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Windmeijer CAA, Biesheuvel JD, Boermans PPBM, Briaire JJ, Frijns JHM. Full-array channel discrimination in cochlear implants: validation and clinical application. Int J Audiol 2023; 62:992-1001. [PMID: 35875843 DOI: 10.1080/14992027.2022.2101028] [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] [Received: 01/31/2022] [Accepted: 07/08/2022] [Indexed: 11/05/2022]
Abstract
OBJECTIVE We sought to validate our proposed tool for estimating channel discrimination of cochlear implant (CI) users along the full electrode array and to assess associations between place-pitch discrimination and speech perception. DESIGN In two tests, participants identified one stimulus (probe) as the odd-one-out compared with two reference stimuli. Probe stimuli were evoked using dual electrode stimulation characterised by the current steering coefficient α. The first test measured psychometric functions (PFs) on pre-defined contacts, with just a noticeable difference (JNDα) as the outcome variable. The second test estimated channel discrimination on the full electrode array, yielding a discrimination score of Dα. We measured speech perception as free-field consonant-vowel-consonant phoneme recognition scores. STUDY SAMPLE We included 25 adults with at least 6 months of CI experience. RESULTS JNDα and Dα scores measured on the same contact correlated significantly (rs = 0.64, p < 0.001). Mean JNDα and speech perception scores showed significant relationships in quiet and in noise. CONCLUSIONS Dα correlated strongly with JNDα scores obtained with the PFs. For poor performers, the full-array test may underestimate JNDα. The full-array pitch discrimination test could be a helpful clinical tool, such as for fitting regions of lesser pitch discrimination ability.
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Affiliation(s)
| | | | | | - Jeroen J Briaire
- ENT Department, Leiden University Medical Centre, Leiden, The Netherlands
| | - Johan H M Frijns
- ENT Department, Leiden University Medical Centre, Leiden, The Netherlands
- Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands
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Lindenbeck MJ, Majdak P, Srinivasan S, Laback B. Pitch discrimination in electric hearing with inconsistent and consistent amplitude-modulation and inter-pulse rate cues. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 153:3268. [PMID: 37307025 PMCID: PMC10264086 DOI: 10.1121/10.0019452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 04/28/2023] [Accepted: 05/01/2023] [Indexed: 06/13/2023]
Abstract
Users of cochlear implants (CIs) struggle in situations that require selective hearing to focus on a target source while ignoring other sources. One major reason for that is the limited access to timing cues such as temporal pitch or interaural time differences (ITDs). Various approaches to improve timing-cue sensitivity while maintaining speech understanding have been proposed, among them inserting extra pulses with short inter-pulse intervals (SIPIs) into amplitude-modulated (AM) high-rate pulse trains. Indeed, SIPI rates matching the naturally occurring AM rates improve pitch discrimination. For ITD, however, low SIPI rates are required, potentially mismatching the naturally occurring AM rates and thus creating unknown pitch effects. In this study, we investigated the perceptual contribution of AM and SIPI rate to pitch discrimination in five CI listeners and with two AM depths (0.1 and 0.5). Our results show that the SIPI-rate cue generally dominated the percept for both consistent and inconsistent cues. When tested with inconsistent cues, also the AM rate contributed, however, at the large AM depth only. These findings have implications when aiming at jointly improving temporal-pitch and ITD sensitivity in a future mixed-rate stimulation approach.
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Affiliation(s)
- Martin J Lindenbeck
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, A-1040 Vienna, Austria
| | - Piotr Majdak
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, A-1040 Vienna, Austria
| | - Sridhar Srinivasan
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, A-1040 Vienna, Austria
| | - Bernhard Laback
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, A-1040 Vienna, Austria
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Lindenbeck MJ, Laback B, Majdak P, Srinivasan S. Temporal-pitch sensitivity in electric hearing with amplitude modulation and inserted pulses with short inter-pulse intervals. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 147:777. [PMID: 32113255 PMCID: PMC7002171 DOI: 10.1121/10.0000610] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 12/26/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
Listeners with cochlear implants (CIs) typically show poor sensitivity to the temporal-envelope pitch of high-rate pulse trains. Sensitivity to interaural time differences improves when adding pulses with short inter-pulse intervals (SIPIs) to high-rate pulse trains. In the current study, monaural temporal-pitch sensitivity with SIPI pulses was investigated for six CI listeners. Amplitude-modulated single-electrode stimuli, representing the coding of the fundamental frequency (F0) in the envelope of a high-rate carrier, were used. Two SIPI-insertion approaches, five modulation depths, two typical speech-F0s, and two carrier rates were tested. SIPI pulses were inserted either in every amplitude-modulation period (full-rate SIPI) to support the F0 cue or in every other amplitude-modulation period (half-rate SIPI) to circumvent a potential rate limitation at higher F0s. The results demonstrate that full-rate SIPI pulses improve temporal-pitch sensitivity across F0s and particularly at low modulation depths where envelope-pitch cues are weak. The half-rate SIPI pulses did not circumvent the limitation and further increased variability across listeners. Further, no effect of the carrier rate was found. Thus, the SIPI approach appears to be a promising approach to enhance CI listeners' access to temporal-envelope pitch cues at pulse rates used clinically.
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Affiliation(s)
- Martin J Lindenbeck
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, 1040 Vienna, Austria
| | - Bernhard Laback
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, 1040 Vienna, Austria
| | - Piotr Majdak
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, 1040 Vienna, Austria
| | - Sridhar Srinivasan
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, 1040 Vienna, Austria
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Interaural Pitch-Discrimination Range Effects for Bilateral and Single-Sided-Deafness Cochlear-Implant Users. J Assoc Res Otolaryngol 2019; 20:187-203. [PMID: 30623318 DOI: 10.1007/s10162-018-00707-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 11/26/2018] [Indexed: 10/27/2022] Open
Abstract
By allowing bilateral access to sound, bilateral cochlear implants (BI-CIs) or unilateral CIs for individuals with single-sided deafness (SSD; i.e., normal or near-normal hearing in one ear) can improve sound localization and speech understanding in noise. Spatial hearing in the horizontal plane is primarily conveyed by interaural time and level differences computed from neurons in the superior olivary complex that receive frequency-matched inputs. Because BI-CIs and SSD-CIs do not necessarily convey frequency-matched information, it is critical to understand how to align the inputs to CI users. Previous studies show that interaural pitch discrimination for SSD-CI listeners is highly susceptible to contextual biases, questioning its utility for establishing interaural frequency alignment. Here, we replicate this finding for SSD-CI listeners and show that these biases also extend to BI-CI listeners. To assess the testing-range bias, three ranges of comparison electrodes (BI-CI) or pure-tone frequencies (SSD-CI) were tested: full range, apical/lower half, or basal/upper half. To assess the reference bias, the reference electrode was either held fixed throughout a testing block or randomly chosen from three electrodes (basal end, middle, or apical end of the array). Results showed no effect of reference electrode randomization, but a large testing range bias; changing the center of the testing-range shifted the pitch match by an average 63 % (BI-CI) or 43 % (SSD-CI) of the change magnitude. This bias diminished pitch-match accuracy, with a change in reference electrode shifting the pitch match only an average 34 % (BI-CI) or 40 % (SSD-CI) of the expected amount. Because these effects extended to the relatively more symmetric BI-CI listeners, the results suggest that the bias cannot be attributed to interaural asymmetry. Unless the range effect can be minimized or accounted for, a pitch-discrimination task will produce interaural place-of-stimulation estimates that are highly influenced by the conditions tested, rather than reflecting a true interaural place-pitch comparison.
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Grasmeder ML, Verschuur CA, van Besouw RM, Wheatley AMH, Newman TA. Measurement of pitch perception as a function of cochlear implant electrode and its effect on speech perception with different frequency allocations. Int J Audiol 2018; 58:158-166. [PMID: 30370800 DOI: 10.1080/14992027.2018.1516048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
OBJECTIVE An experiment was conducted to investigate the possibility that speech perception could be improved for some cochlear implant (CI) users by adjustment of the frequency allocation to the electrodes, following assessment of pitch perception along the electrode array. STUDY SAMPLE Thirteen adult CI users with MED-EL devices participated in the study. DESIGN Pitch perception was assessed for individual CI electrode pairs using the Pitch Contour Test (PCT), giving information on pitch discrimination and pitch ranking for adjacent electrodes. Sentence perception in noise was also assessed with ten different frequency allocations, including the default. RESULTS Pitch perception was found to be poorer for both discrimination and ranking scores at either end of the electrode array. A significant effect of frequency allocation was found for sentence scores [F(4.24,38.2) = 7.14, p < 0.001] and a significant interaction between sentence score and PCT ranking score for basal electrodes was found [F(4.24,38.2) = 2.95, p = 0.03]. Participants with poorer pitch perception at the basal end had poorer scores for some allocations with greater basal shift. CONCLUSIONS The results suggest that speech perception could be improved for CI users by assessment of pitch perception using the PCT and subsequent adjustment of pitch-related stimulation parameters.
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Affiliation(s)
- M L Grasmeder
- a Auditory Implant Service University of Southampton , Southampton , UK
| | - C A Verschuur
- a Auditory Implant Service University of Southampton , Southampton , UK
| | - R M van Besouw
- b Institute of Sound and Vibration Research, University of Southampton , UK
| | - A M H Wheatley
- b Institute of Sound and Vibration Research, University of Southampton , UK
| | - T A Newman
- c Southampton Neuroscience Group , University of Southampton , UK
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Landsberger DM, Vermeire K, Claes A, Van Rompaey V, Van de Heyning P. Qualities of Single Electrode Stimulation as a Function of Rate and Place of Stimulation with a Cochlear Implant. Ear Hear 2018; 37:e149-59. [PMID: 26583480 DOI: 10.1097/aud.0000000000000250] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Although it has been shown previously that changes in temporal coding produce changes in pitch in all cochlear regions, research has suggested that temporal coding might be best encoded in relatively apical locations. The authors hypothesized that although temporal coding may provide useable information at any cochlear location, low rates of stimulation might provide better sound quality in apical regions that are more likely to encode temporal information in the normal ear. In the present study, sound qualities of single electrode pulse trains were scaled to provide insight into the combined effects of cochlear location and stimulation rate on sound quality. DESIGN Ten long-term users of MED-EL cochlear implants with 31-mm electrode arrays (Standard or FLEX) were asked to scale the sound quality of single electrode pulse trains in terms of how "Clean," "Noisy," "High," and "Annoying" they sounded. Pulse trains were presented on most electrodes between 1 and 12 representing the entire range of the long electrode array at stimulation rates of 100, 150, 200, 400, or 1500 pulses per second. RESULTS Although high rates of stimulation are scaled as having a Clean sound quality across the entire array, only the most apical electrodes (typically 1 through 3) were considered Clean at low rates. Low rates on electrodes 6 through 12 were not rated as Clean, whereas the low-rate quality of electrodes 4 and 5 were typically in between. Scaling of Noisy responses provided an approximately inverse pattern as Clean responses. High responses show the trade-off between rate and place of stimulation on pitch. Because High responses did not correlate with Clean responses, subjects were not rating sound quality based on pitch. CONCLUSIONS If explicit temporal coding is to be provided in a cochlear implant, it is likely to sound better when provided apically. In addition, the finding that low rates sound clean only at apical places of stimulation is consistent with previous findings that a change in rate of stimulation corresponds to an equivalent change in perceived pitch at apical locations. Collectively, the data strongly suggest that temporal coding with a cochlear implant is optimally provided by electrodes placed well into the second cochlear turn.
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Affiliation(s)
- David M Landsberger
- 1Department of Otolaryngology, New York University School of Medicine, New York, New York, USA; 2Department of Otorhinolaryngology & Head and Neck Surgery, Antwerp University Hospital, Antwerp, Belgium; 3Hearing and Speech Center, Long Island Jewish Medical Center, New Hyde Park, New York, USA; and 4Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium
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Todd AE, Mertens G, Van de Heyning P, Landsberger DM. Encoding a Melody Using Only Temporal Information for Cochlear-Implant and Normal-Hearing Listeners. Trends Hear 2017; 21:2331216517739745. [PMID: 29161987 PMCID: PMC5703098 DOI: 10.1177/2331216517739745] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 10/05/2017] [Indexed: 11/16/2022] Open
Abstract
One way to provide pitch information to cochlear implant users is through amplitude-modulation rate. It is currently unknown whether amplitude-modulation rate can provide cochlear implant users with pitch information adequate for perceiving melodic information. In the present study, the notes of a song were encoded via amplitude-modulation rate of pulse trains on single electrodes at the apex or middle of long electrode arrays. The melody of the song was either physically correct or modified by compression or expansion. Nine cochlear implant users rated the extent to which the song was out of tune in the different conditions. Cochlear implant users on average did not show sensitivity to melody compression or expansion regardless of place of stimulation. These results were found despite the fact that three of the cochlear implant users showed the expected sensitivity to melody compression and expansion with the same task using acoustic pure tones in a contralateral acoustic ear. Normal-hearing listeners showed an inconsistent and weak effect of melody compression and expansion when the notes of the song were encoded with acoustic pulse rate. The results suggest that amplitude-modulation rate provides insufficient access to melodic information for cochlear-implant and normal-hearing listeners.
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Affiliation(s)
- Ann E. Todd
- Department of Otolaryngology, New York University School of Medicine, NY, USA
| | - Griet Mertens
- Department of Otorhinolaryngology, Head and Neck Surgery, Antwerp University Hospital, University of Antwerp, Belgium
| | - Paul Van de Heyning
- Department of Otorhinolaryngology, Head and Neck Surgery, Antwerp University Hospital, University of Antwerp, Belgium
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Landsberger DM, Svrakic M, Roland JT, Svirsky M. The Relationship Between Insertion Angles, Default Frequency Allocations, and Spiral Ganglion Place Pitch in Cochlear Implants. Ear Hear 2016; 36:e207-13. [PMID: 25860624 DOI: 10.1097/aud.0000000000000163] [Citation(s) in RCA: 172] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Commercially available cochlear implant systems attempt to deliver frequency information going down to a few hundred Hertz, but the electrode arrays are not designed to reach the most apical regions of the cochlea, which correspond to these low frequencies. This may cause a mismatch between the frequencies presented by a cochlear implant electrode array and the frequencies represented at the corresponding location in a normal-hearing cochlea. In the following study, the mismatch between the frequency presented at a given cochlear angle and the frequency expected by an acoustic hearing ear at the corresponding angle is examined for the cochlear implant systems that are most commonly used in the United States. DESIGN The angular insertion of each of the electrodes on four different electrode arrays (MED-EL Standard, MED-EL Flex28, Advanced Bionics HiFocus 1J, and Cochlear Contour Advance) was estimated from X-ray. For the angular location of each electrode on each electrode array, the predicted spiral ganglion frequency was estimated. The predicted spiral ganglion frequency was compared with the center frequency provided by the corresponding electrode using the manufacturer's default frequency-to-electrode allocation. RESULTS Differences across devices were observed for the place of stimulation for frequencies below 650 Hz. Longer electrode arrays (i.e., the MED-EL Standard and Flex28) demonstrated smaller deviations from the spiral ganglion map than the other electrode arrays. For insertion angles up to approximately 270°, the frequencies presented at a given location were typically approximately an octave below what would be expected by a spiral ganglion frequency map, while the deviations were larger for angles deeper than 270°. For frequencies above 650 Hz, the frequency to angle relationship was consistent across all four electrode models. CONCLUSIONS A mismatch was observed between the predicted frequency and the default frequency provided by every electrode on all electrode arrays. The mismatch can be reduced by changing the default frequency allocations, inserting electrodes deeper into the cochlea, or allowing cochlear implant users to adapt to the mismatch. Further studies are required to fully assess the clinical significance of the frequency mismatch.
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Affiliation(s)
- David M Landsberger
- Department of Otolaryngology, New York University School of Medicine, New York, USA
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Perception and coding of interaural time differences with bilateral cochlear implants. Hear Res 2015; 322:138-50. [DOI: 10.1016/j.heares.2014.10.004] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 10/01/2014] [Accepted: 10/07/2014] [Indexed: 11/21/2022]
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Place pitch versus electrode location in a realistic computational model of the implanted human cochlea. Hear Res 2014; 315:10-24. [PMID: 24975087 DOI: 10.1016/j.heares.2014.06.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 06/06/2014] [Accepted: 06/15/2014] [Indexed: 11/23/2022]
Abstract
Place pitch was investigated in a computational model of the implanted human cochlea containing nerve fibres with realistic trajectories that take the variable distance between the organ of Corti and spiral ganglion into account. The model was further updated from previous studies by including fluid compartments in the modiolus and updating the electrical conductivity values of (temporal) bone and the modiolus, based on clinical data. Four different cochlear geometries are used, modelled with both lateral and perimodiolar implants, and their neural excitation patterns were examined for nerve fibres modelled with and without peripheral processes. Additionally, equations were derived from the model geometries that describe Greenwood's frequency map as a function of cochlear angle at the basilar membrane as well as at the spiral ganglion. The main findings are: (I) in the first (basal) turn of the cochlea, cochlear implant induced pitch can be predicted fairly well using the Greenwood function. (II) Beyond the first turn this pitch becomes increasingly unpredictable, greatly dependent on stimulus level, state of the cochlear neurons and the electrode's distance from the modiolus. (III) After the first turn cochlear implant induced pitch decreases as stimulus level increases, but the pitch does not reach values expected from direct spiral ganglion stimulation unless the peripheral processes are missing. (IV) Electrode contacts near the end of the spiral ganglion or deeper elicit very unpredictable pitch, with broad frequency ranges that strongly overlap with those of neighbouring contacts. (V) The characteristic place pitch for stimulation at either the organ of Corti or the spiral ganglion can be described as a function of cochlear angle by the equations presented in this paper.
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Landsberger DM, Mertens G, Punte AK, Van De Heyning P. Perceptual changes in place of stimulation with long cochlear implant electrode arrays. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 135:EL75-EL81. [PMID: 25234918 PMCID: PMC3985910 DOI: 10.1121/1.4862875] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 12/17/2013] [Indexed: 06/02/2023]
Abstract
Long (31.5 mm) electrode arrays are inserted deeper into the cochlea than the typical 1.25 turn insertion. With these electrode arrays, the apical electrodes are closer to (and possibly extend past) the end of the spiral ganglion. Using multi-dimensional scaling with patients implanted with a 31.5 mm electrode array, the perceptual space between electrodes was measured. The results suggest that deeper insertion increases the range of place pitches, but the perceptual differences between adjacent electrodes become smaller in the apex.
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Affiliation(s)
- David M Landsberger
- Division of Communication and Auditory Neuroscience, House Research Institute, 2100 West 3rd Street, Los Angeles, California 90057
| | - Griet Mertens
- University Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Antwerp, University of Antwerp, Antwerp, Belgium , ,
| | - Andrea Kleine Punte
- University Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Antwerp, University of Antwerp, Antwerp, Belgium , ,
| | - Paul Van De Heyning
- University Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Antwerp, University of Antwerp, Antwerp, Belgium , ,
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Arnoldner C, Lin VYW. Expanded selection criteria in adult cochlear implantation. Cochlear Implants Int 2013; 14 Suppl 4:S10-3. [DOI: 10.1179/1467010013z.000000000123] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Digeser FM, Hast A, Wesarg T, Hessel H, Hoppe U. Melody identification for cochlear implant users and normal hearers using expanded pitch contours. Eur Arch Otorhinolaryngol 2011; 269:2317-26. [DOI: 10.1007/s00405-011-1885-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 12/09/2011] [Indexed: 11/29/2022]
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Abstract
OBJECTIVES This review examines evidence for potential benefits of using cochlear implant electrodes that extend into the apical regions of the cochlea. Most cochlear implant systems use electrode arrays that extend 1 to 1.5 turns from the basal cochleostomy, but one manufacturer (MED-EL GmbH) uses an electrode array that is considerably longer. The fundamental rationale for using electrodes extending toward the apex of the cochlea is to provide additional low-pitched auditory percepts and thereby increase the spectral information available to the user. Several experimental long arrays have also been produced by other manufacturers to assess potential benefits of this approach. DESIGN In addition to assessing the effects of deeply inserted electrodes on performance, this review examines several underlying and associated issues, including cochlear anatomy, electrode design, surgical considerations (including insertion trauma), and pitch scaling trials. Where possible, the aim is to draw conclusions regarding the potential from apical electrodes in general, rather than relating to the performance of specific and current devices. RESULTS Imaging studies indicate that currently available electrode arrays rarely extend more than two turns into the cochlea, the mean insertion angle for full insertions of the MED-EL electrodes being about 630°. This is considerably shorter than the total length of the cochlea and more closely approximates the length of the spiral ganglion. Anatomical considerations, and some modelling studies, suggest that fabrication of even longer electrodes is unlikely to provide additional spectral information. The issue of potential benefit from the most apical electrodes, therefore, is whether they are able to selectively stimulate discrete and tonotopically ordered neural populations near the apex of the spiral ganglion, where the ganglion cells are closely grouped. Pitch scaling studies, using the MED-EL and experimental long arrays, suggest that this is achieved in many cases, but that a significant number of individuals show evidence of pitch confusions or reversals among the most apical electrodes, presumably reducing potential performance benefit and presenting challenges for processor programming. CONCLUSIONS Benefits in terms of speech recognition and other performance measures are less clear. Several studies have indicated that deactivation of apical electrodes results in poorer speech recognition performance, but these have been mostly acute studies where the subjects have been accustomed to the full complement of electrodes, thus making interpretation difficult. Some chronic studies have suggested that apical electrodes do provide additional performance benefit, but others have shown performance improvement after deactivating some of the apical electrodes. Whether or not deeply inserted electrodes can offer performance benefits, there is evidence that currently available designs tend to produce more intracochlear trauma than shorter arrays, in terms of loss of residual acoustic hearing and reduction of the neural substrate. This may have important long-term consequences for the user. Furthermore, as it is possible that subjects with better low-frequency residual hearing are more likely to benefit from the inclusion of apical electrodes, there may be a potential clinical dilemma as the same subjects are those most likely to benefit from bimodal electroacoustic stimulation, requiring a relatively shallow insertion.
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von Ilberg CA, Baumann U, Kiefer J, Tillein J, Adunka OF. Electric-Acoustic Stimulation of the Auditory System: A Review of the First Decade. ACTA ACUST UNITED AC 2011; 16 Suppl 2:1-30. [DOI: 10.1159/000327765] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 02/21/2011] [Indexed: 11/19/2022]
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Carlyon RP, Long CJ, Deeks JM. Pulse-rate discrimination by cochlear-implant and normal-hearing listeners with and without binaural cues. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2008; 123:2276-86. [PMID: 18397032 PMCID: PMC2376257 DOI: 10.1121/1.2874796] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Experiment 1 measured rate discrimination of electric pulse trains by bilateral cochlear implant (CI) users, for standard rates of 100, 200, and 300 pps. In the diotic condition the pulses were presented simultaneously to the two ears. Consistent with previous results with unilateral stimulation, performance deteriorated at higher standard rates. In the signal interval of each trial in the dichotic condition, the standard rate was presented to the left ear and the (higher) signal rate was presented to the right ear; the non-signal intervals were the same as in the diotic condition. Performance in the dichotic condition was better for some listeners than in the diotic condition for standard rates of 100 and 200 pps, but not at 300 pps. It is concluded that the deterioration in rate discrimination observed for CI users at high rates cannot be alleviated by the introduction of a binaural cue, and is unlikely to be limited solely by central pitch processes. Experiment 2 performed an analogous experiment in which 300-pps acoustic pulse trains were bandpass filtered (3900-5400 Hz) and presented in a noise background to normal-hearing listeners. Unlike the results of experiment 1, performance was superior in the dichotic than in the diotic condition.
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Affiliation(s)
- Robert P Carlyon
- MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 7EF, United Kingdom.
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Variance of Angular Insertion Depths in Free-Fitting and Perimodiolar Cochlear Implant Electrodes. Otol Neurotol 2008; 29:131-6. [DOI: 10.1097/mao.0b013e318157f0ea] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Arnoldner C, Riss D, Baumgartner WD, Kaider A, Hamzavi JS. Cochlear Implant Channel Separation and Its Influence on Speech Perception – Implications for a New Electrode Design. Audiol Neurootol 2007; 12:313-24. [PMID: 17536200 DOI: 10.1159/000103212] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Accepted: 03/30/2007] [Indexed: 11/19/2022] Open
Abstract
There are a variety of factors which can influence cochlear implantation outcome. Channel interaction is one of the variables responsible for audiological performance deterioration in multichannel implants. Electrode design is--among others--one way to decrease the incidence of channel interaction. At present, electrodes differ in overall length, diameter, contact design and distribution, but none of the electrodes available have a distinct variability in the amount of space between contacts across the length of the electrode. The aim of this study was to investigate whether a new electrode design featuring larger contact spacing in the apical part of deeply inserted electrodes would lead to an increase in speech perception. Eighteen postlingually deafened patients fitted with MedEl Combi 40+ or MedEl Pulsar cochlear implants using the MedEl implementation of continuous interleaved sampling participated in this study. Patients were tested in 6 conditions, in which the channel spacing and distribution of electrode contacts in each patient were artificially varied by activating or deactivating different channels. Performance was tested immediately after each change in setup with a monosyllable and sentence test (Hochmaier, Schultz and Moser). Our results showed that the condition with the highest distance between contacts in the apical part (up to 6.4 mm instead of 2.4 mm) is the most effective for the matched map condition: the results improved statistically significantly for the sentence test from 72% in the standard 12-channel condition to 83.2% and from 40.8 to 50% for the monosyllable test. Based on these findings, we present a new electrode design which can help achieve further increases in speech perception with cochlear implants.
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Affiliation(s)
- Christoph Arnoldner
- Department of Otorhinolaryngology, Medical University of Vienna, Vienna, Austria
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Haumann S, Mühler R, Ziese M, von Specht H. Diskrimination musikalischer Tonhöhen bei Patienten mit Kochleaimplantat. HNO 2006; 55:613-9. [PMID: 17136415 DOI: 10.1007/s00106-006-1485-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
BACKGROUND Numerous people with cochlear implants (CI) report difficulties in listening to music even though they understand speech quite well. One reason for this is a limited perception of pitch and timbre. In this study ability of adult CI subjects to discriminate musical pitch is investigated. PATIENTS AND METHODS In two psychoacoustic experiments, each conducted in 10 adult CI subjects provided with MED-EL Combi 40+ cochlear implant devices and a control group of subjects with normal hearing, individual discrimination abilities for musical pitch perception were determined. To investigate the influence of the group of instruments on discrimination ability, stimuli representing four different groups of instruments were used: woodwind (clarinet), brass (trumpet), strings (violin) and keyboard instruments (piano). RESULTS The discrimination thresholds determined varied between individual CI subjects, and on average they were significantly higher for the piano than for the other three instruments. CONCLUSIONS The results show that in subjects with CI pitch perception differs from instrument to instrument and is in general worse than in persons with normal hearing.
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Affiliation(s)
- S Haumann
- Abt. Experimentelle Audiologie und Medizinische Physik, Universitätsklinikum Magdeburg, Leipziger Str. 44, 39120, Magdeburg.
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Baumann U, Nobbe A. The cochlear implant electrode-pitch function. Hear Res 2006; 213:34-42. [PMID: 16442249 DOI: 10.1016/j.heares.2005.12.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Revised: 12/12/2005] [Accepted: 12/12/2005] [Indexed: 10/25/2022]
Abstract
The cochlear frequency-place function in normal hearing ears has been found to be an exponential relationship in a wide variety of species [D.D. Greenwood, J. Acoust. Soc. Am. 87 (1990) 2592-2605]. Although it seems reasonable to assume a similar function for electrical stimulation by means of an intra-cochlear electrode array, the exact frequency-place function for this special type of stimulation needs to be investigated. Six users of the MED-EL COMBI 40+ cochlear implant device with moderate to profound hearing loss between 125 and 1000 Hz in the non-implanted ear took part in a binaural pitch adjustment experiment. The COMBI 40+ electrode array provides a deep insertion into the scala tympani and a wide spatial separation between the stimulating electrodes. Insertion depth was controlled by Stenver's view plain radiographs and the insertion angle was estimated. The task of the subjects was to adjust the frequency of a sinusoid presented in the non-implanted ear by means of an adjusting knob until they perceived the same pitch as was elicited by a reference stimulus in the implanted ear. The results show adjustments corresponding to electrode positions along the cochlea, with the exception of the two most apical electrodes for most of the subjects. Pitch increased in an orderly fashion with an average of 98 Hz per electrode separation (40 Hz/mm). In contrast to the exponential predictions according to [D.D. Greenwood, J. Acoust. Soc. Am. 87 (1990) 2592-2605] for normal hearing, the average electrode-pitch function shows a linear relationship.
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Affiliation(s)
- Uwe Baumann
- Department of Otorhinolaryngology, University of Munich, Marchioninistr. 15, 81377 München, Germany.
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Baumann U, Nobbe A. Pulse rate discrimination with deeply inserted electrode arrays. Hear Res 2005; 196:49-57. [PMID: 15464301 DOI: 10.1016/j.heares.2004.06.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Accepted: 06/22/2004] [Indexed: 11/20/2022]
Abstract
Pulse rate difference limen (PRDL) and amplitude modulation difference limen (AMDL) were assessed as a function of base rate and cochlear electrode location in seven (three for AMDL) subjects implanted with the MED-EL COMBI 40+ implant. The MED-EL COMBI 40+ electrode array allows deep insertion of the electrode up to the apex of the cochlea to minimize the rate/place mismatch for pulse rates below 500 pps. A three interval, two alternative forced-choice procedure with feedback was used to measure the difference limen. The base rate was in the range between 200 and 800 pps. The carrier rate for the AMDL measurement was 5081 pps. The PRDL increased with increasing base pulse rate. At 200 pps the average PRDL measured at the apical electrode amounted to 48.7 pps, at 400 pps the average PRDL reached 206.6 pps. No significant difference between PRDL obtained from apical or basal electrodes could be observed. AMDL was higher than PRDL at all tested base rates. The ability to discriminate rate changes is limited to base rates up to about 283 pps. The results indicate that rate changes smaller than a major third do not elicit distinguishable auditory perceptions in electrical hearing. The absence of a difference between apical and basal electrode locations indicates that a reduction of the rate/place mismatch does not improve discrimination performance.
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Affiliation(s)
- Uwe Baumann
- Department of Otorhinolaryngology, ENT - Audiology, University of Munich, Marchioninistr. 15, 81377 München, Germany.
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