1
|
Lambriks L, van Hoof M, Debruyne J, Janssen M, Chalupper J, van der Heijden K, Hof J, Hellingman K, Devocht E, George E. Imaging-based frequency mapping for cochlear implants - Evaluated using a daily randomized controlled trial. Front Neurosci 2023; 17:1119933. [PMID: 37123376 PMCID: PMC10133468 DOI: 10.3389/fnins.2023.1119933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/03/2023] [Indexed: 05/02/2023] Open
Abstract
Background Due to variation in electrode design, insertion depth and cochlear morphology, patients with a cochlear implant (CI) often have to adapt to a substantial mismatch between the characteristic response frequencies of cochlear neurons and the stimulus frequencies assigned to electrode contacts. We introduce an imaging-based fitting intervention, which aimed to reduce frequency-to-place mismatch by aligning frequency mapping with the tonotopic position of electrodes. Results were evaluated in a novel trial set-up where subjects crossed over between intervention and control using a daily within-patient randomized approach, immediately from the start of CI rehabilitation. Methods Fourteen adult participants were included in this single-blinded, daily randomized clinical trial. Based on a fusion of pre-operative imaging and a post-operative cone beam CT scan (CBCT), mapping of electrical input was aligned to natural place-pitch arrangement in the individual cochlea. That is, adjustments to the CI's frequency allocation table were made so electrical stimulation of frequencies matched as closely as possible with corresponding acoustic locations in the cochlea. For a period of three months, starting at first fit, a scheme was implemented whereby the blinded subject crossed over between the experimental and standard fitting program using a daily randomized wearing schedule, and thus effectively acted as their own control. Speech outcomes (such as speech intelligibility in quiet and noise, sound quality and listening effort) were measured with both settings throughout the study period. Results On a group level, standard fitting obtained subject preference and showed superior results in all outcome measures. In contrast, two out of fourteen subjects preferred the imaging-based fitting and correspondingly had better speech understanding with this setting compared to standard fitting. Conclusion On average, cochlear implant fitting based on individual tonotopy did not elicit higher speech intelligibility but variability in individual results strengthen the potential for individualized frequency fitting. The novel trial design proved to be a suitable method for evaluation of experimental interventions in a prospective trial setup with cochlear implants.
Collapse
Affiliation(s)
- Lars Lambriks
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Marc van Hoof
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Joke Debruyne
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Miranda Janssen
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
- Department of Methodology and Statistics, Care and Public Health Research Institute, Maastricht University, Maastricht, Netherlands
| | - Josef Chalupper
- Advanced Bionics European Research Centre, Hannover, Germany
| | - Kiki van der Heijden
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Janny Hof
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Katja Hellingman
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Elke Devocht
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Erwin George
- Department of ENT/Audiology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| |
Collapse
|
2
|
Roux J, Hanekom JJ. Effect of stimulation parameters on sequential current-steered stimuli in cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 152:609. [PMID: 35931549 DOI: 10.1121/10.0012763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 07/01/2022] [Indexed: 06/15/2023]
Abstract
Manipulation of cochlear implant (CI) place pitch was carried out with current steering by stimulating two CI electrodes sequentially. The objective was to investigate whether shifts in activated neural populations could be achieved to produce salient pitch differences and to determine which stimulation parameters would be more effective in steering of current. These were the pulse rate and pulse width of electrical stimuli and the distance between the two current-steering electrodes. Nine CI users participated, and ten ears were tested. The pattern of pitch changes was not consistent across listeners, but the data suggest that individualized selection of stimulation parameters may be used to effect place pitch changes with sequential current steering. Individual analyses showed that pulse width generally had little influence on the effectiveness of current steering with sequential stimuli, while more salient place pitch shifts were often achieved at wider electrode spacing or when the stimulation pulse rate was the same as that indicated on the clinical MAP (the set of stimulation parameters) of the listener. Results imply that current steering may be used in CIs that allow only sequential stimulation to achieve place pitch manipulation.
Collapse
Affiliation(s)
- Johanie Roux
- Bioengineering, Department of Electrical, Electronic, and Computer Engineering, University of Pretoria, University Road, Pretoria 0002, South Africa
| | - Johan J Hanekom
- Bioengineering, Department of Electrical, Electronic, and Computer Engineering, University of Pretoria, University Road, Pretoria 0002, South Africa
| |
Collapse
|
3
|
Phantom Stimulation for Cochlear Implant Users With Residual Low-Frequency Hearing. Ear Hear 2021; 43:631-645. [PMID: 34593687 PMCID: PMC8862773 DOI: 10.1097/aud.0000000000001121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In cochlear implants (CIs), phantom stimulation can be used to extend the pitch range toward apical regions of the cochlea. Phantom stimulation consists of partial bipolar stimulation, in which current is distributed across two intracochlear electrodes and one extracochlear electrode as defined by the compensation coefficient σ. The aim of this study was, (1) to evaluate the benefit of conveying low-frequency information through phantom stimulation for cochlear implant (CI) subjects with low-frequency residual hearing using electric stimulation alone, (2) to compare the speech reception thresholds obtained from electric-acoustic stimulation (EAS) and electric stimulation in combination with phantom stimulation (EPS), and (3) to investigate the effect of spectrally overlapped bandwidth of speech conveyed via simultaneous acoustic and phantom stimulation on speech reception thresholds.
Collapse
|
4
|
Imsiecke M, Krüger B, Büchner A, Lenarz T, Nogueira W. Interaction Between Electric and Acoustic Stimulation Influences Speech Perception in Ipsilateral EAS Users. Ear Hear 2021; 41:868-882. [PMID: 31592902 PMCID: PMC7676483 DOI: 10.1097/aud.0000000000000807] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 08/30/2019] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The aim of this study was to determine electric-acoustic masking in cochlear implant users with ipsilateral residual hearing and different electrode insertion depths and to investigate the influence on speech reception. The effects of different fitting strategies-meet, overlap, and a newly developed masking adjusted fitting (UNMASKfit)-on speech reception are compared. If electric-acoustic masking has a detrimental effect on speech reception, the individualized UNMASKfit map might be able to reduce masking and thereby enhance speech reception. DESIGN Fifteen experienced MED-EL Flex electrode recipients with ipsilateral residual hearing participated in a crosssover design study using three fitting strategies for 4 weeks each. The following strategies were compared: (1) a meet fitting, dividing the frequency range between electric and acoustic stimulation, (2) an overlap fitting, delivering part of the frequency range both acoustically and electrically, and (3) the UNMASKfit, reducing the electric stimulation according to the individual electric-on-acoustic masking strength. A psychoacoustic masking procedure was used to measure the changes in acoustic thresholds due to the presence of electric maskers. Speech reception was measured in noise with the Oldenburg Matrix Sentence test. RESULTS Behavioral thresholds of acoustic probe tones were significantly elevated in the presence of electric maskers. A maximum of masking was observed when the difference in location between the electric and acoustic stimulation was around one octave in place frequency. Speech reception scores and strength of masking showed a dependency on residual hearing, and speech reception was significantly reduced in the overlap fitting strategy. Electric- acoustic stimulation significantly improved speech reception over electric stimulation alone, with a tendency toward a larger benefit with the UNMASKfit map. In addition, masking was significantly inversely correlated to the speech reception performance difference between the overlap and the meet fitting. CONCLUSIONS (1) This study confirmed the interaction between ipsilateral electric and acoustic stimulation in a psychoacoustic masking experiment. (2) The overlap fitting yielded poorer speech reception performance in stationary noise especially in subjects with strong masking. (3) The newly developed UNMASKfit strategy yielded similar speech reception thresholds with an enhanced acoustic benefit, while at the same time reducing the electric stimulation. This could be beneficial in the long-term if applied as a standard fitting, as hair cells are exposed to less possibly adverse electric stimulation. In this study, the UNMASKfit allowed the participants a better use of their natural hearing even after 1 month of adaptation. It might be feasible to transfer these results to the clinic, by fitting patients with the UNMASKfit upon their first fitting appointment, so that longer adaptation times can further improve speech reception.
Collapse
Affiliation(s)
- Marina Imsiecke
- Department of Otorhinolaryngology, Hanover Medical School, Hannover, Germany
| | - Benjamin Krüger
- Department of Otorhinolaryngology, Hanover Medical School, Hannover, Germany
- Cluster of Excellence ‘Hearing4all,' Hanover, Germany
| | - Andreas Büchner
- Department of Otorhinolaryngology, Hanover Medical School, Hannover, Germany
- Cluster of Excellence ‘Hearing4all,' Hanover, Germany
| | - Thomas Lenarz
- Department of Otorhinolaryngology, Hanover Medical School, Hannover, Germany
- Cluster of Excellence ‘Hearing4all,' Hanover, Germany
| | - Waldo Nogueira
- Department of Otorhinolaryngology, Hanover Medical School, Hannover, Germany
- Cluster of Excellence ‘Hearing4all,' Hanover, Germany
| |
Collapse
|
5
|
Lamping W, Deeks JM, Marozeau J, Carlyon RP. The Effect of Phantom Stimulation and Pseudomonophasic Pulse Shapes on Pitch Perception by Cochlear Implant Listeners. J Assoc Res Otolaryngol 2020; 21:511-526. [PMID: 32804337 PMCID: PMC7644600 DOI: 10.1007/s10162-020-00768-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 07/31/2020] [Indexed: 01/04/2023] Open
Abstract
It has been suggested that a specialized high-temporal-acuity brainstem pathway can be activated by stimulating more apically in the cochlea than is achieved by cochlear implants (CIs) when programmed with contemporary clinical settings. We performed multiple experiments to test the effect on pitch perception of phantom stimulation and asymmetric current pulses, both supposedly stimulating beyond the most apical electrode of a CI. The two stimulus types were generated using a bipolar electrode pair, composed of the most apical electrode of the array and a neighboring, more basal electrode. Experiment 1 used a pitch-ranking procedure where neural excitation was shifted apically or basally using so-called phantom stimulation. No benefit of apical phantom stimulation was found on the highest rate up to which pitch ranks increased (upper limit), nor on the slopes of the pitch-ranking function above 300 pulses per second (pps). Experiment 2 used the same procedure to study the effects of apical pseudomonophasic pulses, where the locus of excitation was manipulated by changing stimulus polarity. A benefit of apical stimulation was obtained for the slopes above 300 pps. Experiment 3 used an adaptive rate discrimination procedure and found a small but significant benefit of both types of apical stimulation. Overall, the results show some benefit for apical stimulation on temporal pitch processing at high pulse rates but reveal that the effect is smaller and more variable across listeners than suggested by previous research. The results also provide some indication that the benefit of apical stimulation may decline over time since implantation.
Collapse
Affiliation(s)
- Wiebke Lamping
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark.
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK.
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0SZ, UK.
| | - John M Deeks
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK
| | - Jeremy Marozeau
- Hearing Systems Section, Department of Health Technology, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark
| | - Robert P Carlyon
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, 15 Chaucer Road, Cambridge, CB2 7EF, UK
| |
Collapse
|
6
|
Luo X, Wu CC, Pulling K. Combining current focusing and steering in a cochlear implant processing strategy. Int J Audiol 2020; 60:232-237. [PMID: 32967485 DOI: 10.1080/14992027.2020.1822551] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To evaluate the benefit of combined current focusing and steering to speech recognition in noise with cochlear implants (CIs). DESIGN Combined current focusing and steering was implemented using focused partial tripolar (pTP) mode with two current steering ranges. The two pTPsteering strategies were compared to a monopolar (MP) strategy without current focusing or steering and a pTP strategy with only current focusing using the Hearing in Noise Test. The strategies differed only in stimulation mode. STUDY SAMPLE Ten post-lingually deafened adult CI users participated in this study. RESULTS Compared to the MP strategy, both pTPsteering strategies produced significantly better speech reception thresholds, while the pTP strategy did not. Subjects with better baseline MP performance had less improvements with the pTPsteering strategies. All four strategies were experimental low-rate strategies and none of them outperformed subjects' clinical strategies. CONCLUSIONS Speech recognition in noise was better with the pTPsteering strategies than with the MP strategy, but the effect of pTP-mode current steering on spectral resolution is yet to be tested.
Collapse
Affiliation(s)
- Xin Luo
- College of Health Solutions, Arizona State University, Tempe, AZ, USA
| | - Ching-Chih Wu
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
| | - Kathryn Pulling
- College of Health Solutions, Arizona State University, Tempe, AZ, USA
| |
Collapse
|
7
|
Lambriks LJG, van Hoof M, Debruyne JA, Janssen M, Chalupper J, van der Heijden KA, Hof JR, Hellingman CA, George ELJ, Devocht EMJ. Evaluating hearing performance with cochlear implants within the same patient using daily randomization and imaging-based fitting - The ELEPHANT study. Trials 2020; 21:564. [PMID: 32576247 PMCID: PMC7310427 DOI: 10.1186/s13063-020-04469-x] [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] [Received: 01/20/2020] [Accepted: 05/30/2020] [Indexed: 02/08/2023] Open
Abstract
Background Prospective research in the field of cochlear implants is hampered by methodological issues and small sample sizes. The ELEPHANT study presents an alternative clinical trial design with a daily randomized approach evaluating individualized tonotopical fitting of a cochlear implant (CI). Methods A single-blinded, daily-randomized clinical trial will be implemented to evaluate a new imaging-based CI mapping strategy. A minimum of 20 participants will be included from the start of the rehabilitation process with a 1-year follow-up period. Based on a post-operative cone beam CT scan (CBCT), mapping of electrical input will be aligned to natural place-pitch arrangement in the individual cochlea. The CI’s frequency allocation table will be adjusted to match the electrical stimulation of frequencies as closely as possible to corresponding acoustic locations in the cochlea. A randomization scheme will be implemented whereby the participant, blinded to the intervention allocation, crosses over between the experimental and standard fitting program on a daily basis, and thus effectively acts as his own control, followed by a period of free choice between both maps to incorporate patient preference. With this new approach the occurrence of a first-order carryover effect and a limited sample size is addressed. Discussion The experimental fitting strategy is thought to give rise to a steeper learning curve, result in better performance in challenging listening situations, improve sound quality, better complement residual acoustic hearing in the contralateral ear and be preferred by recipients of a CI. Concurrently, the suitability of the novel trial design will be considered in investigating these hypotheses. Trial registration ClinicalTrials.gov: NCT03892941. Registered 27 March 2019.
Collapse
Affiliation(s)
- L J G Lambriks
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands.
| | - M van Hoof
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands
| | - J A Debruyne
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands
| | - M Janssen
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Methodology and Statistics, School for Public Health and Primary Care (CAPHRI), Maastricht University Medical Center, Maastricht, The Netherlands
| | - J Chalupper
- Advanced Bionics European Research Centre (AB ERC), Hannover, Germany
| | - K A van der Heijden
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands
| | - J R Hof
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands
| | - C A Hellingman
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands
| | - E L J George
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands
| | - E M J Devocht
- Department of ENT/Audiology, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center, Maastricht, The Netherlands
| |
Collapse
|
8
|
Luo X, Garrett C. Dynamic current steering with phantom electrode in cochlear implants. Hear Res 2020; 390:107949. [PMID: 32200300 DOI: 10.1016/j.heares.2020.107949] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 03/03/2020] [Accepted: 03/10/2020] [Indexed: 12/01/2022]
Abstract
Phantom electrode (PE) stimulation can extend the lower limit of pitch perception with cochlear implants (CIs) by using simultaneous out-of-phase stimulation of the most apical primary electrode and the adjacent basal compensating electrode. The total electrical field may push the excitation pattern beyond the most apical electrode to elicit a lower pitch, depending on the ratio of current between the compensating and primary electrodes (i.e., the compensation coefficient σ). This study tested the hypothesis that dynamic current steering of PE stimuli can be implemented by varying σ over time to encode spectral details in low frequencies. To determine the range of σ for current steering and the corresponding current levels, Experiment 1 tested CI users' loudness balance and pitch ranking of static PE stimuli with σ from 0 to 0.6 in steps of 0.2. It was found that the equal-loudness most comfortable level significantly increased with σ and can be modeled by a piecewise linear function of σ. Consistent with the previous findings, higher σ elicited either lower or similar pitches without salient pitch reversals than lower σ. Based on the results of Experiment 1, Experiment 2 created flat, rising, and falling pitch contours of 300-1000 ms using dynamic PE stimuli with time-varying σ from 0 to 0.6 and equal-loudness current levels. In a pitch contour identification (PCI) task, CI users scored 80% and above on average. Increasing the stimulus duration from 300 to 1000 ms slightly but did not significantly improve the PCI scores. Across subjects, the 1000-ms PCI scores in Experiment 2 were significantly correlated with the cumulative pitch-ranking sensitivity in Experiment 1. It is thus feasible to use dynamic current steering with PE to encode low-frequency pitch cues for CI users.
Collapse
Affiliation(s)
- Xin Luo
- Program of Speech and Hearing Science, College of Health Solutions, Arizona State University, 975 S. Myrtle Av., P.O. Box 870102, Tempe, AZ, 85287, USA.
| | - Christopher Garrett
- Program of Speech and Hearing Science, College of Health Solutions, Arizona State University, 975 S. Myrtle Av., P.O. Box 870102, Tempe, AZ, 85287, USA
| |
Collapse
|
9
|
Effectiveness of Phantom Stimulation in Shifting the Pitch Percept in Cochlear Implant Users. Ear Hear 2020; 41:1258-1269. [PMID: 31977727 DOI: 10.1097/aud.0000000000000845] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Phantom electrode stimulation was developed for cochlear implant (CI) systems to provide a lower pitch percept by stimulating more apical regions of the cochlea, without inserting the electrode array deeper into the cochlea. Phantom stimulation involves simultaneously stimulating a primary and a compensating electrode with opposite polarity, thereby shifting the electrical field toward the apex and eliciting a lower pitch percept. The current study compared the effect sizes (in shifts of place of excitation) of multiple phantom configurations by matching the perceived pitch with phantom stimulation to that perceived with monopolar stimulation. Additionally, the effects of electrode location, type of electrode array, and stimulus level on the perceived pitch were investigated. DESIGN Fifteen adult advanced bionics CI users participated in this study, which included four experiments to eventually measure the shifts in place of excitation with five different phantom configurations. The proportions of current delivered to the compensating electrode, expressed as σ, were 0.5, 0.6, 0.7, and 0.8 for the symmetrical biphasic pulses (SBC0.5, SBC0.6, SBC0.7, and SBC0.8) and 0.75 for the pseudomonophasic pulse shape (PSA0.75). A pitch discrimination experiment was first completed to determine which basal and apical electrode contacts should be used for the subsequent experiments. An extensive loudness balancing experiment followed where both the threshold level (T-level) and most comfortable level (M-level) were determined to enable testing at multiple levels of the dynamic range. A pitch matching experiment was then performed to estimate the shift in place of excitation at the chosen electrode contacts. These rough shifts were then used in the subsequent experiment, where the shifts in place of excitation were determined more accurately. RESULTS Reliable data were obtained from 20 electrode contacts. The average shifts were 0.39, 0.53, 0.64, 0.76, and 0.53 electrode contacts toward the apex for SBC0.5, SBC0.6, SBC0.7, SBC0.8, and PSA0.75, respectively. When only the best configurations per electrode contact were included, the average shift in place of excitation was 0.92 electrode contacts (range: 0.25 to 2.0). While PSA0.75 leads to equal results as the SBC configurations in the apex, it did not result in a significant shift at the base. The shift in place of excitation was significantly larger at the apex and with lateral wall electrode contacts. The stimulus level did not affect the shift. CONCLUSIONS Phantom stimulation results in significant shifts in place of excitation, especially at the apical part of the electrode array. The phantom configuration that leads to the largest shift in place of excitation differs between subjects. Therefore, the settings of the phantom electrode should be individualized so that the phantom stimulation is optimized for each CI user. The real added value to the sound quality needs to be established in a take-home trial.
Collapse
|
10
|
Dorman MF, Cook Natale S, Baxter L, Zeitler DM, Carlson ML, Noble JH. Cochlear Place of Stimulation Is One Determinant of Cochlear Implant Sound Quality. Audiol Neurootol 2019; 24:264-269. [PMID: 31661682 PMCID: PMC8091953 DOI: 10.1159/000503217] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 09/05/2019] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Our aim was to determine the effect of acute changes in cochlear place of stimulation on cochlear implant (CI) sound quality. DESIGN In Experiment 1, 5 single-sided deaf (SSD) listeners fitted with a long (28-mm) electrode array were tested. Basal shifts in place of stimulation were implemented by turning off the most apical electrodes and reassigning the filters to more basal electrodes. In Experiment 2, 2 SSD patients fitted with a shorter (16.5-mm) electrode array were tested. Both basal and apical shifts in place of stimulation were implemented. The apical shifts were accomplished by current steering and creating a virtual place of stimulation more apical that that of the most apical electrode. RESULTS Listeners matched basal shifts by shifting, in the normal-hearing ear, the overall spectrum up in frequency and/or increasing voice pitch (F0). Listeners matched apical shifts by shifting down the overall frequency spectrum in the normal-hearing ear. CONCLUSION One factor determining CI voice quality is the location of stimulation along the cochlear partition.
Collapse
Affiliation(s)
- Michael F Dorman
- College of Health Solutions, Speech and Hearing Science, Arizona State University, Tempe, Arizona, USA,
| | - Sarah Cook Natale
- College of Health Solutions, Speech and Hearing Science, Arizona State University, Tempe, Arizona, USA
| | - Leslie Baxter
- Clinical Neuropsychology, Mayo Clinic Arizona, Phoenix, Arizona, USA
| | - Daniel M Zeitler
- Otolaryngology/Head-Neck Surgery, Virginia Mason Medical Center, Seattle, Washington, USA
| | - Mathew L Carlson
- Department of Otolaryngology-Head and Neck Surgery, Mayo Clinic, Rochester, Minnesota, USA
| | - Jack H Noble
- Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
11
|
Litovsky RY, Goupell MJ, Kan A, Landsberger DM. Use of Research Interfaces for Psychophysical Studies With Cochlear-Implant Users. Trends Hear 2019; 21:2331216517736464. [PMID: 29113579 PMCID: PMC5764139 DOI: 10.1177/2331216517736464] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A growing number of laboratories are using research interfaces to conduct experiments with cochlear-implant (CI) users. Because these interfaces bypass a subject’s clinical sound processor, several concerns exist regarding safety and stimulation levels. Here we suggest best-practice approaches for how to safely and ethically perform this type of research and highlight areas of limited knowledge where further research is needed to help clarify safety limits. The article is designed to provide an introductory level of technical detail about the devices and the effects of electrical stimulation on perception and neurophysiology. From this, we summarize what should be the best practices in the field, based on the literature and our experience. Findings from the review of the literature suggest that there are three main safety concerns: (a) to prevent biological or neural damage, (b) to avoid presentation of uncomfortably loud sounds, and (c) to ensure that subjects have control over stimulus presentation. Researchers must pay close attention to the software–hardware interface to ensure that the three main safety concerns are closely monitored. An important area for future research will be the determination of the amount of biological damage that can occur from electrical stimulation from a CI placed in the cochlea, not in direct contact with neural tissue. As technology used in research with CIs evolve, some of these approaches may change. However, the three main safety principles outlined here are not anticipated to undergo change with technological advances.
Collapse
Affiliation(s)
| | - Matthew J Goupell
- 2 Department of Hearing and Speech Sciences, University of Maryland-College Park, MD, USA
| | - Alan Kan
- 1 University of Wisconsin-Madison, WI, USA
| | | |
Collapse
|
12
|
Abstract
OBJECTIVES Cochlear implant (CI) users suffer from a range of speech impairments, such as stuttering and vocal control of pitch and intensity. Though little research has focused on the role of auditory feedback in the speech of CI users, these speech impairments could be due in part to limited access to low-frequency cues inherent in CI-mediated listening. Phantom electrode stimulation (PES) represents a novel application of current steering that extends access to low frequencies for CI recipients. It is important to note that PES transmits frequencies below 300 Hz, whereas Baseline does not. The objective of this study was to explore the effects of PES on multiple frequency-related characteristics of voice production. DESIGN Eight postlingually deafened, adult Advanced Bionics CI users underwent a series of vocal production tests including Tone Repetition, Vowel Sound Production, Passage Reading, and Picture Description. Participants completed all of these tests twice: once with PES and once using their program used for everyday listening (Baseline). An additional test, Automatic Modulation, was included to measure acute effects of PES and was completed only once. This test involved switching between PES and Baseline at specific time intervals in real time as participants read a series of short sentences. Finally, a subjective Vocal Effort measurement was also included. RESULTS In Tone Repetition, the fundamental frequencies (F0) of tones produced using PES and the size of musical intervals produced using PES were significantly more accurate (closer to the target) compared with Baseline in specific gender, target tone range, and target tone type testing conditions. In the Vowel Sound Production task, vowel formant profiles produced using PES were closer to that of the general population compared with those produced using Baseline. The Passage Reading and Picture Description task results suggest that PES reduces measures of pitch variability (F0 standard deviation and range) in natural speech production. No significant results were found in comparisons of PES and Baseline in the Automatic Modulation task nor in the Vocal Effort task. CONCLUSIONS The findings of this study suggest that usage of PES increases accuracy of pitch matching in repeated sung tones and frequency intervals, possibly due to more accurate F0 representation. The results also suggest that PES partially normalizes the vowel formant profiles of select vowel sounds. PES seems to decrease pitch variability of natural speech and appears to have limited acute effects on natural speech production, though this finding may be due in part to paradigm limitations. On average, subjective ratings of vocal effort were unaffected by the usage of PES versus Baseline.
Collapse
|
13
|
Quass GL, Kurt S, Hildebrandt KJ, Kral A. Electrical stimulation of the midbrain excites the auditory cortex asymmetrically. Brain Stimul 2018; 11:1161-1174. [PMID: 29853311 DOI: 10.1016/j.brs.2018.05.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 05/09/2018] [Accepted: 05/10/2018] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Auditory midbrain implant users cannot achieve open speech perception and have limited frequency resolution. It remains unclear whether the spread of excitation contributes to this issue and how much it can be compensated by current-focusing, which is an effective approach in cochlear implants. OBJECTIVE The present study examined the spread of excitation in the cortex elicited by electric midbrain stimulation. We further tested whether current-focusing via bipolar and tripolar stimulation is effective with electric midbrain stimulation and whether these modes hold any advantage over monopolar stimulation also in conditions when the stimulation electrodes are in direct contact with the target tissue. METHODS Using penetrating multielectrode arrays, we recorded cortical population responses to single pulse electric midbrain stimulation in 10 ketamine/xylazine anesthetized mice. We compared monopolar, bipolar, and tripolar stimulation configurations with regard to the spread of excitation and the characteristic frequency difference between the stimulation/recording electrodes. RESULTS The cortical responses were distributed asymmetrically around the characteristic frequency of the stimulated midbrain region with a strong activation in regions tuned up to one octave higher. We found no significant differences between monopolar, bipolar, and tripolar stimulation in threshold, evoked firing rate, or dynamic range. CONCLUSION The cortical responses to electric midbrain stimulation are biased towards higher tonotopic frequencies. Current-focusing is not effective in direct contact electrical stimulation. Electrode maps should account for the asymmetrical spread of excitation when fitting auditory midbrain implants by shifting the frequency-bands downward and stimulating as dorsally as possible.
Collapse
Affiliation(s)
- Gunnar Lennart Quass
- Institute of AudioNeuroTechnology (VIANNA), Dept. of Experimental Otology, ENT Clinics, Hannover Medical School, 30625 Hannover, Germany; Cluster of Excellence "Hearing4all", Germany.
| | - Simone Kurt
- Institute of AudioNeuroTechnology (VIANNA), Dept. of Experimental Otology, ENT Clinics, Hannover Medical School, 30625 Hannover, Germany; Cluster of Excellence "Hearing4all", Germany
| | - K Jannis Hildebrandt
- Cluster of Excellence "Hearing4all", Germany; Research Center Neurosensory Science, University of Oldenburg, 26111 Oldenburg, Germany
| | - Andrej Kral
- Institute of AudioNeuroTechnology (VIANNA), Dept. of Experimental Otology, ENT Clinics, Hannover Medical School, 30625 Hannover, Germany; Cluster of Excellence "Hearing4all", Germany
| |
Collapse
|
14
|
Perceptual changes with monopolar and phantom electrode stimulation. Hear Res 2017; 359:64-75. [PMID: 29325874 DOI: 10.1016/j.heares.2017.12.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 12/17/2017] [Accepted: 12/23/2017] [Indexed: 11/21/2022]
Abstract
Phantom electrode (PE) stimulation is achieved by simultaneously stimulating out-of-phase from two adjacent intra-cochlear electrodes with different amplitudes. If the basal electrode stimulates with a smaller amplitude than the apical electrode of the pair, the resulting electrical field is pushed away from the basal electrode producing a lower pitch. There is great interest in using PE stimulation in a processing strategy as it can be used to provide stimulation to regions of the cochlea located more apically than the most apical contact on the electrode array. The result is that even lower pitch sensations can be provided without additional risk of a deeper insertion. However, it is unknown if there are perceptual differences between monopolar (MP) and PE stimulation other than a shift in place pitch. Furthermore, it is unknown if the effect and magnitude of changing from MP to PE stimulation is dependent on electrode location. This study investigates the perceptual differences (including pitch and other sound quality differences) at multiple electrode positions using MP and PE stimulation using both a multidimensional scaling procedure (MDS) and a traditional scaling procedure. 10 Advanced Bionics users reported the perceptual distances between 5 single electrode (typically 1, 3, 5, 7, and 9) stimuli in either MP or PE (σ = 0.5) mode. Subjects were asked to report how perceptually different each pair of stimuli were using any perceived differences except loudness. Subsequently, each stimulus was presented in isolation and subjects scaled how "high" or how "clean" each sounded. Results from the MDS task suggest that perceptual differences between MP and PE stimulation can be explained by a single dimension. The traditional scaling suggests that the single dimension is place pitch. PE stimulation elicits lower pitch perceptions in all cochlear regions. Analysis of Cone Beam Computer Tomography (CBCT) data suggests that PE stimulation may be more effective at the apical part of the cochlea. PE stimulation can be used for new sound coding strategies in order to extend the pitch range for cochlear implant (CI) users without perceptual side effects.
Collapse
|
15
|
Carlyon RP, Deeks JM, Undurraga J, Macherey O, van Wieringen A. Spatial Selectivity in Cochlear Implants: Effects of Asymmetric Waveforms and Development of a Single-Point Measure. J Assoc Res Otolaryngol 2017; 18:711-727. [PMID: 28755309 PMCID: PMC5612920 DOI: 10.1007/s10162-017-0625-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 05/05/2017] [Indexed: 01/07/2023] Open
Abstract
Three experiments studied the extent to which cochlear implant users' spatial selectivity can be manipulated using asymmetric waveforms and tested an efficient method for comparing spatial selectivity produced by different stimuli. Experiment 1 measured forward-masked psychophysical tuning curves (PTCs) for a partial tripolar (pTP) probe. Maskers were presented on bipolar pairs separated by one unused electrode; waveforms were either symmetric biphasic ("SYM") or pseudomonophasic with the short high-amplitude phase being either anodic ("PSA") or cathodic ("PSC") on the more apical electrode. For the SYM masker, several subjects showed PTCs consistent with a bimodal excitation pattern, with discrete excitation peaks on each electrode of the bipolar masker pair. Most subjects showed significant differences between the PSA and PSC maskers consistent with greater masking by the electrode where the high-amplitude phase was anodic, but the pattern differed markedly across subjects. Experiment 2 measured masked excitation patterns for a pTP probe and either a monopolar symmetric biphasic masker ("MP_SYM") or pTP pseudomonophasic maskers where the short high-amplitude phase was either anodic ("TP_PSA") or cathodic ("TP_PSC") on the masker's central electrode. Four of the five subjects showed significant differences between the masker types, but again the pattern varied markedly across subjects. Because the levels of the maskers were chosen to produce the same masking of a probe on the same channel as the masker, it was correctly predicted that maskers that produce broader masking patterns would sound louder. Experiment 3 exploited this finding by using a single-point measure of spread of excitation to reveal significantly better spatial selectivity for TP_PSA compared to TP_PSC maskers.
Collapse
Affiliation(s)
- Robert P Carlyon
- MRC Cognition and Brain Sciences Unit, 15 Chaucer Rd, Cambridge, CB1 3DA, UK
| | - John M Deeks
- MRC Cognition and Brain Sciences Unit, 15 Chaucer Rd, Cambridge, CB1 3DA, UK.
| | - Jaime Undurraga
- ExpORL, Department of Neurosciences, KULeuven, Herestraat 49 bus 721, 3000, Leuven, Belgium
| | - Olivier Macherey
- MRC Cognition and Brain Sciences Unit, 15 Chaucer Rd, Cambridge, CB1 3DA, UK
- LMA-CNRS, UPR 7051, Aix-Marseille University, Centrale Marseille, 4, Impasse Nikola Tesla, CS40006, 13453, Marseille Cedex 13, France
| | - Astrid van Wieringen
- ExpORL, Department of Neurosciences, KULeuven, Herestraat 49 bus 721, 3000, Leuven, Belgium
| |
Collapse
|
16
|
Pure-Tone Masking Patterns for Monopolar and Phantom Electrical Stimulation in Cochlear Implants. Ear Hear 2017; 39:124-130. [PMID: 28700446 DOI: 10.1097/aud.0000000000000471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Monopolar stimulation of the most apical electrode produces the lowest pitch sensation in cochlear implants clinically. A phantom electrode that uses out-of-phase electrical stimulation between the most apical and the neighboring basal electrode can produce a lower pitch sensation than that associated with the most apical electrode. However, because of the absence of contacts beyond the apical tip of the array, the ability to assess the spread of electrical excitation associated with phantom stimulation is limited in the typical cochlear implant subject with no residual hearing. In the present study, the spread of electrical excitation associated with monopolar and phantom stimulation of the most apical electrode was assessed using electrical masking of acoustic thresholds in cochlear implant subjects with residual, low-frequency, acoustic hearing. DESIGN Eight subjects with an Advanced Bionics cochlear implant and residual hearing in the implanted ear participated in this study (nine ears in total). Unmasked and masked thresholds for acoustic pure tones were measured at 125, 250, 500, 750, 1000, and 2000 Hz in the presence of monopolar and phantom electrode stimulation presented at the apical-most end of the array. The current compensation for phantom electrode stimulation was fixed at 50%. The two electrical maskers were loudness balanced. Differences between the unmasked and masked acoustic thresholds can be attributed to (1) the electrical stimulus-induced interference in the transduction/conduction of the acoustic signal through cochlear periphery and the auditory nerve and/or (2) masking at the level of the central auditory system. RESULTS The results show a significant elevation in pure-tone thresholds in the presence of the monopolar and phantom electrical maskers. The unmasked thresholds were subtracted from the masked thresholds to derive masking patterns as a function of the acoustic probe frequency. The masking patterns show that phantom stimulation was able to produce more masking than that associated with the monopolar stimulation of the most apical electrode. CONCLUSION These results suggest that for some cochlear implant subjects, phantom electrode stimulation can shift the neural stimulation pattern more apically in the cochlea, which is consistent with reports that phantom electrode stimulation produces lower pitch sensations than those associated with monopolar stimulation of the most apical electrode alone.
Collapse
|
17
|
Caldwell MT, Jiam NT, Limb CJ. Assessment and improvement of sound quality in cochlear implant users. Laryngoscope Investig Otolaryngol 2017; 2:119-124. [PMID: 28894831 PMCID: PMC5527361 DOI: 10.1002/lio2.71] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 01/19/2017] [Accepted: 01/21/2017] [Indexed: 11/29/2022] Open
Abstract
Objectives Cochlear implants (CIs) have successfully provided speech perception to individuals with sensorineural hearing loss. Recent research has focused on more challenging acoustic stimuli such as music and voice emotion. The purpose of this review is to evaluate and describe sound quality in CI users with the purposes of summarizing novel findings and crucial information about how CI users experience complex sounds. Data Sources Here we review the existing literature on PubMed and Scopus to present what is known about perceptual sound quality in CI users, discuss existing measures of sound quality, explore how sound quality may be effectively studied, and examine potential strategies of improving sound quality in the CI population. Results Sound quality, defined here as the perceived richness of an auditory stimulus, is an attribute of implant‐mediated listening that remains poorly studied. Sound quality is distinct from appraisal, which is generally defined as the subjective likability or pleasantness of a sound. Existing studies suggest that sound quality perception in the CI population is limited by a range of factors, most notably pitch distortion and dynamic range compression. Although there are currently very few objective measures of sound quality, the CI‐MUSHRA has been used as a means of evaluating sound quality. There exist a number of promising strategies to improve sound quality perception in the CI population including apical cochlear stimulation, pitch tuning, and noise reduction processing strategies. Conclusions In the published literature, sound quality perception is severely limited among CI users. Future research should focus on developing systematic, objective, and quantitative sound quality metrics and designing therapies to mitigate poor sound quality perception in CI users. Level of Evidence NA
Collapse
Affiliation(s)
- Meredith T Caldwell
- Department of Otolaryngology-Head & Neck Surgery University of California San Francisco California
| | - Nicole T Jiam
- Department of Otolaryngology-Head & Neck Surgery University of California San Francisco California.,Johns Hopkins University School of Medicine Baltimore Maryland
| | - Charles J Limb
- Department of Otolaryngology-Head & Neck Surgery University of California San Francisco California
| |
Collapse
|
18
|
Munjal T, Roy AT, Carver C, Jiradejvong P, Limb CJ. Use of the Phantom Electrode strategy to improve bass frequency perception for music listening in cochlear implant users. Cochlear Implants Int 2016; 16 Suppl 3:S121-8. [PMID: 26561883 DOI: 10.1179/1467010015z.000000000270] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES The Phantom Electrode strategy makes use of partial bipolar stimulation on the two most apical electrodes in an effort to extend the frequency range available to cochlear implant (CI) users. This study aimed to quantify the effect of the Phantom Electrode strategy on bass frequency perception in music listening in CI users. METHODS Eleven adult Advanced Bionics users with the Fidelity 120 processing strategy and 16 adult normal hearing (NH) individuals participated in the study. All subjects completed the CI-multiple stimulus with hidden reference and anchor (MUSHRA), a test of an individual's ability to make discriminations in sound quality following the removal of bass frequency information. NH participants completed the CI-MUSHRA once, whereas CI users completed the task twice - once with their baseline clinical program and once with the Phantom Electrode strategy, in random order. CI users' performance was assessed in comparison with NH performance. RESULTS The Phantom Electrode strategy improved CI users performance on the CI-MUSHRA compared with Fidelity 120. DISCUSSION Creation of a Phantom Electrode percept through partial bipolar stimulation of the two most apical electrodes appears to improve CI users' perception of bass frequency information in music, contributing to greater accuracy in the ability to detect alterations in musical sound quality. CONCLUSION The Phantom Electrode processing strategy may enhance the experience of listening to music and thus acoustic stimuli more broadly by improving perception of bass frequencies, through direction of current towards the apical portion of the cochlea beyond the termination of the electrode.
Collapse
|
19
|
Nogueira W, Litvak LM, Saoji AA, Büchner A. Design and evaluation of a cochlear implant strategy based on a "Phantom" channel. PLoS One 2015; 10:e0120148. [PMID: 25806818 PMCID: PMC4373925 DOI: 10.1371/journal.pone.0120148] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 01/19/2015] [Indexed: 11/30/2022] Open
Abstract
Unbalanced bipolar stimulation, delivered using charge balanced pulses, was used to produce "Phantom stimulation", stimulation beyond the most apical contact of a cochlear implant's electrode array. The Phantom channel was allocated audio frequencies below 300 Hz in a speech coding strategy, conveying energy some two octaves lower than the clinical strategy and hence delivering the fundamental frequency of speech and of many musical tones. A group of 12 Advanced Bionics cochlear implant recipients took part in a chronic study investigating the fitting of the Phantom strategy and speech and music perception when using Phantom. The evaluation of speech in noise was performed immediately after fitting Phantom for the first time (Session 1) and after one month of take-home experience (Session 2). A repeated measures of analysis of variance (ANOVA) within factors strategy (Clinical, Phantom) and interaction time (Session 1, Session 2) revealed a significant effect for the interaction time and strategy. Phantom obtained a significant improvement in speech intelligibility after one month of use. Furthermore, a trend towards a better performance with Phantom (48%) with respect to F120 (37%) after 1 month of use failed to reach significance after type 1 error correction. Questionnaire results show a preference for Phantom when listening to music, likely driven by an improved balance between high and low frequencies.
Collapse
Affiliation(s)
- Waldo Nogueira
- Department of Otolaryngology, Medical University Hannover, Cluster of Excellence “Hearing4all”, Hannover, Germany
| | - Leonid M. Litvak
- Research and Technology Group, Advanced Bionics LLC, Valencia CA, USA
| | - Aniket A. Saoji
- Research and Technology Group, Advanced Bionics LLC, Valencia CA, USA
| | - Andreas Büchner
- Department of Otolaryngology, Medical University Hannover, Cluster of Excellence “Hearing4all”, Hannover, Germany
| |
Collapse
|
20
|
Carlyon RP, Monstrey J, Deeks JM, Macherey O. Evaluation of a cochlear-implant processing strategy incorporating phantom stimulation and asymmetric pulses. Int J Audiol 2014; 53:871-9. [PMID: 25358027 PMCID: PMC4266076 DOI: 10.3109/14992027.2014.932024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE To evaluate a speech-processing strategy in which the lowest frequency channel is conveyed using an asymmetric pulse shape and "phantom stimulation", where current is injected into one intra-cochlear electrode and where the return current is shared between an intra-cochlear and an extra-cochlear electrode. This strategy is expected to provide more selective excitation of the cochlear apex, compared to a standard strategy where the lowest-frequency channel is conveyed by symmetric pulses in monopolar mode. In both strategies all other channels were conveyed by monopolar stimulation. DESIGN Within-subjects comparison between the two strategies. Four experiments: (1) discrimination between the strategies, controlling for loudness differences, (2) consonant identification, (3) recognition of lowpass-filtered sentences in quiet, (4) sentence recognition in the presence of a competing speaker. STUDY SAMPLE Eight users of the Advanced Bionics CII/Hi-Res 90k cochlear implant. RESULTS Listeners could easily discriminate between the two strategies but no consistent differences in performance were observed. CONCLUSIONS The proposed method does not improve speech perception, at least in the short term.
Collapse
|
21
|
Wu CC, Luo X. Electrode spanning with partial tripolar stimulation mode in cochlear implants. J Assoc Res Otolaryngol 2014; 15:1023-36. [PMID: 24865767 DOI: 10.1007/s10162-014-0464-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 05/07/2014] [Indexed: 11/26/2022] Open
Abstract
The perceptual effects of electrode spanning (i.e., the use of nonadjacent return electrodes) in partial tripolar (pTP) mode were tested on a main electrode EL8 in five cochlear implant (CI) users. Current focusing was controlled by σ (the ratio of current returned within the cochlea), and current steering was controlled by α (the ratio of current returned to the basal electrode). Experiment 1 tested whether asymmetric spanning with α = 0.5 can create additional channels around standard pTP stimuli. It was found that in general, apical spanning (i.e., returning current to EL6 rather than EL7) elicited a pitch between those of standard pTP stimuli on main electrodes EL8 and EL9, while basal spanning (i.e., returning current to EL10 rather than EL9) elicited a pitch between those of standard pTP stimuli on main electrodes EL7 and EL8. The pitch increase caused by apical spanning was more salient than the pitch decrease caused by basal spanning. To replace the standard pTP channel on the main electrode EL8 when EL7 or EL9 is defective, experiment 2 tested asymmetrically spanned pTP stimuli with various α, and experiment 3 tested symmetrically spanned pTP stimuli with various σ. The results showed that pitch increased with decreasing α in asymmetric spanning, or with increasing σ in symmetric spanning. Apical spanning with α around 0.69 and basal spanning with α around 0.38 may both elicit a similar pitch as the standard pTP stimulus. With the same σ, the symmetrically spanned pTP stimulus was higher in pitch than the standard pTP stimulus. A smaller σ was thus required for symmetric spanning to match the pitch of the standard pTP stimulus. In summary, electrode spanning is an effective field-shaping technique that is useful for adding spectral channels and handling defective electrodes with CIs.
Collapse
Affiliation(s)
- Ching-Chih Wu
- School of Electrical and Computer Engineering, Purdue University, 500 Oval Drive, West Lafayette, IN, 47907, USA,
| | | |
Collapse
|
22
|
Limb CJ, Roy AT. Technological, biological, and acoustical constraints to music perception in cochlear implant users. Hear Res 2014; 308:13-26. [DOI: 10.1016/j.heares.2013.04.009] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 04/04/2013] [Accepted: 04/22/2013] [Indexed: 11/30/2022]
|
23
|
Saoji AA, Landsberger DM, Padilla M, Litvak LM. Masking patterns for monopolar and phantom electrode stimulation in cochlear implants. Hear Res 2013; 298:109-16. [PMID: 23299125 PMCID: PMC3755121 DOI: 10.1016/j.heares.2012.12.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 12/05/2012] [Accepted: 12/12/2012] [Indexed: 11/16/2022]
Abstract
Phantom electrode (PE) stimulation consists of out-of-phase stimulation of two electrodes. When presented at the apex of the electrode array, phantom stimulation is known to produce a lower pitch sensation than monopolar (MP) stimulation on the most apical electrode. The ratio of the current between the primary electrode (PEL) and the compensating electrode (CEL) is represented by the coefficient σ, which ranges from 0 (monopolar) to 1 (full bipolar). The exact mechanism by which PE stimulation produces a lower pitch sensation is unclear. In the present study, unmasked and masked thresholds were obtained using a forward masking paradigm to estimate the spread of current for MP and PE stimulation. Masked thresholds were measured for two phantom electrode configurations (1) PEL = 4, CEL = 5 (lower pitch phantom) and (2) PEL = 4, CEL = 3 (higher pitch phantom). The unmasked thresholds were subtracted from the masked thresholds to obtain masking patterns which were normalized to their peak. The masking patterns reveal (1) differences in the spread of excitation that are consistent with the direction of pitch shift produced by PE stimulation, and (2) narrower spread of electrical excitation for PE stimulation relative to MP stimulation.
Collapse
Affiliation(s)
- Aniket A. Saoji
- Research and Technology group, Advanced Bionics, LLC, 28515 Westinghouse Place, Valencia CA 91355, USA
| | | | - Monica Padilla
- House Research Institute, 2100 West 3rd Street, Los Angeles, CA 90057, USA
| | - Leonid M. Litvak
- Research and Technology group, Advanced Bionics, LLC, 28515 Westinghouse Place, Valencia CA 91355, USA
| |
Collapse
|
24
|
Srinivasan AG, Padilla M, Shannon RV, Landsberger DM. Improving speech perception in noise with current focusing in cochlear implant users. Hear Res 2013; 299:29-36. [PMID: 23467170 DOI: 10.1016/j.heares.2013.02.004] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 02/11/2013] [Accepted: 02/15/2013] [Indexed: 10/27/2022]
Abstract
Cochlear implant (CI) users typically have excellent speech recognition in quiet but struggle with understanding speech in noise. It is thought that broad current spread from stimulating electrodes causes adjacent electrodes to activate overlapping populations of neurons which results in interactions across adjacent channels. Current focusing has been studied as a way to reduce spread of excitation, and therefore, reduce channel interactions. In particular, partial tripolar stimulation has been shown to reduce spread of excitation relative to monopolar stimulation. However, the crucial question is whether this benefit translates to improvements in speech perception. In this study, we compared speech perception in noise with experimental monopolar and partial tripolar speech processing strategies. The two strategies were matched in terms of number of active electrodes, microphone, filterbanks, stimulation rate and loudness (although both strategies used a lower stimulation rate than typical clinical strategies). The results of this study showed a significant improvement in speech perception in noise with partial tripolar stimulation. All subjects benefited from the current focused speech processing strategy. There was a mean improvement in speech recognition threshold of 2.7 dB in a digits in noise task and a mean improvement of 3 dB in a sentences in noise task with partial tripolar stimulation relative to monopolar stimulation. Although the experimental monopolar strategy was worse than the clinical, presumably due to different microphones, frequency allocations and stimulation rates, the experimental partial-tripolar strategy, which had the same changes, showed no acute deficit relative to the clinical.
Collapse
Affiliation(s)
- Arthi G Srinivasan
- Department of Communication and Auditory Neuroscience, House Research Institute, 2100 West 3rd Street, Los Angeles, CA 90057, USA.
| | | | | | | |
Collapse
|
25
|
Current steering with partial tripolar stimulation mode in cochlear implants. J Assoc Res Otolaryngol 2012; 14:213-31. [PMID: 23250685 DOI: 10.1007/s10162-012-0366-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 12/02/2012] [Indexed: 11/27/2022] Open
Abstract
The large spread of excitation is a major cause of poor spectral resolution for cochlear implant (CI) users. Partial tripolar (pTP) mode has been proposed to reduce current spread by returning an equally distributed fraction (0.5 × σ) of current to two flanking electrodes and the rest to an extra-cochlear ground. This study tested the efficacy of incorporating current steering into pTP mode to add spectral channels. Different proportions of current [α × σ and (1 - α) × σ] were returned to the basal and apical flanking electrodes respectively to shape the electric field. Loudness and pitch perception with α from 0 to 1 in steps of 0.1 was simulated with a computational model of CI stimulation and tested on the apical, middle, and basal electrodes of six CI subjects. The highest σ allowing for full loudness growth within the implant compliance limit was chosen for each main electrode. Pitch ranking was measured between pairs of loudness-balanced steered pTP stimuli with an α interval of 0.1 at the most comfortable level. Results demonstrated that steered pTP stimuli with α around 0.5 required more current to achieve equal loudness than those with α around 0 or 1, maybe due to more focused excitation patterns. Subjects usually perceived decreasing pitches as α increased from 0 to 1, somewhat consistent with the apical shift of the center of gravity of excitation pattern in the model. Pitch discrimination was not better with α around 0.5 than with α around 0 or 1, except for some subjects and electrodes. For three subjects with better pitch discrimination, about half of the pitch ranges of two adjacent main electrodes overlapped with each other in steered pTP mode. These results suggest that current steering with focused pTP mode may improve spectral resolution and pitch perception with CIs.
Collapse
|
26
|
Srinivasan AG, Shannon RV, Landsberger DM. Improving virtual channel discrimination in a multi-channel context. Hear Res 2012; 286:19-29. [PMID: 22616092 DOI: 10.1016/j.heares.2012.02.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Improving spectral resolution in cochlear implants is key to improving performance in difficult listening conditions (e.g. speech in noise, music, etc.). Current focusing might reduce channel interaction, thereby increasing spectral resolution. Previous studies have shown that combining current steering and current focusing reduces spread of excitation and improves virtual channel discrimination in a single-channel context. It is unclear whether the single-channel benefits from current focusing extend to a multi-channel context, in which the physical and perceptual interference of multiple stimulated channels might overwhelm the benefits of improved spectral resolution. In this study, signal discrimination was measured with and without current focusing, in the presence of competing stimuli on nearby electrodes. Results showed that signal discrimination was consistently better with current focusing than without, regardless of the amplitude of the competing stimuli. Therefore, combining current steering and current focusing may provide more effective spectral cues than are currently available.
Collapse
Affiliation(s)
- Arthi G Srinivasan
- Department of Communication and Auditory Neuroscience, House Research Institute, 2100 West 3rd Street, Los Angeles, CA 90057, USA.
| | | | | |
Collapse
|
27
|
Macherey O, Carlyon RP. Place-pitch manipulations with cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2012; 131:2225-36. [PMID: 22423718 PMCID: PMC3383798 DOI: 10.1121/1.3677260] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Pitch can be conveyed to cochlear implant listeners via both place of excitation and temporal cues. The transmission of place cues may be hampered by several factors, including limitations on the insertion depth and number of implanted electrodes, and the broad current spread produced by monopolar stimulation. The following series of experiments investigate several methods to partially overcome these limitations. Experiment 1 compares two recently published techniques that aim to activate more apical fibers than produced by monopolar or bipolar stimulation of the most apical contacts. The first technique (phantom stimulation) manipulates the current spread by simultaneously stimulating two electrodes with opposite-polarity pulses of different amplitudes. The second technique manipulates the neural spread of excitation by using asymmetric pulses and exploiting the polarity-sensitive properties of auditory nerve fibers. The two techniques yielded similar results and were shown to produce lower place-pitch percepts than stimulation of monopolar and bipolar symmetric pulses. Furthermore, combining these two techniques may be advantageous in a clinical setting. Experiment 2 proposes a method to create place pitches intermediate to those produced by physical electrodes by using charge-balanced asymmetric pulses in bipolar mode with different degrees of asymmetry.
Collapse
Affiliation(s)
- Olivier Macherey
- MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 7EF, United Kingdom.
| | | |
Collapse
|
28
|
Vanpoucke FJ, Boermans PPB, Frijns JH. Assessing the placement of a cochlear electrode array by multidimensional scaling. IEEE Trans Biomed Eng 2011; 59:307-10. [PMID: 22042122 DOI: 10.1109/tbme.2011.2173198] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Correct placement of the electrode is crucial for cochlear implantation (CI) surgery. It determines the access to the auditory nerve and subsequent hearing performance. Here, we propose an objective measures tool that can partially verify the electrode position. The intracochlear spread of the electrical fields is measured and analyzed by means of multidimensional scaling resulting in an intuitive visual representation. The user can then detect major issues, such as electrode foldover or ossification. Other implantation issues, such as electrode migration into the scala vestibuli, may not significantly alter the electrical conduction pattern and remain undetected. Still, as the measurement is quick and readily available, it may be a valuable intraoperative verification tool.
Collapse
|
29
|
Use of “Phantom Electrode” Technique to Extend the Range of Pitches Available Through a Cochlear Implant: Erratum. Ear Hear 2011. [DOI: 10.1097/aud.0b013e31820407f7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
30
|
Macherey O, Deeks JM, Carlyon RP. Extending the limits of place and temporal pitch perception in cochlear implant users. J Assoc Res Otolaryngol 2010; 12:233-51. [PMID: 21116672 PMCID: PMC3046333 DOI: 10.1007/s10162-010-0248-x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 10/26/2010] [Indexed: 11/30/2022] Open
Abstract
A series of experiments investigated the effects of asymmetric current waveforms on the perception of place and temporal pitch cues. The asymmetric waveforms were trains of pseudomonophasic (PS) pulses consisting of a short, high-amplitude phase followed by a longer (and lower amplitude) opposite-polarity phase. When such pulses were presented in a narrow bipolar ("BP+1") mode and with the first phase anodic relative to the most apical electrode (so-called PSA pulses), pitch was lower than when the first phase was anodic re the more basal electrode. For a pulse rate of 12 pulses per second (pps), pitch was also lower than with standard symmetric biphasic pulses in either monopolar or bipolar mode. This suggests that PSA pulses can extend the range of place-pitch percepts available to cochlear implant listeners by focusing the spread of excitation in a more apical region than common stimulation techniques. Temporal pitch was studied by requiring subjects to pitch-rank single-channel pulse trains with rates ranging from 105 to 1,156 pps; this task was repeated at several intra-cochlear stimulation sites and using both symmetric and pseudomonophasic pulses. For PSA pulses presented to apical electrodes, the upper limit of temporal pitch was significantly higher than that for all the other conditions, averaging 713 pps. Measures of discriminability obtained using the method of constant stimuli indicated that this pitch percept was probably weak. However, a multidimensional scaling study showed that the percept associated with a rate change, even at high rates, was orthogonal to that of a place change and therefore reflected a genuine change in the temporal pattern of neural activity.
Collapse
Affiliation(s)
- Olivier Macherey
- Medical Research Council, Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge, UK.
| | | | | |
Collapse
|