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Camarena A, Goldsworthy RL. Characterizing the relationship between modulation sensitivity and pitch resolution in cochlear implant users. Hear Res 2024; 448:109026. [PMID: 38776706 DOI: 10.1016/j.heares.2024.109026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 03/28/2024] [Accepted: 04/30/2024] [Indexed: 05/25/2024]
Abstract
Cochlear implants are medical devices that have restored hearing to approximately one million people around the world. Outcomes are impressive and most recipients attain excellent speech comprehension in quiet without relying on lip-reading cues, but pitch resolution is poor compared to normal hearing. Amplitude modulation of electrical stimulation is a primary cue for pitch perception in cochlear implant users. The experiments described in this article focus on the relationship between sensitivity to amplitude modulations and pitch resolution based on changes in the frequency of amplitude modulations. In the first experiment, modulation sensitivity and pitch resolution were measured in adults with no known hearing loss and in cochlear implant users with sounds presented to and processed by their clinical devices. Stimuli were amplitude-modulated sinusoids and amplitude-modulated narrow-band noises. Modulation detection and modulation frequency discrimination were measured for modulation frequencies centered on 110, 220, and 440 Hz. Pitch resolution based on changes in modulation frequency was measured for modulation depths of 25 %, 50 %, 100 %, and for a half-waved rectified modulator. Results revealed a strong linear relationship between modulation sensitivity and pitch resolution for cochlear implant users and peers with no known hearing loss. In the second experiment, cochlear implant users took part in analogous procedures of modulation sensitivity and pitch resolution but bypassing clinical sound processing using single-electrode stimulation. Results indicated that modulation sensitivity and pitch resolution was better conveyed by single-electrode stimulation than by clinical processors. Results at 440 Hz were worse, but also not well conveyed by clinical sound processing, so it remains unclear whether the 300 Hz perceptual limit described in the literature is a technological or biological limitation. These results highlight modulation depth and sensitivity as critical factors for pitch resolution in cochlear implant users and characterize the relationship that should inform the design of modulation enhancement algorithms for cochlear implants.
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Affiliation(s)
- Andres Camarena
- Auditory Research Center, Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States of America
| | - Raymond L Goldsworthy
- Auditory Research Center, Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States of America.
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2
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Anderson SR, Burg E, Suveg L, Litovsky RY. Review of Binaural Processing With Asymmetrical Hearing Outcomes in Patients With Bilateral Cochlear Implants. Trends Hear 2024; 28:23312165241229880. [PMID: 38545645 PMCID: PMC10976506 DOI: 10.1177/23312165241229880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 01/11/2024] [Accepted: 01/16/2024] [Indexed: 04/01/2024] Open
Abstract
Bilateral cochlear implants (BiCIs) result in several benefits, including improvements in speech understanding in noise and sound source localization. However, the benefit bilateral implants provide among recipients varies considerably across individuals. Here we consider one of the reasons for this variability: difference in hearing function between the two ears, that is, interaural asymmetry. Thus far, investigations of interaural asymmetry have been highly specialized within various research areas. The goal of this review is to integrate these studies in one place, motivating future research in the area of interaural asymmetry. We first consider bottom-up processing, where binaural cues are represented using excitation-inhibition of signals from the left ear and right ear, varying with the location of the sound in space, and represented by the lateral superior olive in the auditory brainstem. We then consider top-down processing via predictive coding, which assumes that perception stems from expectations based on context and prior sensory experience, represented by cascading series of cortical circuits. An internal, perceptual model is maintained and updated in light of incoming sensory input. Together, we hope that this amalgamation of physiological, behavioral, and modeling studies will help bridge gaps in the field of binaural hearing and promote a clearer understanding of the implications of interaural asymmetry for future research on optimal patient interventions.
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Affiliation(s)
- Sean R. Anderson
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical School, Aurora, CO, USA
| | - Emily Burg
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
- Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Lukas Suveg
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Ruth Y. Litovsky
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
- Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, USA
- Department of Surgery, Division of Otolaryngology, University of Wisconsin-Madison, Madison, WI, USA
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Andren KG, Duffin K, Ryan MT, Riley CA, Tolisano AM. Postoperative optimization of cochlear implantation for single sided deafness and asymmetric hearing loss: a systematic review. Cochlear Implants Int 2023; 24:342-353. [PMID: 37490782 DOI: 10.1080/14670100.2023.2239512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
OBJECTIVE Identify and evaluate the effectiveness of methods for improving postoperative cochlear implant (CI) hearing performance in subjects with single-sided deafness (SSD) and asymmetric hearing loss (AHL). DATA SOURCES Embase, PubMed, Scopus. REVIEW METHODS Systematic review and narrative synthesis. English language studies of adult CI recipients with SSD and AHL reporting a postoperative intervention and comparative audiometric data pertaining to speech in noise, speech in quiet and sound localization were included. RESULTS 32 studies met criteria for full text review and 6 (n = 81) met final inclusion criteria. Interventions were categorized as: formal auditory training, programming techniques, or hardware optimization. Formal auditory training (n = 10) found no objective improvement in hearing outcomes. Experimental CI maps did not improve audiologic outcomes (n = 9). Programed CI signal delays to improve synchronization demonstrated improved sound localization (n = 12). Hardware optimization, including multidirectional (n = 29) and remote (n = 11) microphones, improved sound localization and speech in noise, respectively. CONCLUSION Few studies meeting inclusion criteria and small sample sizes highlight the need for further study. Formal auditory training did not appear to improve hearing outcomes. Programming techniques, such as CI signal delay, and hardware optimization, such as multidirectional and remote microphones, show promise to improve outcomes for SSD and AHL CI users.
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Affiliation(s)
- Kristofer G Andren
- Department of Otolaryngology - Head & Neck Surgery, San Antonio Uniformed Services Health Education Consortium, San Antonio, TX, USA
| | - Kevin Duffin
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Matthew T Ryan
- Department of Otolaryngology - Head & Neck Surgery, Walter Reed National Military Medical Center, Bethesda, MD, USA
| | - Charles A Riley
- Department of Otolaryngology - Head & Neck Surgery, Walter Reed National Military Medical Center, Bethesda, MD, USA
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Anthony M Tolisano
- Department of Otolaryngology - Head & Neck Surgery, Walter Reed National Military Medical Center, Bethesda, MD, USA
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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4
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Zhou N, Shi X, Dixit O, Firszt JB, Holden TA. Relationship between electrode position and temporal modulation sensitivity in cochlear implant users: Are close electrodes always better? Heliyon 2023; 9:e12467. [PMID: 36852047 PMCID: PMC9958279 DOI: 10.1016/j.heliyon.2022.e12467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 10/21/2022] [Accepted: 12/11/2022] [Indexed: 12/24/2022] Open
Abstract
Temporal modulation sensitivity has been studied extensively for cochlear implant (CI) users due to its strong correlation to speech recognition outcomes. Previous studies reported that temporal modulation detection thresholds (MDTs) vary across the tonotopic axis and attributed this variation to patchy neural survival. However, correlates of neural health identified in animal models depend on electrode position in humans. Nonetheless, the relationship between MDT and electrode location has not been explored. We tested 13 ears for the effect of distance on modulation sensitivity, specifically targeting the question of whether electrodes closer to the modiolus are universally beneficial. Participants in this study were postlingually deafened and users of Cochlear Nucleus CIs. The distance of each electrode from the medial wall (MW) of the cochlea and mid-modiolar axis (MMA) was measured from scans obtained using computerized tomography (CT) imaging. The distance measures were correlated with slopes of spatial tuning curves measured on selected electrodes to investigate if electrode position accounts, at least in part, for the width of neural excitation. In accordance with previous findings, electrode position explained 24% of the variance in slopes of the spatial tuning curves. All functioning electrodes were also measured for MDTs. Five ears showed a positive correlation between MDTs and at least one distance measure across the array; 6 ears showed negative correlations and the remaining two ears showed no relationship. The ears showing positive MDT-distance correlations, thus benefiting from electrodes being close to the neural elements, were those who performed better on the two speech recognition measures, i.e., speech reception thresholds (SRTs) and recognition of the AzBio sentences. These results could suggest that ears able to take advantage of the proximal placement of electrodes are likely to have better speech recognition outcomes. Previous histological studies of humans demonstrated that speech recognition is correlated with spiral ganglion cell counts. Alternatively, ears with good speech recognition outcomes may have good overall neural health, which is a precondition for close electrodes to produce spatially confined neural excitation patterns that facilitate modulation sensitivity. These findings suggest that the methods to reduce channel interaction, e.g., perimodiolar electrode array or current focusing, may only be beneficial for a subgroup of CI users. Additionally, it suggests that estimating neural survival preoperatively is important for choosing the most appropriate electrode array type (perimodiolar vs. lateral wall) for optimal implant function.
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Affiliation(s)
- Ning Zhou
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, 27834, USA
| | - Xuyang Shi
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, 27834, USA
| | - Omkar Dixit
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, 27834, USA
| | - Jill B Firszt
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
| | - Timothy A Holden
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
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Anderson SR, Kan A, Litovsky RY. Asymmetric temporal envelope sensitivity: Within- and across-ear envelope comparisons in listeners with bilateral cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 152:3294. [PMID: 36586876 PMCID: PMC9731674 DOI: 10.1121/10.0016365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 11/14/2022] [Accepted: 11/16/2022] [Indexed: 06/17/2023]
Abstract
For listeners with bilateral cochlear implants (BiCIs), patient-specific differences in the interface between cochlear implant (CI) electrodes and the auditory nerve can lead to degraded temporal envelope information, compromising the ability to distinguish between targets of interest and background noise. It is unclear how comparisons of degraded temporal envelope information across spectral channels (i.e., electrodes) affect the ability to detect differences in the temporal envelope, specifically amplitude modulation (AM) rate. In this study, two pulse trains were presented simultaneously via pairs of electrodes in different places of stimulation, within and/or across ears, with identical or differing AM rates. Results from 11 adults with BiCIs indicated that sensitivity to differences in AM rate was greatest when stimuli were paired between different places of stimulation in the same ear. Sensitivity from pairs of electrodes was predicted by the poorer electrode in the pair or the difference in fidelity between both electrodes in the pair. These findings suggest that electrodes yielding poorer temporal fidelity act as a bottleneck to comparisons of temporal information across frequency and ears, limiting access to the cues used to segregate sounds, which has important implications for device programming and optimizing patient outcomes with CIs.
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Affiliation(s)
- Sean R Anderson
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | - Alan Kan
- School of Engineering, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Ruth Y Litovsky
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
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Dillon MT, O'Connell BP, Canfarotta MW, Buss E, Hopfinger J. Effect of Place-Based Versus Default Mapping Procedures on Masked Speech Recognition: Simulations of Cochlear Implant Alone and Electric-Acoustic Stimulation. Am J Audiol 2022; 31:322-337. [PMID: 35394798 DOI: 10.1044/2022_aja-21-00123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Cochlear implant (CI) recipients demonstrate variable speech recognition when listening with a CI-alone or electric-acoustic stimulation (EAS) device, which may be due in part to electric frequency-to-place mismatches created by the default mapping procedures. Performance may be improved if the filter frequencies are aligned with the cochlear place frequencies, known as place-based mapping. Performance with default maps versus an experimental place-based map was compared for participants with normal hearing when listening to CI-alone or EAS simulations to observe potential outcomes prior to initiating an investigation with CI recipients. METHOD A noise vocoder simulated CI-alone and EAS devices, mapped with default or place-based procedures. The simulations were based on an actual 24-mm electrode array recipient, whose insertion angles for each electrode contact were used to estimate the respective cochlear place frequency. The default maps used the filter frequencies assigned by the clinical software. The filter frequencies for the place-based maps aligned with the cochlear place frequencies for individual contacts in the low- to mid-frequency cochlear region. For the EAS simulations, low-frequency acoustic information was filtered to simulate aided low-frequency audibility. Performance was evaluated for the AzBio sentences presented in a 10-talker masker at +5 dB signal-to-noise ratio (SNR), +10 dB SNR, and asymptote. RESULTS Performance was better with the place-based maps as compared with the default maps for both CI-alone and EAS simulations. For instance, median performance at +10 dB SNR for the CI-alone simulation was 57% correct for the place-based map and 20% for the default map. For the EAS simulation, those values were 59% and 37% correct. Adding acoustic low-frequency information resulted in a similar benefit for both maps. CONCLUSIONS Reducing frequency-to-place mismatches, such as with the experimental place-based mapping procedure, produces a greater benefit in speech recognition than maximizing bandwidth for CI-alone and EAS simulations. Ongoing work is evaluating the initial and long-term performance benefits in CI-alone and EAS users. SUPPLEMENTAL MATERIAL https://doi.org/10.23641/asha.19529053.
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Affiliation(s)
- Margaret T. Dillon
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
- Division of Speech and Hearing Sciences, Department of Allied Health Sciences, University of North Carolina at Chapel Hill
| | - Brendan P. O'Connell
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
| | - Michael W. Canfarotta
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
| | - Emily Buss
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
| | - Joseph Hopfinger
- Department of Psychology and Neuroscience, University of North Carolina at Chapel Hill
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Garadat SN, Colesa DJ, Swiderski DL, Raphael Y, Pfingst BE. Estimating health of the implanted cochlea using psychophysical strength-duration functions and electrode configuration. Hear Res 2022; 414:108404. [PMID: 34883366 PMCID: PMC8761176 DOI: 10.1016/j.heares.2021.108404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 11/17/2021] [Accepted: 11/25/2021] [Indexed: 02/03/2023]
Abstract
It is generally believed that the efficacy of cochlear implants is partly dependent on the condition of the stimulated neural population. Cochlear pathology is likely to affect the manner in which neurons respond to electrical stimulation, potentially resulting in differences in perception of electrical stimuli across cochlear implant recipients and across the electrode array in individual cochlear implant users. Several psychophysical and electrophysiological measures have been shown to predict cochlear health in animals and were used to assess conditions near individual stimulation sites in humans. In this study, we examined the relationship between psychophysical strength-duration functions and spiral ganglion neuron density in two groups of guinea pigs with cochlear implants who had minimally-overlapping cochlear health profiles. One group was implanted in a hearing ear (N = 10) and the other group was deafened by cochlear perfusion of neomycin, inoculated with an adeno-associated viral vector with an Ntf3-gene insert (AAV.Ntf3) and implanted (N = 14). Psychophysically measured strength-duration functions for both monopolar and tripolar electrode configurations were then compared for the two treatment groups. Results were also compared to their histological outcomes. Overall, there were considerable differences between the two treatment groups in terms of their psychophysical performance as well as the relation between their functional performance and histological data. Animals in the neomycin-deafened, neurotrophin-treated, and implanted group (NNI) exhibited steeper strength-duration function slopes; slopes were positively correlated with SGN density (steeper slopes in animals that had higher SGN densities). In comparison, the implanted hearing (IH) group had shallower slopes and there was no relation between slopes and spiral ganglion density. Across all animals, slopes were negatively correlated with ensemble spontaneous activity levels (shallower slopes with higher ensemble spontaneous activity levels). We hypothesize that differences in strength-duration function slopes between the two treatment groups were related to the condition of the inner hair cells, which generate spontaneous activity that could affect the across-fiber synchrony and/or the size of the population of neural elements responding to electrical stimulation. In addition, it is likely that spiral ganglion neuron peripheral processes were present in the IH group, which could affect membrane properties of the stimulated neurons. Results suggest that the two treatment groups exhibited distinct patterns of variation in conditions near the stimulating electrodes that altered detection thresholds. Overall, the results of this study suggest a complex relationship between psychophysical detection thresholds for cochlear implant stimulation and nerve survival in the implanted cochlea. This relationship seems to depend on the characteristics of the electrical stimulus, the electrode configuration, and other biological features of the implanted cochlea such as the condition of the inner hair cells and the peripheral processes.
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Affiliation(s)
- Soha N. Garadat
- Department of Hearing and Speech Sciences, The University of Jordan, Amman, 11942, Jordan,Kresge Hearing Research Institute, Department of Otolaryngology—Head and Neck Surgery, University of Michigan, Ann Arbor, MI 48109-5616, USA
| | - Deborah J. Colesa
- Kresge Hearing Research Institute, Department of Otolaryngology—Head and Neck Surgery, University of Michigan, Ann Arbor, MI 48109-5616, USA
| | - Donald L. Swiderski
- Kresge Hearing Research Institute, Department of Otolaryngology—Head and Neck Surgery, University of Michigan, Ann Arbor, MI 48109-5616, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology—Head and Neck Surgery, University of Michigan, Ann Arbor, MI 48109-5616, USA
| | - Bryan E. Pfingst
- Kresge Hearing Research Institute, Department of Otolaryngology—Head and Neck Surgery, University of Michigan, Ann Arbor, MI 48109-5616, USA
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Predictors of Postoperative Electrode Deactivation Among Adult Cochlear Implantees. Otol Neurotol 2021; 42:e675-e683. [PMID: 33625193 DOI: 10.1097/mao.0000000000003093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To characterize postoperative electrode functionality after adult cochlear implantation; to identify rationale and risk factors for electrode deactivation. STUDY DESIGN Retrospective Chart Review. SETTING Academic Cochlear Implant Center. SUBJECT POPULATION Five hundred nineteen cochlear implants in 433 adult patients over 5 years. INTERVENTIONS Unilateral or bilateral cochlear implantation. MAIN OUTCOME MEASURES Rate of electrode deactivation after adult cochlear implantation. RESULTS One hundred twenty (27.7%) patients experienced electrode deactivation postoperatively, involving a total of 447 electrodes. The most common reasons for deactivation were bothersome nonauditory symptoms (n = 170, 38.0%), perceived benefit by patients (n = 64, 14.3%), and bothersome auditory symptoms (n = 60, 13.4%). Four hundred nineteen (93.7%) of involved electrodes remained deactivated at most recent follow-up, whereas 28 (6.3%) were able to be reactivated. Deactivation was most likely to occur within the first 4 weeks after activation (n = 90 patients,75.0%; p < 0.01). Among affected patients, the average number of electrodes deactivated was 3.44 (range 1-13; SD 2.50). Age was not associated with electrode deactivation. CONCLUSIONS While 98% of cochlear implants had full insertions, more than a quarter of implantees may experience electrode deactivation postoperatively for a multitude of reasons, with bothersome nonauditory symptoms most prevalent. Deactivation of five or more electrodes and simultaneous deactivation of two or three electrodes seems to increase the odds of subsequent device failure. However, deactivation encompasses a wide range of issues that likely include patient factors, surgical technique, and device-specific issues. Prognosis varies greatly at the individual level and further evaluation is required to better identify the issues underlying deactivation and identify true predictors of failure.
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Liu JS, Liu YW, Yu YF, Galvin JJ, Fu QJ, Tao DD. Segregation of competing speech in adults and children with normal hearing and in children with cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:339. [PMID: 34340485 DOI: 10.1121/10.0005597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 06/22/2021] [Indexed: 06/13/2023]
Abstract
Children with normal hearing (CNH) have greater difficulty segregating competing speech than do adults with normal hearing (ANH). Children with cochlear implants (CCI) have greater difficulty segregating competing speech than do CNH. In the present study, speech reception thresholds (SRTs) in competing speech were measured in Chinese Mandarin-speaking ANH, CNH, and CCIs. Target sentences were produced by a male Mandarin-speaking talker. Maskers were time-forward or -reversed sentences produced by a native Mandarin-speaking male (different from the target) or female or a non-native English-speaking male. The SRTs were lowest (best) for the ANH group, followed by the CNH and CCI groups. The masking release (MR) was comparable between the ANH and CNH group, but much poorer in the CCI group. The temporal properties differed between the native and non-native maskers and between forward and reversed speech. The temporal properties of the maskers were significantly associated with the SRTs for the CCI and CNH groups but not for the ANH group. Whereas the temporal properties of the maskers were significantly associated with the MR for all three groups, the association was stronger for the CCI and CNH groups than for the ANH group.
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Affiliation(s)
- Ji-Sheng Liu
- Department of Ear, Nose, and Throat, The First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Yang-Wenyi Liu
- Department of Otology and Skull Base Surgery, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China
| | - Ya-Feng Yu
- Department of Ear, Nose, and Throat, The First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - John J Galvin
- House Ear Institute, Los Angeles, California 90057, USA
| | - Qian-Jie Fu
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, California 90095, USA
| | - Duo-Duo Tao
- Department of Ear, Nose, and Throat, The First Affiliated Hospital of Soochow University, Suzhou 215006, China
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Schvartz-Leyzac KC, Zwolan TA, Pfingst BE. Using the electrically-evoked compound action potential (ECAP) interphase gap effect to select electrode stimulation sites in cochlear implant users. Hear Res 2021; 406:108257. [PMID: 34020316 DOI: 10.1016/j.heares.2021.108257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 03/25/2021] [Accepted: 04/19/2021] [Indexed: 10/21/2022]
Abstract
Studies in cochlear implanted animals show that the IPG Effect for ECAP growth functions (i.e., the magnitude of the change in ECAP amplitude growth function (AGF) slope or peak amplitude when the interphase gap (IPG) is increased) can be used to estimate the densities of spiral ganglion neurons (SGNs) near the electrode stimulation and recording sites. In humans, the same ECAP IPG Effect measures correlate with speech recognition performance. The present study examined the efficacy of selecting electrode sites for stimulation based on the IPG Effect, in order to improve performance of CI users on speech recognition tasks. We measured the ECAP IPG Effect for peak amplitude in adult (>18 years old) CI users (N= 18 ears), and created experimental programs to stimulate electrodes with either the highest or lowest ECAP IPG Effect for peak amplitude. Subjects also listened to a program without any electrodes deactivated. In a subset of subject ears (11/18), we compared performance differences between the experimental programs to post-operative computerized tomography (CT) scans to examine underlying factors that might contribute to the efficacy of an electrode site-selection approach. For sentences-in-noise, average performance was better when subjects listened to the experimental program that stimulated electrodes with the highest rather than the lowest IPG Effect for ECAP peak amplitude. A similar pattern was noted for transmission and perception of consonant place cues in a consonant recognition task. However, on average, performance when listening to a program with higher IPG Effect values was equal to that when listening with all electrodes activated. Results also suggest that scalar location (scala tympani or vestibuli) should be considered when using an ECAP-based electrode site-selection procedure to optimize CI performance.
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Affiliation(s)
- Kara C Schvartz-Leyzac
- Kresge Hearing Research Institute, Department of Otolaryngology, Michigan Medicine, 1150 West Medical Center Drive, Ann Arbor, MI 48109-5616, United States; Hearing Rehabilitation Center, Department of Otolaryngology, Michigan Medicine, 475 W. Market Place, Building 1, Suite A, Ann Arbor, MI 48108, United States.
| | - Teresa A Zwolan
- Hearing Rehabilitation Center, Department of Otolaryngology, Michigan Medicine, 475 W. Market Place, Building 1, Suite A, Ann Arbor, MI 48108, United States
| | - Bryan E Pfingst
- Kresge Hearing Research Institute, Department of Otolaryngology, Michigan Medicine, 1150 West Medical Center Drive, Ann Arbor, MI 48109-5616, United States
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Zhou N, Dixon S, Zhu Z, Dong L, Weiner M. Spectrotemporal Modulation Sensitivity in Cochlear-Implant and Normal-Hearing Listeners: Is the Performance Driven by Temporal or Spectral Modulation Sensitivity? Trends Hear 2020; 24:2331216520948385. [PMID: 32895024 PMCID: PMC7482033 DOI: 10.1177/2331216520948385] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
This study examined the contribution of temporal and spectral modulation sensitivity to discrimination of stimuli modulated in both the time and frequency domains. The spectrotemporally modulated stimuli contained spectral ripples that shifted systematically across frequency over time at a repetition rate of 5 Hz. As the ripple density increased in the stimulus, modulation depth of the 5 Hz amplitude modulation (AM) reduced. Spectrotemporal modulation discrimination was compared with subjects’ ability to discriminate static spectral ripples and the ability to detect slow AM. The general pattern from both the cochlear implant (CI) and normal hearing groups showed that spectrotemporal modulation thresholds were correlated more strongly with AM detection than with static ripple discrimination. CI subjects’ spectrotemporal modulation thresholds were also highly correlated with speech recognition in noise, when partialing out static ripple discrimination, but the correlation was not significant when partialing out AM detection. The results indicated that temporal information was more heavily weighted in spectrotemporal modulation discrimination, and for CI subjects, it was AM sensitivity that drove the correlation between spectrotemporal modulation thresholds and speech recognition. The results suggest that for the rates tested here, temporal information processing may limit performance more than spectral information processing in both CI users and normal hearing listeners.
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Affiliation(s)
- Ning Zhou
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, North Carolina, United States
| | - Susannah Dixon
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, North Carolina, United States
| | - Zhen Zhu
- Department of Engineering, East Carolina University, Greenville, North Carolina, United States
| | - Lixue Dong
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, North Carolina, United States
| | - Marti Weiner
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, North Carolina, United States
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12
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Effects of noise on integration of acoustic and electric hearing within and across ears. PLoS One 2020; 15:e0240752. [PMID: 33057396 PMCID: PMC7561114 DOI: 10.1371/journal.pone.0240752] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 10/01/2020] [Indexed: 11/19/2022] Open
Abstract
In bimodal listening, cochlear implant (CI) users combine electric hearing (EH) in one ear and acoustic hearing (AH) in the other ear. In electric-acoustic stimulation (EAS), CI users combine EH and AH in the same ear. In quiet, integration of EH and AH has been shown to be better with EAS, but with greater sensitivity to tonotopic mismatch in EH. The goal of the present study was to evaluate how external noise might affect integration of AH and EH within or across ears. Recognition of monosyllabic words was measured for normal-hearing subjects listening to simulations of unimodal (AH or EH alone), EAS, and bimodal listening in quiet and in speech-shaped steady noise (10 dB, 0 dB signal-to-noise ratio). The input/output frequency range for AH was 0.1–0.6 kHz. EH was simulated using an 8-channel noise vocoder. The output frequency range was 1.2–8.0 kHz to simulate a shallow insertion depth. The input frequency range was either matched (1.2–8.0 kHz) or mismatched (0.6–8.0 kHz) to the output frequency range; the mismatched input range maximized the amount of speech information, while the matched input resulted in some speech information loss. In quiet, tonotopic mismatch differently affected EAS and bimodal performance. In noise, EAS and bimodal performance was similarly affected by tonotopic mismatch. The data suggest that tonotopic mismatch may differently affect integration of EH and AH in quiet and in noise.
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Auditory performance of post-lingually deafened adult cochlear implant recipients using electrode deactivation based on postoperative cone beam CT images. Eur Arch Otorhinolaryngol 2020; 278:977-986. [PMID: 32588169 DOI: 10.1007/s00405-020-06156-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 06/18/2020] [Indexed: 01/04/2023]
Abstract
PURPOSE The use of image processing techniques to estimate the position of intra-cochlear electrodes has enabled the creation of personalized maps to meet the individual stimulation needs of cochlear implant (CI) recipients. The aim of this study was to evaluate a novel technique of electrode deactivation based on postoperative cone beam computed tomography (CBCT) images in post-lingually deafened adult CI recipients. METHODS Based on postoperative CBCT images, the positioning of the electrodes was estimated in relation to the modiolus in 14 ears of 13 post-lingually deafened adult CI recipients. The electrodes sub-optimally positioned or involved in kinking and tip fold-over were deactivated. Speech perception scores in silence and in noise were obtained from subjects using the standard map and were followed up 4 weeks after image-based electrode deactivation reprogramming technique (IBEDRT). The participants selected their preferred map after 4 weeks of IBEDRT use. RESULTS There were statistically significant improvements in the speech recognition tests in silence and noise when comparing IBEDRT performance to the standard map. All participants elected the IBEDRT as their new preferred map. CONCLUSIONS IBEDRT is a promising technique for fitting CI recipients and minimizing channel interaction increased by the positioning of the electrodes sub-optimally placed, thereby improving their auditory performance. We propose a novel electrode deactivation technique based on postoperative CBCT imaging, with a limited number of deactivated electrodes and a low-dosing scanning which could be applied for clinical routine.
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Kreft HA, DeVries LA, Arenberg JG, Oxenham AJ. Comparing Rapid and Traditional Forward-Masked Spatial Tuning Curves in Cochlear-Implant Users. Trends Hear 2019; 23:2331216519851306. [PMID: 31134842 PMCID: PMC6540501 DOI: 10.1177/2331216519851306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A rapid forward-masked spatial tuning curve measurement procedure, based on Bekesy tracking, was adapted and evaluated for use with cochlear implants. Twelve postlingually-deafened adult cochlear-implant users participated. Spatial tuning curves using the new procedure and using a traditional forced-choice adaptive procedure resulted in similar estimates of parameters. The Bekesy-tracking method was almost 3 times faster than the forced-choice procedure, but its test-retest reliability was significantly poorer. Although too time-consuming for general clinical use, the new method may have some benefits in individual cases, where identifying electrodes with poor spatial selectivity as candidates for deactivation is deemed necessary.
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Affiliation(s)
- Heather A Kreft
- 1 Department of Psychology, University of Minnesota, Minneapolis, MN, USA
| | - Lindsay A DeVries
- 2 Department Hearing and Speech Sciences, University of Maryland, College Park, MD, USA
| | - Julie G Arenberg
- 3 Department of Otolaryngology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA
| | - Andrew J Oxenham
- 1 Department of Psychology, University of Minnesota, Minneapolis, MN, USA
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Anderson SR, Kan A, Litovsky RY. Asymmetric temporal envelope encoding: Implications for within- and across-ear envelope comparison. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:1189. [PMID: 31472559 PMCID: PMC7051005 DOI: 10.1121/1.5121423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Revised: 07/24/2019] [Accepted: 07/24/2019] [Indexed: 05/17/2023]
Abstract
Separating sound sources in acoustic environments relies on making ongoing, highly accurate spectro-temporal comparisons. However, listeners with hearing impairment may have varying quality of temporal encoding within or across ears, which may limit the listeners' ability to make spectro-temporal comparisons between places-of-stimulation. In this study in normal hearing listeners, depth of amplitude modulation (AM) for sinusoidally amplitude modulated (SAM) tones was manipulated in an effort to reduce the coding of periodicity in the auditory nerve. The ability to judge differences in AM rates was studied for stimuli presented to different cochlear places-of-stimulation, within- or across-ears. It was hypothesized that if temporal encoding was poorer for one tone in a pair, then sensitivity to differences in AM rate of the pair would decrease. Results indicated that when the depth of AM was reduced from 50% to 20% for one SAM tone in a pair, sensitivity to differences in AM rate decreased. Sensitivity was greatest for AM rates near 90 Hz and depended upon the places-of-stimulation being compared. These results suggest that degraded temporal representations in the auditory nerve for one place-of-stimulation could lead to deficits comparing that temporal information with other places-of-stimulation.
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Affiliation(s)
- Sean R Anderson
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | - Alan Kan
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | - Ruth Y Litovsky
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
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Goehring T, Archer-Boyd A, Deeks JM, Arenberg JG, Carlyon RP. A Site-Selection Strategy Based on Polarity Sensitivity for Cochlear Implants: Effects on Spectro-Temporal Resolution and Speech Perception. J Assoc Res Otolaryngol 2019; 20:431-448. [PMID: 31161338 PMCID: PMC6646483 DOI: 10.1007/s10162-019-00724-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 05/08/2019] [Indexed: 01/04/2023] Open
Abstract
Thresholds of asymmetric pulses presented to cochlear implant (CI) listeners depend on polarity in a way that differs across subjects and electrodes. It has been suggested that lower thresholds for cathodic-dominant compared to anodic-dominant pulses reflect good local neural health. We evaluated the hypothesis that this polarity effect (PE) can be used in a site-selection strategy to improve speech perception and spectro-temporal resolution. Detection thresholds were measured in eight users of Advanced Bionics CIs for 80-pps, triphasic, monopolar pulse trains where the central high-amplitude phase was either anodic or cathodic. Two experimental MAPs were then generated for each subject by deactivating the five electrodes with either the highest or the lowest PE magnitudes (cathodic minus anodic threshold). Performance with the two experimental MAPs was evaluated using two spectro-temporal tests (Spectro-Temporal Ripple for Investigating Processor EffectivenesS (STRIPES; Archer-Boyd et al. in J Acoust Soc Am 144:2983–2997, 2018) and Spectral-Temporally Modulated Ripple Test (SMRT; Aronoff and Landsberger in J Acoust Soc Am 134:EL217–EL222, 2013)) and with speech recognition in quiet and in noise. Performance was also measured with an experimental MAP that used all electrodes, similar to the subjects’ clinical MAP. The PE varied strongly across subjects and electrodes, with substantial magnitudes relative to the electrical dynamic range. There were no significant differences in performance between the three MAPs at group level, but there were significant effects at subject level—not all of which were in the hypothesized direction—consistent with previous reports of a large variability in CI users’ performance and in the potential benefit of site-selection strategies. The STRIPES but not the SMRT test successfully predicted which strategy produced the best speech-in-noise performance on a subject-by-subject basis. The average PE across electrodes correlated significantly with subject age, duration of deafness, and speech perception scores, consistent with a relationship between PE and neural health. These findings motivate further investigations into site-specific measures of neural health and their application to CI processing strategies.
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Affiliation(s)
- Tobias Goehring
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK.
| | - Alan Archer-Boyd
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK
| | - John M Deeks
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK
| | - Julie G Arenberg
- Department of Speech and Hearing Sciences, University of Washington, 1417 NE 42nd St., Seattle, WA, 98105, USA
| | - Robert P Carlyon
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK
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Pulse-rate discrimination deficit in cochlear implant users: is the upper limit of pitch peripheral or central? Hear Res 2018; 371:1-10. [PMID: 30423498 DOI: 10.1016/j.heares.2018.10.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 10/04/2018] [Accepted: 10/31/2018] [Indexed: 11/20/2022]
Abstract
Cochlear implant (CI) users do not reliably associate an increase in pulse rate above 300 pulses per second (pps) with an increase in pitch. The locus of this upper limit of pitch remains unknown. The present study tested the hypothesis that this deficit resides at least initially at the auditory nerve. The hypothesis was tested by comparing pulse rate discrimination in different neural excitation patterns, in which a large versus small population of auditory nerve fibers was activated. If poorer pulse rate discrimination was found under conditions where narrower spread of neural excitation (SOE) was anticipated where a relatively small neural population was activated, then it would support the hypothesis that the rate processing deficit found in CI users is related to peripheral neural degeneration. Nine listeners (12 ears) implanted with the Cochlear Americas Nucleus® devices participated in the study. Different SOE conditions were created by (1) selecting electrodes that showed narrow versus broad forward-masked psychophysical spatial tuning curves, and (2) by measuring these electrodes in monopolar (MP) and narrow bipolar (BP0) electrode configurations. Rate discrimination difference limen (DL) was measured at the selected electrodes in two electrode configurations at three base rates (200, 300 and 500 pps). Consistent with the prediction, group mean DL was better (1) at stimulation sites measured with broader tuning, and (2) in MP relative to BP stimulation. These effects were more salient at the more challenging base rates. There was a weak relationship between rate discrimination (above thresholds) and the effect of rate on detection thresholds. Finally, rate discrimination at rates above the known upper limit (i.e., 500 pps) was correlated with duration of deafness and highly predicted the subjects' speech recognition performance in noise. These findings support that pulse rate discrimination depends, at least partially, on neural conditions at the auditory periphery and this peripheral limit predicts speech recognition outcomes with a CI.
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Sagi E, Svirsky MA. Deactivating cochlear implant electrodes to improve speech perception: A computational approach. Hear Res 2018; 370:316-328. [PMID: 30396747 DOI: 10.1016/j.heares.2018.10.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 10/10/2018] [Accepted: 10/17/2018] [Indexed: 10/28/2022]
Abstract
A potential bottleneck to improving speech perception performance in cochlear implant (CI) users is that some of their electrodes may poorly encode speech information. Several studies have examined the effect of deactivating poorly encoding electrodes on speech perception with mixed results. Many of these studies focused on identifying poorly encoding electrodes by some measure (e.g. electrode discrimination, pitch ordering, threshold, CT-guided, masked modulation detection), but provide inconsistent criteria about which electrodes, and how many, should be deactivated, and without considering how speech information becomes distributed across the electrode array. The present simulation study addresses this issue using computational approaches. Previously validated models were used to generate predictions of speech scores as a function of all possible combinations of active electrodes in a 22-electrode array in three groups of hypothetical subjects representative of relatively better, moderate, and poorer performing CI users. Using high-performance computing, over 500 million predictions were generated. Although deactivation of the poorest encoding electrodes sometimes resulted in predicted benefit, this benefit was significantly less relative to predictions resulting from model-optimized deactivations. This trend persisted when using novel stimuli (i.e. other than those used for optimization) and when using different processing strategies. Optimum electrode deactivation patterns produced an average predicted increase in word scores of 10% with some scores increasing by more than 20%. Optimum electrode deactivation patterns typically included 11 to 19 (out of 22) active electrodes, depending on the performance group. Optimal active electrode combinations were those that maximized discrimination of speech cues, maintaining 80%-100% of the physical span of the array. The present study demonstrates the potential for further improving CI users' speech scores with appropriate selection of active electrodes.
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Affiliation(s)
- Elad Sagi
- New York University School of Medicine, New York, NY, USA.
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Comparison of the Spectral-Temporally Modulated Ripple Test With the Arizona Biomedical Institute Sentence Test in Cochlear Implant Users. Ear Hear 2018; 38:760-766. [PMID: 28957975 DOI: 10.1097/aud.0000000000000496] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Although speech perception is the gold standard for measuring cochlear implant (CI) users' performance, speech perception tests often require extensive adaptation to obtain accurate results, particularly after large changes in maps. Spectral ripple tests, which measure spectral resolution, are an alternate measure that has been shown to correlate with speech perception. A modified spectral ripple test, the spectral-temporally modulated ripple test (SMRT) has recently been developed, and the objective of this study was to compare speech perception and performance on the SMRT for a heterogeneous population of unilateral CI users, bilateral CI users, and bimodal users. DESIGN Twenty-five CI users (eight using unilateral CIs, nine using bilateral CIs, and eight using a CI and a hearing aid) were tested on the Arizona Biomedical Institute Sentence Test (AzBio) with a +8 dB signal to noise ratio, and on the SMRT. All participants were tested with their clinical programs. RESULTS There was a significant correlation between SMRT and AzBio performance. After a practice block, an improvement of one ripple per octave for SMRT corresponded to an improvement of 12.1% for AzBio. Additionally, there was no significant difference in slope or intercept between any of the CI populations. CONCLUSION The results indicate that performance on the SMRT correlates with speech recognition in noise when measured across unilateral, bilateral, and bimodal CI populations. These results suggest that SMRT scores are strongly associated with speech recognition in noise ability in experienced CI users. Further studies should focus on increasing both the size and diversity of the tested participants, and on determining whether the SMRT technique can be used for early predictions of long-term speech scores, or for evaluating differences among different stimulation strategies or parameter settings.
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Zhou N, Cadmus M, Dong L, Mathews J. Temporal Modulation Detection Depends on Sharpness of Spatial Tuning. J Assoc Res Otolaryngol 2018; 19:317-330. [PMID: 29696448 DOI: 10.1007/s10162-018-0663-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 03/22/2018] [Indexed: 01/04/2023] Open
Abstract
Prior research has shown that in electrical hearing, cochlear implant (CI) users' speech recognition performance is related in part to their ability to detect temporal modulation (i.e., modulation sensitivity). Previous studies have also shown better speech recognition when selectively stimulating sites with good modulation sensitivity rather than all stimulation sites. Site selection based on channel interaction measures, such as those using imaging or psychophysical estimates of spread of neural excitation, has also been shown to improve speech recognition. This led to the question of whether temporal modulation sensitivity and spatial selectivity of neural excitation are two related variables. In the present study, CI users' modulation sensitivity was compared for sites with relatively broad or narrow neural excitation patterns. This was achieved by measuring temporal modulation detection thresholds (MDTs) at stimulation sites that were significantly different in their sharpness of the psychophysical spatial tuning curves (PTCs) and measuring MDTs at the same sites in monopolar (MP) and bipolar (BP) stimulation modes. Nine postlingually deafened subjects implanted with Cochlear Nucleus® device took part in the study. Results showed a significant correlation between the sharpness of PTCs and MDTs, indicating that modulation detection benefits from a more spatially restricted neural activation pattern. There was a significant interaction between stimulation site and mode. That is, using BP stimulation only improved MDTs at stimulation sites with broad PTCs but had no effect or sometimes a detrimental effect on MDTs at stimulation sites with sharp PTCs. This interaction could suggest that a criterion number of nerve fibers is needed to achieve optimal temporal resolution, and, to achieve optimized speech recognition outcomes, individualized selection of site-specific current focusing strategies may be necessary. These results also suggest that the removal of stimulation sites measured with poor MDTs might improve both temporal and spectral resolution.
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Affiliation(s)
- Ning Zhou
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, 27858, USA.
| | - Matthew Cadmus
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, 27858, USA
| | - Lixue Dong
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, 27858, USA
| | - Juliana Mathews
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, 27858, USA
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Assessment of Spectral and Temporal Resolution in Cochlear Implant Users Using Psychoacoustic Discrimination and Speech Cue Categorization. Ear Hear 2018; 37:e377-e390. [PMID: 27438871 DOI: 10.1097/aud.0000000000000328] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES This study was conducted to measure auditory perception by cochlear implant users in the spectral and temporal domains, using tests of either categorization (using speech-based cues) or discrimination (using conventional psychoacoustic tests). The authors hypothesized that traditional nonlinguistic tests assessing spectral and temporal auditory resolution would correspond to speech-based measures assessing specific aspects of phonetic categorization assumed to depend on spectral and temporal auditory resolution. The authors further hypothesized that speech-based categorization performance would ultimately be a superior predictor of speech recognition performance, because of the fundamental nature of speech recognition as categorization. DESIGN Nineteen cochlear implant listeners and 10 listeners with normal hearing participated in a suite of tasks that included spectral ripple discrimination, temporal modulation detection, and syllable categorization, which was split into a spectral cue-based task (targeting the /ba/-/da/ contrast) and a timing cue-based task (targeting the /b/-/p/ and /d/-/t/ contrasts). Speech sounds were manipulated to contain specific spectral or temporal modulations (formant transitions or voice onset time, respectively) that could be categorized. Categorization responses were quantified using logistic regression to assess perceptual sensitivity to acoustic phonetic cues. Word recognition testing was also conducted for cochlear implant listeners. RESULTS Cochlear implant users were generally less successful at utilizing both spectral and temporal cues for categorization compared with listeners with normal hearing. For the cochlear implant listener group, spectral ripple discrimination was significantly correlated with the categorization of formant transitions; both were correlated with better word recognition. Temporal modulation detection using 100- and 10-Hz-modulated noise was not correlated either with the cochlear implant subjects' categorization of voice onset time or with word recognition. Word recognition was correlated more closely with categorization of the controlled speech cues than with performance on the psychophysical discrimination tasks. CONCLUSIONS When evaluating people with cochlear implants, controlled speech-based stimuli are feasible to use in tests of auditory cue categorization, to complement traditional measures of auditory discrimination. Stimuli based on specific speech cues correspond to counterpart nonlinguistic measures of discrimination, but potentially show better correspondence with speech perception more generally. The ubiquity of the spectral (formant transition) and temporal (voice onset time) stimulus dimensions across languages highlights the potential to use this testing approach even in cases where English is not the native language.
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DeVries L, Arenberg JG. Current Focusing to Reduce Channel Interaction for Distant Electrodes in Cochlear Implant Programs. Trends Hear 2018; 22:2331216518813811. [PMID: 30488764 PMCID: PMC6277758 DOI: 10.1177/2331216518813811] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 10/17/2018] [Accepted: 10/26/2018] [Indexed: 11/17/2022] Open
Abstract
Speech understanding abilities are highly variable among cochlear implant (CI) listeners. Poor electrode-neuron interfaces (ENIs) caused by sparse neural survival or distant electrode placement may lead to increased channel interaction and reduced speech perception. Currently, it is not possible to directly measure neural survival in CI listeners; therefore, obtaining information about electrode position is an alternative approach to assessing ENIs. This information can be estimated with computerized tomography (CT) imaging; however, postoperative CT imaging is not often available. A reliable method to assess channel interaction, such as the psychophysical tuning curve (PTC), offers an alternative way to identify poor ENIs. This study aimed to determine (a) the within-subject relationship between CT-estimated electrode distance and PTC bandwidths, and (b) whether using focused stimulation on channels with suspected poor ENI improves vowel identification and sentence recognition. In 13 CI listeners, CT estimates of electrode-to-modiolus distance and PTCs bandwidths were measured for all available electrodes. Two test programs were created, wherein a subset of electrodes used focused stimulation based on (a) broad PTC bandwidth (Tuning) and (b) far electrode-to-modiolus distance (Distance). Two control programs were also created: (a) Those channels not focused in the Distance program (Inverse-Control), and (b) an all-channel monopolar program (Monopolar-Control). Across subjects, scores on the Distance and Tuning programs were significantly higher than the Inverse-Control program, and similar to the Monopolar-Control program. Subjective ratings were similar for all programs. These findings suggest that focusing channels suspected to have a high degree of channel interaction result in quite different outcomes, acutely.
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Affiliation(s)
- Lindsay DeVries
- Department of Hearing and Speech Sciences, University of Maryland, College Park, MD, USA
| | - Julie G. Arenberg
- Department of Speech and Hearing Sciences, University of Washington, Seattle, WA, USA
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Aronoff JM, Stelmach J, Padilla M, Landsberger DM. Interleaved Processors Improve Cochlear Implant Patients' Spectral Resolution. Ear Hear 2016; 37:e85-90. [PMID: 26656190 DOI: 10.1097/aud.0000000000000249] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Cochlear implant patients have difficulty in noisy environments, in part, because of channel interaction. Interleaving the signal by sending every other channel to the opposite ear has the potential to reduce channel interaction by increasing the space between channels in each ear. Interleaving still potentially provides the same amount of spectral information when the two ears are combined. Although this method has been successful in other populations such as hearing aid users, interleaving with cochlear implant patients has not yielded consistent benefits. This may be because perceptual misalignment between the two ears, and the spacing between stimulation locations must be taken into account before interleaving. DESIGN Eight bilateral cochlear implant users were tested. After perceptually aligning the two ears, 12-channel maps were made that spanned the entire aligned portions of the array. Interleaved maps were created by removing every other channel from each ear. Participants' spectral resolution and localization abilities were measured with perceptually aligned processing strategies both with and without interleaving. RESULTS There was a significant improvement in spectral resolution with interleaving. However, there was no significant effect of interleaving on localization abilities. CONCLUSIONS The results indicate that interleaving can improve cochlear implant users' spectral resolution. However, it may be necessary to perceptually align the two ears and/or use relatively large spacing between stimulation locations.
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Affiliation(s)
- Justin M Aronoff
- 1Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA; 2Department of Otolaryngology - Head and Neck Surgery, University of Illinois at Chicago, Chicago, Illinois, USA; 3Communication and Neuroscience Division, House Ear Institute, Los Angeles, California, USA; and 4Department of Otolaryngology, New York University, New York, New York, USA
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Zhou N. Monopolar Detection Thresholds Predict Spatial Selectivity of Neural Excitation in Cochlear Implants: Implications for Speech Recognition. PLoS One 2016; 11:e0165476. [PMID: 27798658 PMCID: PMC5087957 DOI: 10.1371/journal.pone.0165476] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 10/12/2016] [Indexed: 12/12/2022] Open
Abstract
The objectives of the study were to (1) investigate the potential of using monopolar psychophysical detection thresholds for estimating spatial selectivity of neural excitation with cochlear implants and to (2) examine the effect of site removal on speech recognition based on the threshold measure. Detection thresholds were measured in Cochlear Nucleus® device users using monopolar stimulation for pulse trains that were of (a) low rate and long duration, (b) high rate and short duration, and (c) high rate and long duration. Spatial selectivity of neural excitation was estimated by a forward-masking paradigm, where the probe threshold elevation in the presence of a forward masker was measured as a function of masker-probe separation. The strength of the correlation between the monopolar thresholds and the slopes of the masking patterns systematically reduced as neural response of the threshold stimulus involved interpulse interactions (refractoriness and sub-threshold adaptation), and spike-rate adaptation. Detection threshold for the low-rate stimulus most strongly correlated with the spread of forward masking patterns and the correlation reduced for long and high rate pulse trains. The low-rate thresholds were then measured for all electrodes across the array for each subject. Subsequently, speech recognition was tested with experimental maps that deactivated five stimulation sites with the highest thresholds and five randomly chosen ones. Performance with deactivating the high-threshold sites was better than performance with the subjects' clinical map used every day with all electrodes active, in both quiet and background noise. Performance with random deactivation was on average poorer than that with the clinical map but the difference was not significant. These results suggested that the monopolar low-rate thresholds are related to the spatial neural excitation patterns in cochlear implant users and can be used to select sites for more optimal speech recognition performance.
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Affiliation(s)
- Ning Zhou
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, United States of America
- * E-mail:
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Bierer JA, Litvak L. Reducing Channel Interaction Through Cochlear Implant Programming May Improve Speech Perception: Current Focusing and Channel Deactivation. Trends Hear 2016; 20:20/0/2331216516653389. [PMID: 27317668 PMCID: PMC4948253 DOI: 10.1177/2331216516653389] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Speech perception among cochlear implant (CI) listeners is highly variable. High degrees of channel interaction are associated with poorer speech understanding. Two methods for reducing channel interaction, focusing electrical fields, and deactivating subsets of channels were assessed by the change in vowel and consonant identification scores with different program settings. The main hypotheses were that (a) focused stimulation will improve phoneme recognition and (b) speech perception will improve when channels with high thresholds are deactivated. To select high-threshold channels for deactivation, subjects’ threshold profiles were processed to enhance the peaks and troughs, and then an exclusion or inclusion criterion based on the mean and standard deviation was used. Low-threshold channels were selected manually and matched in number and apex-to-base distribution. Nine ears in eight adult CI listeners with Advanced Bionics HiRes90k devices were tested with six experimental programs. Two, all-channel programs, (a) 14-channel partial tripolar (pTP) and (b) 14-channel monopolar (MP), and four variable-channel programs, derived from these two base programs, (c) pTP with high- and (d) low-threshold channels deactivated, and (e) MP with high- and (f) low-threshold channels deactivated, were created. Across subjects, performance was similar with pTP and MP programs. However, poorer performing subjects (scoring < 62% correct on vowel identification) tended to perform better with the all-channel pTP than with the MP program (1 > 2). These same subjects showed slightly more benefit with the reduced channel MP programs (5 and 6). Subjective ratings were consistent with performance. These finding suggest that reducing channel interaction may benefit poorer performing CI listeners.
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Ozmeral EJ, Buss E, Hall JW. The Effects of Sensorineural Hearing Impairment on Asynchronous Glimpsing of Speech. PLoS One 2016; 11:e0154920. [PMID: 27144601 PMCID: PMC4856319 DOI: 10.1371/journal.pone.0154920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 04/21/2016] [Indexed: 11/18/2022] Open
Abstract
In a previous study with normal-hearing listeners, we evaluated consonant identification masked by two or more spectrally contiguous bands of noise, with asynchronous square-wave modulation applied to neighboring bands. Speech recognition thresholds were 5.1–8.5 dB better when neighboring bands were presented to different ears (dichotic) than when all bands were presented to one ear (monaural), depending on the spectral width of the frequency bands. This dichotic advantage was interpreted as reflecting masking release from peripheral spread of masking from neighboring frequency bands. The present study evaluated this effect in listeners with sensorineural hearing loss, a population more susceptible to spread of masking. Speech perception (vowel-consonant-vowel stimuli, as in /aBa/) was measured in the presence of fluctuating noise that was either modulated synchronously across frequency or asynchronously. Hearing-impaired listeners (n = 9) and normal-hearing controls were tested at either the same intensity (n = 7) or same sensation level (n = 8). Hearing-impaired listeners had mild-to-moderate hearing loss and symmetrical, flat audiometric thresholds. While all groups of listeners performed better in the dichotic than monaural condition, this effect was smaller for the hearing-impaired (3.5 dB) and equivalent-sensation-level controls (3.3 dB) than controls tested at the same intensity (11.0 dB). The present study is consistent with the idea that dichotic presentation can improve speech-in-noise listening for hearing-impaired listeners, and may be enhanced when combined with amplification.
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Affiliation(s)
- Erol J. Ozmeral
- Department of Communication Sciences and Disorders, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
| | - Emily Buss
- Department of Otolaryngology/Head and Neck Surgery, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Joseph W. Hall
- Department of Otolaryngology/Head and Neck Surgery, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
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Zhou N, Kraft CT, Colesa DJ, Pfingst BE. Integration of Pulse Trains in Humans and Guinea Pigs with Cochlear Implants. J Assoc Res Otolaryngol 2015; 16:523-34. [PMID: 25990549 DOI: 10.1007/s10162-015-0521-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 04/29/2015] [Indexed: 01/07/2023] Open
Abstract
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 (< 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 "multiple 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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Affiliation(s)
- Ning Zhou
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI, 48109-5616, USA,
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Pfingst BE, Zhou N, Colesa DJ, Watts MM, Strahl SB, Garadat SN, Schvartz-Leyzac KC, Budenz CL, Raphael Y, Zwolan TA. Importance of cochlear health for implant function. Hear Res 2015; 322:77-88. [PMID: 25261772 PMCID: PMC4377117 DOI: 10.1016/j.heares.2014.09.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 08/14/2014] [Accepted: 09/16/2014] [Indexed: 01/17/2023]
Abstract
Amazing progress has been made in providing useful hearing to hearing-impaired individuals using cochlear implants, but challenges remain. One such challenge is understanding the effects of partial degeneration of the auditory nerve, the target of cochlear implant stimulation. Here we review studies from our human and animal laboratories aimed at characterizing the health of the implanted cochlea and the auditory nerve. We use the data on cochlear and neural health to guide rehabilitation strategies. The data also motivate the development of tissue-engineering procedures to preserve or build a healthy cochlea and improve performance obtained by cochlear implant recipients or eventually replace the need for a cochlear implant. This article is part of a Special Issue entitled .
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Affiliation(s)
- Bryan E Pfingst
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA.
| | - Ning Zhou
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA; East Carolina University, Greenville, NC, USA
| | - Deborah J Colesa
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA
| | - Melissa M Watts
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA
| | | | - Soha N Garadat
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA; The University of Jordan, Amman, Jordan
| | | | - Cameron L Budenz
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA
| | - Yehoash Raphael
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA
| | - Teresa A Zwolan
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, USA
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Zhou N, Pfingst BE. Relationship between multipulse integration and speech recognition with cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 136:1257. [PMID: 25190399 PMCID: PMC4165232 DOI: 10.1121/1.4890640] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Comparisons of performance with cochlear implants and postmortem conditions in the cochlea in humans have shown mixed results. The limitations in those studies favor the use of within-subject designs and non-invasive measures to estimate cochlear conditions. One non-invasive correlate of cochlear health is multipulse integration, established in an animal model. The present study used this measure to relate neural health in human cochlear implant users to their speech recognition performance. The multipulse-integration slopes were derived based on psychophysical detection thresholds measured for two pulse rates (80 and 640 pulses per second). A within-subject design was used in eight subjects with bilateral implants where the direction and magnitude of ear differences in the multipulse-integration slopes were compared with those of the speech-recognition results. The speech measures included speech reception threshold for sentences and phoneme recognition in noise. The magnitude of ear difference in the integration slopes was significantly correlated with the magnitude of ear difference in speech reception thresholds, consonant recognition in noise, and transmission of place of articulation of consonants. These results suggest that multipulse integration predicts speech recognition in noise and perception of features that use dynamic spectral cues.
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Affiliation(s)
- Ning Zhou
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, North Carolina 27834
| | - Bryan E Pfingst
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, Michigan 48109-5616
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Abstract
OBJECTIVES Modulation detection thresholds (MDTs) vary across stimulation sites in a cochlear implant (CI) electrode array in a manner that is subject and ear specific. Previous studies have demonstrated that speech recognition with a CI can be improved by site-selection strategies, where selected stimulation sites with poor modulation sensitivity are removed from a subject's processor MAP. Limitations of site-selection strategies are that they can compromise spectral resolution and distort frequency-place mapping because the frequencies assigned to the removed sites are usually reallocated to other sites, and site bandwidths are broadened. The objective of the present study was to test an alternative approach for rehabilitation that aimed at improving the across-site mean MDTs by adjusting stimulation parameters at the poorly performing sites. On the basis of previous findings that modulation detection contributes to speech recognition and improves significantly with stimulus level, the authors hypothesized that modulation sensitivity at the poor sites could be improved by artificially increasing stimulation levels at those sites in the speech processor, which then would lead to improved speech recognition. DESIGN Nine postlingually deafened ears implanted with Nucleus CIs were evaluated for MDTs, absolute-detection threshold levels (T levels), and the maximum loudness levels (C levels) on each of the available stimulation sites. For each ear, the minimum stimulation level settings in the speech-processor MAP were raised by 5%, and alternatively by 10%, of the dynamic range (DR) from true thresholds on five stimulation sites with the poorest MDTs. For comparison, a 5% level raise was applied globally to all stimulation sites. The C levels were fixed during these level manipulations. MDTs at the five poorest stimulation sites were compared at 20% DR before and after the level adjustments. Speech-reception thresholds (SRTs), that is, signal to noise ratios required for 50% correct speech recognition, were evaluated for these MAPs using CUNY sentences. The site-specific level-adjusted MAPs were compared with the global-level-adjusted MAP and the MAP without level adjustment. The effects on speech recognition of adjusting the minimal stimulation level settings on the five poorest stimulation sites were also compared with effects of removing these sites from the speech-processor MAP. RESULTS The 5% level increase on the five electrodes with the worst MDTs resulted in an improvement in the group mean SRT of 2.36 dB SNR relative to the MAP without level adjustment. The magnitude of level increase that resulted in the greatest SRT improvement for individuals varied across ears. MDTs measured at 20% DR significantly improved on the poor sites after the level adjustment that resulted in the best SRT for that ear was applied. Increasing the minimal stimulation levels on all stimulation sites or removing sites selected for rehabilitation, the parsimonious approaches, did not improve SRTs. CONCLUSIONS The site-specific adjustments of the T level settings improved modulation sensitivity at low levels and significantly improved subjects' SRTs. Thus, this site-rehabilitation strategy was an effective alternative to site-selection strategies for improving speech recognition in CI users.
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Galvin JJ, Oba S, Fu QJ, Başkent D. Single- and multi-channel modulation detection in cochlear implant users. PLoS One 2014; 9:e99338. [PMID: 24918605 PMCID: PMC4053447 DOI: 10.1371/journal.pone.0099338] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 05/14/2014] [Indexed: 11/18/2022] Open
Abstract
Single-channel modulation detection thresholds (MDTs) have been shown to predict cochlear implant (CI) users' speech performance. However, little is known about multi-channel modulation sensitivity. Two factors likely contribute to multichannel modulation sensitivity: multichannel loudness summation and the across-site variance in single-channel MDTs. In this study, single- and multi-channel MDTs were measured in 9 CI users at relatively low and high presentation levels and modulation frequencies. Single-channel MDTs were measured at widely spaced electrode locations, and these same channels were used for the multichannel stimuli. Multichannel MDTs were measured twice, with and without adjustment for multichannel loudness summation (i.e., at the same loudness as for the single-channel MDTs or louder). Results showed that the effect of presentation level and modulation frequency were similar for single- and multi-channel MDTs. Multichannel MDTs were significantly poorer than single-channel MDTs when the current levels of the multichannel stimuli were reduced to match the loudness of the single-channel stimuli. This suggests that, at equal loudness, single-channel measures may over-estimate CI users' multichannel modulation sensitivity. At equal loudness, there was no significant correlation between the amount of multichannel loudness summation and the deficit in multichannel MDTs, relative to the average single-channel MDT. With no loudness compensation, multichannel MDTs were significantly better than the best single-channel MDT. The across-site variance in single-channel MDTs varied substantially across subjects. However, the across-site variance was not correlated with the multichannel advantage over the best single channel. This suggests that CI listeners combined envelope information across channels instead of attending to the best channel.
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Affiliation(s)
- John J. Galvin
- Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, California, United States of America
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
- Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen, Groningen, The Netherlands
- * E-mail:
| | - Sandy Oba
- Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, California, United States of America
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Qian-Jie Fu
- Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, California, United States of America
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Deniz Başkent
- Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
- Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen, Groningen, The Netherlands
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