Characterizing the relationship between modulation sensitivity and pitch resolution in cochlear implant users.

Cochlear implants are medical devices that have restored hearing to approximately one million people around the world. Outcomes are impressive and most recipients attain excellent speech comprehension in quiet without relying on lip-reading cues, but pitch resolution is poor compared to normal hearing. Amplitude modulation of electrical stimulation is a primary cue for pitch perception in cochlear implant users. The experiments described in this article focus on the relationship between sensitivity to amplitude modulations and pitch resolution based on changes in the frequency of amplitude modulations. In the first experiment, modulation sensitivity and pitch resolution were measured in adults with no known hearing loss and in cochlear implant users with sounds presented to and processed by their clinical devices. Stimuli were amplitude-modulated sinusoids and amplitude-modulated narrow-band noises. Modulation detection and modulation frequency discrimination were measured for modulation frequencies centered on 110, 220, and 440 Hz. Pitch resolution based on changes in modulation frequency was measured for modulation depths of 25 %, 50 %, 100 %, and for a half-waved rectified modulator. Results revealed a strong linear relationship between modulation sensitivity and pitch resolution for cochlear implant users and peers with no known hearing loss. In the second experiment, cochlear implant users took part in analogous procedures of modulation sensitivity and pitch resolution but bypassing clinical sound processing using single-electrode stimulation. Results indicated that modulation sensitivity and pitch resolution was better conveyed by single-electrode stimulation than by clinical processors. Results at 440 Hz were worse, but also not well conveyed by clinical sound processing, so it remains unclear whether the 300 Hz perceptual limit described in the literature is a technological or biological limitation. These results highlight modulation depth and sensitivity as critical factors for pitch resolution in cochlear implant users and characterize the relationship that should inform the design of modulation enhancement algorithms for cochlear implants.

Involvement of the superior colliculi in crossmodal correspondences.

There is an increasing body of evidence suggesting that there are low-level perceptual processes involved in crossmodal correspondences. In this study, we investigate the involvement of the superior colliculi in three basic crossmodal correspondences: elevation/pitch, lightness/pitch, and size/pitch. Using a psychophysical design, we modulate visual input to the superior colliculus to test whether the superior colliculus is required for behavioural crossmodal congruency effects to manifest in an unspeeded multisensory discrimination task. In the elevation/pitch task, superior colliculus involvement is required for a behavioural elevation/pitch congruency effect to manifest in the task. In the lightness/pitch and size/pitch task, we observed a behavioural elevation/pitch congruency effect regardless of superior colliculus involvement. These results suggest that the elevation/pitch correspondence may be processed differently to other low-level crossmodal correspondences. The implications of a distributed model of crossmodal correspondence processing in the brain are discussed.

Dual-task interference: Bottleneck constraint or capacity sharing? Evidence from automatic and controlled processes.

This study investigated whether the interference between two tasks in dual-task processing stems from bottleneck limitations or insufficient cognitive resources due to resource sharing. Experiment 1 used tone discrimination as Task 1 and word or pseudoword classification as Task 2 to evaluate the effect of automatic versus controlled processing on dual-task interference under different SOA conditions. Experiment 2 reversed the task order. The results showed that dual-task interference persisted regardless of task type or order. Neither experiment found evidence that automatic tasks could eliminate interference. This suggests that resource limitations, rather than bottlenecks, may better explain dual-task costs. Specifically, when tasks compete for limited resources, the processing efficiency of both tasks is significantly reduced. Future research should explore how cognitive resources are dynamically allocated between tasks to better account for dual-task interference effects.

Musical training is not associated with spectral context effects in instrument sound categorization.

Musicians display a variety of auditory perceptual benefits relative to people with little or no musical training; these benefits are collectively referred to as the "musician advantage." Importantly, musicians consistently outperform nonmusicians for tasks relating to pitch, but there are mixed reports as to musicians outperforming nonmusicians for timbre-related tasks. Due to their experience manipulating the timbre of their instrument or voice in performance, we hypothesized that musicians would be more sensitive to acoustic context effects stemming from the spectral changes in timbre across a musical context passage (played by a string quintet then filtered) and a target instrument sound (French horn or tenor saxophone; Experiment 1). Additionally, we investigated the role of a musician's primary instrument of instruction by recruiting French horn and tenor saxophone players to also complete this task (Experiment 2). Consistent with the musician advantage literature, musicians exhibited superior pitch discrimination to nonmusicians. Contrary to our main hypothesis, there was no difference between musicians and nonmusicians in how spectral context effects shaped instrument sound categorization. Thus, musicians may only outperform nonmusicians for some auditory skills relevant to music (e.g., pitch perception) but not others (e.g., timbre perception via spectral differences).

Not fully remembered, but not forgotten: interfering sounds worsen but do not eliminate the representation of pitch in working memory.

Recent research has begun measuring auditory working memory with a continuous adjustment task in which listeners adjust attributes of a sound to match a stimulus presented earlier. This approach captures auditory memory's continuous nature better than standard change detection paradigms that collect binary ("same or different") memory measurements. In two experiments, we assessed the impact of different interference stimuli (multitone complexes vs. white noise vs. silence) on the precision and accuracy of participants' reproductions of pitch from memory. Participants were presented with a target multitone complex stimulus followed by eight successive interference signals. Across trials, these signals alternated between additional multitone complexes, randomly generated white noise samples, or (in Experiment 2) silence. This was followed by a response period where participants adjusted the pitch of a response stimulus using a MIDI touchpad to match the target. Experiment 1 found a significant effect of interference type on performance, with tone interference signals producing the greatest impairments to participants' accuracy and precision compared to white noise. Interestingly, it also found a compression in the participants' responses, with overestimations of low-frequency targets and underestimations for high-frequency targets. Experiment 2 replicated results from Experiment 1, with an additional silence condition showing the best performance, suggesting that non-tonal signals also generate interference. In general, results support a shared resource model of working memory with a limited capacity that can be flexibly allocated to hold items in memory with varying levels of fidelity. Interference does not appear to knock items out of a fixed precision slot, but rather robs a portion of capacity from stored items.

Cochlear Implant Users can Effectively Combine Place and Timing Cues for Pitch Perception.

OBJECTIVES: The study objective was to characterize cochlear implant (CI) pitch perception for pure, complex, and modulated tones for frequencies and fundamental frequencies in the ecologically essential range between 110 and 440 Hz. Stimulus manipulations were used to examine CI users' reliance on stimulation place and rate cues for pitch discrimination. DESIGN: The study was a within-subjects design with 21 CI users completing pitch discrimination measures using pure, complex, and modulated tones. Stimulus manipulations were used to test whether CI users have better pitch discrimination for low-pass compared with high-pass filtered harmonic complexes, and to test whether they have better pitch discrimination when provided a covarying place cue when listening to amplitude-modulated tones. RESULTS: Averaged across conditions, participants had better pitch discrimination for pure tones compared with either complex or amplitude-modulated tones. Participants had better pitch discrimination for low-pass compared with high-pass harmonic complexes and better pitch discrimination for amplitude-modulated tones when provided a covarying place cue. CONCLUSIONS: CI users integrate place and rate cues across the ecologically essential pitch range between 110 and 440 Hz. We interpret the observed better pitch discrimination for low-pass compared with high-pass filtered harmonics complexes, and for amplitude-modulated tones when provided a covarying place cue, as evidence for the importance of providing place-of-excitation cues for fundamental frequencies below 440 Hz. Discussion considers how such encoding could be implemented with existing devices.

Effect of diotic versus dichotic presentation on the pitch perception of tone complexes at medium and very high frequencies.

Difference limens for fundamental frequency (F0), F0DLs, are usually small for complex tones containing low harmonics that are resolved in the auditory periphery, but worsen when the rank of the lowest harmonic increases above about 6-8 and harmonics become less resolved. The traditional explanation for this, in terms of resolvability, has been challenged and an alternative explanation in terms of harmonic rank was suggested. Here, to disentangle the effects of resolvability and harmonic rank the complex tones were presented either diotically (all harmonics to both ears) or dichotically (even and odd harmonics to opposite ears); the latter increases resolvability but does not affect harmonic rank. F0DLs were measured for 14 listeners for complex tones containing harmonics 6-10 with F0s of 280 and 1400 Hz, presented diotically or dichotically. For the low F0, F0DLs were significantly lower for the dichotic than for the diotic condition. This is consistent with a benefit of increased resolvability of harmonics for F0 discrimination and extends previous results to harmonics as low as the sixth. In contrast, for the high F0, F0DLs were similar for the two presentation modes, adding to evidence for differences in pitch perception between tones with low-to-medium and very-high frequency content.

Auditory cortex and beyond: Deficits in congenital amusia.

Congenital amusia is a neuro-developmental disorder of music perception and production, with the observed deficits contrasting with the sophisticated music processing reported for the general population. Musical deficits within amusia have been hypothesized to arise from altered pitch processing, with impairments in pitch discrimination and, notably, short-term memory. We here review research investigating its behavioral and neural correlates, in particular the impairments at encoding, retention, and recollection of pitch information, as well as how these impairments extend to the processing of pitch cues in speech and emotion. The impairments have been related to altered brain responses in a distributed fronto-temporal network, which can be observed also at rest. Neuroimaging studies revealed changes in connectivity patterns within this network and beyond, shedding light on the brain dynamics underlying auditory cognition. Interestingly, some studies revealed spared implicit pitch processing in congenital amusia, showing the power of implicit cognition in the music domain. Building on these findings, together with audiovisual integration and other beneficial mechanisms, we outline perspectives for training and rehabilitation and the future directions of this research domain.

No Musician Advantage in the Perception of Degraded-Fundamental Frequency Speech in Noisy Environments.

PURPOSE: Pitch variations of the fundamental frequency (fo) contour contribute to speech perception in noisy environments, but whether musicians confer an advantage in speech in noise (SIN) with altered fo information remains unclear. This study investigated the effects of different levels of degraded fo contour (i.e., conveying lexical tone or intonation information) on musician advantage in speech-in-noise perception. METHOD: A cohort of native Mandarin Chinese speakers, comprising 30 trained musicians and 30 nonmusicians, were tested on the intelligibility of Mandarin Chinese sentences with natural, flattened-tone, flattened-intonation, and flattened-all fo contours embedded in background noise masked under three signal-to-noise ratios (0, -5, and -9 dB). Pitch difference thresholds and innate musical skills associated with speech-in-noise benefits were also assessed. RESULTS: Speech intelligibility score improved with increasing signal-to-noise level for both musicians and nonmusicians. However, no musician advantage was observed for identifying any type of flattened-fo contour SIN. Musicians exhibited smaller fo pitch discrimination limens than nonmusicians, which correlated with benefits for perceiving speech with intact tone-level fo information. Regardless of musician status, performance on the pitch and accent musical-skill subtests correlated with speech intelligibility score. CONCLUSIONS: Collectively, these results provide no evidence for a musician advantage for perceiving speech with distorted fo information in noisy environments. Results further show that perceptual musical skills on pitch and accent processing may benefit the perception of SIN, independent of formal musical training. Our findings suggest that the potential application of music training in speech perception in noisy backgrounds is not contingent on the ability to process fo pitch contours, at least for Mandarin Chinese speakers. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.23706354.

The role of carrier spectral composition in the perception of musical pitch.

Temporal envelope fluctuations of natural sounds convey critical information to speech and music processing. In particular, musical pitch perception is assumed to be primarily underlined by temporal envelope encoding. While increasing evidence demonstrates the importance of carrier fine structure to complex pitch perception, how carrier spectral information affects musical pitch perception is less clear. Here, transposed tones designed to convey identical envelope information across different carriers were used to assess the effects of carrier spectral composition to pitch discrimination and musical-interval and melody identifications. Results showed that pitch discrimination thresholds became lower (better) with increasing carrier frequencies from 1k to 10k Hz, with performance comparable to that of pure sinusoids. Musical interval and melody defined by the periodicity of sine- or harmonic complex envelopes across carriers were identified with greater than 85% accuracy even on a 10k-Hz carrier. Moreover, enhanced interval and melody identification performance was observed with increasing carrier frequency up to 6k Hz. Findings suggest a perceptual enhancement of temporal envelope information with increasing carrier spectral region in musical pitch processing, at least for frequencies up to 6k Hz. For carriers in the extended high-frequency region (8-20k Hz), the use of temporal envelope information to music pitch processing may vary depending on task requirement. Collectively, these results implicate the fidelity of temporal envelope information to musical pitch perception is more pronounced than previously considered, with ecological implications.

Pitch discrimination in electric hearing with inconsistent and consistent amplitude-modulation and inter-pulse rate cues.

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.

Partial inactivation of songbird auditory cortex impairs both tempo and pitch discrimination.

Neuronal tuning for spectral and temporal features has been studied extensively in the auditory system. In the auditory cortex, diverse combinations of spectral and temporal tuning have been found, but how specific feature tuning contributes to the perception of complex sounds remains unclear. Neurons in the avian auditory cortex are spatially organized in terms of spectral or temporal tuning widths, providing an opportunity for investigating the link between auditory tuning and perception. Here, using naturalistic conspecific vocalizations, we asked whether subregions of the auditory cortex that are tuned for broadband sounds are more important for discriminating tempo than pitch, due to the lower frequency selectivity. We found that bilateral inactivation of the broadband region impairs performance on both tempo and pitch discrimination. Our results do not support the hypothesis that the lateral, more broadband subregion of the songbird auditory cortex contributes more to processing temporal than spectral information.

A detailed examination of pitch discrimination deficits associated with auditory verbal hallucinations in schizophrenia.

Individuals with schizophrenia spectrum disorders (SSD) and a history of experiencing auditory verbal hallucinations (AVH) exhibit poor pitch discrimination relative to those with an SSD but no AVH history. The present study extended this research, asking if a lifetime history, and the current presence, of AVH exacerbated the pitch discrimination challenges that are seen in SSD. Participants completed a pitch discrimination task, where the tones presented differed in pitch by either 2 %, 5 %, 10 %, 25 % or 50 %. Pitch discrimination accuracy, sensitivity, reaction time (RT) and intra-individual RT variability (IIV) were examined in individuals with SSD and AVHs (AVH+; n = 46), or without AVHs (AVH-; n = 31), and healthy controls (HC; n = 131). Secondary analyses split the AVH+ group into state (i.e., actively experiencing AVH; n = 32) and trait hallucinators (i.e., a history of, but not actively experiencing, AVH; n = 16). Relative to HC, significantly poorer accuracy and sensitivity was detected in individuals with SSD at 2 % and 5 % pitch deviants, and in hallucinators at 10 %; however, no significant differences in accuracy, sensitivity, RT nor IIV were found between AVH+ and AVH- groups. No differences between state and trait hallucinators were observed. A general SSD deficit drove the current findings. The findings may inform future research into the auditory processing capabilities of AVH+ individuals.

Development of Achieving Constancy in Lexical Tone Identification With Contextual Cues.

PURPOSE: The aim of this study was to explore when and how Mandarin-speaking children use contextual cues to normalize speech variability in perceiving lexical tones. Two different cognitive mechanisms underlying speech normalization (lower level acoustic normalization and higher level acoustic-phonemic normalization) were investigated through the lexical tone identification task in nonspeech contexts and speech contexts, respectively. Besides, another aim of this study was to reveal how domain-general cognitive abilities contribute to the development of the speech normalization process. METHOD: In this study, 94 five- to eight-year-old Mandarin-speaking children (50 boys, 44 girls) and 24 young adults (14 men, 10 women) were asked to identify ambiguous Mandarin high-level and mid-rising tones in either speech or nonspeech contexts. Furthermore, in this study, we tested participants' pitch sensitivity through a nonlinguistic pitch discrimination task and their working memory using the digit span task. RESULTS: Higher level acoustic-phonemic normalization of lexical tones emerged at the age of 6 years and was relatively stable thereafter. However, lower level acoustic normalization was less stable across different ages. Neither pitch sensitivity nor working memory affected children's lexical tone normalization. CONCLUSIONS: Mandarin-speaking children above 6 years of age successfully achieved constancy in lexical tone normalization based on speech contextual cues. The perceptual normalization of lexical tones was not affected by pitch sensitivity and working memory capacity.

Enduring musician advantage among former musicians in prosodic pitch perception.

Musical training has been associated with various cognitive benefits, one of which is enhanced speech perception. However, most findings have been based on musicians taking part in ongoing music lessons and practice. This study thus sought to determine whether the musician advantage in pitch perception in the language domain extends to individuals who have ceased musical training and practice. To this end, adult active musicians (n = 22), former musicians (n = 27), and non-musicians (n = 47) were presented with sentences spoken in a native language, English, and a foreign language, French. The final words of the sentences were either prosodically congruous (spoken at normal pitch height), weakly incongruous (pitch was increased by 25%), or strongly incongruous (pitch was increased by 110%). Results of the pitch discrimination task revealed that although active musicians outperformed former musicians, former musicians outperformed non-musicians in the weakly incongruous condition. The findings suggest that the musician advantage in pitch perception in speech is retained to some extent even after musical training and practice is discontinued.

Adapting to the Sound of Music - Development of Music Discrimination Skills in Recently Implanted CI Users.

Cochlear implants (CIs) are optimized for speech perception but poor in conveying musical sound features such as pitch, melody, and timbre. Here, we investigated the early development of discrimination of musical sound features after cochlear implantation. Nine recently implanted CI users (CIre) were tested shortly after switch-on (T1) and approximately 3 months later (T2), using a musical multifeature mismatch negativity (MMN) paradigm, presenting four deviant features (intensity, pitch, timbre, and rhythm), and a three-alternative forced-choice behavioral test. For reference, groups of experienced CI users (CIex; n = 13) and normally hearing (NH) controls (n = 14) underwent the same tests once. We found significant improvement in CIre's neural discrimination of pitch and timbre as marked by increased MMN amplitudes. This was not reflected in the behavioral results. Behaviorally, CIre scored well above chance level at both time points for all features except intensity, but significantly below NH controls for all features except rhythm. Both CI groups scored significantly below NH in behavioral pitch discrimination. No significant difference was found in MMN amplitude between CIex and NH. The results indicate that development of musical discrimination can be detected neurophysiologically early after switch-on. However, to fully take advantage of the sparse information from the implant, a prolonged adaptation period may be required. Behavioral discrimination accuracy was notably high already shortly after implant switch-on, although well below that of NH listeners. This study provides new insight into the early development of music-discrimination abilities in CI users and may have clinical and therapeutic relevance.

Generalizing across tonal context, timbre, and octave in rapid absolute pitch training.

Absolute pitch (AP) is the rare ability to name any musical note without the use of a reference note. Given that genuine AP representations are based on the identification of isolated notes by their tone chroma, they are considered to be invariant to (1) surrounding tonal context, (2) changes in instrumental timbre, and (3) changes in octave register. However, there is considerable variability in the literature in terms of how AP is trained and tested along these dimensions, making recent claims about AP learning difficult to assess. Here, we examined the effect of tonal context on participant success with a single-note identification training paradigm, including how learning generalized to an untested instrument and octave. We found that participants were able to rapidly learn to distinguish C from other notes, with and without feedback and regardless of the tonal context in which C was presented. Participants were also able to partly generalize this skill to an untrained instrument. However, participants displayed the weakest generalization in recognizing C in a higher octave. The results indicate that participants were likely attending to pitch height in addition to pitch chroma - a conjecture that was supported by analyzing the pattern of response errors. These findings highlight the complex nature of note representation in AP, which requires note identification across contexts, going beyond the simple storage of a note fundamental. The importance of standardizing testing that spans both timbre and octave in assessing AP and further implications on past literature and future work are discussed.

Absolute pitch: neurophysiological evidence for early brain activity in prefrontal cortex.

Absolute pitch (AP) is the ability to rapidly label pitch without an external reference. The speed of AP labeling may be related to faster sensory processing. We compared time needed for auditory processing in AP musicians, non-AP musicians, and nonmusicians (NM) using high-density electroencephalographic recording. Participants responded to pure tones and sung voice. Stimuli evoked a negative deflection peaking at ~100 ms (N1) post-stimulus onset, followed by a positive deflection peaking at ~200 ms (P2). N1 latency was shortest in AP, intermediate in non-AP musicians, and longest in NM. Source analyses showed decreased auditory cortex and increased frontal cortex contributions to N1 for complex tones compared with pure tones. Compared with NM, AP musicians had weaker source currents in left auditory cortex but stronger currents in left inferior frontal gyrus (IFG) during N1, and stronger currents in left IFG during P2. Compared with non-AP musicians, AP musicians exhibited stronger source currents in right insula and left IFG during N1, and stronger currents in left IFG during P2. Non-AP musicians had stronger N1 currents in right auditory cortex than nonmusicians. Currents in left IFG and left auditory cortex were correlated to response times exclusively in AP. Findings suggest a left frontotemporal network supports rapid pitch labeling in AP.

Hearing aid delay in open-fit devices - coloration-pitch discrimination in normal-hearing and hearing-impaired.

OBJECTIVE: The delay in digital hearing aids is known to cause distortions due to the mixing of the delayed hearing aid sound with the undelayed direct sound. The most apparent delay-based distortion is a pitch sensation referred to as coloration-pitch. This study investigated coloration-pitch discrimination at the lower end of typical hearing aid delays and aimed at establishing thresholds where a large change in coloration-pitch is just perceptible. DESIGN: Simulations were verified against a reference hearing aid for numerous conditions of delay, insertion gain and incident direction. The simulations were used in a psycho-acoustics experiment in which coloration-pitch discrimination thresholds were measured as a function of hearing aid delay and gain. Participants discriminated between coloration-pitches produced by delay changes of 12%. Insertion gains compensating for mild to moderate hearing losses were used. STUDY SAMPLE: Nine normal-hearing and twelve hearing-impaired participants with mild to moderate hearing loss participated. RESULTS: The simulations accurately reflected the acoustics of the open-fit hearing aid. Discrimination thresholds were between 0.3 ms and 1 ms depending on insertion gain and hearing status. CONCLUSIONS: High sensitivity for changes in coloration-pitch was found for delays >1 ms. For shorter delays participants were increasingly insensitive to changes in coloration-pitch.