scholarly journals The cochlear amplifier as a standing wave: “Squirting” waves between rows of outer hair cells?

2004 ◽  
Vol 116 (2) ◽  
pp. 1016-1024 ◽  
Author(s):  
Andrew Bell ◽  
Neville H. Fletcher
Keyword(s):  
Standing Wave ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Cochlear Amplifier

scholarly journals Limiting Frequency of the Cochlear Amplifier Based on Electromotility of Outer Hair Cells

2003 ◽  
Vol 84 (2) ◽  
pp. 739-749 ◽  
Author(s):  
Mark Ospeck ◽  
Xiao-xia Dong ◽  
Kuni H. Iwasa
Keyword(s):  
Hair Cells ◽  
Outer Hair Cells ◽  
Cochlear Amplifier

THE COCHLEAR AMPLIFIER: IS IT HAIR BUNDLE MOTION OF OUTER HAIR CELLS?

2006 ◽  
Author(s):  
SHUPING JIA ◽  
JIAN ZUO ◽  
PETER DALLOS ◽  
DAVID Z. Z. HE
Keyword(s):  
Hair Cells ◽  
Outer Hair Cells ◽  
Hair Bundle ◽  
Cochlear Amplifier

scholarly journals Single-unit labeling of medial olivocochlear neurons: the cochlear frequency map for efferent axons

2014 ◽  
Vol 111 (11) ◽  
pp. 2177-2186 ◽  
Author(s):  
M. Christian Brown
Keyword(s):  
Hair Cells ◽  
Single Unit ◽  
Dynamic Range ◽  
Organ Of Corti ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Cochlear Amplifier ◽  
Noise Masking ◽  
Efferent Neurons ◽  
Medial Olivocochlear

Medial olivocochlear (MOC) neurons are efferent neurons that project axons from the brain to the cochlea. Their action on outer hair cells reduces the gain of the “cochlear amplifier,” which shifts the dynamic range of hearing and reduces the effects of noise masking. The MOC effects in one ear can be elicited by sound in that ipsilateral ear or by sound in the contralateral ear. To study how MOC neurons project onto the cochlea to mediate these effects, single-unit labeling in guinea pigs was used to study the mapping of MOC neurons for neurons responsive to ipsilateral sound vs. those responsive to contralateral sound. MOC neurons were sharply tuned to sound frequency with a well-defined characteristic frequency (CF). However, their labeled termination spans in the organ of Corti ranged from narrow to broad, innervating between 14 and 69 outer hair cells per axon in a “patchy” pattern. For units responsive to ipsilateral sound, the midpoint of innervation was mapped according to CF in a relationship generally similar to, but with more variability than, that of auditory-nerve fibers. Thus, based on CF mappings, most of the MOC terminations miss outer hair cells involved in the cochlear amplifier for their CF, which are located more basally. Compared with ipsilaterally responsive neurons, contralaterally responsive neurons had an apical offset in termination and a larger span of innervation (an average of 10.41% cochlear distance), suggesting that when contralateral sound activates the MOC reflex, the actions are different than those for ipsilateral sound.

High-frequency motility of outer hair cells and the cochlear amplifier

Science ◽  
1995 ◽  
Vol 267 (5206) ◽  
pp. 2006-2009 ◽  
Author(s):  
P Dallos ◽  
B. Evans
Keyword(s):  
Hair Cells ◽  
High Frequency ◽  
Outer Hair Cells ◽  
Cochlear Amplifier

Evidence for an Active Process and a Cochlear Amplifier in Nonmammals

2001 ◽  
Vol 86 (2) ◽  
pp. 541-549 ◽  
Author(s):  
Geoffrey A. Manley
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Lateral Line System ◽  
Cochlear Amplifier ◽  
Fluid Viscosity ◽  
Active Process ◽  
Line System ◽  
Active Processes

The last two decades have produced a great deal of evidence that in the mammalian organ of Corti outer hair cells undergo active shape changes that are part of a “cochlear amplifier” mechanism that increases sensitivity and frequency selectivity of the hearing epithelium. However, many signs of active processes have also been found in nonmammals, raising the question as to the ancestry and commonality of these mechanisms. Active movements would be advantageous in all kinds of sensory hair cells because they help signal detection at levels near those of thermal noise and also help to overcome fluid viscosity. Such active mechanisms therefore presumably arose in the earliest kinds of hair cells that were part of the lateral line system of fish. These cells were embedded in a firm epithelium and responded to relative motion between the hair bundle and the hair cell, making it highly likely that the first active motor mechanism was localized in the hair-cell bundle. In terrestrial nonmammals, there are many auditory phenomena that are best explained by the presence of a cochlear amplifier, indicating that in this respect the mammalian ear is not unique. The latest evidence supports siting the active process in nonmammals in the hair-cell bundle and in intimate association with the transduction process.

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