scholarly journals Frequency selectivity of hair cells and nerve fibres in the alligator lizard cochlea.

1983 ◽  
Vol 345 (1) ◽  
pp. 241-260 ◽  
Author(s):  
T Holton ◽  
T F Weiss
Keyword(s):  
Hair Cells ◽  
Frequency Selectivity ◽  
Nerve Fibres ◽  
Alligator Lizard

Extracellular Receptor Potentials from the Lateral-Line Organ of Xenopus Laevis

1980 ◽  
Vol 86 (1) ◽  
pp. 63-77
Author(s):  
ALFONS B. A. KROESE ◽  
JOHAN M. VAN DER ZALM ◽  
JOEP VAN DEN BERCKEN
Keyword(s):  
Xenopus Laevis ◽  
Lateral Line ◽  
Hair Cells ◽  
Water Displacement ◽  
Stimulus Amplitude ◽  
Nerve Fibres ◽  
Large Stimulus ◽  
Sensory Hair ◽  
Lateral Line Organ ◽  
Line Organ

1. The response of the epidermal lateral-line organ of Xenopus laevis to stimulation was studied by recording extracellular receptor potentials from the hair cells in single neuromasts in isolated preparations. One neuromast was stimulated by local, sinusoidal water movements induced by a glass sphere positioned at a short distance from the neuromast. 2. The amplitudes of the extracellular receptor potentials were proportional to the stimulus amplitude over a range of 20 dB. The phase of the extracellular receptor potentials with respect to water displacement was independent of the stimulus amplitude. 3. With large stimulus amplitude, and stimulus frequencies between 0.5 Hz and 2 Hz, the extracellular receptor potentials, and responses of single afferent nerve fibres, showed a phase lead of 1.2 π radians with respect to water displacement, i.e. they were almost in phase with water acceleration. 4. It is concluded that under conditions of stimulation with small-amplitude water movements, the hair cells respond to sensory hair displacement, whereas under conditions of stimulation with large-amplitude water movements they respond to sensory hair velocity.

Cochlear implantation in a case of Wegener's granulomatosis

1996 ◽  
Vol 110 (10) ◽  
pp. 958-961 ◽  
Author(s):  
K. A. Abou-Elhmd ◽  
M. R. Hawthorne ◽  
L. M. Flood
Keyword(s):  
Hair Cells ◽  
Cochlear Implantation ◽  
Wegener’S Granulomatosis ◽  
Free Field ◽  
Wegener's Granulomatosis ◽  
Nerve Fibres ◽  
Immune Disease ◽  
Cochlear Hair Cells ◽  
Male Predominance ◽  
Speech Test

AbstractCochlear implantation is now a routine clinical procedure for deaf patients in many countries (Gibson, 1987). It replaces the function of damaged cochlear hair cells and, therefore, detects sound and by electrical stimulation produces an appropriate signal in the remaining cochlear nerve fibres (House and Berliner, 1991). Wegener's granulomatosis is an uncommon auto-immune disease. It has a peak incidence at the fifth decade with slight male predominance. Nasal problems are the predominant presentation with otological manifestations presenting rarely. We report a case of Wegener's granulomatosis presenting with total hearing loss and after right cochlear implantation a free field threshold of 40 dB and 20 per cent Bamford-Kowal-Bench (BKB) speech test.We conclude that Wegener's granulomatosis is not an absolute contraindication for cochlear implantation.

Connections between stereocilia in auditory hair cells of the alligator lizard

1987 ◽  
Vol 30 (2-3) ◽  
pp. 147-155 ◽  
Author(s):  
Seema R. Csukas ◽  
Thomas H. Rosenquist ◽  
Michael J. Mulroy
Keyword(s):  
Hair Cells ◽  
Auditory Hair Cells ◽  
Alligator Lizard

scholarly journals Static length changes of cochlear outer hair cells can tune low-frequency hearing

2017 ◽  
Author(s):  
Nikola Ciganović ◽  
Rebecca L. Warren ◽  
Batu Keçeli ◽  
Stefan Jacob ◽  
Anders Fridberger ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Frequency Selectivity ◽  
Apical Region ◽  
Low Frequencies ◽  
Inner Hair Cells ◽  
Length Changes ◽  
The Brain

AbstractThe cochlea not only transduces sound-induced vibration into neural spikes, it also amplifies weak sound to boost its detection. Actuators of this active process are sensory outer hair cells in the organ of Corti, whereas the inner hair cells transduce the resulting motion into electric signals that propagate via the auditory nerve to the brain. However, how the outer hair cells modulate the stimulus to the inner hair cells remains unclear. Here, we combine theoretical modeling and experimental measurements near the cochlear apex to study the way in which length changes of the outer hair cells deform the organ of Corti. We develop a geometry-based kinematic model of the apical organ of Corti that reproduces salient, yet counter-intuitive features of the organ’s motion. Our analysis further uncovers a mechanism by which a static length change of the outer hair cells can sensitively tune the signal transmitted to the sensory inner hair cells. When the outer hair cells are in an elongated state, stimulation of inner hair cells is largely inhibited, whereas outer hair cell contraction leads to a substantial enhancement of sound-evoked motion near the hair bundles. This novel mechanism for regulating the sensitivity of the hearing organ applies to the low frequencies that are most important for the perception of speech and music. We suggest that the proposed mechanism might underlie frequency discrimination at low auditory frequencies, as well as our ability to selectively attend auditory signals in noisy surroundings.Author summaryOuter hair cells are highly specialized force producers inside the inner ear: they can change length when stimulated electrically. However, how exactly this electromotile effect contributes to the astonishing sensitivity and frequency selectivity of the inner ear has remained unclear. Here we show for the first time that static length changes of outer hair cells can sensitively regulate how much of a sound signal is passed on to the inner hair cells that forward the signal to the brain. Our analysis holds for the apical region of the inner ear that is responsible for detecting the low frequencies that matter most in speech and music. This shows a mechanisms for how frequency-selectivity can be achieved at low frequencies. It also opens a path for the efferent neural system to regulate hearing sensitivity.

scholarly journals The organization of actin filaments in the stereocilia of cochlear hair cells.

1980 ◽  
Vol 86 (1) ◽  
pp. 244-259 ◽  
Author(s):  
L G Tilney ◽  
D J Derosier ◽  
M J Mulroy
Keyword(s):  
Hair Cells ◽  
Actin Filaments ◽  
Optical Diffraction ◽  
Careful Examination ◽  
Intestinal Epithelial ◽  
Cochlear Hair Cells ◽  
Cuticular Plate ◽  
Detergent Extraction ◽  
Alligator Lizard ◽  
Paracrystalline Array

Within each tapering stereocilium of the cochlea of the alligator lizard is a bundle of actin filaments with > 3,000 filaments near the tip and only 18-29 filaments at the base where the bundle enters into the cuticular plate; there the filaments splay out as if on the surface of a cone, forming the rootlet. Decoration of the hair cells with subfragment 1 of myosin reveals that all the filaments in the stereocilia, including those that extend into the cuticular plate forming the rootlet, have unidirectional polarity, with the arrowheads pointing towards the cell center. The rest of the cuticular plate is composed of actin filaments that show random polarity, and numerous fine, 30 A filaments that connect the rootlet filaments to each other, to the cuticular plate, and to the membrane. A careful examination of the packing of the actin filaments in the stereocilia by thin sectin and by optical diffraction reveals that the filaments are packed in a paracrystalline array with the crossover points of all the actin helices in hear-perfect register. In transverse sections, the actin filaments are not hexagonally packed but, rather, are arranged in scalloped rows that present a festooned profile. We demonstrated that this profile is a product of the crossbridges by examining serial sections, sections of different thicknesses, and the same stereocilium at two different cutting angles. The filament packing is not altered by fixation in different media, removal of the limiting membrane by detergent extraction, or incubation of extracted hair cells in EGTA, EDTA, and Ca++ and ATP. From our results, we conclude that the stereocilia of the ear, unlike the brush border of intestinal epithelial cells, are not designed to shorten, nor do the filaments appear to slide past one another. In fact, the stereocilium is like a large, rigid structure designed to move as a lever.

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