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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.

To investigate the music perception skills of adult cochlear implant (CI) users in comparison with hearing aid (HA) users who have similar levels of hearing impairment. It was hypothesized that the HA users would perform better than the CI recipients on tests involving pitch, instrument, and melody perception, but similarly for rhythm perception. Fifteen users of the Nucleus CI system and 15 HA users participated in a series of music perception tests. All subjects were postlingually deafened adults, with the HA subjects being required to meet the current audiological criteria for CI candidacy. A music test battery was designed for the study incorporating four major tasks: (1) discrimination of 38 pairs of rhythms; (2) pitch ranking of one-octave, half-octave, and quarter-octave intervals; (3) instrument recognition incorporating three subtests, each with 12 different instruments or ensembles; and (4) recognition of 10 familiar melodies. Stimuli were presented via direct audio input at comfortable presentation levels. The test battery was administered to each subject on two separate occasions, approximately 4 mo apart. The results from the rhythm test were 93% correct for the CI group and 94% correct for the HA group; these scores were not significantly different. For the pitch test, there was a significant difference between the HA group and the CI group (p < 0.001), with higher mean scores recorded by the HA group for all three interval sizes. The CI subject group was unable to rank pitches a quarter-octave apart, only scoring at chance level for this interval size. In the instrument recognition test, although there was no significant difference between the mean scores of the two groups, both groups obtained significantly higher scores for the subtest incorporating single instrument stimuli than those incorporating multiple instrumentations (p < 0.001). In the melody test, there was a significant difference between the implantees' mean score of 52% correct and the HA group's mean of 91% (p < 0.001). As hypothesized, results from the two groups were almost identical for the rhythm test, with the HA group performing significantly better than the CI group on the pitch and melody tests. However, there was no difference between the groups in their ability to identify musical instruments or ensembles. The results of this study indicate that HA users with similar levels of hearing loss perform at least equal to, if not better than, CI users on these music perception tests. However, despite the differences between scores obtained by the CI and HA subject groups, both these subject groups were largely unable to achieve accurate or effective music perception, regardless of the device they used.

To determine whether chronic use of experimental computed tomography (CT)-based frequency allocations would improve cochlear implant (CI) user performance in the areas of speech and music perception, as compared to the clinical default frequency mapping provided by the CI manufacturer. CIs utilize default frequency maps to distribute the frequency range important for speech perception across their electrode array. Clinical default frequency maps do not address the significant frequency-place mismatch that is inherent after cochlear implantation, nor the variability between individual anatomy or array lengths. Recent research has utilized postoperative high-resolution flat-panel CT imaging to measure the precise location of electrode contacts within an individual's cochlea, in order to generate a custom frequency map and decrease the frequency-place mismatch. A cohort of 10 experienced CI users (14 CI ears) was recruited to receive CT scans and then use an experimental CT-based frequency map for 1 month. The efficacy of these maps was measured using a battery of speech and music tests. No change in speech or music performance between the Experimental and Clinical Maps was found at the group level, although there was large variability within the cohort. Greater benefit from the Experimental Map on speech in quiet tasks was correlated with better electrode array alignment in the apical (low frequency) region (rho 14 = -0.55 to -0.72, p < 0.05). This application of strict CT-based mapping was most beneficial for CI users with the least amount of apical-mid array frequency-place mismatch, and least beneficial for CI users with overly deep or shallow insertions. Results may be limited by long acclimation periods to clinical default frequency maps prior to CT map usage, intervention bias, and small sample size.

Figure: © iStock/chaossCochlear implants (CIs) have allowed users to understand speech and interact with the auditory world. However, CI recipients still have difficulty perceiving nonspeech sounds, especially music. Music appreciation is important to evaluate in CI users because of its association with quality of life, personal expression, and social connectedness.Figure: Alice HeCochlear implant recipients have difficulty recognizing musical melodies, identifying instrument sounds, and differentiating pitch. However, perceptual accuracy is not the only important aspect in music listening. The way music sounds as a whole through the cochlear implant has clinical relevance, as it relates to the user's ability to appreciate and enjoy music in everyday life.Figure: Charles J. Limb, MDWhile one might anticipate a direct link between cochlear implant recipients’ ability to perceive music accurately and their degree of music appreciation, the early literature has not supported this idea. In fact, some studies suggest exactly the opposite—that there is little to no relationship between music perception and appraisal in CI users ( J Am Acad Audiol 2012;23[5]:350-365http://aaa.publisher.ingentaconnect.com/content/aaa/jaaa/2012/00000023/00000005/art00006). However, these previous results were obtained from small cohorts of cochlear implant recipients in controlled laboratory settings, with tests that require significant time to administer, limiting their applicability in clinical settings. In a new study, Ward R. Drennan, PhD, and colleagues evaluated the correlation between music perception and appraisal among a large cohort of CI users in clinical settings. The authors used shorter music tests to determine if these assessments could be administered in the clinic and whether findings would be consistent with previous results from smaller sample sizes. Clinical Evaluation of Music Perception, Appraisal, and Experience in Cochlear Implant Users Drennan WR, Oleson JJ, Gfeller K, et al Int J Audiol Sept. 1, 2014; e-pub ahead of printhttp://informahealthcare.com/doi/abs/10.3109/14992027.2014.948219 The Clinical Assessment of Music Perception (CAMP) test is commonly used in some laboratories to study CI users’ music perception ( Otol Neurotol 2008;29[2]:149-155http://journals.lww.com/otology-neurotology/Abstract/2008/02000/Clinical_Assessment_of_Music_Perception_in.10.aspx; Ear Hear 2009;30[4]:411-418http://journals.lww.com/ear-hearing/Abstract/2009/08000/Development_and_Validation_of_the_University_of.4.aspx). The CAMP includes three separate perception tests, each designed to evaluate a different element of music perception ability: pitch direction discrimination, familiar melody recognition, and timbre recognition. Since these three elements are relevant to music listening and enjoyment, Dr. Drennan et al used the CAMP test to study music perception. To assess music appraisal, the researchers used the Iowa Musical Background Questionnaire (IMBQ). In the IMBQ, CI recipients described the quality of music heard through their cochlear implant by rating six bipolar adjectives on a scale of zero to 10: clear versus fuzzy, easy to follow versus difficult to follow, like versus dislike, sounds unlike music versus sounds like music, unnatural versus natural, and unpleasant versus pleasant. Prior research identified these comparisons as relevant to music listening. The CAMP test and IMBQ were administered to 145 CI listeners across 14 clinical sites in the United States and Canada. It took 30 minutes to 35 minutes to administer the CAMP test, and another 15 minutes to 25 minutes to complete the IMBQ. These time frames are reasonable for administration in the clinic—a major advantage in terms of practical feasibility, the authors noted. WEAK RELATIONSHIP REPORTED In their group of cochlear implant users from several clinical settings, Dr. Drennan and colleagues found weak relationships between CAMP results and IMBQ musical sound quality scores. There was a statistically significant but slight correlation between the CAMP's timbre test component and music appraisal, suggesting a relatively weak association between the two. All other relationships were deemed insignificant. This lack of a strong association, which is consistent with the findings of previous studies ( J Am Acad Audiol 2012;23[5]:350-365http://aaa.publisher.ingentaconnect.com/content/aaa/jaaa/2012/00000023/00000005/art00006; J Am Acad Audiol 2008;19[2]:120-134http://aaa.publisher.ingentaconnect.com/content/aaa/jaaa/2008/00000019/00000002/art00003) means that in order to fully evaluate CI music functionality, it is not sufficient to test either music perception or music appraisal alone. Both measures need to be evaluated, as sufficiency or deficiency in one aspect does not correlate with the same result in the other aspect. These results also highlight the limitations of subjective musical sound quality assessment and the possible benefits of objective approaches ( Otol Neurotol 2012;33[3]:319-327http://journals.lww.com/otology-neurotology/Abstract/2012/04000/Assessment_of_Sound_Quality_Perception_in_Cochlear.7.aspx). In an objective approach, the goal is not to evaluate how pleasant or unpleasant music may sound, or whether the CI user enjoys it. Rather, the goal is to measure the capacity of a cochlear implant user to detect a deterioration of sound quality in response to experimental manipulation of any given sound parameter. MANY FACTORS AFFECT ENJOYMENT Dr. Drennan and colleagues noted limitations of their study design. For example, the CAMP was conducted without hearing aids, even if listeners used hearing aids regularly. While the IMBQ questionnaire asked about music appraisal based on real-world musical listening experiences, the CAMP used simple, controlled sound stimuli to assess basic music perception abilities instead of using real-world stimuli. To some extent, these study design decisions might have affected CI users’ music test scores. Despite these potential limitations, the authors make a compelling argument that perceptual acuity is not closely related to music appraisal ratings. In other words, cochlear implant users can have poor perceptual abilities and still feel that music sounds good or is highly enjoyable. Conversely, CI users can perceive various aspects of music well while feeling that music sounds poor or not enjoying what they are able to hear. The study by Dr. Drennan and colleagues underscores the notion that the musical experience is linked to many factors. Furthermore, these findings suggest that studying individual elements of music in isolation may not accurately reflect the perceptual salience of music when it's presented in its natural form—a composite of a wide range of components. In this study, the authors demonstrated that there is little to no relationship between music acuity and music appraisal. Both aspects are important clinical outcomes, as one addresses patient functionality and ability (acuity), while the other addresses patient feeling and overall satisfaction with music quality (appraisal). These findings strongly suggest the need for further research to overcome limitations in cochlear implant users’ ability to perceive music, and to understand the factors that limit enjoyment or satisfaction in music listening.

Four experiments measured the perceptual and neural correlates of the temporal pattern of electrical stimulation applied to one cochlear-implant (CI) electrode, for several subjects. Neural effects were estimated from the electrically evoked compound action potential (ECAP) to each pulse. Experiment 1 attenuated every second pulse of a 200-pps pulse train. Increasing attenuation caused pitch to drop and the ECAP to become amplitude modulated, thereby providing an estimate of the relationship between neural modulation and pitch. Experiment 2 showed that the pitch of a 200-pps pulse train can be reduced by delaying every second pulse, so that the inter-pulse-intervals alternate between longer and shorter intervals. This caused the ECAP to become amplitude modulated, but not by enough to account for the change in pitch. Experiment 3 replicated the finding that rate discrimination deteriorates with increases in baseline rate. This was accompanied by an increase in ECAP modulation, but by an amount that produced only a small effect on pitch in experiment 1. Experiment 4 showed that preceding a pulse train with a carefully selected "pre-pulse" could reduce ECAP modulation, but did not improve rate discrimination. Implications for theories of pitch and for limitations of pitch perception in CI users are discussed.

Objective: This review aims to highlight the key elements of music perception and its mechanisms in normal hearing people and people with hearing impairments. Design: A systematic literature search was conducted using the National Library of Medicine's search service – PubMed (website: http://www.ncbi.nlm.nih.gov/sites/entrez), with the subject headings ‘Music perception’, ‘Hearing impairment’ and ‘Normal hearing people’ or ‘Cochlear implant’ or ‘Hearing aid’. Results: The key evidence available and the mechanisms of poor music perception in hearing impaired people with hearing devices were reviewed, including hearing aid (HA) alone, cochlear implant (CI) alone or bimodal (HA+ CI) stimulation. People with hearing impairment have limited ability to fully utilize fine temporal structure and frequency selectivity, and consequently musical pitch, melody and timbre perception in people with hearing impairment is significantly impaired. Conclusion: The poor ability to accurately perceive music for hearing aids users is mainly due to the damaged cochlea and device distortion, whereas cochlear implant recipients typically have poor music perception because of reduced extraction of temporal and spectral information in music.

A cochlear implant (CI) is a surgically implanted electronic device that partially restores hearing to people suffering from profound hearing loss. Although CI users, in general, obtain a very good reception of continuous speech in the absence of background noise, they face severe limitations in the context of music perception and appreciation. The main reasons for these limitations are related to channel interactions created by the broad spread of electrical fields in the cochlea and to the low number of electrodes that stimulate it. Moreover, CIs have severe limitations when it comes to transmitting the temporal fine structure of acoustic signals, and hence, these devices elicit poor pitch and timber perception. For these reasons, several signal processing algorithms have been proposed to make music more accessible for CI users, trying to reduce the complexity of music signals or remixing them to enhance certain components, such as the lead singing voice. In this work, a deep neural network that performs real-time audio source separation to remix music for CI users is presented. The implementation is based on multi-layer perception (MLP) and has been evaluated using objective instrumental measurements to ensure clean source estimation. Furthermore, experiments in 10 normal hearing (NH) and 13 CI users to investigate how the vocals to instruments ratio (VIR) set by the tested listeners were affected in realistic environments with and without visual information. The objective instrumental results fulfill the benchmark reported in previous studies by introducing distortions that are shown to not be perceived by CI users. Moreover, the implemented model was optimized to perform real-time source separation. The experimental results show that CI users prefer vocals 8 dB enhanced with the respect to the instruments independent of acoustic sound scenarios and visual information. In contrast, NH listeners did not prefer a VIR different than zero dB.

Disorders of music and speech perception, known as amusia and aphasia, have traditionally been regarded as dissociated deficits based on studies of brain damaged patients. This has been taken as evidence that music and speech are perceived by largely separate and independent networks in the brain. However, recent studies of congenital amusia have broadened this view by showing that the deficit is associated with problems in perceiving speech prosody, especially intonation and emotional prosody. In the present study the association between the perception of music and speech prosody was investigated with healthy Finnish adults (n = 61) using an on-line music perception test including the Scale subtest of Montreal Battery of Evaluation of Amusia (MBEA) and Off-Beat and Out-of-key tasks as well as a prosodic verbal task that measures the perception of word stress. Regression analyses showed that there was a clear association between prosody perception and music perception, especially in the domain of rhythm perception. This association was evident after controlling for music education, age, pitch perception, visuospatial perception, and working memory. Pitch perception was significantly associated with music perception but not with prosody perception. The association between music perception and visuospatial perception (measured using analogous tasks) was less clear. Overall, the pattern of results indicates that there is a robust link between music and speech perception and that this link can be mediated by rhythmic cues (time and stress).

Spatial and non-spatial multisensory cueing in unilateral cochlear implant users

Music plays an important role in the daily life of cochlear implant (CI) users, but electrical hearing and speech processing pose challenges for enjoying music. Studies of unilateral CI (UCI) users’ music perception have found that these subjects have little difficulty recognizing tempo and rhythm but great difficulty with pitch, interval and melody. The present study is an initial step towards understanding music perception in bilateral CI (BCI) users. The Munich Music Questionnaire was used to investigate music listening habits and enjoyment in 23 BCI users compared to 2 control groups: 23 UCI users and 23 normal-hearing (NH) listeners. Bilateral users appeared to have a number of advantages over unilateral users, though their enjoyment of music did not reach the level of NH listeners.

To determine whether exaggerating the variations in fundamental frequency (F0) contours of Mandarin-based pitch fluctuations could improve tone identification by cochlear implant (CI) users. Twelve normal-hearing (NH) listeners and 11 CI users were tested for their ability to recognize F0 contours modeled after Mandarin tones, in 4- or 5-alternatives forced-choice paradigms. Two types of stimuli were used: computer-generated complex tones and voice recordings. Four contours were tested with voice recordings: flat, rise, fall, and dip. A fifth contour, peak, was added for complex tones. The F0 range of each contour was varied in an adaptive manner. A maximum-likelihood technique was used to fit a psychometric function to the performance data and extract threshold at 70% accuracy. As F0 range increased, performance in tone identification improved but did not reach 100% for some CI users, suggesting that confusions between contours could always be made even with extremely exaggerated contours. Compared with NH participants, CI users required substantially larger F0 ranges to identify tones, on the order of 9.3 versus 0.4 semitones. CI users achieved better performance for complex tones than for voice recordings, whereas the reverse was true for NH participants. Confusion matrices showed that the "flat" tone was often a default option when the tone contour's F0 range presented was too narrow for participants to respond correctly. These results demonstrate markedly impaired ability for CI users to identify tonal contours, but suggest that the use of exaggerated pitch contours may be helpful for tonal language perception.

Auditory cross-modal reorganization in cochlear implant users indicates audio-visual integration.

In cochlear implants (CIs), an electrode’s pitch is largely determined by the excitation pattern produced by stimulation. For CI users, is pitch perception most strongly influenced by the peak, edge or some intermediate location within the excitation pattern? By varying the stimulation mode at four evenly spaced electrode locations, four spectral profiles were hypothesized: single-peaked, apically weighted, basally weighted or multi-peaked (with an intermediate pitch). Forward-masked excitation patterns and pitch judgments were obtained for the four electrode locations, for all experimental stimulation modes, relative to a standard set of BP1 electrodes. Results showed individual differences in CI users’ excitation patterns and pitch judgments produced by the different stimulation modes. Most subjects’ pitch judgments were sensitive to single, sharp peaks in the excitation pattern; however, subjects differed in their sensitivity to broader, multi-peaked patterns. For widely spaced electrode configurations, some subjects consistently judged pitch according to the apical edge of stimulation, some to the basal edge and others to an intermediate location. For some electrode locations, varying the stimulation mode produced significantly different pitches and excitation patterns. Future speech processing strategies may wish to combine stimulation modes to improve the spectral resolution available with a fixed number of implanted electrodes.

Various neural health estimates have been shown to indicate the density of spiral ganglion neurons in animal and modeling studies of cochlear implants (CIs). However, when applied to human CI users, these neural health estimates based on psychophysical and electrophysiological measures are not consistently correlated with each other or with the speech recognition performance. This study investigated whether the neural health estimates have stronger correlations with the temporal and place pitch sensitivity than with the speech recognition performance. On five electrodes in 12 tested ears of eight adult CI users, polarity effect (PE), multipulse integration (MPI), and interphase gap (IPG) effect on the amplitude growth function (AGF) of electrically evoked compound action potential (ECAP) were measured to estimate neural health, while thresholds of amplitude modulation frequency ranking (AMFR) and virtual channel ranking (VCR) were measured to indicate temporal and place pitch sensitivity. AzBio sentence recognition in noise was measured using the clinical CI processor for each ear. The results showed significantly poorer AMFR and VCR thresholds on the basal electrodes than on the apical and middle electrodes. Across ears and electrodes, only the IPG offset effect on ECAP AGF had a nearly significant negative correlation with the VCR threshold after removing the outliers. No significant across-ear correlations were found between the mean neural health estimates, mean pitch-ranking thresholds, and AzBio sentence recognition score. This study suggests that the central axon demyelination reflected by the IPG offset effect may be important for the place pitch sensitivity of CI users and that the IPG offset effect may be used to predict the perceptual resolution of virtual channels for CI programming.

Musical and vocal emotion perception for cochlear implants users