A Frequency-Position Function for the Human Cochlear Spiral Ganglion

Sridhar, Divya; Stakhovskaya, Olga; Leake, Patricia A.

doi:10.1159/000095609

Cited by 57 publications

(59 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because it is logical to assume that our normalized data should cover the region from 0 to 100% of both the OC and SG, that polynomial function was constrained to begin at the point x = 0, y = 0, to end at x = 100, y = 100, and to be monotonic (Sridhar et al 2006). The addition of two more cochlear specimens to the data set did not eliminate a systematic bias observed near the base (up to 20%) for the thirdorder polynomial, so the final set of data in this report was fit by a different mathematical function:…”

Section: Sg Frequency-position Functionmentioning

confidence: 99%

See 1 more Smart Citation

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

Stakhovskaya

Sridhar

Bonham

et al. 2007

JARO

Self Cite

345

357

View full text Add to dashboard Cite

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.

show abstract

Section: Sg Frequency-position Functionmentioning

confidence: 99%

“…Some preliminary data on the frequency-position map for the SG from a subset of the cochlear specimens included in this study were reported previously in the proceedings of the First International Electro-Acoustic Workshop (Sridhar et al 2006).…”

Section: Introductionmentioning

confidence: 99%

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

Stakhovskaya

Sridhar

Bonham

et al. 2007

JARO

Self Cite

345

357

View full text Add to dashboard Cite

show abstract

“…To express the frequency-position function of a normal ear versus angles, we used the reconstruction work of Kawano et al (1996, Table 2), where they listed angles (-) versus percentage lengths of the organ of Corti. We also drew the frequency-position function that could result from the excitation of the spiral ganglion cells (hairline), using the function modeling the projection of fibers from the organ of Corti to the spiral ganglion as described by Sridhar et al (2005) and using again the reconstruction work of Kawano et al to assign angles to percentages of the length of the spiral ganglion. The frequencies of acoustic stimuli at match were again lower than estimated by the frequency position function of a normal ear.…”

Section: Pitch Comparisonsmentioning

confidence: 99%

Acoustic to Electric Pitch Comparisons in Cochlear Implant Subjects with Residual Hearing

Boëx

Baud

Cosendai

et al. 2006

JARO

104

View full text Add to dashboard Cite

The aim of this study was to assess the frequencyposition function resulting from electric stimulation of electrodes in cochlear implant subjects with significant residual hearing in their nonimplanted ear. Six cochlear implant users compared the pitch of the auditory sensation produced by stimulation of an intracochlear electrode to the pitch of acoustic pure tones presented to their contralateral nonimplanted ear. Subjects were implanted with different Clarion \ electrode arrays, designed to lie close to the inner wall of the cochlea. High-resolution radiographs were used to determine the electrode positions in the cochlea. Four out of six subjects presented electrode insertions deeper than 450-. We used a two-interval (one acoustic, one electric), two-alternative forced choice protocol (2I-2AFC), asking the subject to indicate which stimulus sounded the highest in pitch. Pure tones were used as acoustic stimuli. Electric stimuli consisted of trains of biphasic pulses presented at relatively high rates [higher than 700 pulses per second (pps)]. First, all electric stimuli were balanced in loudness across electrodes. Second, acoustic pure tones, chosen to approximate roughly the pitch sensation produced by each electrode, were balanced in loudness to electric stimuli. When electrode insertion lengths were used to describe electrode positions, the pitch sensations produced by electric stimulation were found to be more than two octaves lower than predicted by Greenwood's frequency-position function. When insertion angles were used to describe electrode positions, the pitch sensations were found about one octave lower than the frequency-position function of a normal ear. The difference found between both descriptions is because of the fact that these electrode arrays were designed to lie close to the modiolus. As a consequence, the site of excitation produced at the level of the organ of Corti corresponds to a longer length than the electrode insertion length, which is used in Greenwood's function. Although exact measurements of the round window position as well as the length of the cochlea could explain the remaining one octave difference found when insertion angles were used, physiological phenomena (e.g., stimulation of the spiral ganglion cells) could also create this difference. From these data, analysis filters could be determined in sound coding strategies to match the pitch percepts elicited by electrode stimulation. This step might be of main importance for music perception and for the fitting of bilateral cochlear implants.

show abstract

“…However, hair cells are usually absent in implant patients after conventional implant surgery. The remaining neural targets, dendrites and cell bodies in the spiral ganglion, do not have the same relationship to distance along the cochlear partition as hair cells (Kawano et al 1996;Sridhar et al 2006). Thus, the Greenwood frequency-place (or frequency to distance along the cochlea) map is not likely to be appropriate for cochlear implant patients.…”

mentioning

confidence: 99%

An Electric Frequency-to-place Map for a Cochlear Implant Patient with Hearing in the Nonimplanted Ear

Dorman

Spahr

Gifford

et al. 2007

JARO

View full text Add to dashboard Cite

The aim of this study was to relate the pitch of high-rate electrical stimulation delivered to individual cochlear implant electrodes to electrode insertion depth and insertion angle. The patient (CH1) was able to provide pitch matches between electric and acoustic stimulation because he had auditory thresholds in his nonimplanted ear ranging between 30 and 60 dB HL over the range, 250 Hz to 8 kHz. Electrode depth and insertion angle were measured from high-resolution computed tomography (CT) scans of the patient_s temporal bones. The scans were used to create a 3D image volume reconstruction of the cochlea, which allowed visualization of electrode position within the scala. The method of limits was used to establish pitch matches between acoustic pure tones and electric stimulation (a 1,652-pps, unmodulated, pulse train). The pitch matching data demonstrated that, for insertion angles of greater than 450 degrees or greater than approximately 20 mm insertion depth, pitch saturated at approximately 420 Hz. From 20 to 15 mm insertion depth pitch estimates were about one-half octave lower than the Greenwood function. From 13 to 3 mm insertion depth the pitch estimates were approximately one octave lower than the Greenwood function. The pitch match for an electrode only 3.4 mm into the cochlea was 3,447 Hz. These data are consistent with other reports, e.g., Boëx et al. (2006), of a frequency-to-place map for the electrically stimulated cochlea in which perceived pitches for stimulation on individual electrodes are significantly lower than those predicted by the Greenwood function for stimulation at the level of the hair cell.

show abstract

A Frequency-Position Function for the Human Cochlear Spiral Ganglion

Cited by 57 publications

References 16 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

Acoustic to Electric Pitch Comparisons in Cochlear Implant Subjects with Residual Hearing

An Electric Frequency-to-place Map for a Cochlear Implant Patient with Hearing in the Nonimplanted Ear

Contact Info

Product

Resources

About