Electric to acoustic pitch matching: a possible way to improve individual cochlear implant fitting (original) (raw)
Acoustic to Electric Pitch Comparisons in Cochlear Implant Subjects with Residual Hearing
Journal of the Association for Research in Otolaryngology, 2006
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.
Comparisons of electrophysiological and psychophysical fitting methods for cochlear implants
International Journal of Audiology, 2021
Objective: This study compared two different versions of an electrophysiology-based softwareguided cochlear implant fitting method with a procedure employing standard clinical software. The two versions used electrically evoked compound action potential (ECAP) thresholds for either five or all twenty-two electrodes to determine sound processor stimulation level profiles. Objective and subjective performance results were compared between software-guided and clinical fittings. Design: Prospective, double-blind, single-subject repeated-measures with permuted ABCA sequences. Study sample: 48 post linguistically deafened adults with 15 years of severe-to-profound deafness who were newly unilaterally implanted with a Nucleus device. Results: Speech recognition in noise and quiet was not significantly different between software-guided and standard methods, but there was a visit/learning-effect. However, the 5-electrode method gave scores on the SSQ speech subscale 0.5 points lower than the standard method. Clinicians judged usability for all methods as acceptable, as did subjects for comfort. Analysis of stimulation levels and ECAP thresholds suggested that the 5-electrode method could be refined. Conclusions: Speech recognition was not inferior using either version of the electrophysiology-based software-guided fitting method compared with the standard method. Subject-reported speech perception was slightly inferior with the five-electrode method. Software-guided methods saved about 10 min of clinician's time versus standard fittings.
Implications of Deep Electrode Insertion on Cochlear Implant Fitting
Journal of the Association for Research in Otolaryngology, 2007
Using long Med-El Combi40+ electrode arrays, it is now possible to cover the whole range of the cochlea, up to about two turns. Such insertion depths have received little attention. To evaluate the contribution of deeply inserted electrodes, five Med-El cochlear implant users were tested on vowel and consonant identification tests with fittings with first one, two, and up to five apical electrodes being deactivated. In addition, subjects performed pitch-ranking experiments, using loudness-balanced stimuli, to identify electrodes creating pitch confusions. Radiographs were taken to measure each electrode insertion depth. All subjects used each modified fitting for two periods of about 3 weeks. During the experiment, the same stimulation rate and frequency range were maintained across all the fittings used for each individual subject. After each trial period the subject had to perform three consonant and three vowel identification tests. All subjects showed deep electrode insertions ranging from 605-to 720-. The two subjects with the deepest electrode insertions showed significantly increased vowel-and consonant-identification performances with fittings with the two or three most apical electrodes deactivated compared to their standard fitting with all available electrodes activated. The other three subjects did not show significant improvements in performance when one or two of their most apical electrodes were deactivated. Four out of five subjects preferred to continue use of a fitting with one or more apical electrodes deactivated. The two subjects with the deepest insertions also showed pitch confusions between their most apical electrodes. Two possible reasons for these results are discussed. One is to reduce neural interactions related to electrodes producing pitch confusions. Another is to improve the alignment of the frequency components of sounds coded by the electrical signals delivered to each electrode to the overall pitch of the auditory perception produced by the electrical stimulation of auditory nerve fibers.
Cochlear Implant Research and Development in the Twenty-first Century: A Critical Update
Journal of the Association for Research in Otolaryngology
Cochlear implants (CIs) are the world’s most successful sensory prosthesis and have been the subject of intense research and development in recent decades. We critically review the progress in CI research, and its success in improving patient outcomes, from the turn of the century to the present day. The review focuses on the processing, stimulation, and audiological methods that have been used to try to improve speech perception by human CI listeners, and on fundamental new insights in the response of the auditory system to electrical stimulation. The introduction of directional microphones and of new noise reduction and pre-processing algorithms has produced robust and sometimes substantial improvements. Novel speech-processing algorithms, the use of current-focusing methods, and individualised (patient-by-patient) deactivation of subsets of electrodes have produced more modest improvements. We argue that incremental advances have and will continue to be made, that collectively th...
Journal of the American Academy of Audiology, 2012
The Laboratory of Translational Auditory Research (LTAR/NYUSM) is part of the Department of Otolaryngology at the New York University School of Medicine and has close ties to the New York University Cochlear Implant Center. LTAR investigators have expertise in multiple related disciplines including speech and hearing science, audiology, engineering, and physiology. The lines of research in the laboratory deal mostly with speech perception by hearing impaired listeners, and particularly those who use cochlear implants (CIs) or hearing aids (HAs). Although the laboratory's research interests are diverse, there are common threads that permeate and tie all of its work. In particular, a strong interest in translational research underlies even the most basic studies carried out in the laboratory. Another important element is the development of engineering and computational tools, which range from mathematical models of speech perception to software and hardware that bypass clinical speech processors and stimulate cochlear implants directly, to novel ways of analyzing clinical outcomes data. If the appropriate tool to conduct an important experiment does not exist, we may work to develop it, either in house or in collaboration with academic or industrial partners. Another notable characteristic of the laboratory is its interdisciplinary nature where, for example, an audiologist and an engineer might work closely to develop an approach that would not have been feasible if each had worked singly on the project. Similarly, investigators with expertise in hearing aids and cochlear implants might join forces to study how human listeners integrate information provided by a CI and a HA. The following pages provide a flavor of the diversity and the commonalities of our research interests.
Objectives: Recent studies suggest that pitch perceived through co-chlear implants (CIs) changes with experience to minimize spectral mismatches between electric and acoustic hearing. This study aimed to test whether perceived spectral mismatches are similarly minimized between two electric inputs. Design: Pitch perception was studied in a subject with a 10-mm CI in one ear and a 24-mm CI in the other ear. Both processors were programmed to allocate information from the same frequency range of 188 –7938 Hz, despite the large differences in putative insertion depth and stimulated cochlear locations between the CIs. Results: After 2 and 3 years of experience, pitch-matched electrode pairs between CIs were aligned closer to the processor-provided frequencies than to cochlear position. Conclusions: Pitch perception may have adapted to reduce perceived spectral discrepancies between bilateral CI inputs, despite 2–3 octave differences in tonotopic mapping.
What matched comparisons can and cannot tell us: the case of cochlear implants
Ear and hearing, 2007
Objectives: To examine the conclusions and possible misinterpretations that may or may not be drawn from the "outcome-matching method," a study design recently used in the cochlear implant literature. In this method, subject groups are matched not only on potentially confounding variables but also on an outcome measure that is closely related to the outcome measure under analysis. For example, subjects may be matched according to their speech perception scores in quiet, and their speech perception in noise is compared.
Valid Acoustic Models of Cochlear Implants: One Size Does Not Fit All
Otology & Neurotology, 2021
Hypothesis: This study tests the hypothesis that it is possible to find tone or noise vocoders that sound similar and result in similar speech perception scores to a cochlear implant (CI). This would validate the use of such vocoders as acoustic models of CIs. We further hypothesize that those valid acoustic models will require a personalized amount of frequency mismatch between input filters and output tones or noise bands. Background: Noise or tone vocoders have been used as acoustic models of CIs in hundreds of publications but never been convincingly validated.
Current Research with Cochlear Implants at Arizona State University
Journal of the American Academy of Audiology, 2000
In this article we review, and discuss the clinical implications of, five projects currently underway in the Cochlear Implant Laboratory at Arizona State University. The projects are (1) norming the AzBio sentence test, (2) comparing the performance of bilateral and bimodal cochlear implant (CI) patients in realistic listening environments, (3) accounting for the benefit provided to bimodal patients by low-frequency acoustic stimulation, (4) assessing localization by bilateral hearing aid patients and the implications of that work for hearing preservation patients, and (5) studying heart rate variability as a possible measure for quantifying the stress of listening via an implant. The long-term goals of the laboratory are to improve the performance of patients fit with cochlear implants and to understand the mechanisms, physiological or electronic, that underlie changes in performance. We began our work with cochlear implant patients in the mid-1980s and received our first grant from the National Institutes of Health (NIH) for work with implanted patients in 1989. Since that date our work with cochlear implant patients has been funded continuously by the NIH. In this report we describe some of the research currently being conducted in our laboratory.
12th International Conference on Cochlear Implants and Other Implantable Auditory Technologies
2012
Background and aims: State-of-the-art cochlear implant programming software is essentially technical. It exposes many control parameters, such as strategy options, electrical mapping levels, audio input control,... to the CI expert audiologist. The role of the CI audiologist is to know how to set these parameters in order to optimize the hearing performance of the CI user. The FOX® fitting system, developed by the Eargroup takes a different approach: it proposes an audiological workflow with specific hearing milestones such as detection of soft sounds, phoneme discrimination and speech in quiet. The FOX agent proposes fitting recommendations based on the outcomes. Multicentric study is ongoing to evaluate this approach in new users and to evaluate its efficacy and time efficiency.Methods: Two subject groups, the control and the FOX group are being investigated from the initial switch on over a period of six months. Fitting time requirements, learning trajectory and overall performan...
Cochlear implants: A remarkable past and a brilliant future
Hearing Research, 2008
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. Ó 2008 Elsevier B.V. All rights reserved. ''.. .I am just as deaf as I am blind. The problems of deafness are deeper and more complex, if not more important, than those of blindness. Deafness is a much worse misfortune. For it means the loss of the most vital stimulus-the sound of the voice that brings language, sets thoughts astir and keeps us in the intellectual company of man." These poignant descriptions convey the feelings of isolation that often accompany deafness. Beethoven stressed loneliness as the major hardship, as opposed to a separation from his music. Helen Keller stressed that ''blindness cuts one off from things, but deafness cuts one off from people." Just thirty years ago there were no effective treatments for deafness or severe hearing impairments. The advent of cochlear implants (CIs) changed that, and today implants are widely regarded as one of the great achievements of modern medicine.
Proceedings of the Annual Symposium of the American Cochlear Implant Alliance
Cochlear implants international, 2016
In 2015, four US cochlear implant centers had FDA approved Investigational Device Exemptions (IDE) protocols for the implantation of children with deficient or absent cochleae or cochlear nerve deficiency. Approximately, 20 US children had been implanted as of October 2015 under IDEs. Among the key considerations for ABI use in children are the candidacy evaluation, audiological management, provision of a cochlear implant before ABI (to aide/confirm decision-making), surgical placement and complications, and expected speech and language development benefits. Objective measures and outcomes of ABI in children have been utilized to inform the decision-making in the provision of the ABI device.
Representation of acoustic signals in the human cochlea in presence of a cochlear implant electrode
Hearing Research, 2006
Background: In subjects with remaining low frequency hearing, combined electric-acoustic stimulation (EAS) of the auditory system is a new therapeutic perspective. Intracochlear introduction of a cochlear implant electrode, however, may alter the biomechanical properties of the inner ear and thus affect perception of acoustic stimuli. Study design: Based on histological observations of morphologic changes after cochlear implantation in cadaveric and post mortem studies the effects of basilar membrane (BM) stiffening in the ascending basal and middle turns of the cochlea due to close contact of the BM with the electrode were simulated in a 3D-computational finite element model of the inner ear. To verify our simulated results, pre-and postoperative pure-tone audiograms of 13 subjects with substantial residual hearing, who underwent cochlear implantation, were evaluated. Results: In the scenario of partial BM-fixation, acoustic energy of middle (2 kHz) and high (6 kHz) frequency was focused basally and apically to the fixed section, increasing BM displacement amplitudes up to 6 dB at a stimulation level of 94 dB (SPL). Lower frequencies were not affected by fixation in the basal and middle turn of the cochlea. In implanted subjects, a small but significant decrease of thresholds was observed at 1.5 kHz, a place in tonotopy adjacent to the tip region of the implanted electrode. Conclusion: Our model suggests that stiffening of the basilar membrane adjacent to an implanted electrode into the basal and middle cochlear turn did not affect BM movement in the low frequency area. Focussing of acoustic energy may increase perception in regions adjacent to the fixed section. Observations in implanted subjects were concordant with our model predictions. High frequencies, however, should not be amplified in patients using EAS to avoid disturbances in discrimination due to tonotopically incorrect frequency representation.
The cochlear implant has not only provided partial hearing to more than 120,000 persons worldwide but also served as a model for successful academic and industrial collaboration. The present chapter reviews the development of modern cochlear implants and the dynamic interactions between academia and industry. The chapter takes a system approach to the cochlear implant system design and specifications. The design goals, principles, and methods of the subsystem components are identified from the external speech processor and radio frequency transmission link to the internal receiver, stimulator, and electrode arrays. Safety and reliability issues are considered in the context of the system design and the regulatory requirements. Future directions are discussed with regard to the expanded role of the cochlear implant in treatment of hearing impairment and in development of other neural prostheses.
Cochlear infrastructure for electrical hearing.
Hearing …, 2011
Although the cochlear implant is already the world's most successful neural prosthesis, opportunities for further improvement abound. Promising areas of current research include work on improving the biological infrastructure in the implanted cochlea to optimize reception of cochlear implant stimulation and on designing the pattern of electrical stimulation to take maximal advantage of conditions in the implanted cochlea. In this review we summarize what is currently known about conditions in the cochlea of deaf, implanted humans and then review recent work from our animal laboratory investigating the effects of preserving or reinnervating tissues on psychophysical and electrophysiological measures of implant function. Additionally we review work from our human laboratory on optimizing the pattern of electrical stimulation to better utilize strengths in the cochlear infrastructure. Histological studies of human temporal bones from implant users and from people who would have been candidates for implants show a range of pathologic conditions including spiral ganglion cell counts ranging from approximately 2% to 92% of normal and partial hair cell survival in some cases. To duplicate these conditions in a guinea pig model, we use a variety of deafening and implantation procedures as well as post-deafening therapies designed to protect neurons and/or regenerate neurites. Across populations of human patients, relationships between nerve survival and functional measures such as speech have been difficult to demonstrate, possibly due to the numerous subject variables that can affect implant function and the elapsed time between functional measures and postmortem histology. However, psychophysical studies across stimulation sites within individual human subjects suggest that biological conditions near the implanted electrodes contribute significantly to implant function, and this is supported by studies in animal models comparing histological findings to psychophysical and electrophysiological data. Results of these studies support the efforts to improve the biological infrastructure in the implanted ear and guide strategies which optimize stimulation patterns to match patient-specific conditions in the cochlea.
Cochlear implants: the view from the brain
Current Opinion in Neurobiology, 2005
The cochlear implant arguably is the most successful neural prosthesis. Studies of the responses of the central auditory system to prosthetic electrical stimulation of the cochlea are revealing the success with which electrical stimulation of a deaf ear can mimic acoustic stimulation of a normal-hearing ear. Understanding of the physiology of central auditory structures can lead to improved restoration of hearing with cochlear implants. In turn, the cochlear implant can be exploited as an experimental tool for examining central hearing mechanisms isolated from the effects of cochlear mechanics and transduction. The cochlear implants Middlebrooks, Arenberg Bierer and Snyder 491 www.sciencedirect.com Current Opinion in Neurobiology 2005, 15:488-493 55. Bierer JA, Middlebrooks JC: Cortical responses to cochlear implant stimulation: channel interactions. J Assoc Res Otolaryngol 2004, 5:32-48. 56. Middlebrooks JC: Effects of cochlear-implant pulse rate and inter-channel timing on channel interactions and thresholds.