HISTOPATHOLOGY OF PROFOUND SENSORINEURAL DEAFNESSa

Hinojosa, Raäl; Marion, Mitchell S.

doi:10.1111/j.1749-6632.1983.tb31662.x

Cited by 140 publications

(82 citation statements)

References 29 publications

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“…In deaf human ears, many auditory nerve fibers survive for long periods after deafness, possibly due to neurotrophin support from supporting cells. SGN density levels in the absence of hair cells in humans can be much higher than those in neomycin-deafened guinea pigs (Hinojosa and Marion 1983;Nadol et al 2001;Fayad and Linthicum 2006). It is unknown if the auditory nerve is spontaneously active in these human subjects, but it seems unlikely given what is known about the requirements for spontaneous activity in animals.…”

Section: Discussionmentioning

confidence: 99%

Integration of Pulse Trains in Humans and Guinea Pigs with Cochlear Implants

Zhou

Kraft

Colesa

et al. 2015

JARO

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Temporal integration (TI; threshold versus stimulus duration) functions and multipulse integration (MPI; threshold versus pulse rate) functions were measured behaviorally in guinea pigs and humans with cochlear implants. Thresholds decreased with stimulus duration at a fixed pulse rate and with pulse rate at a fixed stimulus duration. The rates of threshold decrease (slopes) of the TI and MPI functions were not statistically different between the guinea pig and human subject groups. A characteristic of the integration functions that the two groups shared was that the slopes of the TI functions were similar in magnitude to slopes of the MPI function only at low pulse rates (G approximately 300 pulses per second). This is consistent with the notion that the TI functions and the MPI functions at the low rates are mediated by a mechanism of long-term integration described in the statistical Bmultiple looks^model. Histological analysis of the guinea pig cochleae suggested that the slopes of both the MPI and the TI functions were dependent on sensory and neural health near the stimulated regions. The strongest predictor for spiral ganglion cell densities measured near the stimulation sites was the slope of the MPI functions below 1,000 pps. Several mechanisms may be considered to account for the association of shallow integration functions with poor sensory and neural status. These mechanisms are related to abnormal across-fiber synchronization, increased refractoriness and adaptation with impaired neural function, and steep growth of neural excitation with current level associated with neural pathology. The slope of the integration functions can potentially be used as a non-invasive measure for identifying stimulation sites with poor neural health and selecting those sites for removal or rehabilitation, but these applications remain to be tested.

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Section: Discussionmentioning

confidence: 99%

Integration of Pulse Trains in Humans and Guinea Pigs with Cochlear Implants

Zhou

Kraft

Colesa

et al. 2015

JARO

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“…Figure 6 shows the normalized ECAP patterns for the probes pTP EL8, α = 0 (upward triangles), pTP EL8, α = 0.5 (circles), and pTP EL8, α = 1 (downward triangles) as a function of masker electrode for each subject. S2 showed much larger original unnormalized ECAP amplitudes than the other subjects, possibly because she was much younger and had used CI for more years, although meningitis may have led to poorer neural survival for her (Hinojosa and Marion 1983). For the bilateral CI user S3, the original ECAP responses of her first CI (S3R) were stronger with higher SNRs than those of her second CI (S3L), likely due to better neural survival in her first implanted ear with a shorter duration of deafness.…”

Section: Efi Patternsmentioning

confidence: 93%

Excitation Patterns of Standard and Steered Partial Tripolar Stimuli in Cochlear Implants

Luo

2015

JARO

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Current steering in partial tripolar (pTP) mode has been shown to improve pitch perception and spectral resolution with cochlear implants (CIs). In this mode, a fraction (σ) of the main electrode current is returned within the cochlea and steered between the basal and apical flanking electrodes (with a proportion of α and 1 − α, respectively). Pitch generally decreases when α increases from 0 to 1, although the salience of pitch change varies across CI users. This study aimed to identify the mechanism of pitch changes with pTP-mode current steering and the factors contributing to the intersubject variability in pitch-ranking sensitivity. The electrical fields were measured for steered pTP stimuli on the same main electrode with α = 0, 0.5, and 1 in five implanted ears using electrical field imaging (EFI). The related excitation patterns were also measured physiologically using evoked compound action potential (ECAP) and psychophysically using psychophysical forward masking (PFM). Consistent with the pitch-ranking results in this study, the EFI, ECAP, and PFM centroids shifted apically with increasing α. An apical shift was also observed for the PFM peak but not for the EFI or ECAP peak. The pattern width was similar with different α values within a given measure (e.g., EFI, ECAP, or PFM), but the ECAP patterns were broader than the EFI and PFM patterns, possibly because ECAP was measured with smaller σ values than EFI and PFM. The amount of pattern shift with α depended on σ (i.e., the total amount of current used for steering) but was not correlated with the pitchranking sensitivity across subjects. The results revealed that the pitch changes elicited by pTP-mode current steering were not only driven by the shifts of excitation centroid.

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“…In the deaf cochlea, and without the normal stimulation provided by the hair cells, the peripheral parts of the neurons -between the cell bodies in the spiral ganglion and the terminals within the organ of Corti -undergo retrograde degeneration and cease to function (Hinojosa and Marion, 1983). Fortunately, the cell bodies are far more robust.…”

Section: Electrical Stimulation Of the Auditory Nervementioning

confidence: 99%

“…Fortunately, the cell bodies are far more robust. At least some usually survive, even for prolonged deafness or for virulent etiologies such as meningitis (Hinojosa and Marion, 1983;Miura et al, 2002;Leake and Rebscher, 2004). These cells, or more specifically the nodes of Ranvier just distal or proximal to them, are the putative sites of excitation for CIs.…”

Section: Electrical Stimulation Of the Auditory Nervementioning

confidence: 99%

Cochlear implants: A remarkable past and a brilliant future

2008

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The aims of this paper are to (i) provide a brief history of cochlear implants; (ii) present a status report on the current state of implant engineering and the levels of speech understanding enabled by that engineering; (iii) describe limitations of current signal processing strategies and (iv) suggest new directions for research. With current technology the "average" implant patient, when listening to predictable conversations in quiet, is able to communicate with relative ease. However, in an environment typical of a workplace the average patient has a great deal of difficulty. Patients who are "above average" in terms of speech understanding, can achieve 100% correct scores on the most difficult tests of speech understanding in quiet but also have significant difficulty when signals are presented in noise. The major factors in these outcomes appear to be (i) a loss of low-frequency, fine structure information possibly due to the envelope extraction algorithms common to cochlear implant signal processing; (ii) a limitation in the number of effective channels of stimulation due to overlap in electric fields from electrodes, and (iii) central processing deficits, especially for patients with poor speech understanding. Two recent developments, bilateral implants and combined electric and acoustic stimulation, have promise to remediate some of the difficulties experienced by patients in noise and to reinstate low-frequency fine structure information. If other possibilities are realized, e.g., electrodes that emit drugs to inhibit cell death following trauma and to induce the growth of neurites toward electrodes, then the future is very bright indeed.

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HISTOPATHOLOGY OF PROFOUND SENSORINEURAL DEAFNESSa

Cited by 140 publications

References 29 publications

Integration of Pulse Trains in Humans and Guinea Pigs with Cochlear Implants

Integration of Pulse Trains in Humans and Guinea Pigs with Cochlear Implants

Excitation Patterns of Standard and Steered Partial Tripolar Stimuli in Cochlear Implants

Cochlear implants: A remarkable past and a brilliant future

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