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Fast Waves at the Base of the Cochlea.

Recio-Spinoso A, Rhode WS - PLoS ONE (2015)

Bottom Line: He noticed that the speed of signal propagation along the cochlea is slow when compared with the speed of sound in water.A similar conclusion is reached by analyzing onset times of time-domain gain functions, which correspond to BM click responses normalized by middle-ear input.Our results suggest that BM responses to clicks arise from a combination of fast and slow traveling waves.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigación en Discapacidades Neurológicas, Universidad de Castilla-La Mancha, Albacete, Spain.

ABSTRACT
Georg von Békésy observed that the onset times of responses to brief-duration stimuli vary as a function of distance from the stapes, with basal regions starting to move earlier than apical ones. He noticed that the speed of signal propagation along the cochlea is slow when compared with the speed of sound in water. Fast traveling waves have been recorded in the cochlea, but their existence is interpreted as the result of an experiment artifact. Accounts of the timing of vibration onsets at the base of the cochlea generally agree with Békésy's results. Some authors, however, have argued that the measured delays are too short for consistency with Békésy's theory. To investigate the speed of the traveling wave at the base of the cochlea, we analyzed basilar membrane (BM) responses to clicks recorded at several locations in the base of the chinchilla cochlea. The initial component of the BM response matches remarkably well the initial component of the stapes response, after a 4-μs delay of the latter. A similar conclusion is reached by analyzing onset times of time-domain gain functions, which correspond to BM click responses normalized by middle-ear input. Our results suggest that BM responses to clicks arise from a combination of fast and slow traveling waves.

No MeSH data available.


Gain function without frequency plateau.Panel (A) displays the original gain function (red lines) and the modified version (black lines) of the original waveform (see main text). The inset in panel (A) shows the onset of both gain functions. Modification of the original phase function was achieved by replacing the plateau with phase values having a group delay of 1.08 ms (black line in (B)). Original amplitude plateaus (red line in inset in (A)) were replaced with values that decrease at a slope of -51 dB per octave.
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pone.0129556.g006: Gain function without frequency plateau.Panel (A) displays the original gain function (red lines) and the modified version (black lines) of the original waveform (see main text). The inset in panel (A) shows the onset of both gain functions. Modification of the original phase function was achieved by replacing the plateau with phase values having a group delay of 1.08 ms (black line in (B)). Original amplitude plateaus (red line in inset in (A)) were replaced with values that decrease at a slope of -51 dB per octave.

Mentions: Fig 6A (red line) shows a gain function, which was previously displayed in Fig 4A and 4B, along with a plot of its onset (red line in the inset). Phase and amplitude functions—obtained using the Fourier transform function fft() in MATLAB—are respectively shown in the main panel in Fig 6B and its inset (red lines). Amplitude and phase plateaus are evident in the results in Fig 6B (red lines) for frequencies much higher than CF (i.e., > 9–10 kHz). The other waveform in Fig 6A, which is depicted with a black line, represents the impulse response of a filter whose amplitude and phase functions are shown using black lines in Fig 6B. We conclude that removing the amplitude and phase plateaus from the frequency representation and replacing them with new values, as depicted by the black lines in Fig 6B and its inset, has little effect on the resulting gain function (black lines in Fig 6A and the inset).


Fast Waves at the Base of the Cochlea.

Recio-Spinoso A, Rhode WS - PLoS ONE (2015)

Gain function without frequency plateau.Panel (A) displays the original gain function (red lines) and the modified version (black lines) of the original waveform (see main text). The inset in panel (A) shows the onset of both gain functions. Modification of the original phase function was achieved by replacing the plateau with phase values having a group delay of 1.08 ms (black line in (B)). Original amplitude plateaus (red line in inset in (A)) were replaced with values that decrease at a slope of -51 dB per octave.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4465671&req=5

pone.0129556.g006: Gain function without frequency plateau.Panel (A) displays the original gain function (red lines) and the modified version (black lines) of the original waveform (see main text). The inset in panel (A) shows the onset of both gain functions. Modification of the original phase function was achieved by replacing the plateau with phase values having a group delay of 1.08 ms (black line in (B)). Original amplitude plateaus (red line in inset in (A)) were replaced with values that decrease at a slope of -51 dB per octave.
Mentions: Fig 6A (red line) shows a gain function, which was previously displayed in Fig 4A and 4B, along with a plot of its onset (red line in the inset). Phase and amplitude functions—obtained using the Fourier transform function fft() in MATLAB—are respectively shown in the main panel in Fig 6B and its inset (red lines). Amplitude and phase plateaus are evident in the results in Fig 6B (red lines) for frequencies much higher than CF (i.e., > 9–10 kHz). The other waveform in Fig 6A, which is depicted with a black line, represents the impulse response of a filter whose amplitude and phase functions are shown using black lines in Fig 6B. We conclude that removing the amplitude and phase plateaus from the frequency representation and replacing them with new values, as depicted by the black lines in Fig 6B and its inset, has little effect on the resulting gain function (black lines in Fig 6A and the inset).

Bottom Line: He noticed that the speed of signal propagation along the cochlea is slow when compared with the speed of sound in water.A similar conclusion is reached by analyzing onset times of time-domain gain functions, which correspond to BM click responses normalized by middle-ear input.Our results suggest that BM responses to clicks arise from a combination of fast and slow traveling waves.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigación en Discapacidades Neurológicas, Universidad de Castilla-La Mancha, Albacete, Spain.

ABSTRACT
Georg von Békésy observed that the onset times of responses to brief-duration stimuli vary as a function of distance from the stapes, with basal regions starting to move earlier than apical ones. He noticed that the speed of signal propagation along the cochlea is slow when compared with the speed of sound in water. Fast traveling waves have been recorded in the cochlea, but their existence is interpreted as the result of an experiment artifact. Accounts of the timing of vibration onsets at the base of the cochlea generally agree with Békésy's results. Some authors, however, have argued that the measured delays are too short for consistency with Békésy's theory. To investigate the speed of the traveling wave at the base of the cochlea, we analyzed basilar membrane (BM) responses to clicks recorded at several locations in the base of the chinchilla cochlea. The initial component of the BM response matches remarkably well the initial component of the stapes response, after a 4-μs delay of the latter. A similar conclusion is reached by analyzing onset times of time-domain gain functions, which correspond to BM click responses normalized by middle-ear input. Our results suggest that BM responses to clicks arise from a combination of fast and slow traveling waves.

No MeSH data available.