scholarly journals Prediction of Click Responses of Cochlear Nerve Fibers from Responses to Sinusoidal Stimuli

1974 ◽  
Vol 55 (2) ◽  
pp. 467-467
Author(s):  
Warren M. Little‐Field ◽  
Russell R. Pfeiffer ◽  
Charles E. Molnar
Keyword(s):  
Nerve Fibers ◽  
Cochlear Nerve

The response of the cochlear nerve fibers to ultrasonic sounds in rats

1985 ◽  
Vol 1 ◽  
pp. S2
Author(s):  
Zheng Chang-Mu ◽  
Susumu Ito ◽  
Junsei Horikawa ◽  
Keiichi Murata
Keyword(s):  
Nerve Fibers ◽  
Cochlear Nerve

Histologic Findings in Two Very Small Intracanalicular Solitary Schwannomas of the Eighth Nerve

1986 ◽  
Vol 95 (5) ◽  
pp. 460-465 ◽  
Author(s):  
J. Gail Neely ◽  
Jack Hough
Keyword(s):  
Nerve Fiber ◽  
Longitudinal Direction ◽  
Nerve Fibers ◽  
Vestibular Nerve ◽  
Cochlear Nerve ◽  
The Other ◽  
En Bloc ◽  
Hearing Conservation ◽  
Eighth Nerve ◽  
Conservation Surgery

Two very small intracanalicular tumors, resected en bloc with the complete eighth nerve, were serially sectioned in order to study the relationship between the tumors and the nerves of origin. Both cases met the size criteria for hearing conservation surgery; however, the patient with the smaller tumor and the better hearing had no recognizable cochlear nerve fibers passing the tumor. The cochlear nerve in the patient with poorer hearing was completely free of tumor. The tumor with the infiltrated cochlear nerve seemed to originate from the inferior vestibular nerve. The other tumor seemed to arise from the superior vestibular nerve. Proximally, the tumors occupied a more central location in the involved nerves, but they abruptly became eccentric and exophytic as they proceeded laterally. Nerve fibers remaining about the tumors were displaced to the periphery. These nerve fiber aggregates became quite thin and attenuated, frequently separating into smaller aggregates which, ultimately, were incorporated into the tumors. As fibers came closer to the tumors, they tended to change from their longitudinal direction toward a more circumferential orientation about the surface of the tumors. The tumor-nerve fiber interfaces were quite variable throughout the course of the tumor, ranging from large aggregates of nerve fibers distinctly separate from the tumors to aggregates separate but tightly applied to the tumors without a tissue plane between, to aggregates partially incorporated within the periphery of the tumors, to aggregates completely incorporated into the periphery of the tumors. Frequently several types of interfaces were seen in the same section. These findings showed that in one case the cochlear nerve could have been surgically separated from the acoustic tumor; in the other specimen, it could not have been separated. It was impossible to predict between the two. In these two very small tumors, the gross specimen observation correlated reasonably well with the histology, thus suggesting that intraoperative observation may be a predictor in hearing conservation surgery; however, previous studies in slightly larger tumors make this an extremely guarded concept.

scholarly journals Golgi Stains of the Cochlear Nerve Fibers

1973 ◽  
Vol 54 (1) ◽  
pp. 283-284 ◽  
Author(s):  
Catherine A. Smith ◽  
Betty J. Haglan
Keyword(s):  
Nerve Fibers ◽  
Cochlear Nerve

Histological considerations of the cleavage plane for preservation of facial and cochlear nerve functions in vestibular schwannoma surgery

2009 ◽  
Vol 110 (4) ◽  
pp. 648-655 ◽  
Author(s):  
Tomio Sasaki ◽  
Tadahisa Shono ◽  
Kimiaki Hashiguchi ◽  
Fumiaki Yoshida ◽  
Satoshi O. Suzuki
Keyword(s):  
Connective Tissue ◽  
Basic Protein ◽  
Cleavage Plane ◽  
Nerve Fibers ◽  
Vestibular Nerve ◽  
Cochlear Nerve ◽  
Tissue Layer ◽  
Connective Tissue Layer ◽  
Tumor Capsule ◽  
Tumor Parenchyma

Object The authors analyzed the tumor capsule and the tumor–nerve interface in vestibular schwannomas (VSs) to define the ideal cleavage plane for maximal tumor removal with preservation of facial and cochlear nerve functions. Methods Surgical specimens from 21 unilateral VSs were studied using classical H & E, Masson trichrome, and immunohistochemical staining against myelin basic protein. Results The authors observed a continuous thin connective tissue layer enveloping the surfaces of the tumors. Some nerve fibers, which were immunopositive to myelin basic protein and considered to be remnants of vestibular nerve fibers, were also identified widely beneath the connective tissue layer. These findings indicated that the socalled “tumor capsule” in VSs is the residual vestibular nerve tissue itself, consisting of the perineurium and underlying nerve fibers. There was no structure bordering the tumor parenchyma and the vestibular nerve fibers. In specimens of tumors removed en bloc with the cochlear nerves, the authors found that the connective tissue layer, corresponding to the perineurium of the cochlear nerve, clearly bordered the nerve fibers and tumor tissue. Conclusions Based on these histological observations, complete tumor resection can be achieved by removal of both tumor parenchyma and tumor capsule when a clear border between the tumor capsule and facial or cochlear nerve fibers can be identified intraoperatively. Conversely, when a severe adhesion between the tumor and facial or cochlear nerve fibers is observed, dissection of the vestibular nerve–tumor interface (the subcapsular or subperineurial dissection) is recommended for preservation of the functions of these cranial nerves.

scholarly journals Synaptic events and discharge patterns of cochlear nucleus cells. II. Frequency-modulated tones

1976 ◽  
Vol 39 (1) ◽  
pp. 179-194 ◽  
Author(s):  
R. Britt ◽  
A. Starr
Keyword(s):  
Cochlear Nucleus ◽  
Tone Burst ◽  
Nerve Fibers ◽  
Cochlear Nerve ◽  
Response Patterns ◽  
Eighth Nerve ◽  
Rate Dependent ◽  
Fm Signals ◽  
Symmetry Factor ◽  
Modulation Rate

Responses of 99 cochlear nucleus cells and 24 cochlear nerve fibers were studied with FM signals; 14 cochlear nerve fibers and 57 cochlear nucleus cells were studied at four rates of modulation and several signal intensities. Classification of FM response patterns as symmetrical, asymmetrical, or unidirectional was based on the calculation of a symmetry factor (S), which compared the number of discharges evoked by the ascending and by the descending phases of the FM sweep. Certain FM response patterns could not adequately be described by the symmetry factor along and variables of modulation rate and signal intensity had significant influence. A correspondence was found between the four response classes evoked by a steady-frequency tone burst (primarylike, buildup, onset, and pause) and the FM response pattern. Cochlear nerve fibers showed symmetrical response patterns to FM stimulation. Primarylike units were similar to eighth nerve fibers and generally showed symmetrical FM responses. Occasional eighth nerve fibers and primarylike cells developed asymmetry at the fastest rate of modulation (50 sps). Buildup units showed a variety of response patterns to FM signals. Onset units generally showed asymmetrical response patterns with the greater response occurring to the ascending than to the descending phase of the FM sweep. Pause units showed a characteristic inhibition of activity at 5 sps (rate-dependent inhibition). Of the 57 cochlear nuclear cells studied in response to FM signals, 16 were symmetrical, another 16 were symmetrical except at the fastest modulation rate, 12 were asymmetrical, 3 were unidirectional, and 10 showed complex responses to certain signal rates or intensities. It is clear the the cat cochlear with its complex cytoarchitecture is involved in the recoding of acoustic information. Some units in cochlear nucleus demonstrate differential responses to the direction and to the rate of frequency movement. Other cochlear nucleus cells respond as eighth nerve fibers and may serve as simple "relays" in transmitting information from the cochlea to higher auditory centers.

Neural correlates of auditory fatigue: frequency-dependent changes in activity of single cochlear nerve fibers

1978 ◽  
Vol 41 (4) ◽  
pp. 987-1006 ◽  
Author(s):  
B. L. Lonsbury-Martin ◽  
M. B. Meikle
Keyword(s):  
Extended Period ◽  
Standard Test ◽  
Nerve Fibers ◽  
Cochlear Nerve ◽  
Frequency Dependent ◽  
Exposure Frequency ◽  
Discharge Rates ◽  
Elevated Activity ◽  
Resting Activity ◽  
Auditory Fatigue

1. These experiments were designed to test whether intense pure tones produced greater depression of cochlear nerve fibers tuned to the exposure frequency or of those tuned to frequencies above the exposure frequency. Spike discharges of single fibers were studied in anesthetized cats before, during, and after exposures lasting 1 min. Exposure frequency was varied relative to each fiber's characteristic frequency (CF), and was either at the CF or 1/2 octave above (+1/2 oct) or 1/2 octave below (-1/2 oct) the CF. Exposure levels were 85 or 90 dB SPL. Effects of the various exposures on driven discharge rates were evaluated using standard test stimuli at each fiber's CF. In addition, nonevoked discharges were measured during the brief quiet intervals between test stimuli ("interstimulus activity") as well as during extended quiet periods ("resting activity"). Major results were as follows: 2. All the exposures resulted in depression of the driven discharge rates; however, these effects were strongly dependent on the exposure frequency. The depression was greatest and endured the longest following -1/2 oct exposures at 90 dB. The CF exposures at 85 and 90 dB were much less depressant, as were exposures at -1/2 oct at 85 dB; these three exposures resulted in very similar recovery functions. The +1/2 oct exposures produced little or no depression, whether at 85 or 90 dB. 3. Interstimulus activity was depressed immediately following all exposures, but recovered to normal quickly than did driven discharge rates. Following exposures at -1/2 oct at 90 dB, recovery was non-monotonic in that an extended period of supernormality preceded the return to normal rates. During this period of elevated activity, the interstimulus activity approached but never exceeded the resting rate of the same fiber. 4. Resting activity recovered even more rapidly than interstimulus activity, being completely normal by 1 min following all exposures. 5. These results constitute the first demonstration that the CF is not necessarily the most depressant exposure frequency for a given cochlear nerve fiber. Further, the results imply that the half-octave (or greater) shifts of the point of maximum hearing loss, so characteristic of auditory fatigue, may be accounted for by frequency-dependent alterations in the responsiveness of cochlear nerve fibers.

Exploration of the Range of Linear Response Activity of Cochlear Nerve Fibers

1973 ◽  
Vol 54 (1) ◽  
pp. 283-283
Author(s):  
Warren M. Littlefield ◽  
Duck On Kim ◽  
Charles E. Molnar ◽  
Russell R. Pfeiffer
Keyword(s):  
Linear Response ◽  
Nerve Fibers ◽  
Cochlear Nerve
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