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PubMedDate not supplied

Effects of perilymphatic perfusion with neomycin on the cochlear microphonic potential in the guinea pig.

The effects of three concentrations of neomycin, administered by a method of acute perilymphatic perfusion of the guinea pig cochlea, on the cochlear microphonic potential (CM) at 4 kHz and 500 Hz are described. A concentration-dependent reduction in CM occured during the 60 minute perfusion period. Neomycin at 10-4 M did not change the CM magnitude, while at 10-3 and 102 M it caused 4 kHz (and 500 Hz) CM reductions which began within 24 (for both frequencies) minutes and 10 (and 12) minutes of drug application respectively. CM reduction proceeded at a higher rate for greater neomycin concentration. The perfusion technique, the implication of the frequency indifference, and the potential of the perfusion technique for inner ear biochemical analysis are discussed.

Action Potentials↗
PubMed1980

[Dynamics of the harmonic components of the cochlear microphonic potential during acoustic overloading and exposure to ototoxic substances].

The 2nd and the 3rd harmonic components of microphonic potentials in the rabbit cochlear, under the influence of sound stimuli of different intensity, developed simultaneous and equal changes of their characteristics of the odd harmonic as well as of the basic tone. The even harmonic did not depend on the dynamic characteristics of the basic tone of microphonic potentials. The even harmonic developed its own specific changes. In separate experiments, the effects of sound overload, etacrine acid and streptomycin on the dynamic characteristics of the even harmonic, were studied.

Animals↗
PubMed1980

The source along the basilar membrane of the cochlear microphonic potential recorded by surface electrodes in man.

In order to determine the region along the basilar membrane which contributes to the recorded CM, an attempt was made to record CM responses in subjects with normal hearing and in subjects with high frequency cochlear hearing losses (e.g. acoustic trauma). In such cases of high frequency hearing loss, one may assume that damage has occurred to the hair cells in the basal turn of the cochlea. The CM, elicited by one cycle sinusoidal stimuli of various frequencies, intensities, phases, etc., was recorded by means of earlobe and scalp vertex electrodes. The CM recorded in subjects with normal hearing to high frequency sounds showed (besides the previously reported properties of the CM) large amplitudes and short latencies in response to low frequency stimuli. On the other hand, the CM recorded in subjects with high frequency hearing loss were either prolonged in latency and small in amplitude or completely absent. A plot of the relationship between CM lastency to high intensity 500 HZ stimuli stimuli and audiometric hearing loss in 66 ears shows clearly that in those cases in which hearing was normal at frequencies up to about 8 kHZ, CM latency was very short. On the other hand, in those cases in which the high frequency hearing loss progressed to include more and more lower frequencies, CM latency was more prolonged and smaller in amplitude until CM could no longer be observed. These results indicate that the CM recorded in normally hearing subjects from skin electrodes in response to low frequency (500 HZ) stimuli is generated in the basal turn of the cochlea. This finding is probably a consequence of the form of the mechanical response of the basilar membrane (travelling wave) to low frequency stimuli.

Acoustic Stimulation↗
PubMed1995

[Cochlear microphonic potential (CM) recordable at non-shielded bedside--with reference to the development of a new earphone (NC-3)].

By making several improvements in current hearing aid earphones, a new earphone (NC-3) for CM measurement in electrocochleography (ECochG) has been developed. A silicone tube with a 1.5mm inside diameter, 175mm in length, was attached to the acoustic hole side of the earphone. The earphone proper was shielded with aluminum foil and one end of the foil was connected to a low noise cable. Human forearm was used as a dummy ear and the electrode HN-5 was fixed thereon, and a sound stimulus of 90dBnHL was delivered by the earphone (NC-3). No measurable artifacts, such as electromagnetic conductions and the CM-like mechanical vibrations generated by the acoustic output system, were recorded. By placing the earphone (NC-3) from a right-angle to a diagonal direction toward the electrode circuit, electromagnetic conduction contamination was prevented. With an extratympanic procedure using the electrode HN-5, ECochG-CM was recorded from normal hearing subjects in both a shielded sound-proof room and a non-shielded ordinary but quiet room. Short tone bursts at 1 and 4kHz were employed as acoustic stimuli and delivered by the earphone (NC-3). In the non-shielded quiet room, no electromagnetic conduction contamination or mechanical vibration was observed and there were no differences in CM responses between the two rooms. These results suggest that this earphone (NC-3), making CM recordings possible at the ordinary bedside without shielding, may contribute significantly to the subsequent spread of ECochG-CM measurement, by compensating for the disadvantages of a loudspeaker.

Acoustic Stimulation↗
PubMed1977

[Effect of single impulses on cochlear microphone potentials of the guinea-pig cochlea].

The influence of highly intensive single impulses on the cochlea of guinea pig was studied in an acute experiment. Very short impulses of less than or equal to 0.1 ms duration were produced by a sparknoise generator. The cochlear microphonics (CM) to a test stimulus (sinus tone, 3150 Hz) were recorded from the round window and measured prior to, during, and following impulse treatment. During the impulse treatment, the greatest amplitude reduction of CM occurred after the first impulse, while the further impulses caused a decreasing reduction. At first the number of impulses was varied: 1, 3, and 5 impulses were applied at intervals of 15 s each, at an impulse sound level of 164 dB sound pressure level re. 0.002 mubar (SPL). After these impulse treatments, in all cases a continual decrease of CM amplitudes up to a constant end value without recovery was found within a 2-hrs period of observation. The height of the end value depends on the number of impulses applied. Subsequently, at an exposure to 5 impluses the impulse sound level was stepwise reduced (164, 153, 144, 139 and 133 dB SPL). Again, a characteristic decrease of CM amplitudes was observed during the 2-hrs period of observation. The height of the end value is now dependent on the impluse sound level. Impulses of 164, 153 and 144 dB SPL cause a strong decrease of CM while the effect of impulses of 139 and 133 dB SPL is distinctly lower.

Acoustic Stimulation↗
PubMed2006

Columella footplate motion and the cochlear microphonic potential in the embryo and hatchling chicken.

A piezoelectric (PZE) vibrator was used to mechanically drive the columella footplate and stimulate the cochlea of chicken embryos and hatchlings. Our objectives were to characterize the motion of the PZE driver and determine the relationship between columella footplate motion (displacement/ velocity) and the cochlear microphonic recorded from the recessus scala tympani (CMrst). At each frequency, displacement of the PZE driver probe tip was linearly related to the applied voltage over a wide range of attenuation levels (-60 to -20 dBre:50 Vp-p). The mean displacement across frequencies (100-4000 Hz) was 0.221+/-0.042 micromp-p for a constant applied voltage level of -20 dBre:50 Vp-p. Displacement was within 1.5 dB of the mean for this stimulus level at all frequencies except for 4000 Hz, where it was approximately 3 dB higher (p < 0.01). CMrst amplitudes in hatchlings were larger than amplitudes in embryos (p=0.003). For a given frequency, CM was linearly related to footplate displacement and velocity at both ages. The transform ratio of CMrst/A (CM amplitude/displacement) increased at approximately 6 dB/octave at frequencies between 100 and 1000 Hz in hatchlings suggesting that cochlear impedance (Zc) was resistive at these frequencies. In a large fraction of the embryos, Zc exhibited reactive behavior.

Animals↗