Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2020 Dec 1.
Published in final edited form as: Hear Res. 2019 Oct 18;384:107815. doi: 10.1016/j.heares.2019.107815

Impact of Stimulus Frequency and Recording Electrode on Electrocochleography in Hybrid Cochlear Implant Users

VD Tejani 1,2, RL Owen 1,2, PJ Abbas 1,2, CJ Brown 1,2
PMCID: PMC6913176  NIHMSID: NIHMS1544489  PMID: 31678892

Abstract

This report explores the impact of recording electrode position and stimulus frequency on intracochlear electrocochleography (ECoG) responses recorded from six Nucleus L24 Hybrid CI users. Acoustic tone bursts (250 Hz, 500 Hz, 750 Hz, and 1000 Hz) were presented to the implanted ear via an insert earphone. Recordings were obtained from intracochlear electrodes 6 (most basal), 8, 10, 12, 14, 16, 18, 20, and 22 (most apical). Responses to condensation and rarefaction stimuli were subtracted from one another to emphasize hair cell responses (CM/DIF) and added to one another to emphasize neural responses (ANN/SUM). For a fixed stimulus frequency, the CM/DIF and ANN/SUM magnitudes increased as the recording electrode moved apically. For a fixed recording electrode, as the stimulus frequency was lowered, response magnitudes increased. The CM/DIF and ANN/SUM response phase were generally stable across recording electrodes, although substantial phase shifts were noted for a few conditions. Given the recent interest in ECoG for assessing peripheral auditory function in CI users, the impact of stimulus frequency and recording electrode position on response magnitude should be considered. Results suggest optimal ECoG responses are obtained using the most apical recording electrode and a low frequency acoustic stimulus (250 Hz or 500 Hz).

1. Introduction

Traditionally, cochlear implant (CI) candidates had bilateral, severe-to-profound sensorineural hearing loss. However, recent advancements in electrode array design and changes in surgical techniques have made preservation of acoustic hearing in the implanted ear a reality. Today, patients with good low-frequency hearing but high-frequency hearing loss can be implanted using an electrode array designed to preserve their acoustic hearing. These CI users are able to combine acoustic low-frequency information and electric high-frequency information from the same ear (electric-acoustic stimulation, EAS). While hearing preservation post-implant is possible for many patients, a percentage experience some loss of acoustic hearing immediately post-op and others experience a delayed onset hearing loss, typically within the first year post-implant (Kopelovich et al., 2014; Scheperle et al., 2017). This unfortunate outcome led several researchers to consider novel ways to assess cochlear health.

The neural telemetry systems of all three major CI manufacturers (Cochlear Ltd., Advanced Bionics, and MED-EL) have traditionally been used to record electrically evoked compound action potentials from an intracochlear electrode (Brown et al., 1998; Abbas et al., 1999). For patients with residual acoustic hearing post-implant, the telemetry system can be adapted to record acoustically evoked electrocochleograms (ECoG) from an intracochlear electrode (Acharya et al., 2016; Campbell et al, 2015, 2016; Abbas et al, 2017; Koka et al., 2017; Kim et al, 2018; Tejani et al., 2019). The ECoG is a complex response that includes contributions from cochlear hair cells as well as neural components [Cochlear Microphonic (CM), Summating Potential (SP), Compound Action Potential (CAP) and Auditory Nerve Neurophonic (ANN)]. Because it can be recorded noninvasively post-implant, the ECoG is increasingly viewed as a measure that may help characterize and monitor the status of the peripheral auditory system over time and potentially provide clues as to the underlying cause of delayed onset hearing loss that some EAS CI listeners experience.

Typically, the ECoG is recorded from the most apical intracochlear electrode in the array. The assumption is that ECoG response magnitudes will be largest for this recording electrode given its proximity to the region of the basilar membrane where there are more functional hair cells and where residual acoustic hearing is best. However, previous studies have shown that is not always the case (Dalbert et al., 2015; Campbell et al., 2015, 2016; Bester et al., 2017; Harris et al., 2017). For example, Campbell et al. (2015) performed ECoG recordings post-operatively and reported CM amplitudes increased for most individuals as the recording electrode was moved apically across the array. For other subjects, larger CM and ANN amplitudes were recorded from the most basal electrode. Dalbert et al. (2015) reported finding minimal changes in post-operative ECoG magnitude regardless of the intracochlear recording electrode that was used. Intraoperative data, obtained during electrode array insertion (Campbell et al., 2016; Harris et al., 2017) or immediately post-insertion (Bester et al., 2017), has shown CM amplitudes that increase as the recording electrode is inserted toward the apex for some subjects, a maximum response for others occurs at a point midway into the insertion for other subjects, and in some individuals no change is observed with insertion. Most studies used a single stimulus frequency and focused primarily on the CM response. The magnitude of the hearing losses also varied significantly across these studies.

Changes in CM phase as a function of place along the cochlea has also recently received attention in intracochlear ECoG for its potential applications in intraoperative monitoring of cochlear trauma during CI surgeries (Campbell et al, 2017; Koka et al, 2018; Giardina et al, 2019). Preliminary studies have proposed real-time monitoring of CM amplitudes as the electrode array is inserted, as drops in CM amplitude may be indicative of cochlear trauma, leading to partial or complete loss of the patient’s acoustic hearing post-operatively (Campbell et al, 2016; Dalbert et al, 2018; but see Adunka et al, 2016; O’Connell et al, 2017). However, Koka et al. (2018) and Giardina et al. (2019) proposed incorporating CM phase information when interpreting CM magnitude changes. Specifically, they hypothesized that drops in CM magnitudes concurring with large shifts in the starting phase of the ongoing CM response may not be indicative of cochlear trauma, while drops in CM magnitudes with minimum shifts in phase may be indicative of cochlear trauma (e.g. loss of acoustic hearing or scalar translocation of the electrode array). Similarly, normal-hearing animal literature has also shown some evidence of phase shifts for apical recording sites relative to basal recording sites (Tasaki et al., 1952; Pfeiffer & Molnar, 1970; Kohllöffel, 1970; Kim et al, 1980)

In the present study we describe the effect that recording electrode position and stimulus frequency have on both CM and ANN responses for a group of six Cochlear Nucleus L24 Hybrid CI users with good low-frequency acoustic hearing (e.g. thresholds in the mild to moderate range). These are typical EAS CI candidates and patients likely to be interested in preserving acoustic hearing post implant. Our goal is to more fully characterize the impact of recording electrode and stimulus frequency on both CM and ANN response amplitude and to use our data to suggest optimal recording parameters. We hypothesize that for a given frequency tone burst, moving the recording electrode basally should result in reduced CM and ANN amplitudes. Similarly, because these subjects have a sloping audiometric configuration, we hypothesize that for a fixed recording electrode, decreasing the tone burst frequency should result in larger CM and ANN response amplitudes. As a secondary aim, we also explored the effect of recording electrode location on phase of the CM and ANN responses.

2. Methods

2.1. Participants

Six adults (age = 55 – 84 years) participated in this study. All used the Cochlear Nucleus Hybrid L24 electrode array (insertion depth = 16 mm; Roland et al., 2016), and were implanted at the University of Iowa Hospitals and Clinics between 2016 and 2017. Figure 1 shows individual preoperative and postoperative unaided audiograms from the implanted ear. Postoperative audiograms were obtained at the time of testing. Table 1 details subject demographics. The electrode arrays were implanted via the round window. Full electrode insertions were obtained for each subject, however, the exact intracochlear position of the electrodes may vary across subjects depending on cochlear anatomy and position of the electrodes relative to the modiolus and lateral wall. Imaging studies have indicated insertion angles ranging from 220° to 270° when the L24 electrode array is fully inserted via the round window (Briggs et al, 2006; Lenarz et al., 2006; Driscoll et al., 2011), corresponding to the 1500–2000 Hz place in the cochlea (Stakhovskaya et al., 2007).

Figure 1.

Figure 1.

Open in a new tab

Preoperative and postoperative unaided audiograms. NR indicates no response at the limits of the audiometer.

Table 1:

Subject Demographics

Subject Age (yrs) CI use (mo) PTA (dB HL) Etiology
L66R 77 0.5 63 Noise
L68R 73 0.5 74 Unknown (family history)
L61L 54 3 58 Unknown
L58L 83 6 65 Noise
L59R 74 6 83 Noise + family history
L73R 68 0.5 61 Noise + family history
Open in a new tab

2.2. Stimulation Procedures

Intracochlear responses were measured using 250 Hz, 500 Hz, 750 Hz, and 1000 Hz tone bursts presented to the implanted ear via an insert earphone. Tone bursts were 12 milliseconds long and presented in condensation and rarefaction polarities at 100–110 dB SPL at a 10 Hz stimulation rate.

2.3. Recording Procedures

ECoG responses were recorded via an adaptation of Neural Response Telemetry system using methods outlined by Abbas et al. (2017); specific details can be found in that report. Recordings were obtained from electrodes 6 (most basal), 8, 10, 12, 14, 16, 18, 20, and 22 (most apical) for both condensation and rarefaction polarities. (Note that electrodes 1–4 are disabled in our Hybrid L24 CI users by default in the programming software. This is likely due to the increased electrode-neural distance for the basal electrodes, which precludes effective electrical stimulation).

2.4. Data Analysis Procedures

Raw recordings to rarefaction and condensation stimuli were subtracted from one another to emphasize the CM and added to emphasize the ANN (Aran & Charlet de Sauvage, 1976; Henry, 1995; Lichtenhan et al, 2013). Recognizing that this technique does not result in a complete segregation of hair cell and neural responses (Forgues et al., 2014), we refer to the potentials as the CM/DIF and ANN/SUM responses. Both recordings were analyzed in the frequency domain using Fast Fourier Transforms (FFT) to extract both magnitude and phase information. For CM/DIF recordings, we expect to see an FFT peak corresponding to the stimulus frequency because hair cell responses closely follow the acoustic stimulus waveform. For ANN/SUM recordings, we expect the FFT peak to correspond to twice the stimulus frequency. This occurs because neurons will only fire during the depolarizing phase of the stimulus. When responses to opposite polarity are summed, the response latencies for each stimulus differ by ½ cycle and the resulting waveform oscillates at twice the stimulus frequency. To allow for comparison across subjects, the response magnitude at all stimulus frequency and recording electrode combinations was normalized to the response magnitude recorded using the most apical electrode (electrode 22) and a 250 Hz tone burst.

3. Results

Figure 2 shows results obtained using a 500 Hz tone burst from recording electrode 22 for subject L68R. The left panel shows raw condensation and rarefaction recordings, the middle shows the resulting CM/DIF and ANN/SUM potentials and the right shows their FFTs. Higher harmonics are also occasionally present in the FFT. For the CM/DIF FFT, a small peak at 1500 Hz was noted in addition to the 500 Hz peak. The 1500 Hz peak may reflect distortion caused by saturation in hair cell transduction at higher stimulation levels (Forgues et al., 2014). As expected, the ANN/SUM FFT shows a peak at 1000 Hz. Additionally, an onset CAP is apparent in the ANN/SUM waveform at about 9 ms.

Figure 2.

Figure 2.

Open in a new tab

(A) ECoG responses to condensation and rarefaction tone bursts. (B) Subtracting the two recordings emphasizes the hair cell responses (CM/DIF), where the waveform oscillates at the stimulus frequency. Adding the two recordings emphasizes the neural responses (ANN/SUM), where the waveform oscillates at twice the stimulus frequency.

Individual CM/DIF and ANN/SUM FFT response magnitudes and their corresponding phases are plotted as a function of recording electrode for each stimulus frequency (Figure 3). The y-axis scales for Figure 3A should be noted as they are logarithmic as well as larger for CM/DIF responses compared to ANN/SUM responses. Figure 3A shows that at lower stimulus frequencies, e.g. 250 Hz and 500 Hz, FFT magnitudes are larger for electrodes located near the apical end of the electrode array and smaller for basal electrodes. For higher stimulus frequencies, e.g. 750 Hz and 1000 Hz, the FFT magnitude responses tended to be more gently sloping, but apical peaks were still present. Subject L61L is an outlier given his considerably higher ECoG amplitudes compared to other subjects (Figure 3A).

Figure 3.

Figure 3.

Open in a new tab

Individual CM/DIF and ANN/SUM FFT magnitudes (3A) and phase (3B) from recording electrodes 22 to 6 using tone bursts ranging from 250 – 1000 Hz. Note the differing y-axis scales in the CM/DIF and ANN plot for 3A.

Figure 3B indicates that for CM/DIF responses obtained using a 250 Hz and 500 Hz stimulus, the phase is relatively constant as the recording electrode changes, with few exceptions. However, for the other frequencies and for the ANN/SUM responses, phase patterns appear be difficult to interpret, with no obvious patterns. Some of the difficulty may arise because the response magnitudes are also quite small (e.g. subject L59R and L73R, 750 Hz CM/DIF). Subject L61L is once again an outlier given the pronounced phase shifts in the apical recording electrodes, particularly for 750 and 1000 Hz.

FFT magnitudes also plotted as a function of stimulus frequency for selected recording electrodes (Figure 4). As stimulus frequency decreases for a fixed recording electrode, CM/DIF and ANN/SUM amplitude increase. Subject L61L, once again, is an outlier, as he shows increasing ECoG magnitudes as the stimulus frequency increases, particularly for the apical recording electrodes.

Figure 4.

Figure 4.

Open in a new tab

Individual FFT magnitudes as a function of stimulus frequency for recording electrodes 22, 16, 12, and 6. Note the differing y-axis scales for left and right panels.

The 3D plots in Figure 5 show average normalized data recorded from five of the six subjects tested and demonstrate the overall effect that changes in recording electrode and stimulus frequency have on the CM/DIF (left panel) and ANN/SUM (right panel) magnitudes. Subject L61L was excluded from the analysis due to his unusually large response amplitudes (see Figure 3). As the recording electrode is moved basally away from the site of stimulation, the magnitudes of both responses decrease. As the stimulus frequency is lowered and excitation spreads into regions with better hearing, response magnitude increases. (Note that only one subject had an ANN/SUM response at the electrode 6 / 1000 Hz condition, and that only a few subjects had ANN/SUM responses at the basal electrodes at high frequencies)

Figure 5.

Figure 5.

Open in a new tab

3D plot showing the effects of stimulus frequency and recording electrode on ECoG responses.

4. Discussion

The goal of this study was to systematically explore the effect of recording electrode location and stimulus frequency on ECoG recordings. Consistent with our hypothesis, results showed that when stimulus frequency was held constant, moving the recording electrode basally resulted in a decrease in response amplitude (Figure 3A). This trend was most apparent when a low frequency tone burst was used (e.g. 250 Hz and 500 Hz) and is consistent with ECoG studies where an apical peak was observed (Campbell et al., 2016; Bester et al., 2016), but differs from studies that found no impact of recording electrode on ECoG magnitude (Dalbert et al, 2015). It is likely that the surviving hair cells and regions of better hearing play a role in the robustness of the lower stimulus frequency pattern in our results. Subject L61L is our outlier in that electrode 20 yielded the best response for all frequencies (Fig 3A). He is the only subject with measurable acoustic hearing at all frequencies up to 8000 Hz. At high stimulation levels, the peak of the basilar membrane traveling wave broadens and shifts basally (Rhode, 1971; Johnstone et al., 1986). In L61L’s case, the residual high-frequency audiometric hearing (and cochlear function) may have allowed a basal-ward shift in the peak of the ECoG response. Previous studies have also found wide variations in ECoG magnitude responses believed to be due to varying residual cochlear function (Fitzpatrick et al., 2014). Additionally, the presence of the implant itself can impact cochlear mechanics and impede the traveling wave and transmission of sound (DeMason et al, 2012), and this may contribute to some of the variations in ECoG magnitudes across the recording electrode positions.

When the recording electrode was fixed but the tone burst frequency was decreased, the ECoG magnitude increased for five of the six subjects (Figure 4). These results likely reflect the fact that the subjects all had sloping audiograms with better hearing sensitivity in the low frequencies. Bester et al (2017) hypothesized that ECoG recorded from different electrodes reflected the response of the local population of hair cells to the cochlear travelling wave generated by the acoustic signal. Results from five subjects are generally consistent with that hypothesis (see Figure 4). However, subject L61L shows the opposite trend. As stimulus frequency was increased from 250 to 1000 Hz, the response amplitude also increased. This is also the subject with the best hearing at 1000 Hz and the only subject with measurable acoustic hearing at all frequencies up to 8000 Hz. Imaging studies have revealed insertion angles ranging from 220° to 270° when the L24 electrode array is inserted via the round window (Briggs et al, 2006; Lenarz et al., 2006; Driscoll et al, 2011). Considering the 270° depth, this corresponds to the 1500–2000 Hz place in the cochlea (Stakhovskaya et al., 2007). Thus, as stimulus frequency is increased, there is still significant response at the 1500–2000 Hz region in this individual as well as a recording electrode closer to the hair cell/neural potential generators. The result would be a larger response as stimulus frequency is increased.

The interpretation of the phase data may have been complicated by the low CM responses at high stimulus frequencies and as well at the generally low ANN response at all stimulus frequencies. However, it does appear that subjects who generally show increasing CM response magnitudes for more apical recording electrodes also show some relative stability in CM phase, at least for the 250 Hz and 500 Hz stimulus frequencies. This is consistent with one of the magnitude/phase pattern types discussed in Koka et al (2018) and Giardina et al (2019). Our outlier (subject L61L) does have marked CM phase shifts for apical recording sites. Interestingly, his ECoG also demonstrates an unusually large 1–2 order of magnitude CM amplitude increase for the apical recording sites (particularly for the 500, 750, and 1000 Hz stimulus frequencies), as well as large response variations for the 1000 Hz stimulus (Figure 3). Giardina et al (2019) has suggested that magnitude changes in conjunction with phase changes as the recording site is shifted may reflect changes in the relative contribution of hair cell and neural responses, as well as constructive / destructive interferences between both sources. This may indeed be the case for subject L61L at the apical recordings sites, especially since the difference response used to characterize the CM likely contains some ANN contributions (e.g., Forgues et al. 2014).

Except for subject L61L, all of our subjects had high-frequency audiometric thresholds ≥ 100 dB HL pre-operatively and post-operatively. Given the lack of hearing in the high frequencies, our results suggest using the most apical recording electrode and a low-frequency stimulus (250 or 500 Hz) to obtain optimal ECoG recordings in hearing preservation cochlear implant users. In addition, our group has been interested in post-operative longitudinal monitoring of ECoG as a proxy of long-term cochlear health in hearing preservation patients; thus we have experimented with optimizing the recording parameters in the last few years (Abbas et al., 2017; Kim et al., 2018; Tejani et al., 2019). We use stimuli from 250 to 1000 Hz, but prioritize 500 Hz since acoustic responses to higher frequency tone bursts are generally poorer due to the severity of hearing loss. One could theoretically use a subject-specific stimulus frequency and recording electrode to optimize individual responses (e.g. subject L61L), however subject-specific parameters would prevent comparison of ECoG and outcome measures across all subjects, such comparisons with audiometric thresholds (Abbas et al, 2017; Koka et al, 2017; Kim et al, 2018) and word recognition (Fontenot et al, 2019)

Given the potential usefulness of electrocochleograms in assessing cochlear function, knowing the impact of recording electrode and stimulus frequency on ECoG measures will be useful to optimize recording parameters.

Highlights:

  • Intracochlear electrocochleography was recorded from Hybrid cochlear implant users

  • Cochlear microphonics (CM) and auditory nerve neurophonics (ANN) were analyzed

  • Stimulus frequency and recording electrode location affect CM and ANN responses

  • Response magnitudes were higher for apical electrodes and low stimulus frequencies

  • Response phase were generally stable across electrodes, with few exceptions

Acknowledgements

This study was supported by NIH/NIDCD (P50 DC000242). We are grateful to all participants for their time and to the University of Iowa Cochlear Implant team for their clinical care of our study participants.

Footnotes

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Conflicts of Interests

The authors declare that there is no conflict of interest in relation to this work.

References

  1. Abbas PJ, Tejani VD, Scheperle RA, Brown CJ (2017). Using Neural Response Telemetry to Monitor Physiological Responses to Acoustic Stimulation in Hybrid Cochlear Implant Users. Ear Hear. 38(4):409–425. 10.1097/AUD.0000000000000400. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Adunka OF, Giardina CK, Formeister EJ, Choudbury B, Buchman CA, Fitzpatrick DC, 2016. Round window electrocochleography before and after cochlear implant electrode insertion. Laryngoscope 126, 1193e1200 10.1002/lary.25602. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Aran J-M, Charlet de Sauvage R. Clinical value of cochlear microphonic recordings In: Ruben RJ, Elberling C, Salomon G, editors. Electrocochleography. University Park Press; 1976. pp. 55–65. [Google Scholar]
  4. Bester CW, Campbell L, Dragovic A, Collins A, O’Leary SJ (2017). Characterizing Electrocochleography in Cochlear Implant Recipients with Residual Low-Frequency Hearing. Front Neurosci. 11, 141 10.3389/fnins.2017.00141 [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Campbell L, Kaicer A, Sly D, Iseli C, Wei B, Briggs R, O’Leary S (2016). Intra- operative Real-time Cochlear Response Telemetry Predicts Hearing Preservation in Cochlear Implantation. Otol Neurotol. 37 (4), 332e338 10.1097/MAO.0000000000000972 [DOI] [PubMed] [Google Scholar]
  6. Campbell L, Kaicer A, Briggs R, O’Leary S (2014). Cochlear Response Telemetry: Intracochlear Electrocochleography via Cochlear Implant Neural Response Telemetry Pilot Study Results. Otol Neurotol. 36(3): 399–405. 10.1097/MAO.0000000000000678. [DOI] [PubMed] [Google Scholar]
  7. Dalbert A, Pfiffner F, Röösli C, Thoele K, Sim JH, Gerig R, et al. (2015). Extra- and intracochelar electrocochleography in cochlear implant recipients. Audiol Neurotol. 20(5), 339–348. 10.1159/000438742. [DOI] [PubMed] [Google Scholar]
  8. Dalbert A, Pfiffner F, Hoesil M, Koka K, Veraguth D, Roosli C, Huber A (2018). Assessment of cochlear function during cochlear implantation by extra- and intracochlear electrocochleography. Front. Neurosci 12, 18 10.3389/fnins.2018.00018 [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. DeMason C, Choudhury B, Ahmad F, Fitzpatrick DC, Wang J, Buchman CA, Adunka OF (2012). Electrophysiological properties of cochlear implantation in the gerbil using a flexible array. Ear Hear 33(4):534–42. 10.1097/AUD.0b013e3182498c28. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Driscoll CL, Carlson ML, Fama AF, Lane JI. (2011). Evaluation of the Hybrid-L24 electrode using microcomputed tomography. Laryngoscope. 121(7):1508–1516. 10.1002/lary.21837 [DOI] [PubMed] [Google Scholar]
  11. Fitzpatrick DC, Campbell AP, Choudhury B, Dillon MT, Forgues M, Buchman CA, Adunka OF (2013). Round window electrocochleography just before cochlear implantation: relationship to word recognition outcomes in adults. Otol. Neurotol 35(1), 64–71. 10.1097/MAO.0000000000000219 [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Forgues M, Koehn HA, Dunnon AK, Pulver SH, Buchman CA, Adunka OF, Fitzpatrick DC. (2014) Distinguishing hair cell from neural potentials recorded at the round window. J Neurophysiol;111:580–593. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Fontenot TE, Giardina CK, Dillon M, Rooth MA, Teagle HF, Park LR, Brown KD, Adunka OF, Buchman CA, Pillsbury HC, Fitzpatrick DC (2019). Residual Cochlear Function in Adults and Children Receiving Cochlear Implants: Correlations With Speech Perception Outcomes. Ear Hear. 40(3):577–591. 10.1097/AUD.0000000000000630. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Gantz BJ, Turner C, Gfeller KE, Lowder MW. (2005) Preservation of hearing in cochlear implant surgery: advantages of combined electrical and acoustical speech processing. Laryngoscope. 115(5):796–802. 10.1097/01.MLG.0000157695.07536.D2. [DOI] [PubMed] [Google Scholar]
  15. Giardina CK, Brown KD, Adunka OF, Buchman CA, Hutson KA, Pillsbury HC, Fitzpatrick DC. (2019). Intracochlear Electrocochleography: Response Patterns During Cochlear Implantation and Hearing Preservation. Ear Hear. 40(4):833–848. 10.1097/AUD.0000000000000659. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Harris MS, Riggs WJ, Giardina CK, O’Connell BP, Holder JT, Dwyer RT, Koka K, Labadie RF, Fitzpatrick DC, Adunka OF (2017). Patterns Seen During Electrode Insertion Using Intracochlear Electrocochleography Obtained Directly Through a Cochlear Implant. Otol Neurotol. 38(10):1415–1420. 10.1097/MAO.0000000000001559. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Johnstone BM, Patuzzi R, Yates GK. (1986). Basilar membrane measurements and the travelling wave. Hear Res. 22(1–3):147–53. 10.1016/0378-5955(86)90090-0 [DOI] [PubMed] [Google Scholar]
  18. Kim DO, Molnar CE, Matthews JW (1980). Cochlear mechanics: nonlinear behavior in two-tone responses as reflected in cochlear-nerve-fiber responses and in ear-canal sound pressure. J Acoust Soc Am. 67(5):1704–1721. 10.1121/1.384297. [DOI] [PubMed] [Google Scholar]
  19. Kim JS, Tejani VD, Abbas PJ, Brown CJ (2018). Postoperative Electrocochleography from Hybrid Cochlear Implant users: An Alternative Analysis Procedure. Hear Res. 370:304–315. 10.1016/j.heares.2018.10.016. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Kohllöffel LUE (1970). Longitudinal amplitude and phase distribution of the cochlear microphonic (guinea pig) and spatial filtering. Journal of Sound and Vibration. 11(3): 325–334. 10.1016/S0022-460X(70)80036-0. [DOI] [Google Scholar]
  21. Koka K, Riggs WJ, Dwyer R, Holder JT, Noble JH, Dawant BM, Ortmann A, Valenzuela CV, Mattingly JK, Harris MM, O’Connell BP, Litvak LM, Adunka OF, Buchman CA, Labadie RF. (2018). Intra-Cochlear Electrocochleography During Cochear Implant Electrode Insertion Is Predictive of Final Scalar Location. Otol Neurotol. 39(8):e654–e659. 10.1097/MAO.0000000000001906 [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Koka K, Saoji AA, Litvak LM (2017). Electrocochleography in cochlear implant recipients with residual hearing: comparison with audiometric thresholds. Ear Hear. 38(3):e161–e167. 10.1097/AUD.0000000000000385. [DOI] [PubMed] [Google Scholar]
  23. Lenarz T, Stover T, Buechner A, Paasche G, Briggs R, Risi F, Pesch J, Battmer RD. (2006). Temporal bone results and hearing preservation with a new straight electrode. Audiol Neurootol.11 (Suppl 1):34–41. 10.1159/000095612. [DOI] [PubMed] [Google Scholar]
  24. O’Connell BP, Holder JT, Dwyer RT, Gifford RH, et al. , 2017. Intra- and postoperative electrocochleography may be predictive of final electrode position and postoperative hearing preservation. Front. Neurosci 11, 291 10.3389/fnins.2017.00291. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Pfeiffer RR, Molnar CE (1970). Cochlear nerve fiber discharge patterns: relationship to the cochlear microphonic. Science.167(3925):1614–1616. 10.1126/science.167.3925.1614 [DOI] [PubMed] [Google Scholar]
  26. Rhode WS. (1971). Observations of the vibration of the basilar membrane in squirrel monkeys using the Mössbauer technique. J Acoust Soc Am. 49(4):Suppl 2:1218–1231. 10.1121/1.1912485 [DOI] [PubMed] [Google Scholar]
  27. Stakhovskaya O, Sridhar D, Bonham BH, Leake PA. (2007). Frequency map for the human cochlear spiral ganglion: implications for cochlear implants. J Assoc Res Otolaryngol. 8(2): 220–233. 10.1007/s10162-007-0076-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Tasaki I, Davis H, Legouix J-P (1952). The Space-Time Pattern of the Cochlear Microphonics (Guinea Pig), as Recorded by Differential Electrodes. Journal of the Acoustical Society of America 24:5, 502–519. 10.1121/1.1906928. [DOI] [Google Scholar]
  29. Tejani VD, Abbas PJ, Brown CJ, Woo J. (2019). An Improved Method of Obtaining Electrocochleography Recordings from Nucleus Hybrid Cochlear Implant Users. Hearing Research. 373: 113–120. 10.1016/j.heares.2019.01.002. [DOI] [PMC free article] [PubMed] [Google Scholar]

RESOURCES