The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagno... more The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagnosis of the function of the inner ear. However, it is not possible to extract this information over the entire, functionally relevant frequency range because of imperfect coupling of: (1) stapedial to ear-drum vibrations through the ossicular chain of the middle ear and (2) ear-drum
Der Grundmechanismus des Horens — die mechano-elektrische Transduktion — und damit auch die dazug... more Der Grundmechanismus des Horens — die mechano-elektrische Transduktion — und damit auch die dazugehorige Pathophysiologie sind noch nicht vollstandig erforscht. Experimente an isolierten auseren Haarsinneszellen (AHZ) zeigen, das sie fahig sind, auf elektrische, akustische und chemische Reize mit einer Langenanderung ihres Zellkorpers zu antworten. Es wurde deshalb postuliert, das AHZ mechanische Energie in das Cortische Organ einspeisen konnen, dem passiven Widerstand in der Cochlea entgegenwirken und dadurch die auserordentlich hohe Frequenzselektivitat und Empfindlichkeit des Innenohres erzeugen und modulieren. Zu klaren ist jedoch noch, ob AHZ in situ im Cortischen Organ bei physiologisch relevanten Schallintensitaten Motilitat zeigen. Um diese Frage zu beantworten, haben wir an einem Felsenbeinpraparat die Bewegung zellularer Strukturen in der dritten und vierten Windung der Meerschweinchencochlea bei lufthaltigem Mittelohr untersucht.
Proceedings of the National Academy of Sciences of the United States of America, Apr 13, 1999
High-frequency resolution is one of the salient features of peripheral sound processing in the ma... more High-frequency resolution is one of the salient features of peripheral sound processing in the mammalian cochlea. The sensitivity originates in the active amplification of the travelling wave on the basilar membrane by the outer hair cells (OHCs), where electrically induced mechanical action of the OHC on a cycle-by-cycle basis is believed to be the crucial component. However, it is still unclear if this electromechanical action is sufficiently fast and can produce enough force to enhance mechanical tuning up to the highest frequencies perceived by mammals. Here we show that isolated OHCs in the microchamber configuration are able to overcome fluid forces with almost constant displacement amplitude and phase up to frequencies well above their place-frequency on the basilar membrane. The high-frequency limit of the electromotility, defined as the frequency at which the amplitude drops by 3 dB from its asymptotic low-frequency value, is inversely dependent on cell length. The frequency limit is at least 79 kHz. For frequencies up to 100 kHz, the electromotile response was specified by an overdamped (Q = 0.42) second-order resonant system. This finding suggests that the limiting factor for frequencies up to 100 kHz is not the speed of the motor but damping and inertia. The isometric force produced by the OHC was constant at least up to 50 kHz, with amplitudes as high as 53 pN/mV being observed. We conclude that the electromechanical transduction process of OHCs possesses the necessary high-frequency properties to enable amplification of the travelling wave over the entire hearing range.
Viele Untersuchungen im basalen Teil der Cochlea deuten darauf hin, das die auseren Haarsinneszel... more Viele Untersuchungen im basalen Teil der Cochlea deuten darauf hin, das die auseren Haarsinneszellen mit ihrer Fahigkeit zur aktiven, schnellen Langenanderung die Wanderwelle verstarken und verscharfen. Bisherige Untersuchungen konnten jedoch noch nicht klaren, ob durch die Kopplung des elektromechanischen und des mechanoelektrischen Transduktionsprozesses ausreichend Energie in die Wanderwelle eingespeist werden kann, um die bei Saugetieren nachgewiesenen, scharfen Abstimmkurven sowie die niedrigen Schwellen zu erklaren. Dazu haben wir Versuche an frischen Felsenbeinpraparaten des Meerschweinchens durchgefuhrt, die eine Annaherung an die In-vivo-Bedingungen der Mikromechanik der Cochlea erlauben.
Optical and Imaging Techniques for Biomonitoring, 1996
The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagno... more The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagnosis of the function of the inner ear. However, it is not possible to extract this information over the entire, functionally relevant frequency range because of imperfect coupling of: (1) stapedial to ear-drum vibrations through the ossicular chain of the middle ear and (2) ear-drum
Proceedings of the National Academy of Sciences, 1999
High-frequency resolution is one of the salient features of peripheral sound processing in the ma... more High-frequency resolution is one of the salient features of peripheral sound processing in the mammalian cochlea. The sensitivity originates in the active amplification of the travelling wave on the basilar membrane by the outer hair cells (OHCs), where electrically induced mechanical action of the OHC on a cycle-by-cycle basis is believed to be the crucial component. However, it is still unclear if this electromechanical action is sufficiently fast and can produce enough force to enhance mechanical tuning up to the highest frequencies perceived by mammals. Here we show that isolated OHCs in the microchamber configuration are able to overcome fluid forces with almost constant displacement amplitude and phase up to frequencies well above their place-frequency on the basilar membrane. The high-frequency limit of the electromotility, defined as the frequency at which the amplitude drops by 3 dB from its asymptotic low-frequency value, is inversely dependent on cell length. The frequenc...
Outer hair cells (OHC) were isolated from the apical two turns of the guinea-pig cochlea and thei... more Outer hair cells (OHC) were isolated from the apical two turns of the guinea-pig cochlea and their hair-bundle stimulated mechanically by a glass probe. In accordance with in vivo data (Dallos, 1985), the resting membrane potential was typically -64 mV (N = 200). The maximum amplitudes of the receptor potentials were between 0.4 and 5.2 mV peak-to-peak, with mean of 1.5 mV +/- 0.9 mV (N = 81). The sensitivity was 0.015 mV/nm or 2 mV/deg. The frequency response of the receptor potential followed a first order low-pass filter characteristic with a corner frequency of about 63 Hz. For frequencies up to at least 1.6 kHz, the frequency response of mechanoelectrical transduction was dominated by the electrical input impedance of the cell. The presence of a single time constant in the voltage response to stereociliary deflection implies that the frequency response of mechanoelectrical transduction far exceeds that of the electrical input impedance of the cell; its time constant must be faster than 100 microseconds. Under in vivo conditions, OHC should be capable of providing a sufficiently large receptor potential to supply enough energy for electromechanical feedback.
Proceedings of the National Academy of Sciences, 1996
The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of... more The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of the cochlea. In particular, it has been proposed that the tectorial membrane provides a second resonant system, in addition to that of the basilar membrane, which contributes to the amplification of the motion of the cochlear partition. Until now, technical difficulties had prevented vibration measurements of the tectorial membrane and, therefore, precluded direct evidence of a mechanical resonance. In the study reported here, the vibration of the tectorial membrane was measured in two orthogonal directions by using a novel method of combining laser interferometry with a photodiode technique. It is shown experimentally that the motion of the tectorial membrane is resonant at a frequency of 0.5 octave (oct) below the resonant frequency of the basilar membrane and polarized parallel to the reticular lamina. It is concluded that the resonant motion of the tectorial membrane is due to a par...
The Journal of the Acoustical Society of America, 1984
Measurements of group delay were made extracellularly from spiral ganglion cells in the 3.7 to 5.... more Measurements of group delay were made extracellularly from spiral ganglion cells in the 3.7 to 5.0-mm region of the guinea pig cochlea, using sinusoidally amplitude modulated tones with constant modulating frequency (100 Hz) and depth of modulation (0.19). Threshold cochlear tuning was accompanied by frequency-dependent group delays. The group delay on the low-frequency tail was independent of carrier frequency; the interunit variation was 0.28-1.28 ms. The difference in group delay between CF and the low-frequency tail decreased as the CF threshold increased (-0.09 +/- 0.02 ms per 10 dB, beginning at 0.62 +/- 0.07 ms at 0 dB SPL). The group delay decreased above CF; at the units' maximum frequency it was less than the low-frequency tail value, and was sometimes negative. Following arterial injections of furosemide the CF threshold increased and the group delay peak decreased; the low-frequency tail was unaffected. The group delay decreased with increasing intensity; the reduction near and above CF was not only larger than that on the low-frequency tail, but also the change at 5-10 dB above threshold was far greater than expected from the Q10dB of the suprathreshold iso-rate tuning curves. A minimum-phase analysis suggested that the group delay response above CF, together with its nonlinear behavior, can be accounted for by a high-frequency, level-independent, amplitude plateau, in combination with the single unit, amplitude nonlinearity which is known to exist above CF.
By deforming and making incisions in the basilar membrane (BM), von Békésy showed that the BM see... more By deforming and making incisions in the basilar membrane (BM), von Békésy showed that the BM seems to behave as a thin elastic plate, rather than as a membrane. However, it has never been shown whether a traveling wave could be sustained by a prestretched material in which the tension is insufficient to cause a visible retraction of the cut edges of an incision when viewed with a light microscope. We have shown that the necessary radial tension would decrease exponentially along the cochlea, from a value of 39 +/- 9 N/m at the base, with a space constant of 4.3 +/- 1.1 mm, for the guinea pig. This variable tension would be produced by a constant prestretching surface force of 2.4 +/- 0.1 X 10(6) N/m2, acting on the BM edges. Using values of Young's modulus in the radial direction, ranging from that of elastin to collagen, it is shown that this force would most likely cause a visible retraction of the cut edges of an incision. Therefore one must either conclude, once again, that the BM is effectively an unstretched material or question the original interpretation of the incision experiments.
The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagno... more The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagnosis of the function of the inner ear. However, it is not possible to extract this information over the entire, functionally relevant frequency range because of imperfect coupling of: (1) stapedial to ear-drum vibrations through the ossicular chain of the middle ear and (2) ear-drum
Der Grundmechanismus des Horens — die mechano-elektrische Transduktion — und damit auch die dazug... more Der Grundmechanismus des Horens — die mechano-elektrische Transduktion — und damit auch die dazugehorige Pathophysiologie sind noch nicht vollstandig erforscht. Experimente an isolierten auseren Haarsinneszellen (AHZ) zeigen, das sie fahig sind, auf elektrische, akustische und chemische Reize mit einer Langenanderung ihres Zellkorpers zu antworten. Es wurde deshalb postuliert, das AHZ mechanische Energie in das Cortische Organ einspeisen konnen, dem passiven Widerstand in der Cochlea entgegenwirken und dadurch die auserordentlich hohe Frequenzselektivitat und Empfindlichkeit des Innenohres erzeugen und modulieren. Zu klaren ist jedoch noch, ob AHZ in situ im Cortischen Organ bei physiologisch relevanten Schallintensitaten Motilitat zeigen. Um diese Frage zu beantworten, haben wir an einem Felsenbeinpraparat die Bewegung zellularer Strukturen in der dritten und vierten Windung der Meerschweinchencochlea bei lufthaltigem Mittelohr untersucht.
Proceedings of the National Academy of Sciences of the United States of America, Apr 13, 1999
High-frequency resolution is one of the salient features of peripheral sound processing in the ma... more High-frequency resolution is one of the salient features of peripheral sound processing in the mammalian cochlea. The sensitivity originates in the active amplification of the travelling wave on the basilar membrane by the outer hair cells (OHCs), where electrically induced mechanical action of the OHC on a cycle-by-cycle basis is believed to be the crucial component. However, it is still unclear if this electromechanical action is sufficiently fast and can produce enough force to enhance mechanical tuning up to the highest frequencies perceived by mammals. Here we show that isolated OHCs in the microchamber configuration are able to overcome fluid forces with almost constant displacement amplitude and phase up to frequencies well above their place-frequency on the basilar membrane. The high-frequency limit of the electromotility, defined as the frequency at which the amplitude drops by 3 dB from its asymptotic low-frequency value, is inversely dependent on cell length. The frequency limit is at least 79 kHz. For frequencies up to 100 kHz, the electromotile response was specified by an overdamped (Q = 0.42) second-order resonant system. This finding suggests that the limiting factor for frequencies up to 100 kHz is not the speed of the motor but damping and inertia. The isometric force produced by the OHC was constant at least up to 50 kHz, with amplitudes as high as 53 pN/mV being observed. We conclude that the electromechanical transduction process of OHCs possesses the necessary high-frequency properties to enable amplification of the travelling wave over the entire hearing range.
Viele Untersuchungen im basalen Teil der Cochlea deuten darauf hin, das die auseren Haarsinneszel... more Viele Untersuchungen im basalen Teil der Cochlea deuten darauf hin, das die auseren Haarsinneszellen mit ihrer Fahigkeit zur aktiven, schnellen Langenanderung die Wanderwelle verstarken und verscharfen. Bisherige Untersuchungen konnten jedoch noch nicht klaren, ob durch die Kopplung des elektromechanischen und des mechanoelektrischen Transduktionsprozesses ausreichend Energie in die Wanderwelle eingespeist werden kann, um die bei Saugetieren nachgewiesenen, scharfen Abstimmkurven sowie die niedrigen Schwellen zu erklaren. Dazu haben wir Versuche an frischen Felsenbeinpraparaten des Meerschweinchens durchgefuhrt, die eine Annaherung an die In-vivo-Bedingungen der Mikromechanik der Cochlea erlauben.
Optical and Imaging Techniques for Biomonitoring, 1996
The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagno... more The use of spontaneous and evoked otacoustic emissions is now a standard clinical tool for diagnosis of the function of the inner ear. However, it is not possible to extract this information over the entire, functionally relevant frequency range because of imperfect coupling of: (1) stapedial to ear-drum vibrations through the ossicular chain of the middle ear and (2) ear-drum
Proceedings of the National Academy of Sciences, 1999
High-frequency resolution is one of the salient features of peripheral sound processing in the ma... more High-frequency resolution is one of the salient features of peripheral sound processing in the mammalian cochlea. The sensitivity originates in the active amplification of the travelling wave on the basilar membrane by the outer hair cells (OHCs), where electrically induced mechanical action of the OHC on a cycle-by-cycle basis is believed to be the crucial component. However, it is still unclear if this electromechanical action is sufficiently fast and can produce enough force to enhance mechanical tuning up to the highest frequencies perceived by mammals. Here we show that isolated OHCs in the microchamber configuration are able to overcome fluid forces with almost constant displacement amplitude and phase up to frequencies well above their place-frequency on the basilar membrane. The high-frequency limit of the electromotility, defined as the frequency at which the amplitude drops by 3 dB from its asymptotic low-frequency value, is inversely dependent on cell length. The frequenc...
Outer hair cells (OHC) were isolated from the apical two turns of the guinea-pig cochlea and thei... more Outer hair cells (OHC) were isolated from the apical two turns of the guinea-pig cochlea and their hair-bundle stimulated mechanically by a glass probe. In accordance with in vivo data (Dallos, 1985), the resting membrane potential was typically -64 mV (N = 200). The maximum amplitudes of the receptor potentials were between 0.4 and 5.2 mV peak-to-peak, with mean of 1.5 mV +/- 0.9 mV (N = 81). The sensitivity was 0.015 mV/nm or 2 mV/deg. The frequency response of the receptor potential followed a first order low-pass filter characteristic with a corner frequency of about 63 Hz. For frequencies up to at least 1.6 kHz, the frequency response of mechanoelectrical transduction was dominated by the electrical input impedance of the cell. The presence of a single time constant in the voltage response to stereociliary deflection implies that the frequency response of mechanoelectrical transduction far exceeds that of the electrical input impedance of the cell; its time constant must be faster than 100 microseconds. Under in vivo conditions, OHC should be capable of providing a sufficiently large receptor potential to supply enough energy for electromechanical feedback.
Proceedings of the National Academy of Sciences, 1996
The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of... more The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of the cochlea. In particular, it has been proposed that the tectorial membrane provides a second resonant system, in addition to that of the basilar membrane, which contributes to the amplification of the motion of the cochlear partition. Until now, technical difficulties had prevented vibration measurements of the tectorial membrane and, therefore, precluded direct evidence of a mechanical resonance. In the study reported here, the vibration of the tectorial membrane was measured in two orthogonal directions by using a novel method of combining laser interferometry with a photodiode technique. It is shown experimentally that the motion of the tectorial membrane is resonant at a frequency of 0.5 octave (oct) below the resonant frequency of the basilar membrane and polarized parallel to the reticular lamina. It is concluded that the resonant motion of the tectorial membrane is due to a par...
The Journal of the Acoustical Society of America, 1984
Measurements of group delay were made extracellularly from spiral ganglion cells in the 3.7 to 5.... more Measurements of group delay were made extracellularly from spiral ganglion cells in the 3.7 to 5.0-mm region of the guinea pig cochlea, using sinusoidally amplitude modulated tones with constant modulating frequency (100 Hz) and depth of modulation (0.19). Threshold cochlear tuning was accompanied by frequency-dependent group delays. The group delay on the low-frequency tail was independent of carrier frequency; the interunit variation was 0.28-1.28 ms. The difference in group delay between CF and the low-frequency tail decreased as the CF threshold increased (-0.09 +/- 0.02 ms per 10 dB, beginning at 0.62 +/- 0.07 ms at 0 dB SPL). The group delay decreased above CF; at the units' maximum frequency it was less than the low-frequency tail value, and was sometimes negative. Following arterial injections of furosemide the CF threshold increased and the group delay peak decreased; the low-frequency tail was unaffected. The group delay decreased with increasing intensity; the reduction near and above CF was not only larger than that on the low-frequency tail, but also the change at 5-10 dB above threshold was far greater than expected from the Q10dB of the suprathreshold iso-rate tuning curves. A minimum-phase analysis suggested that the group delay response above CF, together with its nonlinear behavior, can be accounted for by a high-frequency, level-independent, amplitude plateau, in combination with the single unit, amplitude nonlinearity which is known to exist above CF.
By deforming and making incisions in the basilar membrane (BM), von Békésy showed that the BM see... more By deforming and making incisions in the basilar membrane (BM), von Békésy showed that the BM seems to behave as a thin elastic plate, rather than as a membrane. However, it has never been shown whether a traveling wave could be sustained by a prestretched material in which the tension is insufficient to cause a visible retraction of the cut edges of an incision when viewed with a light microscope. We have shown that the necessary radial tension would decrease exponentially along the cochlea, from a value of 39 +/- 9 N/m at the base, with a space constant of 4.3 +/- 1.1 mm, for the guinea pig. This variable tension would be produced by a constant prestretching surface force of 2.4 +/- 0.1 X 10(6) N/m2, acting on the BM edges. Using values of Young's modulus in the radial direction, ranging from that of elastin to collagen, it is shown that this force would most likely cause a visible retraction of the cut edges of an incision. Therefore one must either conclude, once again, that the BM is effectively an unstretched material or question the original interpretation of the incision experiments.
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