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

Abstract

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.

The effect of syllable variation on the perception of lexical tones in Cantonese-speaking amusics

“…These findings are in line with previous studies in which categorical perception of native tones is found to be impaired in tonal language speakers [18], [19], [20]. For instance, Zhang et al (2017) [20] found that Cantonese-speaking amusics exhibited less benefit in between-category discriminations than controls in speech contexts, suggesting reduced categorical perception of tones.…”

“…One line of research showed that the deficit of amusia primarily lies in the domain-general auditory pitch processing [13]- [15]. Another line of research confirmed that the deficit already prevails to higher-level phonological processing, affecting categorical perception of lexical tones in native tonal language speakers [19]- [21]. However, due to the scarcity of studies directly comparing lower-level pitch processing and higher-level phonological processing, the mechanism underlying the deficient tone perception performance in amusia is not yet well understood.…”

“…While the aforementioned studies consistently pointed out that the impoverished lexical tone perception in tonal and nontonal language speakers with amusia is due to the domaingeneral pitch deficit, some studies have suggested that highlevel phonological processing of lexical tones might be impaired in native tonal language speakers with amusia. For instance, several studies provided evidence that categorical perception of native tones in tonal language speakers with amusia is impaired [19]- [21]. In contrast to the controls, Mandarin-speaking amusics showed no benefit for betweencategory tone discriminations, suggesting the absence or impairment of categorical perception of lexical tones, though one study found subgroup differences among Mandarinspeaking amusics [18], [19].…”

“…In contrast to the controls, Mandarin-speaking amusics showed no benefit for betweencategory tone discriminations, suggesting the absence or impairment of categorical perception of lexical tones, though one study found subgroup differences among Mandarinspeaking amusics [18], [19]. In another study, Zhang et al found that Cantonese-speaking amusics 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 regardless of between-and within-category discriminations in nonspeech contexts (pure tone), suggesting impaired auditory pitch processing [21].…”

Pre-attentive processing of neutral and emotional sounds in congenital amusia

“…Even if congenital amusia was first described to be music-specific (Ayotte et al, 2002;Peretz et al, 2003), recent evidence suggest that the pitch deficit in congenital amusia could also extend to speech material, even though to a lesser extent (Nguyen et al, 2009;Tillmann, Burnham, et al, 2011;Tillmann, Rusconi, et al, 2011;Zhang et al, 2017). In relation with the present study, congenital amusia is not only a music perception deficit but also a language processing deficit, in particular for non-verbal auditory cues such as emotional prosody (Lolli et al, 2015;Nguyen et al, 2009;Patel et al, 2008;Pralus et al, 2019;Thompson et al, 2012).…”