The cochlear implant electrode–pitch function

Baumann, Uwe; Nobbe, Andrea

doi:10.1016/j.heares.2005.12.010

Cited by 61 publications

(63 citation statements)

References 17 publications

(20 reference statements)

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“…The authors suggested that this disparity was likely due to individual differences in OC length and imprecise estimates of the round window position on cochlear radiographs (Boex et al 2006). Discrepancies (both lower and higher) between the frequency matched with the pitch of the electrode and the frequency predicted by intracochlear position were also reported by Baumann and Nobbe (2006).…”

Section: Electrode Insertion Distances and Sg And Oc Place Frequenciementioning

confidence: 85%

“…Given that the larger numbers of channels available with the latest CI technology (e.g., Bvirtual channels^) may allow more flexibility in the frequency ranges delivered to different cochlear regions, further improvement of CI performance may depend on optimizing the tonotopic mapping of individual channels relative to the actual position of stimulation sites in the cochlea. A number of recent studies have been directed toward providing a better understanding of the role of electrode location and spacing on various perceptual attributes of hearing with a CI (Blamey et al 1996;Ketten et al 1998;Pfingst et al 2001;Skinner et al 2002;Yukawa et al 2004;Baumann and Nobbe 2006;Boex et al 2006). Several psychophysical studies have shown that spectral distortions such as apical or basal shift (Dorman et al 1997;Fu and Shannon 1999), nonlinear warping (Shannon et al 1998), and compression or expansion of the applied frequency map Shannon 2003, 2004) decrease speech perception, thus suggesting that an optimum fit of the frequency map for a given electrode position may significantly improve the performance of the CI listener.…”

Section: Introductionmentioning

confidence: 99%

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Frequency Map for the Human Cochlear Spiral Ganglion: Implications for Cochlear Implants

Stakhovskaya

Sridhar

Bonham

et al. 2007

JARO

348

357

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The goals of this study were to derive a frequencyposition function for the human cochlear spiral ganglion (SG) to correlate represented frequency along the organ of Corti (OC) to location along the SG, to determine the range of individual variability, and to calculate an Baverage^frequency map (based on the trajectories of the dendrites of the SG cells). For both OC and SG frequency maps, a potentially important limitation is that accurate estimates of cochlear place frequency based upon the Greenwood function require knowledge of the total OC or SG length, which cannot be determined in most temporal bone and imaging studies. Therefore, an additional goal of this study was to evaluate a simple metric, basal coil diameter that might be utilized to estimate OC and SG length. Cadaver cochleae (n = 9) were fixed G24 h postmortem, stained with osmium tetroxide, microdissected, decalcified briefly, embedded in epoxy resin, and examined in surface preparations. In digital images, the OC and SG were measured, and the radial nerve fiber trajectories were traced to define a series of frequency-matched coordinates along the two structures. Images of the cochlear turns were reconstructed and measurements of basal turn diameter were made and correlated with OC and SG measurements. The data obtained provide a mathematical function for relating represented frequency along the OC to that of the SG.Results showed that whereas the distance along the OC that corresponds to a critical bandwidth is assumed to be constant throughout the cochlea, estimated critical band distance in the SG varies significantly along the spiral. Additional findings suggest that measurements of basal coil diameter in preoperative images may allow prediction of OC/SG length and estimation of the insertion depth required to reach specific angles of rotation and frequencies. Results also indicate that OC and SG percentage length expressed as a function of rotation angle from the round window is fairly constant across subjects. The implications of these findings for the design and surgical insertion of cochlear implants are discussed.

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Section: Electrode Insertion Distances and Sg And Oc Place Frequenciementioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Frequency Map for the Human Cochlear Spiral Ganglion: Implications for Cochlear Implants

Stakhovskaya

Sridhar

Bonham

et al. 2007

JARO

348

357

View full text Add to dashboard Cite

show abstract

“…Moreover, specific stimulation of fibers from the cochlear apex might enhance low-frequency hearing. Scala tympani electrode arrays in clinical use are inserted in the basal (i.e., high-frequency) turn of the cochlea and terminate in the middle turn at loci representing frequencies no lower than about 600 Hz (Skinner et al 2002;Wardrop et al 2005); recent data suggest that some arrays can reach as far apical as the representation of frequency around 300 Hz (Baumann and Nobbe 2006;Boex et al 2006). Speech processing programs typically assign low frequencies (i.e., lower than õ200 Hz) to the most apical scala tympani electrode, but that creates a mismatch between the normal frequency sensitivity of that cochlear site and the assigned acoustic frequencies that lead to the stimulation of that site.…”

Section: Access To Fibers From the Apical Cochleamentioning

confidence: 99%

Auditory Prosthesis with a Penetrating Nerve Array

Middlebrooks

Snyder

2007

JARO

137

163

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Contemporary auditory prostheses (Bcochlear implants^) employ arrays of stimulating electrodes implanted in the scala tympani of the cochlea. Such arrays have been implanted in some 100,000 profoundly or severely deaf people worldwide and arguably are the most successful of present-day neural prostheses. Nevertheless, most implant users show poor understanding of speech in noisy backgrounds, poor pitch recognition, and poor spatial hearing, even when using bilateral implants. Many of these limitations can be attributed to the remote location of stimulating electrodes relative to excitable cochlear neural elements. That is, a scala tympani electrode array lies within a bony compartment filled with electrically conductive fluid. Moreover, scala tympani arrays typically do not extend to the apical turn of the cochlea in which low frequencies are represented. In the present study, we have tested in an animal model an alternative to the conventional cochlear implant: a multielectrode array implanted directly into the auditory nerve. We monitored the specificity of stimulation of the auditory pathway by recording extracellular unit activity at 32 sites along the tonotopic axis of the inferior colliculus. The results demonstrate the activation of specific auditory nerve populations throughout essentially the entire frequency range that is represented by characteristic frequencies in the inferior colliculus. Compared to conventional scala tympani stimulation, thresholds for neural excitation are as much as 50-fold lower and interference between electrodes stimulated simultaneously is markedly reduced. The results suggest that if an intraneural stimulating array were incorporated into an auditory prosthesis system for humans, it could offer substantial improvement in hearing replacement compared to contemporary cochlear implants.

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“…This insertion depth could affect speech intelligibility substantially, especially if the analysis filters were not matched to the synthesis filters (Baskent andShannon, 2003, 2005), but it was also a realistic value for CI implant depths. Average insertion depths of 25 mm (Baumann and Nobbe, 2006), 21.75 mm (Boex et al, 2006), and 28.8 mm (Baskent and Shannon, 2005) were found in implant users, with an average insertion depth across the 16 listeners in these studies of 23.6 mm. The synthesis filter center frequencies corresponded to simulated electrode positions, with the electrodes spaced at 0.75 mm, as in the Nucleus CI.…”

Section: A Signal Processingmentioning

confidence: 57%

The performance of different synthesis signals in acoustic models of cochlear implants

Strydom

Hanekom

2011

The Journal of the Acoustical Society of America

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Synthesis (carrier) signals in acoustic models embody assumptions about perception of auditory electric stimulation. This study compared speech intelligibility of consonants and vowels processed through a set of nine acoustic models that used Spectral Peak (SPEAK) and Advanced Combination Encoder (ACE)-like speech processing, using synthesis signals which were representative of signals used previously in acoustic models as well as two new ones. Performance of the synthesis signals was determined in terms of correspondence with cochlear implant (CI) listener results for 12 attributes of phoneme perception (consonant and vowel recognition; F1, F2, and duration information transmission for vowels; voicing, manner, place of articulation, affrication, burst, nasality, and amplitude envelope information transmission for consonants) using four measures of performance. Modulated synthesis signals produced the best correspondence with CI consonant intelligibility, while sinusoids, narrow noise bands, and varying noise bands produced the best correspondence with CI vowel intelligibility. The signals that performed best overall (in terms of correspondence with both vowel and consonant attributes) were modulated and unmodulated noise bands of varying bandwidth that corresponded to a linearly varying excitation width of 0.4 mm at the apical to 8 mm at the basal channels.

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The cochlear implant electrode–pitch function

Cited by 61 publications

References 17 publications

Frequency Map for the Human Cochlear Spiral Ganglion: Implications for Cochlear Implants

Frequency Map for the Human Cochlear Spiral Ganglion: Implications for Cochlear Implants

Auditory Prosthesis with a Penetrating Nerve Array

The performance of different synthesis signals in acoustic models of cochlear implants

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