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Is there a fundamental 300 Hz limit to pulse rate discrimination in cochlear implants? J Assoc Res Otolaryngol 2014; 15:849-66. [PMID: 24942704 DOI: 10.1007/s10162-014-0468-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 05/28/2014] [Indexed: 10/25/2022] Open
Abstract
Literature often refers to a 300 pps limit for cochlear implant (CI) electrical stimulation, above which pulse rate discrimination deteriorates or above which rate pitch is not perceived to increase. The present study investigated the effect on pulse rate difference limens (PRDLs) when using compound stimuli in which identical pulse trains were applied to multiple electrodes across the length of the electrode array and compared the results to those of single-electrode stimuli. PRDLs of seven CI users were determined in two stimulus pulse phase conditions, one in which the phase delays between pulses on different electrodes were minimised (burst mode) and a second in which they were maximised (spread mode). PRDLs were measured at base rates of 100 to 600 pps in 100 pps intervals, using compound stimuli on one, two, five, nine and 18 electrodes. As smaller PRDLs were expected to reflect improved rate pitch perception, 18-electrode spread mode stimuli were also included in a pitch ranking task. PRDLs improved markedly when multi-electrode compound stimuli were used, with average spread mode PRDLs across listeners between 6 and 8 % of the base rate in the whole range tested (i.e. up to 600 pps). PRDLs continued to improve as more electrodes were included, up to at least nine electrodes in the compound stimulus. Stimulus pulse phase had a significant influence on the results, with PRDLs being smaller in spread mode. Results indicate that pulse rate discrimination may be manipulated with stimulus parameter choice so that previously observed deterioration of PRDLs at 300 pps probably does not reflect a fundamental limitation to rate discrimination. However, rate pitch perception did not improve in the conditions that resulted in smaller PRDLs. This may indicate that listeners used cues other than pitch to perform the rate discrimination task or may reflect limitations in the electrically evoked neural excitation patterns presented to a rate pitch extraction mechanism.
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Fielden CA, Kluk K, McKay CM. Interpulse interval discrimination within and across channels: comparison of monopolar and tripolar mode of stimulation. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 135:2913-2922. [PMID: 24815271 DOI: 10.1121/1.4869687] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Perception of temporal patterns is crucial to speech understanding and music perception in normal hearing, and is fundamental in the design and implementation of processing strategies for cochlear implants. Two experiments described here investigated the effect of stimulation mode (monopolar versus tripolar) on interpulse interval discrimination using single-electrode stimulation (experiment 1) and dual-electrode stimulation (experiment 2). Experiment 1 required participants to discriminate stimuli containing different interpulse intervals and experiment 2 required listeners to discriminate between two dual-electrode stimuli that had the same temporal pattern on each electrode, but differed in inter-electrode timing. The hypotheses were that (i) stimulation mode would affect the ability to distinguish interpulse interval patterns on a single electrode and (ii) the electrode separation range in which subjects were sensitive to inter-electrode timing would be more restricted in tripolar than in monopolar stimulation. Results in nine cochlear implant users showed that mode did not have a significant mean effect on either the ability to discriminate interpulse intervals in single-electrode stimulation or the range of electrode separation in dual-electrode stimulation in which participants were sensitive to inter-electrode timing. In conclusion, tripolar stimulation did not show any advantage in delivering temporal information within or across channels in this group.
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Affiliation(s)
- Claire A Fielden
- School of Psychological Sciences, Ellen Wilkinson Building, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Karolina Kluk
- School of Psychological Sciences, Ellen Wilkinson Building, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Colette M McKay
- School of Psychological Sciences, Ellen Wilkinson Building, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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Comodulation masking release in electric hearing. J Assoc Res Otolaryngol 2014; 15:279-91. [PMID: 24414194 PMCID: PMC3946139 DOI: 10.1007/s10162-013-0433-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 12/16/2013] [Indexed: 11/25/2022] Open
Abstract
Comodulation masking release (CMR) is an improvement in the detection threshold of a masked signal that occurs when the masker envelopes are correlated across frequency (i.e., comodulation). CMR can be observed when flanking bands (FBs) of noise co-modulated with an on-frequency band (OFB) noise masker are added at remote frequencies (CMR1), or when co-modulated envelopes are used instead of anti-modulated envelopes (OFB and FB envelopes out of phase, CMR2). For FBs widely separated from the OFB, this process is assumed to rely mostly on across-channel comparison of temporal envelopes. Since cochlear implants (CIs) rely predominantly on the transmission of envelope cues, we investigated if CMR can be observed in electric hearing. We stimulated the auditory nerve of eight CI users with trains of modulated electric pulses presented on an OFB electrode alone, or together with pulse trains on one or two FB electrodes. Participants had to detect signal-induced changes in the envelope of an electric pulse train masker presented on the OFB electrode. Envelopes on FB electrodes were either co-modulated or anti-modulated with the envelope of the OFB masker. We observed CMR1 in one of the eight CI users. However, significant CMR2 was observed in most CI users. Reducing amplitude-modulation rate from 20 to 8 Hz, reducing envelopes' randomness or increasing electrode separation did not generally improve CMR1, but increased the prevalence of CMR2. The present results suggest that comodulation of envelopes can aid signal detection in electric hearing.
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Landsberger D, Galvin JJ. Discrimination between sequential and simultaneous virtual channels with electrical hearing. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2011; 130:1559-1566. [PMID: 21895094 PMCID: PMC3188970 DOI: 10.1121/1.3613938] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 06/28/2011] [Accepted: 06/28/2011] [Indexed: 05/31/2023]
Abstract
In cochlear implants (CIs), simultaneous or sequential stimulation of adjacent electrodes can produce intermediate pitch percepts between those of the component electrodes. However, it is unclear whether simultaneous and sequential virtual channels (VCs) can be discriminated. In this study, CI users were asked to discriminate simultaneous and sequential VCs; discrimination was measured for monopolar (MP) and bipolar + 1 stimulation (BP + 1), i.e., relatively broad and focused stimulation modes. For sequential VCs, the interpulse interval (IPI) varied between 0.0 and 1.8 ms. All stimuli were presented at comfortably loud, loudness-balanced levels at a 250 pulse per second per electrode (ppse) stimulation rate. On average, CI subjects were able to reliably discriminate between sequential and simultaneous VCs. While there was no significant effect of IPI or stimulation mode on VC discrimination, some subjects exhibited better VC discrimination with BP + 1 stimulation. Subjects' discrimination between sequential and simultaneous VCs was correlated with electrode discrimination, suggesting that spatial selectivity may influence perception of sequential VCs. To maintain equal loudness, sequential VC amplitudes were nearly double those of simultaneous VCs, presumably resulting in a broader spread of excitation. These results suggest that perceptual differences between simultaneous and sequential VCs might be explained by differences in the spread of excitation.
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Affiliation(s)
- David Landsberger
- Division of Communication and Auditory Neuroscience, House Ear Institute, 2100 West 3rd Street, Los Angeles, California 90057, USA.
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Macherey O, Carlyon RP. Temporal pitch percepts elicited by dual-channel stimulation of a cochlear implant. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2010; 127:339-49. [PMID: 20058981 PMCID: PMC3000475 DOI: 10.1121/1.3269042] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
McKay and McDermott [J. Acoust. Soc. Am. 100, 1081-1092 (1996)] found that when two different amplitude-modulated pulse trains are presented to two channels separated by <1.5 mm, some cochlear implant (CI) listeners perceive the aggregate temporal pattern. The present study attempted to extend this general finding and to test whether dual-electrode stimulation would increase the upper limit of temporal pitch perception in CIs. Six subjects were asked to rank 12 dual-channel stimuli differing in their rate [ranging from 92 to 516 pps (pulses per second) on each individual channel] and in their inter-channel delay (pulses on the two channels being either nearly simultaneous or delayed by half the period). The data showed that, for an electrode separation of 0.75 or 1.1 mm, (a) the perceived pitch was on average slightly higher for the long-delay than for the short-delay stimuli but never matched the pitch corresponding to the aggregate temporal pattern, (b) the upper limit of temporal pitch did not increase using long-delay stimuli, and (c) the pitch differences between short- and long-delay stimuli were largely insensitive to channel order and to electrode configuration. These results suggest that there may be more independence between CI channels than previously thought.
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Affiliation(s)
- Olivier Macherey
- MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 7EF, United Kingdom.
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Drennan WR, Longnion JK, Ruffin C, Rubinstein JT. Discrimination of Schroeder-phase harmonic complexes by normal-hearing and cochlear-implant listeners. J Assoc Res Otolaryngol 2008; 9:138-49. [PMID: 18066624 PMCID: PMC2536810 DOI: 10.1007/s10162-007-0107-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Accepted: 11/13/2007] [Indexed: 10/22/2022] Open
Abstract
The temporal fine structure (TFS) of sound contributes significantly to the perception of music and speech in noise. The evaluation of new strategies to improve TFS delivery in cochlear implants (CIs) relies upon the assessment of fine structure encoding. Most modern CI sound processing schemes do not encode within-channel TFS per se, but some TFS information is delivered through temporal envelope cues across multiple channels. Positive and negative Schroeder-phase harmonic complexes differ primarily in acoustic TFS and provide a potential test of TFS discrimination ability in CI users for current and future processing strategies. The ability to discriminate Schroeder-phase stimuli was evaluated in 24 CI users and 7 normal-hearing listeners at four fundamental frequencies: 50, 100, 200, and 400 Hz. The dependent variables were percent correct at each fundamental frequency, average score across all fundamental frequencies, and a maximum-likelihood-predicted threshold fundamental frequency for 75% correct. CI listeners scored better than chance for all fundamental frequencies tested. The 50-Hz, average, and predicted threshold scores correlated significantly with consonant-nucleus-consonant word scores. The 200-Hz score correlated with a measure of speech perception in speech-shaped noise. Pitch-direction sensitivity is predicted jointly by the 400-Hz Schroeder score and a spectral ripple discrimination task. The results demonstrate that the Schroeder test is a potentially useful measure of clinically relevant temporal processing abilities in CI users.
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Affiliation(s)
- Ward R Drennan
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Washington, Box 357923, Seattle, WA 98195, USA.
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Affiliation(s)
- Colette M McKay
- School of Life and Health Sciences, Aston University, Birmingham B4 7ET, United Kingdom
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Eisen MD, Franck KH. Electrode interaction in pediatric cochlear implant subjects. J Assoc Res Otolaryngol 2005; 6:160-70. [PMID: 15952052 PMCID: PMC2538331 DOI: 10.1007/s10162-005-5057-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Accepted: 02/16/2005] [Indexed: 10/25/2022] Open
Abstract
Multielectrode cochlear implants rely on differential stimulation of the cochlear nerve for presenting the brain with the spectral and timing information required to understand speech. In implant patients, the degree of overlap among cochlear nerve fibers stimulated by the different electrodes constitutes the electrode interaction. Electrode interaction degrades the spectral resolution of the implant's stimulus. We sought to define electrode interaction in a cohort of pediatric cochlear implant subjects as a function of both stimulus intensity and electrode location along the array. The 27 pediatric subjects that completed the study were implanted with either the Clarion Hi-Focus array with or without positioner, the Nucleus 24 Contour array, or the Nucleus 24 Straight array. All but two of the patients had congenital hearing loss, and none of the patients had meningitis prior to the onset of deafness. The cochlear nerve response was measured with the electrically evoked compound action potential (ECAP). A forward masking protocol was used such that a probe stimulus electrode remained fixed while a preceding masker was moved across the array. Electrode interaction was estimated by measuring the unmasked probe response minus the masked probe response. Three probe locations and three probe intensities were examined for each subject. At all probe locations, electrode interaction increased as probe intensity increased (p < 0.05). Interaction at the basal probe was less than that at either the middle or apical probe locations (p < 0.05), and significant correlation found between probe distance from the basal end of the array and electrode interaction (p < 0.001). These results demonstrate that in this cohort of pediatric subjects, electrode interaction depended on both stimulus intensity and probe location. Implications of these findings on future implant array design and current implant fitting strategies are discussed. The impact of electrode interaction on implant performance is yet to be elucidated.
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Affiliation(s)
- Marc D Eisen
- Center for Childhood Communication, Children's Hospital of Philadelphia, Philadelphia, PA, USA.
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Laneau J, Boets B, Moonen M, van Wieringen A, Wouters J. A flexible auditory research platform using acoustic or electric stimuli for adults and young children. J Neurosci Methods 2005; 142:131-6. [PMID: 15652626 DOI: 10.1016/j.jneumeth.2004.08.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Revised: 08/11/2004] [Accepted: 08/13/2004] [Indexed: 11/25/2022]
Abstract
A user-friendly and versatile research platform for use in auditory experiments, referred to as APEX (Application for PsychoElectrical eXperiments), is described. The platform takes care of automatic stimulus presentation and collection of the subject's responses. Acoustical auditory, as well as electrical auditory experiments with CI recipients can be conducted. The platform currently supports LAURA, Nucleus CI22 and Nucleus CI24 cochlear implants. The graphical user interface for the subjects has been extended to allow for testing very young children, by embedding the psychophysical procedures in a computer game. The research platform is available free of charge.
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Affiliation(s)
- Johan Laneau
- Lab. Exp. ORL, Katholieke Universiteit Leuven, Kapucijnenvoer 33, B-3000 Leuven, Belgium.
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Geurts L, Wouters J. A concept for a research tool for experiments with cochlear implant users. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2000; 108:2949-2956. [PMID: 11144586 DOI: 10.1121/1.1321011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
APEX, an acronym for computer Application for Psycho-Electrical eXperiments, is a user friendly tool used to conduct psychophysical experiments and to investigate new speech coding algorithms with cochlear implant users. Most common psychophysical experiments can be easily programmed and all stimuli can be easily created without any knowledge of computer programing. The pulsatile stimuli are composed off-line using custom-made MATLAB (Registered trademark of The Mathworks, Inc., http://www.mathworks.com) functions and are stored on hard disk or CD ROM. These functions convert either a speech signal into a pulse sequence or generate any sequence of pulses based on the parameters specified by the experimenter. The APEX personal computer (PC) software reads a text file which specifies the experiment and the stimuli, controls the experiment, delivers the stimuli to the subject through a digital signal processor (DSP) board, collects the responses via a computer mouse or a graphics tablet, and writes the results to the same file. At present, the APEX system is implemented for the LAURA (Registered trademark of Philips Hearing Implants) cochlear implant. However, the concept-and many parts of the system-is portable to any other device. Also, psycho-acoustical experiments can be conducted by presenting the stimuli acoustically through a sound card.
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Affiliation(s)
- L Geurts
- Laboratoire Experimental ORL, KULeuven, Belgium.
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