Impaired short-term memory for pitch in congenital amusia

Deficits in congenital amusia: Pitch, music, speech, and beyond

Congenital amusia is a neurodevelopmental disorder characterized by deficits of music perception and production, which are related to altered pitch processing. The present study used a wide variety of tasks to test potential patterns of processing impairment in individuals with congenital amusia (N = 18) in comparison to matched controls (N = 19), notably classical pitch processing tests (i.e., pitch change detection, pitch direction of change identification, and pitch short-term memory tasks) together with tasks assessing other aspects of pitch-related auditory cognition, such as emotion recognition in speech, sound segregation in tone sequences, and speech-in-noise perception. Additional behavioral measures were also collected, including text reading/copying tests, visual control tasks, and a subjective assessment of hearing abilities. As expected, amusics' performance was impaired for the three pitch-specific tasks compared to controls. This deficit of pitch perception had a self-perceived impact on amusics' quality of hearing. Moreover, participants with amusia were impaired in emotion recognition in vowels compared to controls, but no group difference was observed for emotion recognition in sentences, replicating previous data. Despite pitch processing deficits, participants with amusia did not differ from controls in sound segregation and speech-in-noise perception. Text reading and visual control tests did not reveal any impairments in participants with amusia compared to controls. However, the copying test revealed more numerous eye-movements and a smaller memory span. These results allow us to refine the pattern of pitch processing and memory deficits in congenital amusia, thus contributing further to understand pitch-related auditory cognition. Together with previous reports suggesting a comorbidity between congenital amusia and dyslexia, the findings call for further investigation of language-related abilities in this disorder even in the absence of neurodevelopmental language disorder diagnosis.

The Relationship Between Autism and Pitch Perception is Modulated by Cognitive Abilities

Previous studies reported mixed findings on autistic individuals' pitch perception relative to neurotypical (NT) individuals. We investigated whether this may be partly due to individual differences in cognitive abilities by comparing their performance on various pitch perception tasks on a large sample (n = 164) of autistic and NT children and adults. Our findings revealed that: (i) autistic individuals either showed similar or worse performance than NT individuals on the pitch tasks; (ii) cognitive abilities were associated with some pitch task performance; and (iii) cognitive abilities modulated the relationship between autism diagnosis and pitch perception on some tasks. Our findings highlight the importance of taking an individual differences approach to understand the strengths and weaknesses of pitch processing in autism.

Do developmental dyslexia and congenital amusia share underlying impairments?

Developmental dyslexia and congenital amusia have common characteristics. Yet, their possible association in some individuals has been addressed only scarcely. Recently, two converging studies reported a sizable comorbidity rate between these two neurodevelopmental disorders (Couvignou et al., Cognitive Neuropsychology 2019; Couvignou & Kolinsky, Neuropsychologia 2021). However, the reason for their association remains unclear. Here, we investigate the hypothesis of shared underlying impairments between dyslexia and amusia. Fifteen dyslexic children with amusia (DYS+A), 15 dyslexic children without amusia (DYS-A), and two groups of 25 typically developing children matched on either chronological age (CA) or reading level (RL) were assessed with a behavioral battery aiming to investigate phonological and pitch processing capacities at auditory memory, perceptual awareness, and attentional levels. Overall, our results suggest that poor auditory serial-order memory increases susceptibility to comorbidity between dyslexia and amusia and may play a role in the development of the comorbid phenotype. In contrast, the impairments observed in the DYS+A children for auditory item memory, perceptual awareness, and attention might be a consequence of their reduced reading experience combined with weaker musical skills. Comparing DYS+A and DYS-A children suggests that the latter are more resourceful and/or have more effective compensatory strategies, or that their phenotype results from a different developmental trajectory. We will discuss the relevance of these findings for delving into the etiology of these two developmental disorders and address their implications for future research and practice.

Tone Deafness in Music Does Not Preclude Distributional Learning of Nonnative Tonal Languages in Individuals With Congenital Amusia

PURPOSE

Previous studies have shown that individuals with congenital amusia exhibit deficient pitch processing across music and language domains. This study investigated whether adult Chinese-speaking listeners with amusia were still able to learn Thai lexical tones based on stimulus frequency of statistical distribution via distributional learning, despite their degraded lexical tone perception.

METHOD

Following a pretest-training-posttest design, 21 amusics and 23 typical, musically intact listeners were assigned into bimodal and unimodal distribution conditions. Listeners were asked to discriminate minimal pairs of Thai mid-level tone and falling tone superimposed on variable base syllables and uttered by different speakers. The perceptual accuracy for each test session and improvement from pretest to posttest were collected and analyzed between the two groups using generalized mixed-effects models.

RESULTS

When discriminating Thai lexical tones, amusics were less accurate than typical listeners. Nonetheless, similarly to control listeners, perceptual gains from pretest to posttest were observed in bimodally rather than unimodally trained amusics, as evidenced by both trained and nontrained test words.

CONCLUSIONS

Amusics are able to learn lexical tones in a second or foreign context of speech. This extends previous research by showing that amusics' distributional learning of linguistic pitch remains largely preserved despite their degraded pitch processing. It is thus likely that manifestations of amusia in speech could not result from their abnormal statistical learning mechanism. This study meanwhile provides a heuristic approach for future studies to apply this paradigm into amusics' treatment to mitigate their pitch-processing disorder.

Explicit processing of melodic structure in congenital amusia can be improved by redescription-associate learning

Congenital amusia is a neurodevelopmental disorder of musical processing. Previous research demonstrates that although explicit musical processing is impaired in congenital amusia, implicit musical processing can be intact. However, little is known about whether implicit knowledge could improve explicit musical processing in individuals with congenital amusia. To this end, we developed a training method utilizing redescription-associate learning, aiming at transferring implicit representations of perceptual states into explicit forms through verbal description and then establishing the associations between the perceptual states reported and responses via feedback, to investigate whether the explicit processing of melodic structure could be improved in individuals with congenital amusia. Sixteen amusics and 11 controls rated the degree of expectedness of melodies during EEG recording before and after training. In the interim, half of the amusics received nine training sessions on melodic structure, while the other half received no training. Results, based on effect size estimation, showed that at pretest, amusics but not controls failed to explicitly distinguish the regular from the irregular melodies and to exhibit an ERAN in response to the irregular endings. At posttest, trained but not untrained amusics performed as well as controls at both the behavioral and neural levels. At the 3-month follow-up, the training effects still maintained. These findings present novel electrophysiological evidence of neural plasticity in the amusic brain, suggesting that redescription-associate learning may be an effective method to remediate impaired explicit processes for individuals with other neurodevelopmental disorders who have intact implicit knowledge.

Individuals with congenital amusia remember music they like

Music is better recognized when it is liked. Does this association remain evident when music perception and memory are severely impaired, as in congenital amusia? We tested 11 amusic and 11 matched control participants, asking whether liking of a musical excerpt influences subsequent recognition. In an initial exposure phase, participants-unaware that their recognition would be tested subsequently-listened to 24 musical excerpts and judged how much they liked each excerpt. In the test phase that followed, participants rated whether they recognized the previously heard excerpts, which were intermixed with an equal number of foils matched for mode, tempo, and musical genre. As expected, recognition was in general impaired for amusic participants compared with control participants. For both groups, however, recognition was better for excerpts that were liked, and the liking enhancement did not differ between groups. These results contribute to a growing body of research that examines the complex interplay between emotions and cognitive processes. More specifically, they extend previous findings related to amusics' impairments to a new memory paradigm and suggest that (1) amusic individuals are sensitive to an aesthetic and subjective dimension of the music-listening experience, and (2) emotions can support memory processes even in a population with impaired music perception and memory.

Music perception in acquired prosopagnosia

BACKGROUND

Acquired prosopagnosia is often associated with other deficits such as dyschromatopsia and topographagnosia, from damage to adjacent perceptual networks. A recent study showed that some subjects with developmental prosopagnosia also have congenital amusia, but problems with music perception have not been described with the acquired variant.

OBJECTIVE

Our goal was to determine if music perception was also impaired in subjects with acquired prosopagnosia, and if so, its anatomic correlate.

METHOD

We studied eight subjects with acquired prosopagnosia, all of whom had extensive neuropsychological and neuroimaging testing. They performed a battery of tests evaluating pitch and rhythm processing, including the Montréal Battery for the Evaluation of Amusia.

RESULTS

At the group level, subjects with anterior temporal lesions were impaired in pitch perception relative to the control group, but not those with occipitotemporal lesions. Three of eight subjects with acquired prosopagnosia had impaired musical pitch perception while rhythm perception was spared. Two of the three also showed reduced musical memory. These three reported alterations in their emotional experience of music: one reported music anhedonia and aversion, while the remaining two had changes consistent with musicophilia. The lesions of these three subjects affected the right or bilateral temporal poles as well as the right amygdala and insula. None of the three prosopagnosic subjects with lesions limited to the inferior occipitotemporal cortex exhibited impaired pitch perception or musical memory, or reported changes in music appreciation.

CONCLUSION

Together with the results of our previous studies of voice recognition, these findings indicate an anterior ventral syndrome that can include the amnestic variant of prosopagnosia, phonagnosia, and various alterations in music perception, including acquired amusia, reduced musical memory, and subjective reports of altered emotional experience of music.

Hemispheric asymmetries for music and speech: Spectrotemporal modulations and top-down influences

Hemispheric asymmetries in auditory cognition have been recognized for a long time, but their neural basis is still debated. Here I focus on specialization for processing of speech and music, the two most important auditory communication systems that humans possess. A great deal of evidence from lesion studies and functional imaging suggests that aspects of music linked to the processing of pitch patterns depend more on right than left auditory networks. A complementary specialization for temporal resolution has been suggested for left auditory networks. These diverse findings can be integrated within the context of the spectrotemporal modulation framework, which has been developed as a way to characterize efficient neuronal encoding of complex sounds. Recent studies show that degradation of spectral modulation impairs melody perception but not speech content, whereas degradation of temporal modulation has the opposite effect. Neural responses in the right and left auditory cortex in those studies are linked to processing of spectral and temporal modulations, respectively. These findings provide a unifying model to understand asymmetries in terms of sensitivity to acoustical features of communication sounds in humans. However, this explanation does not account for evidence that asymmetries can shift as a function of learning, attention, or other top-down factors. Therefore, it seems likely that asymmetries arise both from bottom-up specialization for acoustical modulations and top-down influences coming from hierarchically higher components of the system. Such interactions can be understood in terms of predictive coding mechanisms for perception.

Cross-Frequency Brain Network Dynamics Support Pitch Change Detection

Processing auditory sequences involves multiple brain networks and is crucial to complex perception associated with music appreciation and speech comprehension. We used time-resolved cortical imaging in a pitch change detection task to detail the underlying nature of human brain network activity, at the rapid time scales of neurophysiology. In response to tone sequence presentation to the participants, we observed slow inter-regional signaling at the pace of tone presentations (2-4 Hz) that was directed from auditory cortex toward both inferior frontal and motor cortices. Symmetrically, motor cortex manifested directed influence onto auditory and inferior frontal cortices via bursts of faster (15-35 Hz) activity. These bursts occurred precisely at the expected latencies of each tone in a sequence. This expression of interdependency between slow/fast neurophysiological activity yielded a form of local cross-frequency phase-amplitude coupling in auditory cortex, which strength varied dynamically and peaked when pitch changes were anticipated. We clarified the mechanistic relevance of these observations in relation to behavior by including a group of individuals afflicted by congenital amusia, as a model of altered function in processing sound sequences. In amusia, we found a depression of inter-regional slow signaling toward motor and inferior frontal cortices, and a chronic overexpression of slow/fast phase-amplitude coupling in auditory cortex. These observations are compatible with a misalignment between the respective neurophysiological mechanisms of stimulus encoding and internal predictive signaling, which was absent in controls. In summary, our study provides a functional and mechanistic account of neurophysiological activity for predictive, sequential timing of auditory inputs.SIGNIFICANCE STATEMENT Auditory sequences are processed by extensive brain networks, involving multiple systems. In particular, fronto-temporal brain connections participate in the encoding of sequential auditory events, but so far, their study was limited to static depictions. This study details the nature of oscillatory brain activity involved in these inter-regional interactions in human participants. It demonstrates how directed, polyrhythmic oscillatory interactions between auditory and motor cortical regions provide a functional account for predictive timing of incoming items in an auditory sequence. In addition, we show the functional relevance of these observations in relation to behavior, with data from both normal hearing participants and a rare cohort of individuals afflicted by congenital amusia, which we considered here as a model of altered function in processing sound sequences.

Individuals With Congenital Amusia Show Degraded Speech Perception but Preserved Statistical Learning for Tone Languages

PURPOSE

Individuals with congenital amusia exhibit degraded speech perception. This study examined whether adult Chinese Mandarin listeners with amusia were still able to extract the statistical regularities of Mandarin speech sounds, despite their degraded speech perception.

METHOD

Using the gating paradigm with monosyllabic syllable-tone words, we tested 19 Mandarin-speaking amusics and 19 musically intact controls. Listeners heard increasingly longer fragments of the acoustic signal across eight duration-blocked gates. The stimuli varied in syllable token frequency and syllable-tone co-occurrence probability. The correct syllable-tone word, correct syllable-only, correct tone-only, and correct syllable-incorrect tone responses were compared respectively between the two groups using mixed-effects models.

RESULTS

Amusics were less accurate than controls in terms of the correct word, correct syllable-only, and correct tone-only responses. Amusics, however, showed consistent patterns of top-down processing, as indicated by more accurate responses to high-frequency syllables, high-probability tones, and tone errors all in manners similar to those of the control listeners.

CONCLUSIONS

Amusics are able to learn syllable and tone statistical regularities from the language input. This extends previous work by showing that amusics can track phonological segment and pitch cues despite their degraded speech perception. The observed speech deficits in amusics are therefore not due to an abnormal statistical learning mechanism. These results support rehabilitation programs aimed at improving amusics' sensitivity to pitch.

Development of auditory cognition in 5- to 10-year-old children: Focus on musical and verbal short-term memory

Developmental aspects of auditory cognition were investigated in 5-to-10-year-old children (n = 100). Musical and verbal short-term memory (STM) were assessed by means of delayed matching-to-sample tasks (DMST) (comparison of two four-item sequences separated by a silent retention delay), with two levels of difficulty. For musical and verbal materials, children's performance increased from 5 years to about 7 years of age, then remained stable up to 10 years of age, with performance remaining inferior to performance of young adults. Children and adults performed better with verbal material than with musical material. To investigate auditory cognition beyond STM, we assessed speech-in-noise perception with a four-alternative forced-choice task with two conditions of phonological difficulty and two levels of cocktail-party noise intensity. Partial correlations, factoring out the effect of age, showed a significant link between musical STM and speech-in-noise perception in the condition with increased noise intensity. Our findings reveal that auditory STM improves over development with a critical phase around 6-7 years of age, yet these abilities appear to be still immature at 10 years. Musical and verbal STM might in particular share procedural and serial order processes. Furthermore, musical STM and the ability to perceive relevant speech signals in cocktail-party noise might rely on shared cognitive resources, possibly related to pitch encoding. To the best of our knowledge, this is the first time that auditory STM is assessed with the same paradigm for musical and verbal material during childhood, providing perspectives regarding diagnosis and remediation in developmental learning disorders.

Pitch and Rhythm Perception and Verbal Short-Term Memory in Acute Traumatic Brain Injury

Music perception deficits are common following acquired brain injury due to stroke, epilepsy surgeries, and aneurysmal clipping. Few studies have examined these deficits following traumatic brain injury (TBI), resulting in an under-diagnosis in this population. We aimed to (1) compare TBI patients to controls on pitch and rhythm perception during the acute phase; (2) determine whether pitch and rhythm perception disorders co-occur; (3) examine lateralization of injury in the context of pitch and rhythm perception; and (4) determine the relationship between verbal short-term memory (STM) and pitch and rhythm perception. Music perception was examined using the Scale and Rhythm tests of the Montreal Battery of Evaluation of Amusia, in association with CT scans to identify lesion laterality. Verbal short-term memory was examined using Digit Span Forward. TBI patients had greater impairment than controls, with 43% demonstrating deficits in pitch perception, and 40% in rhythm perception. Deficits were greater with right hemisphere damage than left. Pitch and rhythm deficits co-occurred 31% of the time, suggesting partly dissociable networks. There was a dissociation between performance on verbal STM and pitch and rhythm perception 39 to 42% of the time (respectively), with most individuals (92%) demonstrating intact verbal STM, with impaired pitch or rhythm perception. The clinical implications of music perception deficits following TBI are discussed.

Perception and Production of Statement-Question Intonation in Autism Spectrum Disorder: A Developmental Investigation

Prosody or “melody in speech” in autism spectrum disorder (ASD) is often perceived as atypical. This study examined perception and production of statements and questions in 84 children, adolescents and adults with and without ASD, as well as participants’ pitch direction discrimination thresholds. The results suggested that the abilities to discriminate (in both speech and music conditions), identify, and imitate statement-question intonation were intact in individuals with ASD across age cohorts. Sensitivity to pitch direction predicted performance on intonation processing in both groups, who also exhibited similar developmental changes. These findings provide evidence for shared mechanisms in pitch processing between speech and music, as well as associations between low- and high-level pitch processing and between perception and production of pitch.

Listeners with congenital amusia are sensitive to context uncertainty in melodic sequences

In typical listeners, the perceptual salience of a surprising auditory event depends on the uncertainty of its context. For example, in melodies, pitch deviants are more easily detected and generate larger neural responses when the context is highly predictable than when it is less so. However, it is not known whether amusic listeners with abnormal pitch processing are sensitive to the degree of uncertainty of pitch sequences and, if so, whether they are to a different extent than typical non-musician listeners. To answer this question, we manipulated the uncertainty of short melodies while participants with and without congenital amusia underwent EEG recordings in a passive listening task. Uncertainty was manipulated by presenting melodies with different levels of complexity and familiarity, under the assumption that simpler and more familiar patterns would enhance pitch predictability. We recorded mismatch negativity (MMN) responses to pitch, intensity, timbre, location, and rhythm deviants as a measure of auditory surprise. In both participant groups, we observed reduced MMN amplitudes and longer peak latencies for all sound features with increasing levels of complexity, and putative familiarity effects only for intensity deviants. No significant group-by-complexity or group-by-familiarity interactions were detected. However, in contrast to previous studies, pitch MMN responses in amusics were disrupted in high complexity and unfamiliar melodies. The present results thus indicate that amusics are sensitive to the uncertainty of melodic sequences and that preattentive auditory change detection is greatly spared in this population across sound features and levels of predictability. However, our findings also hint at pitch-specific impairments in this population when uncertainty is high, thus suggesting that pitch processing under high uncertainty conditions requires an intact frontotemporal loop.

Rapid Assessment of Non-Verbal Auditory Perception in Normal-Hearing Participants and Cochlear Implant Users

In the case of hearing loss, cochlear implants (CI) allow for the restoration of hearing. Despite the advantages of CIs for speech perception, CI users still complain about their poor perception of their auditory environment. Aiming to assess non-verbal auditory perception in CI users, we developed five listening tests. These tests measure pitch change detection, pitch direction identification, pitch short-term memory, auditory stream segregation, and emotional prosody recognition, along with perceived intensity ratings. In order to test the potential benefit of visual cues for pitch processing, the three pitch tests included half of the trials with visual indications to perform the task. We tested 10 normal-hearing (NH) participants with material being presented as original and vocoded sounds, and 10 post-lingually deaf CI users. With the vocoded sounds, the NH participants had reduced scores for the detection of small pitch differences, and reduced emotion recognition and streaming abilities compared to the original sounds. Similarly, the CI users had deficits for small differences in the pitch change detection task and emotion recognition, as well as a decreased streaming capacity. Overall, this assessment allows for the rapid detection of specific patterns of non-verbal auditory perception deficits. The current findings also open new perspectives about how to enhance pitch perception capacities using visual cues.

Auditory and visual short-term memory: influence of material type, contour, and musical expertise

Short-term memory has mostly been investigated with verbal or visuospatial stimuli and less so with other categories of stimuli. Moreover, the influence of sensory modality has been explored almost solely in the verbal domain. The present study compared visual and auditory short-term memory for different types of materials, aiming to understand whether sensory modality and material type can influence short-term memory performance. Furthermore, we aimed to assess if music expertise can modulate memory performance, as previous research has reported better auditory memory (and to some extent, visual memory), and better auditory contour recognition for musicians than non-musicians. To do so, we adapted the same recognition paradigm (delayed-matching to sample) across different types of stimuli. In each trial, participants (musicians and non-musicians) were presented with two sequences of events, separated by a silent delay, and had to indicate whether the two sequences were identical or different. The performance was compared for auditory and visual materials belonging to three different categories: (1) verbal (i.e., syllables); (2) nonverbal (i.e., that could not be easily denominated) with contour (based on loudness or luminance variations); and (3) nonverbal without contour (pink noise sequences or kanji letters sequences). Contour and no-contour conditions referred to whether the sequence can entail (or not) a contour (i.e., a pattern of up and down changes) based on non-pitch features. Results revealed a selective advantage of musicians for auditory no-contour stimuli and for contour stimuli (both visual and auditory), suggesting that musical expertise is associated with specific short-term memory advantages in domains close to the trained domain, also extending cross-modally when stimuli have contour information. Moreover, our results suggest a role of encoding strategies (i.e., how the material is represented mentally during the task) for short-term-memory performance.

Individuals with congenital amusia do not show context-dependent perception of tonal categories

Perceptual adaptation is an active cognitive process where listeners re-analyse speech categories based on new contexts/situations/talkers. It involves top-down influences from higher cortical levels on lower-level auditory processes. Individuals with congenital amusia have impaired pitch processing with reduced connectivity between frontal and temporal regions. This study examined whether deficits in amusia would lead to impaired perceptual adaptation in lexical tone perception. Thirteen Mandarin-speaking amusics and 13 controls identified the category of target tones on an 8-step continuum ranging from rising to high-level, either in isolation or in a high-/low-pitched context. For tones with no context, amusics exhibited reduced categorical perception than controls. While controls' lexical tone categorization demonstrated a significant context effect due to perceptual adaptation, amusics showed similar categorization patterns across both contexts. These findings suggest that congenital amusia impacts the extraction of context-dependent tonal categories in speech perception, indicating that perceptual adaptation may depend on listeners' perceptual acuity.

Comorbidity and cognitive overlap between developmental dyslexia and congenital amusia in children

Developmental dyslexia and congenital amusia are two specific neurodevelopmental disorders that affect reading and music perception, respectively. Similarities at perceptual, cognitive, and anatomical levels raise the possibility that a common factor is at play in their emergence, albeit in different domains. However, little consideration has been given to what extent they can co-occur. A first adult study suggested a 30% amusia rate in dyslexia and a 25% dyslexia rate in amusia (Couvignou et al., Cognitive Neuropsychology 2019). We present newly acquired data from 38 dyslexic and 38 typically developing children. These were assessed with literacy and phonological tests, as well as with three musical tests: the Montreal Battery of Evaluation of Musical Abilities, a pitch and time change detection task, and a singing task. Overall, about 34% of the dyslexic children were musically impaired, a proportion that is significantly higher than both the estimated 1.5-4% prevalence of congenital amusia in the general population and the rate of 5% observed within the control group. They were mostly affected in the pitch dimension, both in terms of perception and production. Correlations and prediction links were found between pitch processing skills and language measures after partialing out confounding factors. These findings are discussed with regard to cognitive and neural explanatory hypotheses of a comorbidity between dyslexia and amusia.

Cortical Morphological Changes in Congenital Amusia: Surface-Based Analyses

Background: Congenital amusia (CA) is a rare disorder characterized by deficits in pitch perception, and many structural and functional magnetic resonance imaging studies have been conducted to better understand its neural bases. However, a structural magnetic resonance imaging analysis using a surface-based morphology method to identify regions with cortical features abnormalities at the vertex-based level has not yet been performed. Methods: Fifteen participants with CA and 13 healthy controls underwent structural magnetic resonance imaging. A surface-based morphology method was used to identify anatomical abnormalities. Then, the surface parameters' mean value of the identified clusters with statistically significant between-group differences were extracted and compared. Finally, Pearson's correlation analysis was used to assess the correlation between the Montreal Battery of Evaluation of Amusia (MBEA) scores and surface parameters. Results: The CA group had significantly lower MBEA scores than the healthy controls (p = 0.000). The CA group exhibited a significant higher fractal dimension in the right caudal middle frontal gyrus and a lower sulcal depth in the right pars triangularis gyrus (p < 0.05; false discovery rate-corrected at the cluster level) compared to healthy controls. There were negative correlations between the mean fractal dimension values in the right caudal middle frontal gyrus and MBEA score, including the mean MBEA score (r = -0.5398, p = 0.0030), scale score (r = -0.5712, p = 0.0015), contour score (r = -0.4662, p = 0.0124), interval score (r = -0.4564, p = 0.0146), rhythmic score (r = -0.5133, p = 0.0052), meter score (r = -0.3937, p = 0.0382), and memory score (r = -0.3879, p = 0.0414). There was a significant positive correlation between the mean sulcal depth in the right pars triangularis gyrus and the MBEA score, including the mean score (r = 0.5130, p = 0.0052), scale score (r = 0.5328, p = 0.0035), interval score (r = 0.4059, p = 0.0321), rhythmic score (r = 0.5733, p = 0.0014), meter score (r = 0.5061, p = 0.0060), and memory score (r = 0.4001, p = 0.0349). Conclusion: Individuals with CA exhibit cortical morphological changes in the right hemisphere. These findings may indicate that the neural basis of speech perception and memory impairments in individuals with CA is associated with abnormalities in the right pars triangularis gyrus and middle frontal gyrus, and that these cortical abnormalities may be a neural marker of CA.

Changes in sensorimotor regions of the cerebral cortex in congenital amusia: a case-control study

Perceiving pitch is a central function of the human auditory system; congenital amusia is a disorder of pitch perception. The underlying neural mechanisms of congenital amusia have been actively discussed. However, little attention has been paid to the changes in the motor rain within congenital amusia. In this case-control study, 17 participants with congenital amusia and 14 healthy controls underwent functional magnetic resonance imaging while resting with their eyes closed. A voxel-based degree centrality method was used to identify abnormal functional network centrality by comparing degree centrality values between the congenital amusia group and the healthy control group. We found decreased degree centrality values in the right primary sensorimotor areas in participants with congenital amusia relative to controls, indicating potentially decreased centrality of the corresponding brain regions in the auditory-sensory motor feedback network. We found a significant positive correlation between the degree centrality values and the Montreal Battery of Evaluation of Amusia scores. In conclusion, our study identified novel, hitherto undiscussed candidate brain regions that may partly contribute to or be modulated by congenital amusia. Our evidence supports the view that sensorimotor coupling plays an important role in memory and musical discrimination. The study was approved by the Ethics Committee of the Second Xiangya Hospital, Central South University, China (No. WDX20180101GZ01) on February 9, 2019.

Time-dependent discrimination advantages for harmonic sounds suggest efficient coding for memory

Perceptual systems have finite memory resources and must store incoming signals in compressed formats. To explore whether representations of a sound's pitch might derive from this need for compression, we compared discrimination of harmonic and inharmonic sounds across delays. In contrast to inharmonic spectra, harmonic spectra can be summarized, and thus compressed, using their fundamental frequency (f0). Participants heard two sounds and judged which was higher. Despite being comparable for sounds presented back-to-back, discrimination was better for harmonic than inharmonic stimuli when sounds were separated in time, implicating memory representations unique to harmonic sounds. Patterns of individual differences (correlations between thresholds in different conditions) indicated that listeners use different representations depending on the time delay between sounds, directly comparing the spectra of temporally adjacent sounds, but transitioning to comparing f0s across delays. The need to store sound in memory appears to determine reliance on f0-based pitch and may explain its importance in music, in which listeners must extract relationships between notes separated in time.

Reduced Sensitivity to Between-Category Information but Preserved Categorical Perception of Lexical Tones in Tone Language Speakers With Congenital Amusia

Previous studies have shown that for congenital amusics, long-term tone language experience cannot compensate for lexical tone processing difficulties. However, it is still unknown whether such difficulties are merely caused by domain-transferred insensitivity in lower-level acoustic processing and/or by higher-level phonological processing of linguistic pitch as well. The current P300 study links and extends previous studies by uncovering the neurophysiological mechanisms underpinning lexical tone perception difficulties in Mandarin-speaking amusics. Both the behavioral index (d′) and P300 amplitude showed reduced within-category as well as between-category sensitivity among the Mandarin-speaking amusics regardless of the linguistic status of the signal. The results suggest that acoustic pitch processing difficulties in amusics are manifested profoundly and further persist into the higher-level phonological processing that involves the neural processing of different lexical tone categories. Our findings indicate that long-term tone language experience may not compensate for the reduced acoustic pitch processing in tone language speakers with amusia but rather may extend to the neural processing of the phonological information of lexical tones during the attentive stage. However, from both the behavioral and neural evidence, the peakedness scores of the d′ and P300 amplitude were comparable between amusics and controls. It seems that the basic categorical perception (CP) pattern of native lexical tones is preserved in Mandarin-speaking amusics, indicating that they may have normal or near normal long-term categorical memory.

Altered functional connectivity during speech perception in congenital amusia

Individuals with congenital amusia have a lifelong history of unreliable pitch processing. Accordingly, they downweight pitch cues during speech perception and instead rely on other dimensions such as duration. We investigated the neural basis for this strategy. During fMRI, individuals with amusia (N = 15) and controls (N = 15) read sentences where a comma indicated a grammatical phrase boundary. They then heard two sentences spoken that differed only in pitch and/or duration cues and selected the best match for the written sentence. Prominent reductions in functional connectivity were detected in the amusia group between left prefrontal language-related regions and right hemisphere pitch-related regions, which reflected the between-group differences in cue weights in the same groups of listeners. Connectivity differences between these regions were not present during a control task. Our results indicate that the reliability of perceptual dimensions is linked with functional connectivity between frontal and perceptual regions and suggest a compensatory mechanism.

Music processing deficits in Landau-Kleffner syndrome: Four case studies in adulthood

Verbal-auditory agnosia and aphasia are the most prominent symptoms in Landau-Kleffner syndrome (LKS), a childhood epilepsy that can have sustained long-term effects on language processing. The present study provides the first objective investigation of music perception skills in four adult patients with a diagnosis of LKS during childhood, covering the spectrum of severity of the syndrome from mild to severe. Pitch discrimination, short-term memory for melodic, rhythmic and verbal information, as well as emotion recognition in music and speech prosody were assessed with listening tests, and subjective attitude to music with a questionnaire. We observed amusia in 3 out of 4 patients, with elevated pitch discrimination thresholds and poor short-term memory for melody and rhythm. The two patients with the most severe LKS had impairments in music and prosody emotion recognition, but normal perception of emotional intensity of music. Overall, performance in music processing tasks was proportional to the severity of the syndrome. Nonetheless, the four patients reported that they enjoyed music, felt musical emotions, and used music in their daily life. These new data support the hypothesis that, beyond verbal impairments, cerebral networks involved in sound processing and encoding are deeply altered by the epileptic activity in LKS, well after electrophysiological normalization.

Talker Processing in Mandarin-Speaking Congenital Amusics

Purpose The ability to recognize individuals from their vocalizations is an important trait of human beings. In the current study, we aimed to examine how congenital amusia, an inborn pitch-processing disorder, affects discrimination and identification of talkers' voices. Method Twenty Mandarin-speaking amusics and 20 controls were tested on talker discrimination and identification in four types of contexts that varied in the degree of language familiarity: Mandarin real words, Mandarin pseudowords, Arabic words, and reversed Mandarin speech. Results The language familiarity effect was more evident in the talker identification task than the discrimination task for both participant groups, and talker identification accuracy decreased as native phonological representations were removed from the stimuli. Importantly, amusics demonstrated degraded performance in both native speech conditions that contained phonological/linguistic information to facilitate talker identification and nonnative conditions where talker voice processing primarily relied on phonetics cues, including pitch. Moreover, the performance in talker processing can be predicted by the participants' musical ability and phonological memory capacity. Conclusions The results provided a first set of behavioral evidence that individuals with amusia are impaired in the ability of human voice identification. Meanwhile, it is found that amusia is not only a pitch disorder but is likely to affect the phonological processing of speech, in terms of using phonological information in native speech to analyze a talker's identity. The above findings expanded the understanding of the nature and scope of congenital amusia. Supplemental Material https://doi.org/10.23641/asha.12170379.

Face recognition and memory in congenital amusia

Congenital amusia, commonly known as tone deafness, is a lifelong impairment of music perception and production. It remains a question of debate whether the impairments in musical domain observed in congenital amusia are paralleled in other non-musical perceptual abilities. Using behavioral measures in two experiments, the current study explored face perception and memory in congenital amusics. Both congenital amusics and matched controls performed a face perception task (Experiment 1) and an old/novel object memory task (for both faces and houses, Experiment 2). The results showed that the congenital amusic group had significantly slower reaction times than that in matched control group when identifying whether two faces presented together were the same or different. For different face-pairs, the deficit was greater for upright faces compared with inverted faces. For object memory task, the congenital amusic group also showed worse memory performance than the control group. The results of the present study suggest that the impairment attributed to congenital amusia is not only limited to music, but also extends to visual perception and visual memory domain.

Short- and long-term memory for pitch and non-pitch contours: Insights from congenital amusia

Congenital amusia is a neurodevelopmental disorder characterized by deficits in music perception, including discriminating and remembering melodies and melodic contours. As non-amusic listeners can perceive contours in dimensions other than pitch, such as loudness and brightness, our present study investigated whether amusics' pitch contour deficits also extend to these other auditory dimensions. Amusic and control participants performed an identification task for ten familiar melodies and a short-term memory task requiring the discrimination of changes in the contour of novel four-tone melodies. For both tasks, melodic contour was defined by pitch, brightness, or loudness. Amusic participants showed some ability to extract contours in all three dimensions. For familiar melodies, amusic participants showed impairment in all conditions, perhaps reflecting the fact that the long-term memory representations of the familiar melodies were defined in pitch. In the contour discrimination task with novel melodies, amusic participants exhibited less impairment for loudness-based melodies than for pitch- or brightness-based melodies, suggesting some specificity of the deficit for spectral changes, if not for pitch alone. The results suggest pitch and brightness may not be processed by the same mechanisms as loudness, and that short-term memory for loudness contours may be spared to some degree in congenital amusia.

Decoding Task-Related Functional Brain Imaging Data to Identify Developmental Disorders: The Case of Congenital Amusia

Machine learning classification techniques are frequently applied to structural and resting-state fMRI data to identify brain-based biomarkers for developmental disorders. However, task-related fMRI has rarely been used as a diagnostic tool. Here, we used structural MRI, resting-state connectivity and task-based fMRI data to detect congenital amusia, a pitch-specific developmental disorder. All approaches discriminated amusics from controls in meaningful brain networks at similar levels of accuracy. Interestingly, the classifier outcome was specific to deficit-related neural circuits, as the group classification failed for fMRI data acquired during a verbal task for which amusics were unimpaired. Most importantly, classifier outputs of task-related fMRI data predicted individual behavioral performance on an independent pitch-based task, while this relationship was not observed for structural or resting-state data. These results suggest that task-related imaging data can potentially be used as a powerful diagnostic tool to identify developmental disorders as they allow for the prediction of symptom severity.

Abnormal neural responses to harmonic syntactic structures in congenital amusia

In music, harmonic syntactic structures are organized hierarchically through local and long-distance dependencies. This study investigated whether congenital amusia, a neurodevelopmental disorder of pitch perception, is associated with impaired processing of harmonic syntactic structures. For stimuli, we used harmonic sequences containing two phrases, where the first phrase ended with a half cadence and the second with an authentic cadence. In Experiment 1, we manipulated the ending chord of the authentic cadence to be either syntactically regular or irregular based on local dependencies. Sixteen amusics and 16 controls judged the expectedness of these chords while their EEG waveforms were recorded. In comparison to the regular endings, irregular endings elicited an ERAN, an N5, and a late positive component in controls but not in amusics, indicating that amusics were impaired in processing local syntactic dependencies. In Experiment 2, we manipulated the half cadence of the harmonic sequences to either adhere to or violate long-distance syntactic dependencies. In response to irregular harmonic sequences, an ERAN-like component and an N5 were elicited in controls but not in amusics, suggesting that amusics were impaired in processing long-distance syntactic dependencies. Furthermore, for controls, the neural processing of local and long-distance syntactic dependencies was correlated at the later integration stage but not at the early detection stage. These findings indicate that amusia is associated with impairment in the detection and integration of local and long-distance syntactic violations. The implications of these findings in terms of hierarchical music-syntactic processing are discussed.

Verbal and Musical Short-Term Memory: Evidence for Shared Serial Order Processes?

This study explored the validity of an integrative framework for verbal and musical short-term memory (STM). Following this framework, access to domain-specific long-term knowledge bases supports the processing of musical and verbal item information in STM, while domain-general ordering processes support the representation of serial order information in the two domains. We exposed participants to verbal and musical STM tasks assessing either item information, order information, or both item and order information. Using an interindividual differences approach, we observed that performance in item-based STM tasks was not strongly associated between musical and verbal domains. In contrast, strong between-domain associations were observed for STM tasks assessing processing of verbal order and musical rhythm information. These preliminary results are overall in agreement with an integrative approach of verbal and musical STM. At the same time, the results highlight the difficulty of measuring serial order processing in the musical STM domain in a direct and specific manner.

The Effects of Acoustic Variation on the Perception of Lexical Tone in Cantonese-Speaking Congenital Amusics

Purpose Congenital amusia is an inborn neurogenetic disorder of fine-grained pitch processing. This study attempted to pinpoint the impairment mechanism of speech processing in tonal language speakers with amusia. We designed a series of perception tasks aiming at selectively probing low-level pitch processing and relatively high-level phonological processing of lexical tones, with an aim to illuminate the deficiency mechanism underlying tone perception in amusia. Method Sixteen Cantonese-speaking amusics and 16 matched controls were tested on the effects of acoustic (talker/syllable) variations on the identification and discrimination of Cantonese tones in two conditions. In the low-variation condition, tones were always associated with the same talker or syllable; in the high-variation condition, tones were associated with either different talkers (with the syllable controlled) or different syllables (with the talker controlled). Results Largely similar results were obtained in talker and syllable variation conditions. Amusics exhibited overall poorer performance than controls in tone identification. Although amusics also demonstrated poorer performance in tone discrimination, the group difference was more obvious in low-variation conditions, where more acoustic constancy was provided. Besides, controls exhibited a greater increase in discrimination sensitivity from high- to low-variation conditions, implying a stronger benefit of acoustic constancy. Conclusions The findings suggested that amusics' lexical tone perception abilities, in terms of both low-level pitch processing and high-level phonological processing, as measured in low- and high-variation conditions, are impaired. Importantly, amusics were more impaired in taking advantage of low acoustic variation contexts and thus less efficiently sharpened their perception of tones when perceptual anchors in talker/syllable were provided, suggesting a possible "anchoring deficit" in congenital amusia. Supplemental Material https://doi.org/10.23641/asha.7616555.

Specialized neural dynamics for verbal and tonal memory: fMRI evidence in congenital amusia

Behavioral and neuropsychological studies have suggested that tonal and verbal short-term memory are supported by specialized neural networks. To date however, neuroimaging investigations have failed to confirm this hypothesis. In this study, we investigated the hypothesis of distinct neural resources for tonal and verbal memory by comparing typical nonmusician listeners to individuals with congenital amusia, who exhibit pitch memory impairments with preserved verbal memory. During fMRI, amusics and matched controls performed delayed-match-to-sample tasks with tones and words and perceptual control tasks with the same stimuli. For tonal maintenance, amusics showed decreased activity in the right auditory cortex, inferior frontal gyrus (IFG) and dorso-lateral-prefrontal cortex (DLPFC). Moreover, they exhibited reduced right-lateralized functional connectivity between the auditory cortex and the IFG during tonal encoding and between the IFG and the DLPFC during tonal maintenance. In contrasts, amusics showed no difference compared with the controls for verbal memory, with activation in the left IFG and left fronto-temporal connectivity. Critically, we observed a group-by-material interaction in right fronto-temporal regions: while amusics recruited these regions less strongly for tonal memory than verbal memory, control participants showed the reversed pattern (tonal > verbal). By benefitting from the rare condition of amusia, our findings suggest specialized cortical systems for tonal and verbal short-term memory in the human brain.

Context integration deficit in tone perception in Cantonese speakers with congenital amusia

Congenital amusia is a neuro-developmental disorder of pitch processing. This study investigated how this deficit affects lexical tone perception with and without context. Twenty-three Cantonese-speaking amusics and 23 controls were tested on the identification of high-variation tone stimuli in isolation vs in a carrier sentence. The controls generally achieved a higher accuracy with context than in isolation, suggesting that speech context facilitated tone identification. In contrast, amusics generally failed to benefit from the context, despite some variation among different tones. These findings provide insights into the underlying deficits of amusia, revealing a context integration deficit of tone perception in amusia.

Binaural localization of musical pitch using interaural time differences in congenital amusia

Naturally occurring sounds are routinely periodic. The ability to phase-lock to such periodicity facilitates pitch perception and interaural time differences (ITDs) determination in binaural localization. We examined whether deficient pitch processing in individuals with congenital amusia (tone deafness) is accompanied by impaired ability to lateralize musical pitch at auditory periphery and memorize the location of pitch at the working memory level. If common mechanisms subserve processing of temporal-fine-structure based pitch and ITDs, then deficient processing of one feature should impair performance on the other. Thus, we measured ITD discrimination thresholds using an adaptive-tracking procedure for lateralizing musical tone pairs separated by different semitone intervals. Amusic individuals exhibited normal ITD thresholds comparable to those of matched controls, which were not affected by concurrent pitch changes. For working memory tasks, the amusic group performed significantly worse than matched controls in probed pitch recall, irrespective of the complexity level of concurrent variations along the ITD dimension of the melodic sequence. Interestingly, despite normal peripheral ITD thresholds, amusic individuals performed worse than controls in recalling probed locations of tones within a sequence of musical notes originating from different ITD-simulated locations. Findings suggest that individuals with congenital amusia are unimpaired in temporal fine-structure encoding to determine the location of musical pitch based on binaural ITD information at the auditory periphery. However, working memory for a sequence of sounds' ITD-dependent spatial location is here shown to be impaired and dissociated from the pitch feature of sounds at the working memory level.

Musical and verbal short-term memory: insights from neurodevelopmental and neurological disorders

Auditory short-term memory (STM) is a fundamental ability to make sense of auditory information as it unfolds over time. Whether separate STM systems exist for different types of auditory information (music and speech, in particular) is a matter of debate. The present paper reviews studies that have investigated both musical and verbal STM in healthy individuals and in participants with neurodevelopmental and neurological disorders. Overall, the results are in favor of only partly shared networks for musical and verbal STM. Evidence for a distinction in STM for the two materials stems from (1) behavioral studies in healthy participants, in particular from the comparison between nonmusicians and musicians; (2) behavioral studies in congenital amusia, where a selective pitch STM deficit is observed; and (3) studies in brain-damaged patients with cases of double dissociation. In this review we highlight the need for future studies comparing STM for the same perceptual dimension (e.g., pitch) in different materials (e.g., music and speech), as well as for studies aiming at a more insightful characterization of shared and distinct mechanisms for speech and music in the different components of STM, namely encoding, retention, and retrieval.

Driving working memory with frequency-tuned noninvasive brain stimulation

Frequency-tuned noninvasive brain stimulation is a recent approach in cognitive neuroscience that involves matching the frequency of transcranially applied electromagnetic fields to that of specific oscillatory components of the underlying neurophysiology. The objective of this method is to modulate ongoing/intrinsic brain oscillations, which correspond to rhythmic fluctuations of neural excitability, to causally change behavior. We review the impact of frequency-tuned noninvasive brain stimulation on the research field of human working memory. We argue that this is a powerful method to probe and understand the mechanisms of memory functions, targeting specifically task-related oscillatory dynamics, neuronal representations, and brain networks. We report the main behavioral and neurophysiological outcomes published to date, in particular, how functionally relevant oscillatory signatures in signal power and interregional connectivity yield causal changes of working memory abilities. We also present recent developments of the technique that aim to modulate cross-frequency coupling in polyrhythmic neural activity. Overall, the method has led to significant advances in our understanding of the mechanisms of systems neuroscience, and the role of brain oscillations in cognition and behavior. We also emphasize the translational impact of noninvasive brain stimulation techniques in the development of therapeutic approaches.

Factors affecting pitch discrimination performance in a cohort of extensively phenotyped healthy volunteers

Despite efforts to characterize the different aspects of musical abilities in humans, many elements of this complex area remain unknown. Musical abilities are known to be associated with factors like intelligence, training, and sex, but a comprehensive evaluation of the simultaneous impact of multiple factors has not yet been performed. Here, we assessed 918 healthy volunteers for pitch discrimination abilities—their ability to tell two tones close in pitch apart. We identified the minimal threshold that the participants could detect, and we found that better performance was associated with higher intelligence, East Asian ancestry, male sex, younger age, formal music training–especially before age 6–and English as the native language. All these factors remained significant when controlling for the others, with general intelligence, musical training, and male sex having the biggest impacts. We also performed a small GWAS and gene-based collapsing analysis, identifying no significant associations. Future genetic studies of musical abilities should involve large sample sizes and an unbiased genome-wide approach, with the factors highlighted here included as important covariates.

Revisiting the Neural Basis of Acquired Amusia: Lesion Patterns and Structural Changes Underlying Amusia Recovery

Although, acquired amusia is a common deficit following stroke, relatively little is still known about its precise neural basis, let alone to its recovery. Recently, we performed a voxel-based lesion-symptom mapping (VLSM) and morphometry (VBM) study which revealed a right lateralized lesion pattern, and longitudinal gray matter volume (GMV) and white matter volume (WMV) changes that were specifically associated with acquired amusia after stroke. In the present study, using a larger sample of stroke patients (N = 90), we aimed to replicate and extend the previous structural findings as well as to determine the lesion patterns and volumetric changes associated with amusia recovery. Structural MRIs were acquired at acute and 6-month post-stroke stages. Music perception was behaviorally assessed at acute and 3-month post-stroke stages using the Scale and Rhythm subtests of the Montreal Battery of Evaluation of Amusia (MBEA). Using these scores, the patients were classified as non-amusic, recovered amusic, and non-recovered amusic. The results of the acute stage VLSM analyses and the longitudinal VBM analyses converged to show that more severe and persistent (non-recovered) amusia was associated with an extensive pattern of lesions and GMV/WMV decrease in right temporal, frontal, parietal, striatal, and limbic areas. In contrast, less severe and transient (recovered) amusia was linked to lesions specifically in left inferior frontal gyrus as well as to a GMV decrease in right parietal areas. Separate continuous analyses of MBEA Scale and Rhythm scores showed extensively overlapping lesion pattern in right temporal, frontal, and subcortical structures as well as in the right insula. Interestingly, the recovered pitch amusia was related to smaller GMV decreases in the temporoparietal junction whereas the recovered rhythm amusia was associated to smaller GMV decreases in the inferior temporal pole. Overall, the results provide a more comprehensive picture of the lesions and longitudinal structural changes associated with different recovery trajectories of acquired amusia.

Pitch contour impairment in congenital amusia: New insights from the Self-paced Audio-visual Contour Task (SACT)

Individuals with congenital amusia usually exhibit impairments in melodic contour processing when asked to compare pairs of melodies that may or may not be identical to one another. However, it is unclear whether the impairment observed in contour processing is caused by an impairment of pitch discrimination, or is a consequence of poor pitch memory. To help resolve this ambiguity, we designed a novel Self-paced Audio-visual Contour Task (SACT) that evaluates sensitivity to contour while placing minimal burden on memory. In this task, participants control the pace of an auditory contour that is simultaneously accompanied by a visual contour, and they are asked to judge whether the two contours are congruent or incongruent. In Experiment 1, melodic contours varying in pitch were presented with a series of dots that varied in spatial height. Amusics exhibited reduced sensitivity to audio-visual congruency in comparison to control participants. To exclude the possibility that the impairment arises from a general deficit in cross-modal mapping, Experiment 2 examined sensitivity to cross-modal mapping for two other auditory dimensions: timbral brightness and loudness. Amusics and controls were significantly more sensitive to large than small contour changes, and to changes in loudness than changes in timbre. However, there were no group differences in cross-modal mapping, suggesting that individuals with congenital amusia can comprehend spatial representations of acoustic information. Taken together, the findings indicate that pitch contour processing in congenital amusia remains impaired even when pitch memory is relatively unburdened.

Auditory deficits in amusia extend beyond poor pitch perception

Congenital amusia is a music perception disorder believed to reflect a deficit in fine-grained pitch perception and/or short-term or working memory for pitch. Because most measures of pitch perception include memory and segmentation components, it has been difficult to determine the true extent of pitch processing deficits in amusia. It is also unclear whether pitch deficits persist at frequencies beyond the range of musical pitch. To address these questions, experiments were conducted with amusics and matched controls, manipulating both the stimuli and the task demands. First, we assessed pitch discrimination at low (500Hz and 2000Hz) and high (8000Hz) frequencies using a three-interval forced-choice task. Amusics exhibited deficits even at the highest frequency, which lies beyond the existence region of musical pitch. Next, we assessed the extent to which frequency coding deficits persist in one- and two-interval frequency-modulation (FM) and amplitude-modulation (AM) detection tasks at 500Hz at slow (fm=4Hz) and fast (fm=20Hz) modulation rates. Amusics still exhibited deficits in one-interval FM detection tasks that should not involve memory or segmentation. Surprisingly, amusics were also impaired on AM detection, which should not involve pitch processing. Finally, direct comparisons between the detection of continuous and discrete FM demonstrated that amusics suffer deficits in both coding and segmenting pitch information. Our results reveal auditory deficits in amusia extending beyond pitch perception that are subtle when controlling for memory and segmentation, and are likely exacerbated in more complex contexts such as musical listening.

Neural bases of congenital amusia in tonal language speakers

Congenital amusia is a lifelong neurodevelopmental disorder of fine-grained pitch processing. In this fMRI study, we examined the neural bases of congenial amusia in speakers of a tonal language - Cantonese. Previous studies on non-tonal language speakers suggest that the neural deficits of congenital amusia lie in the music-selective neural circuitry in the right inferior frontal gyrus (IFG). However, it is unclear whether this finding can generalize to congenital amusics in tonal languages. Tonal language experience has been reported to shape the neural processing of pitch, which raises the question of how tonal language experience affects the neural bases of congenital amusia. To investigate this question, we examined the neural circuitries sub-serving the processing of relative pitch interval in pitch-matched Cantonese level tone and musical stimuli in 11 Cantonese-speaking amusics and 11 musically intact controls. Cantonese-speaking amusics exhibited abnormal brain activities in a widely distributed neural network during the processing of lexical tone and musical stimuli. Whereas the controls exhibited significant activation in the right superior temporal gyrus (STG) in the lexical tone condition and in the cerebellum regardless of the lexical tone and music conditions, no activation was found in the amusics in those regions, which likely reflects a dysfunctional neural mechanism of relative pitch processing in the amusics. Furthermore, the amusics showed abnormally strong activation of the right middle frontal gyrus and precuneus when the pitch stimuli were repeated, which presumably reflect deficits of attending to repeated pitch stimuli or encoding them into working memory. No significant group difference was found in the right IFG in either the whole-brain analysis or region-of-interest analysis. These findings imply that the neural deficits in tonal language speakers might differ from those in non-tonal language speakers, and overlap partly with the neural circuitries of lexical tone processing (e.g. right STG).

Music Perception in Dementia

Despite much recent interest in music and dementia, music perception has not been widely studied across dementia syndromes using an information processing approach. Here we addressed this issue in a cohort of 30 patients representing major dementia syndromes of typical Alzheimer's disease (AD, n = 16), logopenic aphasia (LPA, an Alzheimer variant syndrome; n = 5), and progressive nonfluent aphasia (PNFA; n = 9) in relation to 19 healthy age-matched individuals. We designed a novel neuropsychological battery to assess perception of musical patterns in the dimensions of pitch and temporal information (requiring detection of notes that deviated from the established pattern based on local or global sequence features) and musical scene analysis (requiring detection of a familiar tune within polyphonic harmony). Performance on these tests was referenced to generic auditory (timbral) deviance detection and recognition of familiar tunes and adjusted for general auditory working memory performance. Relative to healthy controls, patients with AD and LPA had group-level deficits of global pitch (melody contour) processing while patients with PNFA as a group had deficits of local (interval) as well as global pitch processing. There was substantial individual variation within syndromic groups. Taking working memory performance into account, no specific deficits of musical temporal processing, timbre processing, musical scene analysis, or tune recognition were identified. The findings suggest that particular aspects of music perception such as pitch pattern analysis may open a window on the processing of information streams in major dementia syndromes. The potential selectivity of musical deficits for particular dementia syndromes and particular dimensions of processing warrants further systematic investigation.

Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains

Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.

An investigation of spatial representation of pitch in individuals with congenital amusia

Spatial representation of pitch plays a central role in auditory processing. However, it is unknown whether impaired auditory processing is associated with impaired pitch-space mapping. Experiment 1 examined spatial representation of pitch in individuals with congenital amusia using a stimulus-response compatibility (SRC) task. For amusic and non-amusic participants, pitch classification was faster and more accurate when correct responses involved a physical action that was spatially congruent with the pitch height of the stimulus than when it was incongruent. However, this spatial representation of pitch was not as stable in amusic individuals, revealed by slower response times when compared with control individuals. One explanation is that the SRC effect in amusics reflects a linguistic association, requiring additional time to link pitch height and spatial location. To test this possibility, Experiment 2 employed a colour-classification task. Participants judged colour while ignoring a concurrent pitch by pressing one of two response keys positioned vertically to be congruent or incongruent with the pitch. The association between pitch and space was found in both groups, with comparable response times in the two groups, suggesting that amusic individuals are only slower to respond to tasks involving explicit judgments of pitch.