Amusia results in abnormal brain activity following inappropriate intonation during speech comprehension

Mandarin-Speaking Amusics' Online Recognition of Tone and Intonation

PURPOSE

Congenital amusia is a neurogenetic disorder of musical pitch processing. Its linguistic consequences have been examined separately for speech intonations and lexical tones. However, in a tonal language such as Chinese, the processing of intonations and lexical tones interacts with each other during online speech perception. Whether and how the musical pitch disorder might affect linguistic pitch processing during online speech perception remains unknown.

METHOD

We investigated this question with intonation (question vs. statement) and lexical tone (rising Tone 2 vs. falling Tone 4) identification tasks using the same set of sentences, comparing behavioral and event-related potential measurements between Mandarin-speaking amusics and matched controls. We specifically focused on the amusics without behavioral lexical tone deficits (the majority, i.e., pure amusics).

RESULTS

Results showed that, despite relative to normal performance when tested in word lexical tone test, pure amusics demonstrated inferior recognition than controls during sentence tone and intonation identification. Compared to controls, pure amusics had larger N400 amplitudes in question stimuli during tone task and smaller P600 amplitudes in intonation task.

CONCLUSION

These data indicate that musical pitch disorder affects both tone and intonation processing during sentence processing even for pure amusics, whose lexical tone processing was intact when tested with words.

The Perception of Lexical Tone and Intonation in Whispered Speech by Mandarin-Speaking Congenital Amusics

PURPOSE

A fundamental feature of human speech is variation, including the manner of phonation, as exemplified in the case of whispered speech. In this study, we employed whispered speech to examine an unresolved issue about congenital amusia, a neurodevelopmental disorder of musical pitch processing, which also affects speech pitch processing such as lexical tone and intonation perception. The controversy concerns whether amusia is a pitch-processing disorder or can affect speech processing beyond pitch.

METHOD

We examined lexical tone and intonation recognition in 19 Mandarin-speaking amusics and 19 matched controls in phonated and whispered speech, where fundamental frequency (f _o) information is either present or absent.

RESULTS

The results revealed that the performance of congenital amusics was inferior to that of controls in lexical tone identification in both phonated and whispered speech. These impairments were also detected in identifying intonation (statements/questions) in phonated and whispered modes. Across the experiments, regression models revealed that f _o and non-f _o (duration, intensity, and formant frequency) acoustic cues predicted tone and intonation recognition in phonated speech, whereas non-f _o cues predicted tone and intonation recognition in whispered speech. There were significant differences between amusics and controls in the use of both f _o and non-f _o cues.

CONCLUSION

The results provided the first evidence that the impairments of amusics in lexical tone and intonation identification prevail into whispered speech and support the hypothesis that the deficits of amusia extend beyond pitch processing.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.19302275.

Emotion processing in congenital amusia: the deficits do not generalize to written emotion words

Congenital amusia is a lifelong impairment in musical ability. Individuals with amusia are found to show reduced sensitivity to emotion recognition in speech prosody and silent facial expressions, implying a possible cross-modal emotion-processing deficit. However, it is not clear whether the observed deficits are primarily confined to socio-emotional contexts, where visual cues (facial expression) often co-occur with auditory cues (emotion prosody) to express intended emotions, or extend to linguistic emotion processing. In order to better understand the underlying deficiency mechanism of emotion processing in individuals with amusia, we examined whether reduced sensitivity to emotional processing extends to the recognition of emotion category and valence of written words in individuals with amusia. Twenty Cantonese speakers with amusia and 17 controls were tested in three experiments: (1) emotion prosody rating, in which participants rated how much each spoken sentence was expressed in each of the four emotions on 7-point rating scales; (2) written word emotion recognition, in which participants recognized the emotion of written emotion words; and (3) written word valence judgment, in which participants judged the valence of written words. Results showed that participants with amusia preformed significantly less accurately than controls in emotion prosody recognition; in contrast, the two groups showed no significant difference in accuracy rates in both written word tasks (emotion recognition and valence judgment). The results indicate that the impairment of individuals with amusia in emotion processing may not generalize to linguistic emotion processing in written words, implying that the emotion deficit is likely to be restricted to socio-emotional contexts in individuals with 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.

Dichotic Perception of Lexical Tones in Cantonese-Speaking Congenital Amusics

Congenital amusia is an inborn neurogenetic disorder of musical pitch processing, which also induces impairment in lexical tone perception. However, it has not been examined before how the brain specialization of lexical tone perception is affected in amusics. The current study adopted the dichotic listening paradigm to examine this issue, testing 18 Cantonese-speaking amusics and 18 matched controls on pitch/lexical tone identification and discrimination in three conditions: non-speech tone, low syllable variation, and high syllable variation. For typical listeners, the discrimination accuracy was higher with shorter RT in the left ear regardless of the stimulus types, suggesting a left-ear advantage in discrimination. When the demand of phonological processing increased, as in the identification task, shorter RT was still obtained in the left ear, however, the identification accuracy revealed a bilateral pattern. Taken together, the results of the identification task revealed a reduced LEA or a shift from the right hemisphere to bilateral processing in identification. Amusics exhibited overall poorer performance in both identification and discrimination tasks, indicating that pitch/lexical tone processing in dichotic listening settings was impaired, but there was no evidence that amusics showed different ear preference from controls. These findings provided temporary evidence that although amusics demonstrate deficient neural mechanisms of pitch/lexical tone processing, their ear preference patterns might not be affected. These results broadened the understanding of the nature of pitch and lexical tone processing deficiencies in amusia.

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.

Vowel and Tone Identification for Mandarin Congenital Amusics: Effects of Vowel Type and Semantic Content

Purpose This study aimed to explore the effects of Mandarin congenital amusia with or without lexical tone deficit (i.e., tone agnosia and pure amusia) on Mandarin vowel and tone identification in different types of vowels (e.g., monophthong, diphthongs, and triphthongs) embedded in consonant-vowel contexts with and without semantic content. Method Thirteen pure amusics (i.e., amusics with normal lexical processing), 5 tone agnosics (i.e., with lexical tone deficit), and 12 controls were screened with Montreal Battery of Evaluation of Amusia and lexical tone tests (Nan et al., 2010; Peretz et al., 2003). Vowel-plus-tone identification tasks with the factors of vowel type and syllables with and without semantic content (e.g., real and nonsense words) were examined among the 3 groups, and identification scores were calculated in 3 formats: vowel-plus-tone identification, vowel identification, and tone identification. Results Tone agnosics showed significantly poorer performances on identifications of vowel, tone, and vowel plus tone across monophthongs, diphthongs, and triphthongs in both real and nonsense words compared to pure amusics and controls. Their deficits were similar across the 3 types of vowels, while the deficit on vowel-plus-tone identification was more severe in nonsense words than in real words. On the other hand, pure amusics performed similarly with controls across all these conditions. Conclusions Tone agnosia might affect both musical pitch and phonological processing, resulting in deficits in lexical tone and vowel perception. On the contrary, pure amusics's effect is primarily on musical pitch perception but not on lexical tone or phonemic deficit. Vowel type did not affect speech deficits for tone agnosics, while they relied more on semantic content as a compensation.

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.

The Montreal Protocol for Identification of Amusia

The Montreal Battery for the Evaluation of Amusia (MBEA; Peretz, Champod, & Hyde Annals of the New York Academy of Sciences, 999, 58-75, 2003) is an empirically grounded quantitative tool that is widely used to identify individuals with congenital amusia. The use of such a standardized measure ensures that the individuals tested will conform to a specific neuropsychological profile, allowing for comparisons across studies and research groups. Recently, a number of researchers have published credible critiques of the usefulness of the MBEA as a diagnostic tool for amusia. Here we argue that the MBEA and its online counterpart, the AMUSIA tests (Peretz et al. Music Perception, 25, 331-343, 2008), should be considered steps in a screening process for amusia, rather than standalone diagnostic tools. The goal of this article is to present, in detailed and easily replicable format, the full protocol through which congenital amusics should be identified. In providing information that has often gone unreported in published articles, we aim to clarify the strengths and limitations of the MBEA and to make recommendations for its continued use by the research community as part of the Montreal Protocol for Identification of Amusia.

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.

Normal pre-attentive and impaired attentive processing of lexical tones in Cantonese-speaking congenital amusics

The neural underpinnings of congenital amusia, an innate neurogenetic disorder of musical pitch processing, are not well understood. Previous studies suggest that amusia primarily impairs attentive processing (P300) of small pitch deviations in music, leaving pre-attentive pitch processing (mismatch negativity or MMN) more or less intact. However, it remains unknown whether the same neuro-dynamic mechanism of deficiency underlies pitch processing in speech, where amusics also often show impairment behaviorally. The current study examined how lexical tones are processed in pre-attentive (MMN) and attentive (P300) conditions in 24 Cantonese-speaking amusics and 24 matched controls. At the pre-attentive level, Cantonese-speaking amusics exhibited normal MMN responses to lexical tone changes, even for tone pairs with small pitch differences (mid level vs. low level tone; high rising vs. low rising tone). However, at the attentive level, amusics exhibited reduced P3a amplitude for all tone pairs, and further reduced P3b amplitude for tone pairs with small pitch differences. These results suggest that the amusic brain detects tone changes normally pre-attentively, but shows impairment in consciously detecting the same tone differences. Consistent with previous findings in nonspeech pitch processing, this finding provides support for a domain-general neuro-dynamic mechanism of deficient attentive pitch processing in amusia.

Deficits of congenital amusia beyond pitch: Evidence from impaired categorical perception of vowels in Cantonese-speaking congenital amusics

Congenital amusia is a lifelong disorder of fine-grained pitch processing in music and speech. However, it remains unclear whether amusia is a pitch-specific deficit, or whether it affects frequency/spectral processing more broadly, such as the perception of formant frequency in vowels, apart from pitch. In this study, in order to illuminate the scope of the deficits, we compared the performance of 15 Cantonese-speaking amusics and 15 matched controls on the categorical perception of sound continua in four stimulus contexts: lexical tone, pure tone, vowel, and voice onset time (VOT). Whereas lexical tone, pure tone and vowel continua rely on frequency/spectral processing, the VOT continuum depends on duration/temporal processing. We found that the amusic participants performed similarly to controls in all stimulus contexts in the identification, in terms of the across-category boundary location and boundary width. However, the amusic participants performed systematically worse than controls in discriminating stimuli in those three contexts that depended on frequency/spectral processing (lexical tone, pure tone and vowel), whereas they performed normally when discriminating duration differences (VOT). These findings suggest that the deficit of amusia is probably not pitch specific, but affects frequency/spectral processing more broadly. Furthermore, there appeared to be differences in the impairment of frequency/spectral discrimination in speech and nonspeech contexts. The amusic participants exhibited less benefit in between-category discriminations than controls in speech contexts (lexical tone and vowel), suggesting reduced categorical perception; on the other hand, they performed inferiorly compared to controls across the board regardless of between- and within-category discriminations in nonspeech contexts (pure tone), suggesting impaired general auditory processing. These differences imply that the frequency/spectral-processing deficit might be manifested differentially in speech and nonspeech contexts in amusics—it is manifested as a deficit of higher-level phonological processing in speech sounds, and as a deficit of lower-level auditory processing in nonspeech sounds.

Processing of emotional faces in congenital amusia: An emotional music priming event-related potential study

Congenital amusia is characterized by lifelong impairments in music perception and processing. It is unclear whether pitch detection deficits impact amusic individuals' perception of musical emotion. In the current work, 19 amusics and 21 healthy controls were subjected to electroencephalography (EEG) while being exposed to music excerpts and emotional faces. We assessed each individual's ability to discriminate positive- and negative-valenced emotional faces and analyzed electrophysiological indices, in the form of event-related potentials (ERPs) recorded at 32 sites, following exposure to emotionally positive or negative music excerpts. We observed smaller N2 amplitudes in response to facial expressions in the amusia group than in the control group, suggesting that amusics were less affected by the musical stimuli. The late-positive component (LPC) in amusics was similar to that in controls. Our results suggest that the neurocognitive deficit characteristic of congenital amusia is fundamentally an impairment in musical information processing rather than an impairment in emotional processing.

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Emotional recognition in individuals with amusia was examined by electroencephalography.

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N2 amplitudes generated in response to facial expressions were less affected by musical stimuli in the amusia group than in the control group.

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The late-positive component in amusic participants was similar to that in controls.

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Neurocognitively, amusia appears to be a musical information processing impairment rather than an impairment in emotional processing.

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).

Pitch perception and production in congenital amusia: Evidence from Cantonese speakers

This study investigated pitch perception and production in speech and music in individuals with congenital amusia (a disorder of musical pitch processing) who are native speakers of Cantonese, a tone language with a highly complex tonal system. Sixteen Cantonese-speaking congenital amusics and 16 controls performed a set of lexical tone perception, production, singing, and psychophysical pitch threshold tasks. Their tone production accuracy and singing proficiency were subsequently judged by independent listeners, and subjected to acoustic analyses. Relative to controls, amusics showed impaired discrimination of lexical tones in both speech and non-speech conditions. They also received lower ratings for singing proficiency, producing larger pitch interval deviations and making more pitch interval errors compared to controls. Demonstrating higher pitch direction identification thresholds than controls for both speech syllables and piano tones, amusics nevertheless produced native lexical tones with comparable pitch trajectories and intelligibility as controls. Significant correlations were found between pitch threshold and lexical tone perception, music perception and production, but not between lexical tone perception and production for amusics. These findings provide further evidence that congenital amusia is a domain-general language-independent pitch-processing deficit that is associated with severely impaired music perception and production, mildly impaired speech perception, and largely intact speech production.

Examining pitch and numerical magnitude processing in congenital amusia: A quasi-experimental pilot study

INTRODUCTION

Congenital amusia is a developmental disorder associated with deficits in pitch height discrimination or in integrating pitch sequences into melodies. This quasi-experimental pilot study investigated whether there is an association between pitch and numerical processing deficits in congenital amusia. Since pitch height discrimination is considered a form of magnitude processing, we investigated whether individuals with amusia present an impairment in numerical magnitude processing, which would reflect damage to a generalized magnitude system. Alternatively, we investigated whether the numerical processing deficit would reflect a disconnection between nonsymbolic and symbolic number representations.

METHOD

This study was conducted with 11 adult individuals with congenital amusia and a control comparison group of 6 typically developing individuals. Participants performed nonsymbolic and symbolic magnitude comparisons and number line tasks. Results were available from previous testing using the Montreal Battery of Evaluation of Amusia (MBEA) and a pitch change detection task (PCD).

RESULTS

Compared to the controls, individuals with amusia exhibited no significant differences in their performance on both the number line and the nonsymbolic magnitude tasks. Nevertheless, they showed significantly worse performance on the symbolic magnitude task. Moreover, individuals with congenital amusia, who presented worse performance in the Meter subtest, also presented less precise nonsymbolic numerical representation.

CONCLUSIONS

The relationship between meter and nonsymbolic numerical discrimination could indicate a general ratio processing deficit. The finding of preserved nonsymbolic numerical magnitude discrimination and mental number line representations, with impaired symbolic number processing, in individuals with congenital amusia indicates that (a) pitch height and numerical magnitude processing may not share common neural representations, and (b) in addition to pitch processing, individuals with amusia may present a deficit in accessing nonsymbolic numerical representations from symbolic representations. The symbolic access deficit could reflect a widespread impairment in the establishment of cortico-cortical connections between association areas.

Perception of Melodic Contour and Intonation in Autism Spectrum Disorder: Evidence From Mandarin Speakers

Tone language experience benefits pitch processing in music and speech for typically developing individuals. No known studies have examined pitch processing in individuals with autism who speak a tone language. This study investigated discrimination and identification of melodic contour and speech intonation in a group of Mandarin-speaking individuals with high-functioning autism. Individuals with autism showed superior melodic contour identification but comparable contour discrimination relative to controls. In contrast, these individuals performed worse than controls on both discrimination and identification of speech intonation. These findings provide the first evidence for differential pitch processing in music and speech in tone language speakers with autism, suggesting that tone language experience may not compensate for speech intonation perception deficits in individuals with autism.

Prosodic Structure as a Parallel to Musical Structure

What structural properties do language and music share? Although early speculation identified a wide variety of possibilities, the literature has largely focused on the parallels between musical structure and syntactic structure. Here, we argue that parallels between musical structure and prosodic structure deserve more attention. We review the evidence for a link between musical and prosodic structure and find it to be strong. In fact, certain elements of prosodic structure may provide a parsimonious comparison with musical structure without sacrificing empirical findings related to the parallels between language and music. We then develop several predictions related to such a hypothesis.

Sound frequency affects speech emotion perception: results from congenital amusia

Congenital amusics, or "tone-deaf" individuals, show difficulty in perceiving and producing small pitch differences. While amusia has marked effects on music perception, its impact on speech perception is less clear. Here we test the hypothesis that individual differences in pitch perception affect judgment of emotion in speech, by applying low-pass filters to spoken statements of emotional speech. A norming study was first conducted on Mechanical Turk to ensure that the intended emotions from the Macquarie Battery for Evaluation of Prosody were reliably identifiable by US English speakers. The most reliably identified emotional speech samples were used in Experiment 1, in which subjects performed a psychophysical pitch discrimination task, and an emotion identification task under low-pass and unfiltered speech conditions. Results showed a significant correlation between pitch-discrimination threshold and emotion identification accuracy for low-pass filtered speech, with amusics (defined here as those with a pitch discrimination threshold >16 Hz) performing worse than controls. This relationship with pitch discrimination was not seen in unfiltered speech conditions. Given the dissociation between low-pass filtered and unfiltered speech conditions, we inferred that amusics may be compensating for poorer pitch perception by using speech cues that are filtered out in this manipulation. To assess this potential compensation, Experiment 2 was conducted using high-pass filtered speech samples intended to isolate non-pitch cues. No significant correlation was found between pitch discrimination and emotion identification accuracy for high-pass filtered speech. Results from these experiments suggest an influence of low frequency information in identifying emotional content of speech.

Revising the diagnosis of congenital amusia with the Montreal Battery of Evaluation of Amusia

This article presents a critical survey of the prevalent usage of the Montreal Battery of Evaluation of Amusia (MBEA; Peretz et al., 2003) to assess congenital amusia, a neuro-developmental disorder that has been claimed to be present in 4% of the population (Kalmus and Fry, 1980). It reviews and discusses the current usage of the MBEA in relation to cut-off scores, number of used subtests, manner of testing, and employed statistics, as these vary in the literature. Furthermore, data are presented from a large-scale experiment with 228 German undergraduate students who were assessed with the MBEA and a comprehensive questionnaire. This experiment tested the difference between scores that were obtained in a web-based study (at participants’ homes) and those obtained under laboratory conditions with a computerized version of the MBEA. In addition to traditional statistical procedures, the data were evaluated using Signal Detection Theory (SDT; Green and Swets, 1966), taking into consideration the individual’s ability to discriminate and their response bias. Results show that using SDT for scoring instead of proportion correct offers a bias-free and normally distributed measure of discrimination ability. It is also demonstrated that a diagnosis based on an average score leads to cases of misdiagnosis. The prevalence of congenital amusia is shown to depend highly on the statistical criterion that is applied as cut-off score and on the number of subtests that is considered for the diagnosis. In addition, three different subtypes of amusics were found in our sample. Lastly, significant differences between the web-based and the laboratory group were found, giving rise to questions about the validity of web-based experimentation.

Brainstem encoding of speech and musical stimuli in congenital amusia: evidence from Cantonese speakers

Congenital amusia is a neurodevelopmental disorder of musical processing that also impacts subtle aspects of speech processing. It remains debated at what stage(s) of auditory processing deficits in amusia arise. In this study, we investigated whether amusia originates from impaired subcortical encoding of speech (in quiet and noise) and musical sounds in the brainstem. Fourteen Cantonese-speaking amusics and 14 matched controls passively listened to six Cantonese lexical tones in quiet, two Cantonese tones in noise (signal-to-noise ratios at 0 and 20 dB), and two cello tones in quiet while their frequency-following responses (FFRs) to these tones were recorded. All participants also completed a behavioral lexical tone identification task. The results indicated normal brainstem encoding of pitch in speech (in quiet and noise) and musical stimuli in amusics relative to controls, as measured by FFR pitch strength, pitch error, and stimulus-to-response correlation. There was also no group difference in neural conduction time or FFR amplitudes. Both groups demonstrated better FFRs to speech (in quiet and noise) than to musical stimuli. However, a significant group difference was observed for tone identification, with amusics showing significantly lower accuracy than controls. Analysis of the tone confusion matrices suggested that amusics were more likely than controls to confuse between tones that shared similar acoustic features. Interestingly, this deficit in lexical tone identification was not coupled with brainstem abnormality for either speech or musical stimuli. Together, our results suggest that the amusic brainstem is not functioning abnormally, although higher-order linguistic pitch processing is impaired in amusia. This finding has significant implications for theories of central auditory processing, requiring further investigations into how different stages of auditory processing interact in the human brain.

Congenital amusia: a cognitive disorder limited to resolved harmonics and with no peripheral basis

Pitch plays a fundamental role in audition, from speech and music perception to auditory scene analysis. Congenital amusia is a neurogenetic disorder that appears to affect primarily pitch and melody perception. Pitch is normally conveyed by the spectro-temporal fine structure of low harmonics, but some pitch information is available in the temporal envelope produced by the interactions of higher harmonics. Using 10 amusic subjects and 10 matched controls, we tested the hypothesis that amusics suffer exclusively from impaired processing of spectro-temporal fine structure. We also tested whether the inability of amusics to process acoustic temporal fine structure extends beyond pitch by measuring sensitivity to interaural time differences, which also rely on temporal fine structure. Further tests were carried out on basic intensity and spectral resolution. As expected, pitch perception based on spectro-temporal fine structure was impaired in amusics; however, no significant deficits were observed in amusics' ability to perceive the pitch conveyed via temporal-envelope cues. Sensitivity to interaural time differences was also not significantly different between the amusic and control groups, ruling out deficits in the peripheral coding of temporal fine structure. Finally, no significant differences in intensity or spectral resolution were found between the amusic and control groups. The results demonstrate a pitch-specific deficit in fine spectro-temporal information processing in amusia that seems unrelated to temporal or spectral coding in the auditory periphery. These results are consistent with the view that there are distinct mechanisms dedicated to processing resolved and unresolved harmonics in the general population, the former being altered in congenital amusia while the latter is spared.

Difficulties with pitch discrimination influences pitch memory performance: evidence from congenital amusia

Music processing is influenced by pitch perception and memory. Additionally these features interact, with pitch memory performance decreasing as the perceived distance between two pitches decreases. This study examined whether or not the difficulty of pitch discrimination influences pitch retention by testing individuals with congenital amusia. Pitch discrimination difficulty was equated by determining an individual’s threshold with a two down one up staircase procedure and using this to create conditions where two pitches (the standard and the comparison tones) differed by 1x, 2x, and 3x the threshold setting. For comparison with the literature a condition that employed a constant pitch difference of four semitones was also included. The results showed that pitch memory performance improved as the discrimination between the standard and the comparison tones was made easier for both amusic and control groups, and more importantly, that amusics did not show any pitch retention deficits when the discrimination difficulty was equated. In contrast, consistent with previous literature, amusics performed worse than controls when the physical pitch distance was held constant at four semitones. This impaired performance has been interpreted as evidence for pitch memory impairment in the past. However, employing a constant pitch distance always makes the difference closer to the discrimination threshold for the amusic group than for the control group. Therefore, reduced performance in this condition may simply reflect differences in the perceptual difficulty of the discrimination. The findings indicate the importance of equating the discrimination difficulty when investigating memory.

Speech and music shape the listening brain: evidence for shared domain-general mechanisms

Are there bi-directional influences between speech perception and music perception? An answer to this question is essential for understanding the extent to which the speech and music that we hear are processed by domain-general auditory processes and/or by distinct neural auditory mechanisms. This review summarizes a large body of behavioral and neuroscientific findings which suggest that the musical experience of trained musicians does modulate speech processing, and a sparser set of data, largely on pitch processing, which suggest in addition that linguistic experience, in particular learning a tone language, modulates music processing. Although research has focused mostly on music on speech effects, we argue that both directions of influence need to be studied, and conclude that the picture which thus emerges is one of mutual interaction across domains. In particular, it is not simply that experience with spoken language has some effects on music perception, and vice versa, but that because of shared domain-general subcortical and cortical networks, experiences in both domains influence behavior in both domains.

Reduced sensitivity to emotional prosody in congenital amusia rekindles the musical protolanguage hypothesis

A number of evolutionary theories assume that music and language have a common origin as an emotional protolanguage that remains evident in overlapping functions and shared neural circuitry. The most basic prediction of this hypothesis is that sensitivity to emotion in speech prosody derives from the capacity to process music. We examined sensitivity to emotion in speech prosody in a sample of individuals with congenital amusia, a neurodevelopmental disorder characterized by deficits in processing acoustic and structural attributes of music. Twelve individuals with congenital amusia and 12 matched control participants judged the emotional expressions of 96 spoken phrases. Phrases were semantically neutral but prosodic cues (tone of voice) communicated each of six emotional states: happy, tender, afraid, irritated, sad, and no emotion. Congenitally amusic individuals were significantly worse than matched controls at decoding emotional prosody, with decoding rates for some emotions up to 20% lower than that of matched controls. They also reported difficulty understanding emotional prosody in their daily lives, suggesting some awareness of this deficit. The findings support speculations that music and language share mechanisms that trigger emotional responses to acoustic attributes, as predicted by theories that propose a common evolutionary link between these domains.