Perception In Cochlear Implant Users Research Articles

Music Perception in Older Adult Cochlear Implant Users: Evidence About Age-related Decline in Rapid Temporal Processing

Age-related cognitive decline (ARCD) refers to deterioration of basic cognitive functions in normal human aging that mainly associates with areas of sensory processing, attention, memory, and executive control. Because listening to music involves a highly complex integration in various levels of cognitive processing that extend from basic auditrory fuctions to high-level feature extraction and emotional/aesthetic response, music listening tests have been frequently used in clinical reserch settings in the past two decades as a tool for screening areas of deficits in various kinds of pathological populations (e.g., hearing impaired, neurological patients, children with learning disabilities). There are two main reasons why assessing music listening abilities of older adult Cochlear Implant (CI) users is important for aging researchers. First, it shows how the combined influence of ARCD, and the reduced and/or distorted sensory information provided by a hearing implant may globally or selectively deteriorate an implantee's sensitivity to basic elements of music such as rhythm, melody, harmonic structure, and consonance/dissonance. Second, it provides evidence about cognitive domains or processes that display the greatest decline with age.In this study the effects of CI users’ chronological age on their performance on music listening tests were explored through the use of the MuSIC perception test battery, with special emphasis on the influence of aging in perceiving musical stimuli that require rapid temporal processing (e.g., rhythm patterns). Analysis is based on data from a recently completed European multicenter study on music perception in CI users wearing a MED-EL's PULSARCI100 or a SONATATI100 with an OPUS 2 audio processor (N = 81, age range: 21,2-82,3 years), and Normally Hearing (NH) adults (N = 46, age range: 21,1-58,8 years). Areas of music listening abilities that display noticeable declines in older implant users are highlighted by statistically comparing distributions of test scores among a subgroup of CI users over 60 years (N = 24), the subgroup of users younger than 60, and the group of NH controls. Resultsshowed that older adult CI users appear not to differ significantly from younger ones in processing low-level features of music such as pitch and timbre, although their accuracy is differentially affected in favor of the younger ones when listening tasks are complex and require rapid temporal processing of the stimuli, or attention switching between two or more sources of information (e.g., identification of individual musical instruments playing in ensemble). Aging also appears to negatively affect processing of rhythm patterns in music, a deficit likely attributable to general slowing of information processing in older adults, while, in contrast, processing of melodies and chord structures remains relatively intact.

Relationships Among Peripheral and Central Electrophysiological Measures of Spatial and Spectral Selectivity and Speech Perception in Cochlear Implant Users.

The ability to perceive speech is related to the listener's ability to differentiate among frequencies (i.e., spectral resolution). Cochlear implant (CI) users exhibit variable speech-perception and spectral-resolution abilities, which can be attributed in part to the extent of electrode interactions at the periphery (i.e., spatial selectivity). However, electrophysiological measures of peripheral spatial selectivity have not been found to correlate with speech perception. The purpose of this study was to evaluate auditory processing at the periphery and cortex using both simple and spectrally complex stimuli to better understand the stages of neural processing underlying speech perception. The hypotheses were that (1) by more completely characterizing peripheral excitation patterns than in previous studies, significant correlations with measures of spectral selectivity and speech perception would be observed, (2) adding information about processing at a level central to the auditory nerve would account for additional variability in speech perception, and (3) responses elicited with spectrally complex stimuli would be more strongly correlated with speech perception than responses elicited with spectrally simple stimuli. Eleven adult CI users participated. Three experimental processor programs (MAPs) were created to vary the likelihood of electrode interactions within each participant. For each MAP, a subset of 7 of 22 intracochlear electrodes was activated: adjacent (MAP 1), every other (MAP 2), or every third (MAP 3). Peripheral spatial selectivity was assessed using the electrically evoked compound action potential (ECAP) to obtain channel-interaction functions for all activated electrodes (13 functions total). Central processing was assessed by eliciting the auditory change complex with both spatial (electrode pairs) and spectral (rippled noise) stimulus changes. Speech-perception measures included vowel discrimination and the Bamford-Kowal-Bench Speech-in-Noise test. Spatial and spectral selectivity and speech perception were expected to be poorest with MAP 1 (closest electrode spacing) and best with MAP 3 (widest electrode spacing). Relationships among the electrophysiological and speech-perception measures were evaluated using mixed-model and simple linear regression analyses. All electrophysiological measures were significantly correlated with each other and with speech scores for the mixed-model analysis, which takes into account multiple measures per person (i.e., experimental MAPs). The ECAP measures were the best predictor. In the simple linear regression analysis on MAP 3 data, only the cortical measures were significantly correlated with speech scores; spectral auditory change complex amplitude was the strongest predictor. The results suggest that both peripheral and central electrophysiological measures of spatial and spectral selectivity provide valuable information about speech perception. Clinically, it is often desirable to optimize performance for individual CI users. These results suggest that ECAP measures may be most useful for within-subject applications when multiple measures are performed to make decisions about processor options. They also suggest that if the goal is to compare performance across individuals based on a single measure, then processing central to the auditory nerve (specifically, cortical measures of discriminability) should be considered.

Role of slow temporal modulations in speech identification for cochlear implant users

Objective: This study aimed to assess whether the capacity of cochlear implant (CI) users to identify speech is determined by their capacity to perceive slow (< 20 Hz) temporal modulations. Design: This was achieved by studying the correlation between (1) phoneme identification in quiet and in a steady-state or fluctuating (8 Hz) noises, and (2) amplitude-modulation detection thresholds (MDTs) at 8 Hz (i.e. slow temporal modulations). Study sample: Twenty-one CI users, unilaterally implanted with the same device, were tested in free field with their everyday clinical processor. Results: Extensive variability across subjects was observed for both phoneme identification and MDTs. Vowel and consonant identification scores in quiet were significantly correlated with MDTs at 8 Hz (r = − 0.47 for consonants, r = − 0.44 for vowels; p < 0.05). When the masker was a steady-state noise, only consonant identification scores tended to correlate with MDTs at 8 Hz (r = − 0.4; p = 0.07). When the masker was a fluctuating noise, consonant and vowel identification scores were not significantly correlated with MDTs at 8 Hz. Conclusions: Sensitivity to slow amplitude modulations is correlated with vowel and consonant perception in CI users. However, reduced sensitivity to slow modulations does not entirely explain the limited capacity of CI recipients to understand speech in noise.

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Temporal Feature Perception in Cochlear Implant Users

For the perception of timbre of a musical instrument, the attack time is known to hold crucial information. The first 50 to 150 ms of sound onset reflect the excitation mechanism, which generates the sound. Since auditory processing and music perception in particular are known to be hampered in cochlear implant (CI) users, we conducted an electroencephalography (EEG) study with an oddball paradigm to evaluate the processing of small differences in musical sound onset. The first 60 ms of a cornet sound were manipulated in order to examine whether these differences are detected by CI users and normal-hearing controls (NH controls), as revealed by auditory evoked potentials (AEPs). Our analysis focused on the N1 as an exogenous component known to reflect physical stimuli properties as well as on the P2 and the Mismatch Negativity (MMN). Our results revealed different N1 latencies as well as P2 amplitudes and latencies for the onset manipulations in both groups. An MMN could be elicited only in the NH control group. Together with additional findings that suggest an impact of musical training on CI users’ AEPs, our findings support the view that impaired timbre perception in CI users is at partly due to altered sound onset feature detection.

Assessment of Sound Quality Perception in Cochlear Implant Users During Music Listening

Although cochlear implant (CI) users frequently report deterioration of sound quality when listening to music, few methods exist to quantify these subjective claims. 1) To design a novel research method for quantifying sound quality perception in CI users during music listening; 2) To validate this method by assessing one attribute of music perception, bass frequency perception, which is hypothesized to be relevant to overall musical sound quality perception. Limitations in bass frequency perception contribute to CI-mediated sound quality deteriorations. The proposed method will quantify this deterioration by measuring CI users' impaired ability to make sound quality discriminations among musical stimuli with variable amounts of bass frequency removal. A method commonly used in the audio industry (multiple stimulus with hidden reference and anchor [MUSHRA]) was adapted for CI users, referred to as CI-MUSHRA. CI users and normal hearing controls were presented with 7 sound quality versions of a musical segment: 5 high pass filter cutoff versions (200-, 400-, 600-, 800-, 1000-Hz) with decreasing amounts of bass information, an unaltered version ("hidden reference"), and a highly altered version (1,000-1,200 Hz band pass filter; "anchor"). Participants provided sound quality ratings between 0 (very poor) and 100 (excellent) for each version; ratings reflected differences in perceived sound quality among stimuli. CI users had greater difficulty making overall sound quality discriminations as a function of bass frequency loss than normal hearing controls, as demonstrated by a significantly weaker correlation between bass frequency content and sound quality ratings. In particular, CI users could not perceive sound quality difference among stimuli missing up to 400 Hz of bass frequency information. Bass frequency impairments contribute to sound quality deteriorations during music listening for CI users. CI-MUSHRA provided a systematic and quantitative assessment of this reduced sound quality. Although the effects of bass frequency removal were studied here, we advocate CI-MUSHRA as a user-friendly and versatile research tool to measure the effects of a wide range of acoustic manipulations on sound quality perception in CI users.

Temporal envelope perception in Cochlear Implant users

Background: In timbre and especially instrument perception the attack time is known to hold crucial information to detect differences between instruments. The excitation mechanism by which an instrument is made to sound, is reflected by the first 50 to 150 ms of sound onset. As auditory processing and especially music perception in Cochlear Implant users is known to be hampered we conducted an EEG study with an oddball paradigm to evaluate processing of small differences in musical sound onset manipulations. Auditory evoked potential as elicited in an EEG study yield objective information about processing of auditory stimuli and thus allow to draw conclusions about general hearing abilities of the respective participants. Method: We therefore manipulated a cornet sound in the first 60 ms to examine whether these differences will be detectable for CI users (n=12) and a normal hearing control group (n=12). Our analysis focused on the N1 as an exogenous component known to reflect physical stimuli properties and the Mismatch Negativity (MMN), a component known to reflect detection of any discriminable changes in an ongoing auditory stimulation. Results: We found N1 latencies to differ significantly depending on the onset manipulations in both groups, MMN could be elicited in the normal hearing control group alone and not for the CI users. Conclusions: Our findings suggest that lower order processing as seen in the N1 latencies reflected the manipulation of the attack time in both groups. Higher order processing, such as the MMN, is hampered in the CI user group but robust in the normal hearing control group. These findings might give additional explanation to the general musical impairment of CI users.

Faciliation of Mandarin tone perception by visual speech in clear and degraded audio: Implications for cochlear implants

Cochlear implant (CI) users in tone language environments report great difficulty in perceiving lexical tone. This study investigated the augmentation of simulated cochlear implant audio by visual (facial) speech information for tone. Native speakers of Mandarin and Australian English were asked to discriminate between minimal pairs of Mandarin tones in five conditions: Auditory-Only, Auditory-Visual, CI-simulated Auditory-Only, CI-simulated Auditory-Visual, and Visual-Only (silent video). Discrimination in CI-simulated audio conditions was poor compared with normal audio, and varied according to tone pair, with tone pairs with strong non-F0 cues discriminated the most easily. The availability of visual speech information also improved discrimination in the CI-simulated audio conditions, particularly on tone pairs with strong durational cues. In the silent Visual-Only condition, both Mandarin and Australian English speakers discriminated tones above chance levels. Interestingly, tone-naïve listeners outperformed native listeners in the Visual-Only condition, suggesting firstly that visual speech information for tone is available, and may in fact be under-used by normal-hearing tone language perceivers, and secondly that the perception of such information may be language-general, rather than the product of language-specific learning. This may find application in the development of methods to improve tone perception in CI users in tone language environments.

The MuSIC perception test: A novel battery for testing music perception of cochlear implant users

This study was undertaken to evaluate the musical sounds in cochlear implants (MuSIC) perception test, created to assess the music-listening abilities of cochlear implant (CI) users. Thirty-one unilateral MED-EL COMBI 40+/PULSARCI100 users and a control group of 67 adults with normal hearing (NH) participated. The MuSIC test comprises six objective and two subjective modules employing approximately 2800 musical files recorded from non-synthesized instruments. A subset was used for comparing CI and NH participants’ results. CI and NH participants performed significantly differently on: pitch discrimination, melody discrimination, chord discrimination, instrument detection, and instrument identification. No significant difference in performance was seen on the subtests of rhythm discrimination or dissonance rating and emotion rating. The MuSIC test was found to be a valuable tool for assessing music perception in CI users and NH participants, whether investigating one aspect of music perception in depth or conducting a broad survey of music perception.

Psychoacoustic Abilities Associated With Music Perception in Cochlear Implant Users

This study was designed to determine what acoustic elements are associated with musical perception ability in cochlear implant (CI) users and to understand how acoustic elements, which are important to good speech perception, contribute to music perception in CI users. It was hypothesized that the variability in the performance of music and speech perception may be related to differences in the sensitivity to specific acoustic features such as spectral changes or temporal modulations, or both. A battery of hearing tasks was administered to 42 CI listeners. The Clinical Assessment of Music Perception was used, which evaluates complex-tone pitch-direction discrimination, melody recognition, and timbre recognition. To investigate spectral and temporal processing, spectral-ripple discrimination and Schroeder-phase discrimination abilities were evaluated. Speech perception ability in quiet and noise was also evaluated. Relationships between Clinical Assessment of Music Perception subtest scores, spectral-ripple discrimination thresholds, Schroeder-phase discrimination scores, and speech recognition scores were assessed. Spectral-ripple discrimination was shown to correlate with all three aspects of music perception studied. Schroeder-phase discrimination was generally not predictive of music perception outcomes. Music perception ability was significantly correlated with speech perception ability. Nearly half of the variance in melody and timbre recognition was predicted jointly by spectral-ripple and pitch-direction discrimination thresholds. Similar results were observed on speech recognition as well. This study suggests that spectral-ripple discrimination is significantly associated with music perception in CI users. A previous report showed that spectral-ripple discrimination is significantly correlated with speech recognition in quiet and in noise. This study also showed that speech recognition and music perception are also related to one another. Spectral-ripple discrimination ability seems to reflect a wide range of hearing abilities in CI users. The results suggest that materially improving spectral resolution could provide significant benefits in music and speech perception outcomes in CI users.

Extending the Limits of Place and Temporal Pitch Perception in Cochlear Implant Users

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.

Neurophysiological evidence of impaired musical sound perception in cochlear-implant users

Objective Music perception with a cochlear implant (CI) can be unsatisfactory because current-day implants are primarily designed to enable speech discrimination. The present study aimed at evaluating electrophysiological correlates of musical sound perception in CI users to help achieve the long-term goal of improved restoration of hearing in those individuals. Methods Auditory discrimination accuracy in adult CI users ( n = 12) and matched normal-hearing controls ( n = 12) was measured by behavioral discrimination tasks and mismatch negativity (MMN) recordings. Discrimination profiles were obtained by using a set of clarinet sounds (original/vocoded) varying along different acoustic dimensions (frequency/intensity/duration) and deviation magnitudes (four levels). Results Behavioral results and MMN recordings revealed reduced auditory discrimination accuracy in CI users. An inverse relationship was found between MMN amplitudes and duration of profound deafness. Conclusions CI users have difficulties in discriminating small changes in the acoustic properties of musical sounds. The recently developed multi-feature MMN paradigm ( Pakarinen et al., 2007) can be used to objectively evaluate discrimination abilities of CI users for musical sounds. Significance Measuring auditory discrimination functions by means of a multi-feature MMN paradigm could be of substantial clinical value by providing a comprehensive profile of the extent of restored hearing in CI users.

Modulation rate discrimination using half-wave rectified and sinusoidally amplitude modulated stimuli in cochlear-implant users

Detection and modulation rate discrimination were measured in cochlear-implant users for pulse-trains that were either sinusoidally amplitude modulated or were modulated with half-wave rectified sinusoids, which in acoustic hearing have been used to simulate the response to low-frequency temporal fine structure. In contrast to comparable results from acoustic hearing, modulation rate discrimination was not statistically different for the two stimulus types. The results suggest that, in contrast to binaural perception, pitch perception in cochlear-implant users does not benefit from using stimuli designed to more closely simulate the cochlear response to low-frequency pure tones.

Perceptual fusion of polyphonic pitch in cochlear implant users

In music, multiple pitches often occur simultaneously, an essential feature of harmony. In the present study, the authors assessed the ability of cochlear implant (CI) users to perceive polyphonic pitch. Acoustically presented stimuli consisted of one, two, or three superposed tones with different fundamental frequencies (f(0)). The normal hearing control group obtained significantly higher mean scores than the CI group. CI users performed near chance levels in recognizing two- and three-pitch stimuli, and demonstrated perceptual fusion of multiple pitches as single-pitch units. These results suggest that limitations in polyphonic pitch perception may significantly impair music perception in CI users.

Auditory Cortical Activity During Cochlear Implant-Mediated Perception of Spoken Language, Melody, and Rhythm

Despite the significant advances in language perception for cochlear implant (CI) recipients, music perception continues to be a major challenge for implant-mediated listening. Our understanding of the neural mechanisms that underlie successful implant listening remains limited. To our knowledge, this study represents the first neuroimaging investigation of music perception in CI users, with the hypothesis that CI subjects would demonstrate greater auditory cortical activation than normal hearing controls. H(2) (15)O positron emission tomography (PET) was used here to assess auditory cortical activation patterns in ten postlingually deafened CI patients and ten normal hearing control subjects. Subjects were presented with language, melody, and rhythm tasks during scanning. Our results show significant auditory cortical activation in implant subjects in comparison to control subjects for language, melody, and rhythm. The greatest activity in CI users compared to controls was seen for language tasks, which is thought to reflect both implant and neural specializations for language processing. For musical stimuli, PET scanning revealed significantly greater activation during rhythm perception in CI subjects (compared to control subjects), and the least activation during melody perception, which was the most difficult task for CI users. These results may suggest a possible relationship between auditory performance and degree of auditory cortical activation in implant recipients that deserves further study.

Auditory-visual speech perception in normal-hearing and cochlear-implant listeners

The present study evaluated auditory-visual speech perception in cochlear-implant users as well as normal-hearing and simulated-implant controls to delineate relative contributions of sensory experience and cues. Auditory-only, visual-only, or auditory-visual speech perception was examined in the context of categorical perception, in which an animated face mouthing ba, da, or ga was paired with synthesized phonemes from an 11-token auditory continuum. A three-alternative, forced-choice method was used to yield percent identification scores. Normal-hearing listeners showed sharp phoneme boundaries and strong reliance on the auditory cue, whereas actual and simulated implant listeners showed much weaker categorical perception but stronger dependence on the visual cue. The implant users were able to integrate both congruent and incongruent acoustic and optical cues to derive relatively weak but significant auditory-visual integration. This auditory-visual integration was correlated with the duration of the implant experience but not the duration of deafness. Compared with the actual implant performance, acoustic simulations of the cochlear implant could predict the auditory-only performance but not the auditory-visual integration. These results suggest that both altered sensory experience and improvised acoustic cues contribute to the auditory-visual speech perception in cochlear-implant users.

Influence of Evoked Compound Action Potential on Speech Perception in Cochlear Implant Users

SummaryElectrically Evoked Compound Action Potential is a measure of synchronous cochlear nerve fibers activity elicited by electrical stimulation of the cochlear implant. The electrophysiological nerve responses may contribute to explain the variability in individual performance of cochlear implant recipients.AimTo compare speech perception tests’ performances of cochlear implant users according to the presence or absence of intraoperative neural telemetry responses.Material and MethodProspective study design with 100 “Nucleus 24” cochlear implant users divided in two groups according to the presence or absence of intraoperative neural telemetry responses. Speech perception tests were performed after 6 months of continuous use of the device and compared among groups.ResultsIntraoperative action potentials were observed in 72 % of individuals. Open-set sentence test results were better in implant users who had neural telemetry responses when compared to implant users in whom this potential was absent (averages 82.8 % versus 41 %, p = 0.005). There was a strong association between post meningitis-related deafness and absence of intraoperative potentials.ConclusionThe absence of intraoperative neural telemetry responses was associated with worse performances in speech perception tests and meningitis as etiology of deafness. On the other hand, the presence of these potentials suggests excellent prognosis.

Pitch discrimination of patterned electric stimulation

One reason for the poor pitch performance in current cochlear-implant users may be the highly synchronized neural firing in electric hearing that lacks stochastic properties of neural firing in normal acoustic hearing. This study used three different electric stimulation patterns, jittered, probabilistic, and auditory-model-generated pulses, to mimic some aspects of the normal neural firing pattern in acoustic hearing. Pitch discrimination was measured at standard frequencies of 100, 250, 500, and 1000 Hz on three Nucleus-24 cochlear-implant users. To test the utility of the autocorrelation pitch perception model in electric hearing, one, two, and four electrodes were stimulated independently with the same patterned electric stimulation. Results showed no improvement in performance with any experimental pattern compared to the fixed-rate control. Pitch discrimination was actually worsened with the jittered pattern at low frequencies (125 and 250 Hz) than that of the control, suggesting that externally introduced stochastic properties do not improve pitch perception in electric stimulation. The multiple-electrode stimulation did not improve performance but did not degrade performance either. The present results suggest that both "the right time and the right place" may be needed to restore normal pitch perception in cochlear-implant users.