient intensity will produce irreversible morphological defects in the cochlea, resulting in marked functional injury, if the damaged area is large enough.

Animals↗