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At least 19 recordsLinked to original sources
PubMed1990

Micro-architectures of the osseous spiral laminae and spiral limbus in the mouse cochlea: a scanning electron microscopic study on the morphological basis of the auditory mechanics.

The auditory mechanics in the cochlea are closely related to the structural variations along the cochlear duct. In this study, the auditory teeth of the spiral limbus and the primary and secondary osseous spiral laminae in the mouse were examined along the entire course of the cochlear spiral by scanning electron microscopy (SEM) after removing the cochlear duct epithelium or the organic material with chemical maceration methods. The cochlear canal consisted of a hook and a spiral of one and half turns and the three-dimensional images and surface structures of the connective tissue forming the spiral limbus including the auditory teeth and the osseous spiral laminae are well demonstrated; the widths of the primary and secondary laminae, the spiral fissure between the two laminae, the tympanic lip, and the vestibular lip with the auditory teeth were measured, and the population density of the auditory teeth were determined in the hook and every half turn. The findings suggest that, in the cochlea the width of the basilar membrane increases in the hook and is almost constant in the spiral portion, the amount of fibers in the basilar membrane linearly decreases from the base to the apex, the displacement mode of the pillar cells during basilar membrane vibrations differs between the apical region lacking the bony edge of the tympanic lip and the other regions with bony edge, the connective tissue fibers from the auditory teeth are inserted to the bone surface of the primary lamina to support the teeth, the teeth on the marginal side of the vestibular lip maintain the stability of the tectorial membrane which is vibrating together with the basilar membrane in response to high frequency sounds on the basal side of the cochlear duct and low frequencies on the apical side, and the interdental cells on the Reissner membrane side maintain the size of the tectorial membrane which shows a linear increase in size from the base to the apex of the cochlear duct.

Animals↗
PubMed1986

The vascular anatomy of the spiral lamina and the spiral limbus in the adult rat. A scanning electron microscope study of corrosion cast preparations.

A scanning electron microscope (SEM) study of corrosion cast preparations of the vessels of the spiral lamina and the spiral limbus was carried out in adult rats. This method confirms present knowledge of the modiolar vascularization and also shows its distribution in a three-dimensional model. As a result of this technique we have been able to demonstrate the modiolar vascular supply of the organ of Corti at different levels.

Animals↗
PubMed1992

Microstructures of the osseous spiral laminae in the bat cochlea: a scanning electron microscopic study.

The architecture and surface structures of the primary and secondary osseous spiral laminae in the cochlea of the bat, an animal able to hear high frequency sounds, were examined by scanning electron microscopy to understand the micromechanical adaptations of the bony supportive elements in the inner ear to the specific hearing function. The bat used was Myotis frater kaguyae. The myotis bat cochlea was seen to consist of a hook and a spiral portion with one and three-quarter turns and was characterized by: 1) a distinct ridge-like projection running spirally along the middle line on the vestibular leaf of the primary osseous spiral lamina; 2) a wide secondary osseous spiral lamina; and 3) a narrow spiral fissure between the primary and secondary osseous spiral laminae. The ridge on the primary osseous spiral lamina was 150 microns high in the hook and basal turn, then lowered toward apex, and flattened before the apical end. The surface structures appeared to provide a firm anchorage of the auditory teeth. The secondary osseous spiral lamina, which anchors the fibers of the basilar membrane, was sharply projected and measured 150 microns in width in the hook, and then narrowed gradually toward apex to disappear in the helicotrema. The spiral fissure for the basilar membrane was about 40 microns in width in the hook and about 120 microns in the apical turn. The findings suggest the presence of a narrow and rigid basilar membrane with a high amount of fibers and a strong bony support to the auditory teeth for scaffolding the tectorial membrane during intense vibration in response to high frequency sounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Superposition of binaural influences on single neuron activity in the medial superior olive elicited by electrical stimulation of the osseous spiral laminae.

The single unit response of medial superior olive (accessory nucleus) neurons was investigated, when elicited by electrical stimulation of nervous processes in the osseous spiral laminae in both cochleae and also by antidromic stimulation from the inferior colliculi. The osseous spiral laminae were stimulated at the first, second or third turns with grounding of one of the unstimulated turns. Time of signal arrival differences (delta tau) at the two cochleae and also intensity differences (deltai) were varied. (2) It is concluded that (A) binaural interaction in the MSO is not based on totally excitatory or inhibitory influences from either ear, but on cycles of excitation and inhibition; (B) these influences approximately obey the laws of superposition, i.e., the influences add linearly to determine discharge. (3) It is demonstrated that: (a) electrical stimulation, unlike acoustical stimulation, elicits a regular neural response; (b) the neural response functions elicited by changes in delta tau are deltai exhibit maxima and minima and are not smooth functions; (c) fine latency changes in the neural response are correlated with changes in delta tau and deltai; (d) the stimulation of different turns of the osseous spiral laminae (producing different current flows) elicits a different neural response depending on the turn stimulated, an effect reflecting the anatomical tonotopic arrangement of the medial superior olive; (e) changes in the stimulus differences delta tau and deltai are correlated with the ratio of the spike count in a short period following the stimulus, to the spike count in a longer total period; (f) changes in the stimulus differences delta tau and deltai elicit a neural response which varies according to the turn stimulated.

Animals↗
PubMedDate not supplied

Cochlear communication routes in the guinea pig--spiral ganglia and osseous spiral laminae: an electron microscope study using microsphere tracers.

The microscopic and ultrastructural anatomy of the spiral ganglia and osseous spiral laminae (OSL) of the guinea pig were studied using the transmission and scanning electron microscopes. The nerve and vascular elements within the spiral ganglia and OSL are surrounded by distinct perineural and perivascular spaces maintained by a loose meshwork of cells and connective tissue fibers. The connective tissue cells are fibers within the OSL and spiral ganglia are distinctly different from the arachnoid-like reticular cells and elastin fibers of the modiolus described in an earlier study. The present experiment demonstrates a pathway between the perineural spaces of the modiolus, spiral ganglia, and OSL. The perineural spaces of the modiolus were previously shown to communicate with the subarachnoid space; therefore, perineural communication from the cerebrospinal fluid to the perilymph via this route is likely. Using mircosphere tracers injected intrathecally, this communication route between the subarachnoid space and scala tympani was further defined. The tracer experiment suggests that the perineural spaces within the internal acoustic meatus, modiolus, spiral ganglia, and OSL are normally patent and do not represent artifacts induced during tissue processing.

Animals↗
PubMed2003

Basilar membrane and osseous spiral lamina motion in human cadavers with air and bone conduction stimuli.

It is generally accepted that bone conduction (BC) stimuli yield a traveling wave on the basilar membrane (BM) and hence stimulate the cochlea by the same mechanisms as normal air conduction (AC). The basis for this is the ability to cancel or mask a BC tone with an AC tone and the ability to generate two tone distortion products with a BC tone and an AC tone. The hypothesis is proposed that BC stimulates the BM not only through the hydrodynamics of the scala vestibuli and scala tympani, but also through osseous spiral lamina (OSL) vibrations. To test this hypothesis the BM and OSL response with AC as well as BC stimulation was measured with a laser Doppler vibrometer. Human temporal bones mounted on a shaker were used to record the velocities of the bone per se, the BM and the OSL. The measurements were then converted to relative BM and OSL velocities. The results from the basal turn of the cochlea show similar behavior with AC and BC stimulation. The motion of the OSL at the edge where it connects to the BM is in phase and is typically 6 dB lower than the BM motion. With BC stimulation, there is less phase accumulation in the OSL after the cochlea is drained; the OSL moves due to inertial forces and resonates at approximately 7 kHz. Inertial vibration of the OSL may partially contribute to the total response of BC sound, especially at the high frequencies, although current models of the cochlea assume a rigid OSL. The measurements reported here can be used to include a flexible OSL in cochlear models.

Acoustic Stimulation↗
PubMed2006

Presbycusic neuritic degeneration within the osseous spiral lamina.

OBJECTIVE: To describe a neglected anatomic variant occurring with presbycusis. STUDY DESIGN: Retrospective temporal bone histopathology study. METHODS: Quantitative analysis of peripheral hair cells, neurites, neurons, and the stria vascularis in temporal bones from individuals who had presbycusis. Fifty-three patients aged 65 years or older and with a down-sloping audiogram and clinical diagnosis of presbycusis were reviewed. Nine cases had normal hair and ganglion cell populations but reduced peripheral processes (neuritic presbycusis). These were compared with five normal-hearing controls on measurements of anterior middle and basal turn fiber bundle diameter and the ratio of basal to middle diameters. RESULTS: Thresholds at 4 and 8 kHz were significantly poorer in the neuritic presbycusis group than in the control group (p<or=0.004 and 0.05, respectively), as was speech discrimination score (p<or=0.028). The ratio of basal to middle turn diameters was significantly smaller in the neuritic presbycusis group (p<or=0.003). This effect was quite marked in that there was no overlap in ratios between the groups, with the maximum neuritic presbycusis group ratio smaller than the minimum control group ratio. There was a moderate negative correlation between ratio and threshold at 4 kHz (sigma=-0.49, p<or=0.075). CONCLUSION: Loss of peripheral neurites in the anterior basal cochlear segment is found in conjunction with presbycusis in temporal bones that have no other morphologic abnormalities. These cases can be identified by a gradual down-sloping audiogram in contrast to sensory (hair cell) presbycusis, which is characterized by a precipitous high tone loss.

Aged↗
PubMed1994

Imaging the cochlea by magnetic resonance microscopy.

The isolated, fixed cochlea of the mustached bat was studied with three dimensional magnetic resonance (MR) microscopy. The cochlea of this animal is about 4 mm in diameter and its entire volume was imaged. With the field of view and matrix size used, the volume elements (voxels) making up the volume data set were isotropic 25 x 25 x 25 micron cubes. Three dimensional (3D) MR microscopy based on isotropic voxels has many advantages over commonly used light microscopy: 1) it is non destructive; 2) it is much less time consuming; 3) no dehydration is required and shrinkage is minimized; 4) the data set can be used to create sections in any desired plane; 5) the proper alignment of sections is inherent in the 3D acquisition so that no reference points are required; 6) the entire data set can be viewed from any point of view in a volume rendered image; 7) the data is digital and features can be enhanced by computer image processing; and 8) the isotropic dimensions of the voxels make the data well-suited for structural reconstructions and measurements. Good images of the osseous spiral lamina, spiral ligament, scala tympani, scala vestibuli, and nerve bundles were obtained. The vestibular (Reissner's) membrane was easily identified in the mustached bat and it appears to bulge into the scala vestibuli. The visibility of this structure suggests that MR microscopy would be well-suited for studies of endolymphatic hydrops.

Animals↗
PubMed1989

Analysis of the human auditory nerve.

In human temporal bones of patients with normal hearing or sensory neural deafness, the cochlear neurons were quantitatively and qualitatively evaluated at the level of the osseous spiral lamina, the spiral ganglion and the cochlear nerve. We found from 32,000 to 31,000 myelinated nerve fibres in the cochlear nerve of normal hearing individuals and any lower number in cases of sensory neural deafness. There was in general a good correspondence between the counted numbers of the myelinated nerve fibres in the osseous spiral lamina, the spiral ganglion cells and the myelinated nerve fibres in the cochlear nerve in the inner acoustic meatus. The diameter of the peripheral axons of the type I neurons are about half the diameter of the central axons. The average diameter of the central axons is 2.5 millimicrons with a narrow distribution in children, but an increasingly larger range of fiber calibers with increasing age (0.5 to 7 microns in the 40 to 50 year age group adults).

Adult↗
PubMed1989

Microanatomy of the mouse osseous cochlea: a scanning electron microscopic study.

This is the first scanning electron microscopic demonstration of the three-dimensional architecture and detailed surface structures of the entire osseous labyrinth of the cochlea. Mouse cochleae were observed after dissolving the soft tissues with KOH and NaOCl solutions. The precise shapes, surface structures, and orientations of the primary osseous spiral lamina and secondary osseous spiral lamina in the cochlea were observed along their entire course from the hook at the base to the helicotrema at the apex. The primary osseous spiral lamina showed three half turns after the hook; the lengths of the hook and each half turn and the slope angle of the spiral were obtained. The widths of the primary and secondary spiral laminae and the spiral fissure for the basilar membrane between the free edges of the two spiral laminae were measured along the course of the cochlear duct. The surface of the lateral wall under the stria vascularis was also viewed. Scanning electron microscopy can provide more precise microanatomical data than has been previously available for the osseous cochlea, giving a better understanding of hearing mechanisms with regard to the width, support, and movement of the basilar membrane and the functions of various components of the cochlea.

Animals↗