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Speech-specific categorical perception deficit in autism: An Event-Related Potential study of lexical tone processing in Mandarin- speaking children

Authors:
  • China Rehabilitation Research Center for children with autism

Abstract and Figures

Recent studies reveal that tonal language speakers with autism have enhanced neural sensitivity to pitch changes in nonspeech stimuli but not to lexical tone contrasts in their native language. The present ERP study investigated whether the distinct pitch processing pattern for speech and nonspeech stimuli in autism was due to a speech-specific deficit in categorical perception of lexical tones. A passive oddball paradigm was adopted to examine two groups (16 in the autism group and 15 in the control group) of Chinese children's Mismatch Responses (MMRs) to equivalent pitch deviations representing within-category and between-category differences in speech and nonspeech contexts. To further examine group-level differences in the MMRs to categorical perception of speech/nonspeech stimuli or lack thereof, neural oscillatory activities at the single trial level were further calculated with the inter-trial phase coherence (ITPC) measure for the theta and beta frequency bands. The MMR and ITPC data from the children with autism showed evidence for lack of categorical perception in the lexical tone condition. In view of the important role of lexical tones in acquiring a tonal language, the results point to the necessity of early intervention for the individuals with autism who show such a speech-specific categorical perception deficit.
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Scientific RepoRts | 7:43254 | DOI: 10.1038/srep43254
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Speech-specic categorical
perception decit in autism: An
Event-Related Potential study of
lexical tone processing in Mandarin-
speaking children
Xiaoyue Wang1, Suiping Wang1,2,3, Yuebo Fan4, Dan Huang4 & Yang Zhang5,6
Recent studies reveal that tonal language speakers with autism have enhanced neural sensitivity
to pitch changes in nonspeech stimuli but not to lexical tone contrasts in their native language. The
present ERP study investigated whether the distinct pitch processing pattern for speech and nonspeech
stimuli in autism was due to a speech-specic decit in categorical perception of lexical tones. A passive
oddball paradigm was adopted to examine two groups (16 in the autism group and 15 in the control
group) of Chinese children’s Mismatch Responses (MMRs) to equivalent pitch deviations representing
within-category and between-category dierences in speech and nonspeech contexts. To further
examine group-level dierences in the MMRs to categorical perception of speech/nonspeech stimuli or
lack thereof, neural oscillatory activities at the single trial level were further calculated with the inter-
trial phase coherence (ITPC) measure for the theta and beta frequency bands. The MMR and ITPC data
from the children with autism showed evidence for lack of categorical perception in the lexical tone
condition. In view of the important role of lexical tones in acquiring a tonal language, the results point
to the necessity of early intervention for the individuals with autism who show such a speech-specic
categorical perception decit.
Autism spectrum disorder (ASD) is a neurodevelopmental disorder that aects communication and social inter-
action1. Many individuals with ASD show abnormal linguistic proles in terms of speech perception and pro-
duction2, which may be partially due to a central deciency in processing complex sounds, especially speech3–7.
One area of research that has intrigued experimental and theoretical investigators studying atypical auditory
processing in ASD concerns pitch perception in relation to music and language.
Enhanced pitch percption has been reported in adults and children with autism in contrast to age-matched
adults and typically developing (TD) controls in English and Finnish speaking populations8–10. A recent com-
parative analysis revealed markedly dierent developmental trajectories of pitch discrimination in people with
and without ASD11. While the TD individuals showed increasing sensitivity to pitch dierences with age that was
correlated with receptive vocabulary growth, the ASD group had enhanced pitch discrimination in childhood
which remained stable in development with no correlation with receptive vocabulary scores. In behavioral tasks,
both children and adults with autism outperformed controls in discriminating pure tones as well as pitch pat-
terns in both meaningful spoken sentences andmeaningless vocal sounds8,12. Studies using the neurophysiological
measure known as the mismatch negativity (MMN) response found a complementary pattern of results. Children
1School of Psychology, South China Normal University, Guangzhou, 510631, China. 2Center for Studies of
Psychological Application, South China Normal University, 510631, China. 3Guangdong Provincial Key Laboratory
of Mental Health and Cognitive Science, South China Normal University, Guangzhou, 510631, China. 4Guangzhou
Rehabilitation and Research Center for Children with Autism, Guangzhou Cana School, Guangzhou, 510540, China.
5Department of Speech-Language-Hearing Science, University of Minnesota, Minneapolis, MN, 55455, USA. 6Center
for Neurobehavioral Development, University of Minnesota, Minneapolis, MN, 55455, USA. Correspondence and
requests for materials should be addressed to S.W. (email: wangsuiping@m.scnu.edu.cn) or Y.Z. (email: zhanglab@
umn.edu)
Received: 13 September 2016
Accepted: 20 January 2017
Published: 22 February 2017
OPEN
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with autism showed shortened MMN latencies with enlarged amplitudes for pitch contrasts in pure tones9,13. e
MMN reects pre-attentive automatic detection of acoustic stimulus change independent of attention, which is
correlated with perceptual auditory discrimination14. Several studies have shown that MMN amplitude is corre-
lated strongly with behavioural parameters such as reaction time and discrimination threshold15. Consistent with
these results, functional magnetic resonance imaging (fMRI) studies report greater activity in the supramarginal
gyrus related to pitch processing in the ASD group in comparison with typically developing controls16–18, indicat-
ing enhanced pitch perception in ASD at the group level.
Unlike English or Finnish, lexical tones in tonal languages such as Chinese and ai are dened as a supraseg-
mental pitch contrast feature that serves a phonemic role and is central to the comprehension and production
of speech. Although Chinese infants are able to discriminate lexical tones at 8–10 months of age or even ear-
lier19,20, this ability does not appear to be fully developed at the age of three21. As more than 70% of the world’s
languages are tonal languages22, it is important to ask the question: Does enhanced pitch perception in ASD have
a positive eect on learning a tonal language? While studies on norml adult musicians unanimously indicate a
positive transfer eect of their extraordinary pitch processing skills to lexical tone learning23, two recent studies
on Chinese children with autism have provided both positive evidence for the existence of enhanced pitch per-
ception for the nonspeech stimuli and negative evidence regarding the transfer eect from nonspeech to speech.
In a behavioral study24, Mandarin-speaking children with autism showed better identication and similar dis-
crimination of melodic contours in comparison with TD controls. However, both identication and discrimina-
tion scores were signicantly worse in the ASD group when the task switched to speech intonation judgment. A
similar pattern was found in an ERP study including both ASD and age-matched TD control groups25. In this ERP
study, Mandarin-speaking children with autism showed enhanced MMN response for detecting a pitch change in
pure tones and nonspeech complex stimuli but reduced MMN to lexical tone contrasts in both spoken words and
nonwords. us in tonal language speakers with autism, both studies demonstrate domain specicity of enhanced
pitch perception for nonspeech stimuli combined with a negative impact on pitch processing in speech.
In our previous study, Yu, et al.25 discussed the possibility that impaired pitch perception for lexical tones
in Chinese children with autism might be due to an underlying phonological processing decit resulting from
enhanced pitch processing for within-category variations in each of the four lexical tone categories in Mandarin
Chinese. Due to dierences in speech between the numerous individual speakers in their immediate environ-
ment, Mandarin-speaking children experience a wide variability in pitch information associated with lexical
tones within each lexical tone category. In order to establish stable mental representations of the phonological cat-
egories for the lexical tones, the listener needs to develop enhanced sensitivity to between-category contrasts and
ignore subtle within-category variations, which is known as categorical perception (CP) for speech sounds26,27. In
categorical perception of lexical tones, the continuously variable pitch information is perceptually mapped onto
discrete tonal categories, which has been demonstrated in normal Chinese adults (including musicians) as well
as TD children23,27–29. If the Yu, et al.21 hypothesis is correct, we would expect to see a CP decit for lexical tones
in Chinese children with autism. In other words, Chinese children with autism would not demonstrate enhanced
lexical tone discrimination for between-category stimulus pairs relative to within-category stimulus pairs when
pitch dierences are physically equated. is hypothesis is in line with previous autism studies showing that indi-
viduals with autism show impairment in discriminating higher-level categorical information such as ellipses and
faces30–32, but intact discrimination of pure tones and colors8,33. However, our previous report stopped short of
providing direct empirical evidence to support this theory25.
e present ERP study was specically designed to address the potential speech-specic CP decit in Chinese
children with autism. In particular, we hypothesized that Mandarin-speaking children with autism and age-
and IQ-matched TD controls would show dierent Mismatch Response (MMR) patterns for within-category
and between-category dierences across a lexical tone continuum. To further test domain specicity, we used a
harmonic nonspeech version of the continuum as a rened acoustic control27. e harmonic nonspeech stim-
uli preserved the same pitch contours of the lexical tone stimuli. A passive listening oddball paradigm was
adopted in our study as it has been widely used in developmental research on auditory and linguistic processing
in autism4,25,34–36. Because the experimental protocol does not require focused attention or any overt response,
the neurophysiological approach can serve as an objective tool to measure auditory discrimination and speech
processing37,38. We were specically interested in comparing the MMRs to within- and between- category pitch
dierences in both speech and nonspeech contexts in the two subject groups.
In addition to the conventional ERP latency and amplitude measures, we applied time-frequency analysis to
examine trial-by-trial consistency of neural oscillations in selected frequency bands of interest that could drive
the MMR activity for speech and nonspeech discrimination. e cortical oscillations are thought to reect the
net excitatory and inhibitory neuronal activities that mediate sensory and cognitive events39–45. Time-frequency
analysis on a trial-by-trial basis allows a more detailed examination of what oscillatory activities contribute
to or do not contribute to the observed ERP responses that are averaged across trials. Unlike the ERPs, the
frequency-specic oscillatory activities are not necessarily time- or phase-locked to an event46. us trial-by-trial
time-frequency analysis may reveal additional information about how various EEG frequencies may reect mul-
tiple neural processes co-occurring and interacting in the service of integrative and dynamically adaptive infor-
mation processing47. e phase-synchronized oscillations survive cross-trial averaging and are evident in the
averaged ERPs42,43. Certain frequency bands have been linked to dierent neurocognitive process48,49. In par-
ticular, studies have revealed the contribution of the theta frequency band (4–8 Hz) to the neuronal generation of
the MMN in frontal and temporal areas50–54. e theta activity has also been found to be associated with several
other cognitive functions including memory encoding, retrieval, and maintenance55,56. Activity in the beta fre-
quency band (15–30) is thought to play a prominent role in perceptual binding and network interactions across
modalities49,57,58. In language studies, beta activity was found to be associated with auditory/lexical memory59 as
well as vowel representation in an MMN paradigm60, and the theta frequency band was found to be important for
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processing phonemic contrasts61. Little is known about the eects of phonemic contrast on theta/beta oscillations
during categorical perception of lexical tones and whether there would be between-subject-group dierences in
the theta and beta activities for the speech and nonspeech conditions.
For the present study, we hypothesized that there would be speech-specic abnormalities in the MMR compo-
nent and theta/beta frequency bands for processing the within- vs. across-category distinctions in the ASD group,
which may reect problems in speech categorization at the pre-attentive level. As previous neurophysiological
studies have also shown atypical attention to pure tones and speech sounds in children with autism62–64, the P3a
component indexing involuntary attention switching in novelty detection65 was also examined to assess whether
and how the P3a responses for the speech and nonspeech conditions diered in the two groups of children. With
regard to the time-frequency analysis, we hypothesized that the dierent MMN patterns for within- and across-
category lexical tone discrimination in the Mandarin-speaking children with and without autism would be asso-
ciated with distinct beta/theta phase-locking patterns across the individual trials. In particular, we predicted
that Chinese children with autism would not demonstrate enhanced beta/theta activities for the across-category
stimulus pairs relative to within-category stimulus pairs when pitch dierences are physically equated.
Results
Amplitude and latency data for MMR. For the MMR amplitudes in the speech condition (Table1
and Figs1 and 2), there was a signicant interaction between deviant type and subject group (F(1, 29) = 4.244,
p = 0.048, partial η
2 = 0.128), suggesting that neural discriminatory sensitivity to the within- and between- cate-
gory lexical tone dierences depended on the subject group factor. Further two-tailed tests of simple main eects
showed that the amplitude of the response to the between-category deviant was greater than that to the within-cat-
egory deviant in the control group (t(14) = 3.379, p = 0.004), but not in the ASD group (t(15) = 0.302, p = 0.767).
Moreover, no group eect was found in either the within-category contrast (F(1, 29) = 1.911, p = 0.190, partia l
η
2 = 0.128) or the between-category contrast (F(1, 29) = 0.023, p = 0.882, partial η
2 = 0.002). e MMR latencies
for the speech condition showed no interaction between group and deviant type (F(1, 29) = 0.020, p = 0.889, par-
tial η
2 = 0.000). ere was also no main eect of group (F(1, 29) = 1.488, p = 0.232, partial η
2 = 0.049) or deviant
type (F(1, 29) = 0.542, p = 0.468, partial η
2 = 0.018).
For MMR amplitude in the nonspeech harmonic condition (Table1 and Figs1 and 2), there was no inter-
action between deviant type and subject group (F(1, 29) = 0.172, p = 0.681, partial η
2 = 0.006). e main eect
Condition
Amplitude (μV) (SD)Latency (ms) (SD)
Autism TD Control Autism TD Control
Speech
within 2.94 (1.55) 2.28 (0.48) 160 (35) 154 (35)
between 2.86 (1.56) 2.88 (0.82) 152 (37) 143 (30)
Harmonic
within 2.83 (0.97) 2.35 (0.76) 146 (23) 162 (36)
between 3.41 (1.07) 2.76 (0.90) 161 (25) 167 (31)
Table 1. MMR Mean Amplitude and Latency Data in Children with Autism and TD Controls.
Figure 1. Deviant-minus-standard dierence waves for the speech and harmonic conditions.
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of deviant type was signicant (F(1, 29) = 10.21, p = 0.003, partial η
2 = 0.260), indicating that the response to
between-category deviants was greater than response to within-category deviants in both groups. e main eect
of group was signicant (F(1, 29) = 4.977, p = 0.034, partial η
2 = 0.146), indicating that ASD group evoked greater
responses than control group. MMR latency in the harmonic condition (Fig.2) showed no interaction between
group and deviant type (F(1, 29) = 0.033, p = 0.857, partia l η
2 = 0.001), as well as no main eect of group (F(1,
29) = 0.589, p = 0.448, partial η
2 = 0.019) or deviant type (F(1, 29) = 1.226, p = 0.277, partial η
2 = 0.038).
Amplitude and latency data for P3a. For the P3a amplitudes in the speech condition, the dierence
in the P3a component between deviants and standards was signicant for both types of deviants in both sub-
ject groups (tASD-within(15) = 9.185, p < 0.001; tASD-between(15) = 6.99, p < 0.001; tTD-within(14) = 15.873, p < 0.001;
tTD-between(14) = 18.65, p < 0.001). However, there was no main eect of group (F(1, 29) = 2.295, p = 0.141, partial
η
2 = 0.073) or deviant type (F(1, 29) = 1.055, p = 0.313, partial η
2 = 0.035), and there was also no interaction
between group and deviant type (F(1, 29) = 0.642, p = 0.430, partial η
2 = 0.022). e results for the harmonic con-
dition were similar to the speech condition (Fig.1). While the P3a eects were signicant (tASD-within(15) = 11.14,
p < 0.001; tASD-between(15) = 6.99, p < 0.001; tTD-within(14) = 13.32, p < 0.001; tTD-between(14) = 18.65, p < 0.001).
ere were no main eect of group (F(1, 29) = 0.825, p = 0.371, partial η
2 = 0.028), deviant type (F(1, 29) = 0.016,
p = 0.902, partial η
2 = 0.001), or interaction between group and deviant type (F(1, 29) = 0.491, p = 0.489, partial
η
2 = 0.017).
Inter-trial phase coherence ndings. Table2 shows the trial-by-trial phase locking values for the theta
and beta bands in response to the within/between-contrast stimuli in both speech condition and harmonic con-
dition. e ITPC plots were shown in Fig.3.
For the theta band in the speech condition (Table2 and Figs3 and 4), there was no interaction between devi-
ant type and group (F(1, 29) = 1.071, p = 0.309, partial η
2 = 0.036). e main eect of deviant type was signicant
(F(1, 29) = 7.551, p = 0.010, partial η
2 = 0.207), indicating that trial-to-trial phase locking for between-category
MMRs was consistently greater than that for within-category deviants. e main eect of group was signicant
(F(1, 29) = 6.166, p = .019, partial η
2 = 0.175), indicating that ASD group had higher ITPC values than control
group. Further planned t-tests showed that the ITPC values of the theta band for the between-category MMRs
was greater than those for the within-category MMRs in the control group (t(14) = 3.231, p = 0.006), but there
was no such eect in the ASD group (t(15) = 1.074, p = 0.300). e theta band in the harmonic nonspeech
condition (Table2 and Figs3 and 4) showed no interaction between group and deviant type (F(1, 29) = 0.047,
p = 0.830, partial η
2 = 0.002). ere was also no main eect of deviant type (F(1, 29) = 1.917, p = 0.177, partia l
η
2 = 0.062). Like the speech condition, the main eect of group was signicant (F(1, 29) = 62.412, p < 0.001,
Figure 2. MMR average amplitude (a) and latency (b) values (vertical bars represent standard error,
**P < 0.01). For amplitude values there was an interaction between group and deviant type in the speech
condition, and the main eect of deviant type was signicant in the harmonic condition. No interactions or
main eects were signicant for latency values.
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partial η
2 = 0.683), indicating an overall higher trial-by-trial phase-locking of mismatch response in the ASD
group than in the control group.
For the beta band in the speech condition (Table2 and Figs3 and 4), there was no interaction between devi-
ant type and group (F(1, 29) = 0.378, p = 0.543, partial η
2 = 0.023). ere was also no main eect of deviant
type (F(1, 29) = 0.669, p = 0.420, partial η
2 = 0.023). Consistent with the theta activity, the main eect of group
was signicant (F(1, 29) = 38.099, p < 0.001, p arti al η
2 = 0.568), indicating that ASD group had greater ITPCs
than control group. e beta band in the harmonic nonspeech condition (Table2 and Figs3 and 4) showed no
interaction between group and deviant type (F(1, 29) = 0.097, p = 0.758, partial η
2 = 0.003), as well as no main
eect of deviant type (F(1, 29) = 0.149, p = 0.702, partial η
2 = 0.005). Consistent with the speech condition, we
observed signicant group dierences with greater ITPC values in the ASD group than in the control group
(F(1, 29) = 42.146, p < 0.001, partial η
2 = 0.592).
Discussion
MMRs show speech-specic decit in categorical perception in autism. e present ERP study
employed well-controlled synthesized speech and nonspeech stimuli with equivalent acoustic dierences for
within- and across- category contrasts to investigate whether Mandarin-speaking Chinese children with autism
would show a speech-specic decit in categorical perception of lexical tones. In the speech condition, the TD
control group showed typical enhanced neural sensitivity to the between-category deviant relative to the with-
in-category deviant whereas the ASD group had equivalent MMRs for the two types of deviants. e MMR pat-
terns for the lexical tone in the TD control group were consistent with previous reports on categorical perception
of lexical tones in normal adults and children27,28, indicating that phonological representations of lexical tones
in 10-year-old typically developing Chinese children are similar to those in healthy adults28. e lack of dieren-
tiation in MMRs for within- and between- category contrasts in the autism group conrmed our hypothesized
decit in categorical perception of lexical tones. More importantly, our data revealed that one possible cause for
the CP decit was enhanced within-category MMRs in the ASD group in comparison with the TD control group.
is pattern of greater within-category perceptual sensitivity was predicted on the basis of studies nding that
discrimination of pure tones and more complex musical stimuli are enhanced in autism12,66, and further suggests
that children with ASD may be more sensitive than controls to the acoustic (as opposed to linguistic) stimulus
features at the pre-attentive level. According to the Weak Central Coherence (WCC) theory67 and the Enhanced
Perceptual Functioning (EPF) theory68,69, individuals with ASD show a local processing bias in the auditory mode
(including pitch sensitivity) combined with an over-developed neural network for low-level perceptual analysis.
e lack of CP for lexical tones in the Chinese children with autism implies that, unlike the TD controls,
individuals with autism have not fully established the phonemic boundaries in the acoustic space of fundamental
frequency variations and thus have not acquired full phonological knowledge of the dierent lexical tone catego-
ries. Given the fundamental role of lexical tones in a tonal language such as Mandarin Chinese, this phonological
processing decit at the age of ten is alarming in that it could be a substantial impediment to proper language
development and ecient speech communication. Assuming that MMRs reect speech discriminatory sensitivity
that is preemptively subordinate to the development of language-specic phonemic representations in the rst
year of life4,38, the lack of CP for lexical tones in autism may also be accounted for by top-down mechanisms70.
For instance, Chinese children with autism may not have developed the prototypical representations of the lexical
tone categories to the extent that there is no perceptual magnet eect that would reduce within-category discrim-
ination around the prototypical sound in comparison with a non-prototypical sound71.
In order to determine whether the CP decit reects abnormality in acoustic or phonological processing, the
nonspeech condition using harmonic stimuli was designed. In the nonspeech condition, both subject groups
showed similar enhanced neural sensitivity for the between-category contrast. us there does not appear to be
a CP decit in the nonspeech domain for Chinese children with autism. In other words, the CP decit for lexical
tones in autism is more likely a phonological processing problem rather than an acoustic processing decit25,35,72.
In cross-language studies of normal listeners, it has been shown that speech perception can be selectively com-
promised by language learning experience without a parallel eect in auditory processing of nonspeech stimuli
that share the essential spectral features of the speech sounds73. For example, the normal adult Japanese speakers
who had diculty in identifying and discriminating the third-formant (F3) dierences (rising vs. falling) in the
English /l-r/contrast did not show any CP decit when the exact F3 information was extracted from the syllables
and tested74. But unlike this cross-language example in which the Japanese language does not have the target /l-r/
contrast, the underlying mechanisms for the problem in the acquisition of phonological knowledge can be quite
Condition
eta (SD)Beta (SD)
Autism
TD
Control Autism
TD
Control
Speech
within 0.42 (0.06) 0.36 (0.05) 0.26 (0.03) 0.20 (0.02)
between 0.44 (0.07) 0.41 (0.06) 0.26 (0.04) 0.21 (0.03)
Harmonic
within 0.49 (0.07) 0.36 (0.05) 0.27 (0.04) 0.20 (0.03)
between 0.52 (0.09) 0.38 (0.07) 0.28 (0.04) 0.20 (0.04)
Table 2. eta and Beta ITPC Value in Children with Autism and TD Controls.
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dierent in autism. We suspect that the early learning experience for lexical tones in the Chinese children with
autism may be compromised by their social decits that could interfere with normalizing and representing the
multiple co-existing dimensions of linguistic and paralinguistic (such as speaker age, gender, and aective mood)
information in the speech signal, leading to the relatively poor development of the phonological categories for the
lexical tones and consequently the CP decits for the same pitch information in the speech context.
In normal subjects, categorical perception of pure tones and complex tone stimuli (e.g., tones with rising vs.
falling fundamental frequency) has been previously reported8,27. e similar results between the nonspeech and
speech conditions for the TD controls could be explained by the shared processing mechanisms for pitch per-
ception –the language learning experience exerts a strong inuence on the perception of acoustic features such
as pitch perception for lexical tone categorization, and this inuence could be extended to processing nonspeech
sounds27,75,76. Such shared mechanisms appear to be constrained by domain-specic enhanced pitch processing
for non-speech sounds in Chinese children with autism.
Figure 3. Neural oscillatory response to speech and nonspeech sounds.
Figure 4. eta/Beta ITPC values (vertical bars represent standard error, **P < 0.01).
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Despite the signicant MMR amplitude dierences between the two groups of subjects in the speech con-
dition, our MMR latencies for the speech condition showed no main eect of group as well as no interaction
between group and deviant type. ese results are consistent with previous studies on children with autism12,37
and cross-language studies on categorical perception of lexical tones in normal adult listeners27–29. As the lexical
tones unfold over the entire syllable, it is possible that the MMR latency may be quite variable across individual
listeners and thus become less sensitive to the between-group dierences than expected for ASD vs. TD compar-
ison or native vs. nonnative comparison.
Taking the MMR results from the two conditions together, we have found ERP evidence that Chinese
children with autism have impaired pitch perception for lexical tones at the group level, which appears to be
speech-specic and can be attributed to an underlying phonological processing decit with impaired phonolog-
ical representations of lexical tones accompanied by enhanced pitch processing for within-category variations in
an acoustic mode.
P3a component shows no dierent patterns for small acoustic deviations in autism. For both
types of stimuli, there was no signicant dierence in the P3a response between the two groups of subjects. Our
results are similar to Xi, et al.27 but dier from Yu, et al.25. e P3a typically reects attentional orientation or shi
towards the stimulus change, which becomes prominent when the dierence is large77. In the Yu, et al.25 stu dy,
the lexical tone contrasts were based on naturally produced words or nonsense syllables, which could be com-
pared to the endpoints of our 10-inteval continuum. In our study, similar to Čeponienė, et al.62 and Xi, et al.27,
the physical dierence between the standard and deviants was much smaller. Moreover, the standard sound for
our double oddball paradigm was Stimulus #5, which was a nonprototypical speech sound close to the phonetic
boundary region in our continuum. We suspect that these experimental factors may have minimized dierences
in arousal and attentional orienting resulting from acoustic dierences or other factors such as semantic or social
signicance. As a result, we did not observe signicant P3a dierences between the two subject groups in any of
the comparisons.
Theta band activity reects the presence or absence of categorical perception of lexical tones
in the two subject groups. e time-frequency analysis revealed a new aspect of cortical activities respon-
sible for the speech-specic CP decit in autism. Our results show that theta band activity modulates categorical
perception of lexical tones in control group rather than in ASD group. Moreover, the time-frequency analysis
results revealed cortical network activation patterns that varied across conditions. Consistent with the MMR
results, there was a signicant ITPC dierence in theta activity for the MMRs of within- vs. across-category
contrasts in the control group. Our data further showed equivalent ITPC values in theta band for the two types
of deviant stimulus in speech stimuli in ASD group. For harmonic speech stimuli, both ASD group and control
group showed similar phase locking across trials in theta band for the across-and within-category contrasts.
Although both conditions involved the acoustic presentation of Tone 2 or Tone 4, sensitivity of CP in theta activ-
ity (with enhanced across-category discrimination relative to within-category discrimination) was only observed
in the speech condition for the TD group. We did not nd signicant beta activity dierences between the two
subject groups in any of the comparisons except for the overall group eect with the ASD group showing higher
ITPC values than the TD group regardless of stimulus condition, which might contribute to the enhanced sen-
sitivity to pitch information in ASD as previously reported in the literature. us, enhanced across-category
discrimination for lexical tones in the TD group appears to be associated with stronger phasing locking across
trials in the theta activity (4–8 Hz), which corresponds to oscillatory periods in the range of 125–250 ms in line
with the duration of our stimuli. By contrast, phase locking across trials in the theta band does not appear to
contribute to the within- and across- category distinction in the ASD group. We suspect that learning experience
as well as pathological conditions could fundamentally alter the underlying neural network with dedicated and
frequency-specic oscillatory activities for the ecient processing of the critical acoustic and phonological cues
in service of the native language.
Our results showing the lack of CP for lexical tones in theta activity in the Chinese children with autism are
consistent with previous ndings that reveal the importance of the theta frequency band in the pre-attentive neu-
ral processing of auditory deviant stimuli42,51–54,78. Our results dier from Bidelman79 and Scharinger, et al.60, in
which the beta band activity was correlated with categorical perception of vowel sounds. In the Bidelman79 stu dy,
an identication task were used for the /a/-/u/ vowel continuum. In Scharinger, et al.60 study,sounds from /æ/-/I/
and /ε /-/I/ continuua were used in an oddball paradigm. us both of these studies involved detection of steady
formant dierences at the segmental level in normal adult listeners. However, the speech stimuli in our study
involved time-varying frequency glides (rising vs. falling) beyond the segmental level. We suspect that the neural
oscillation patterns may be aected by phonetic features and acoustic features such as duration of the critical
acoustic cue for eliciting the mismatch response.
Taking the ERP waveform results and neural oscillation results from the two conditions together, we found
that spectral information in speech and nonspeech stimuli may be processed independently rather than executed
as a shared process depending on subject characteristics and stimulus properties. e overall patterns of our
ndings are consistent with other studies on categorical perception in autism. For example, CP of complex visual
stimuli such as ellipses and faces was found to be impaired in autism30–32 while the discrimination of pure tones
and color was normal8,33.
Limitations and Future Directions. e present CP study incorporated two important improvements
in experimental design from our previous study25. First, our CP study employed subject groups that were
age-matched and IQ-matched. Second, our CP study used carefully-controlled synthetic stimuli for the within-
vs. across- category contrasts in both the speech and nonspeech conditions. While we found the rst evidence for
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impaired CP for lexical tones in Chinese children with autism, our study is not without its limitations. One out-
standing limitation is the lack of behavioral data to verify the CP decit at the individual subject level. is lack of
behavioral data appears to be quite common in MMN studies on children with autism due to practical challenges
in implementing behavioral protocols for synthetic speech stimuli25. However, it is important to acknowledge
that a pre-attentive mismatch response and a behavioral judgment that requires focused attention and an overt
response do not necessarily reect the same sensory and cognitive processes. More importantly, as the MMN
measure has been highlighted as a potential clinical biomarker80, it is necessary to conduct further studies to test
the robustness of the relationship between brain and behavioral measures at the individual subject level.
Our results conrmed the hypothesis from the previous Yu, et al.25 study that lexical tone processing impair-
ment in Chinese children with autism has its root cause as a phonological decit in categorical perception. Given
the fundamental role of lexical tones for learning and using a tonal language, it is necessary to consider the
development of feasible training methods for early intervention. Before implementing such an intervention, it
will be important to identify the age at which a clear CP decit for lexical tone emerges in tonal language speaking
children with autism and have a better understanding of how pervasive this problem is. In this regard, future
research could benet from a longitudinal design with a much larger subject sample to identify developmental
changes. Although musical experience has been shown to have a positive eect on the learning of lexical tones23,81,
it remains unknown how to best implement musical training independently of or combined with speech training
to improve categorical perception by suppression of within-category discriminatory sensitivity and enhancement
of between-category sensitivity.
Although the current study is conned to lexical tone processing decits in Chinese children with autism, our
ndings add to the recent literature24,25 that points to the existence of domain-specic pitch perception decit in
autism in relation to the tonal language background. From a theoretical perspective, an important issue regarding
atypical auditory processing associated with ASD is to determine whether it reects domain-general basic audi-
tory sensitivity of enhanced spectral resolution or whether this auditory sensitivity is shaped by language experi-
ence such that language-specic patterns of atypicalities would emerge in children with ASD who speak dierent
languages. Given that dierent languages employ dierent acoustic cues for phonological representations (for
instance, vowel length is used as a phonemic contrast in Finnish and Japanese but not in Chinese or English),
further studies could examine other aspects of auditory hyper- or hypo- sensitivity such as temporal processing
impairment37 in ASD to determine whether similar domain-specic processing issues in autism exist in relation
to eects of language learning experience/decit for the proper acquisition of phonological categories.
Method
Participants. e reported study was conducted with approval from the institutional review board of South
China Normal University, and in compliance with the 1964 Helsinki declaration and its later amendments ethical
standards. All children’s parents gave full, informed, written consent.
Two groups of children participated in this study: 16 children with autism (ASD group, average age 10.4),
and 15 typically developing controls (TD group, average age 10.3) matched on age and IQ scores. Children in
the ASD group were recruited from Guangzhou Cana School (Guangzhou Rehabilitation Research Center for
Children with Autism). e clinical diagnosis of autism was established according to the DSM-V criteria for
autistic disorder2. We conrmed diagnoses using the Chinese version of the Gilliam Autism Rating Scale–Second
Edition82. We chose to use the GARS-2 because Chinese versions of other standardized diagnostic instruments,
i.e., the Autism Diagnostic Interview –Revised83 and the Autism Diagnostic Observation Schedule1, have not
been ocially validated or widely adopted in China84,85. e GARS-2 has previously been used for this pur-
pose in published autism studies conducted in China86,87. Stereotyped Behaviors, Communication, and Social
Interaction, three subtests of GARS-2, are based on the DSM-IV-TR and Autism Society of America (1994) cri-
teria for autism. Children in the TD group were recruited from all classes of a regular local primary school aer
screening for language background, medical history of speech-language-hearing problems and psychiatric/neu-
rological disorders. All of the children had normal hearing (< 20 dB HL) in standard audiometric screening with
pure tones (250~6000 Hz). All of them were right-handed. Non-verbal IQ scores (Raven’s Standard Progressive
Matrices) were obtained to verify that there were no signicant dierences between the two groups. See Table3
for a summary of the participant characteristics.
Stimuli. ree speech stimuli were chosen from a 10-step lexical tone continuum used in previous CP studies27,28
in order to have both a between-category (or across-category) stimulus pair (5 and 9) and a within-category
stimulus pair (1 and 5) equated for acoustic distance (Fig.5). e continuum represented two natural Mandarin
Chinese monosyllables at the two end points, /ba2/ and /ba4/, which diered in pitch contour (Tone 2 is the
high rising tone, and Tone 4 is the falling tone). As described in the previous publications, the raw stimuli were
recorded from a female native Mandarin Chinese speaker. ey were digitally edited to have the duration of
200ms. Pitch tier transfer was performed using the Praat soware (http://www.fon.hum.uva.nl/praat/) to isolate
Autism TD Control
F p valuen M SD Range n M SD Range
Age 16 10.4 1.27 9–13 15 10.3 1.55 8–13 0.273 0.605
Nonverbal IQ 83.7 11.7 75–117 86.3 6.61 75–96 0.369 0.548
Table 3. Descriptive Characteristics of the Sample that were Matched in Age and Nonverbal IQ Scores.
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the lexical tones and keep the rest of the acoustic features identical. A morphing technique was applied in Matlab
(Mathworks Corporation, USA) using STRAIGHT soware (Kawahara, Masuda-Katsues, & de Cheveigne, 1999)
to create the 10-interval speech continuum. e between- and within- category contrasts had equal steps of
acoustic change in fundamental frequency along the continuum.
To test whether the hypothesized eects were speech-specic, nonspeech stimuli were generated to match the
speech stimuli in terms of fundamental frequency (pitch), amplitude and duration parameters. Spectral compo-
nents diered between the speech and nonspeech stimuli. In particular, harmonics (1, 3, 6, 7, 8, and 12) of the
fundamental frequency were kept, and other harmonics were removed to create the nonspeech percept. All the
stimuli were normalized to have equal average root-mean-square (RMS) intensity. See Xi, et al.27 for more details
of synthesis for the speech and nonspeech stimuli; also see Zhang, et al.28 for a study on Chinese children with
dyslexia using similar stimulus materials. Behavioral identication results from normal native Mandarin Chinese
speaking subjects from the same previous study were used to select the three stimuli to represent the between-
and within- category contrasts. Both Stimuli 1 and 5 on the lexical tone continuum were perceived by the native
speakers as Tone 2 and thus was chosen for the within-category contrast. Stimulus 9 was perceived as Tone 427,
and Stimuli 5 and 9 were chosen to represent the across-category contrast.
ERP Procedure. e stimuli were presented binaurally with earphones in a double oddball paradigm fol-
lowing the procedure of previous CP studies27. In particular, the standard stimulus was #5 in the continuum; #9
(between-category) and #1 (within-category) were used as the two deviants. e within-category deviant and
between-category deviant were presented pseudo-randomly among standards; each had a probability of occur-
rence of 10%, and adjacent deviants were separated by a minimum of 4 standards. A total of 600 stimuli were pre-
sented, each with a duration of 200 ms and a stimulus-onset-asynchrony (SOA) of 1000 ms. e sound intensity
level was at approximately 75 dB SPL. Participants were instructed to ignore the presented sounds while watching
a muted movie, which was shown with subtitles.
Data recording and analysis. Continuous EEG was recorded using BrainAmps DC consisting of 32 chan-
nels at 500 Hz sampling. e BrainAmps DC system included electrodes next to and below the eyes for recording
horizontal and vertical eye movements. e impedance of each electrode was kept below 10 K. e le mas-
toid electrode was set as the reference, and the AFz electrode served as ground. For the ERP waveform analysis,
the raw data were digitally ltered oine with a 1~30 Hz bandpass lter and segmented for epochs of 700 ms
duration including a 100 ms baseline prior to the onset of each stimulus. Recorded trials with eye blinks or
other artifactual activities beyond the range of 80 μ V~80 μ V were rejected. Only the standards immediately
preceding a deviant was used for averaging and subtraction to keep the number of standard and deviant trials
equivalent. ere were at least 40 deviant trials accepted in each condition. e MMRs and P3a were derived from
the deviant-minus-standard dierence ERP waveforms in each condition. MMR and P3a were dened as the
response deection within 100–200 ms post stimulus and 250–400 ms post stimulus respectively. e Global Field
Power (GFP) was calculated as a measure of the magnitude of the MMR88. Unlike the waveform peak analysis at
selected electrodes, the GFP provides an objective assessment of spatial scalp distribution in terms of the standard
deviation of potential values for all electrodes at any sampling point in the epoch window89.
To understand how trial-by-trial neural oscillatory activities contributed to the generations of the MMRs,
time-frequency analysis was completed using the subtracted MMR waveforms (deviant–standard preced-
ing deviant with a bandpass lter of 1–40 Hz) for each accepted deviant trial at electrode Cz with the newtimef
function in EEGLAB90. A short-term Fourier Transform (STFT) with Hanning window tapering41, which is
Figure 5. e F0 contour continuum for the speech and nonspeech stimuli. Fundamental frequency patterns
of the tonal continuum from the high rising Tone 2 to the falling Tone 4. Stimuli 1, 5 and 9 used in the ERP
experiment are marked.
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recommended for the analysis of low frequency activities, was adopted for the calculation of inter-trial phase
coherence (ITPC) of theta and beta band activities. e ITPC measure for a chosen latency ranges from 0 (indi-
cating absence of synchronization across trials) to 1 (indicating perfect synchronization). e time window used
for our time-frequency analysis represented the entire analysis epoch, including the pre-stimulus baseline from
100 to 700 ms, and estimated frequencies were from 1 to 40 Hz with a step interval of 0.5 Hz41. Automatic arti-
fact rejection criteria were set at ± 80 μ V. Based on grand mean ERP waveforms, search windows relative to the
pre-stimulus interval were determined for MMR at 100–200 ms for both conditions.
Separate two-way group (TD/ASD) × deviant type (within-category/between-category) repeated measures
ANOVAs were conducted for each of the dependent variables (mean amplitude and mean latency) for both the
MMR/P3a components and band spectral power related to MMR in both the speech and nonspeech (harmonic)
conditions. Further tests of simple eects (in the case of signicant interaction) and planned two-tailed t-tests
were also conducted to verify whether there were signicant within- vs. across- category dierences for each
subject group in the speech and nonspeech conditions.
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Acknowledgements
is work was supported by grants from the National Natural Science Foundation of China (NSFC 31571136),
Key Project of National Social Science Foundation of China (15AZD048) to Suiping Wang and an award from
the Scientic Research Foundation of Graduate School of South China Normal University to Xiaoyue Wang
(2014SSXM73). Yang Zhang was additionally supported by the Grand Challenges Exploratory Research Grant
and Brain Imaging Research Project Award from the University of Minnesota. We thank Guiwen He, Jian Huang,
Junjie Tang, Wei Cao, Xiaoling Peng, and Lai Wei for their assistance.
Author Contributions
Xiaoyue Wang, Suiping Wang and Yang Zhang wrote the main manuscript text. Xiaoyue Wang, Yuebo Fan and
Dan Huang collected and analysized data. Xiaoyue Wang prepared the Figures 1–5. All authors reviewed the
manuscript.
Additional Information
Competing nancial interests: e authors declare no competing nancial interests.
How to cite this article: Wang, X. et al. Speech-specic categorical perception decit in autism: An Event-
Related Potential study of lexical tone processing in Mandarin-speaking children. Sci. Rep. 7, 43254; doi:
10.1038/srep43254 (2017).
Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and
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© e Author(s) 2017
... As shown in the present results, for the ASD children, the pitch pattern for lexical and neutral tones was realized by a narrower F0 range and a relatively shallower tonal shape. The shallower tonal contours for the Mandarin-speaking children with ASD in this study may be a result of the ASD children's high sensitivity to acoustic details, so that they do not need to produce tones as acoustically distinct as the TD children do (Bonnel et al., 2003;Russo et al., 2008;Wang et al., 2017). Consistent with Yu and colleagues' study (2015) that explored different neural processing data for lexical tones in the ASD group, the present study also found that ASD children tended to present inappropriate suppression of the overall F0 range. ...
... Consistent with Yu and colleagues' study (2015) that explored different neural processing data for lexical tones in the ASD group, the present study also found that ASD children tended to present inappropriate suppression of the overall F0 range. Wang et al. (2017) also revealed larger between-category mismatch negativity (MMN) than within-category MMNs for the TD group, while for the ASD group, comparable MMN effects were found for the two types of contrasts, indicating that categorical perception of lexical tones may be less evident for speakers with ASD. Additionally, Russo et al. (2008) raised the possibility that it might be the atypicality in the audio-vocal system that leads to a disturbance on the F0 feedback from their own speech, thus resulting in deficits in pitch regulation. ...
... Moreover, ASD children produced significantly more T2, T3, and T4 errors than T1 errors. Since Mandarin-speaking children with ASD were shown to have pitch processing deficits around 9.3 years of age in Yu et al. (2015) and lack the categorical perception of lexical tones around 10.4 years of age in Wang et al. (2017), it is highly possible that the ASD children in the present study have tone perception difficulties that impact their tone acquisition. For the error rates of neutral tones, we found that the ASD children presented a similar error pattern as the TD groups, with both groups producing similar numbers of errors between T1N and T4N that elicited fewer errors than T2N and T3N. ...
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... In contrast to musical pitch processing, pitch-mediated speech-processing ability is typically viewed as a skill that autistic individuals have difficulty with, especially prosodic and semantic pitch processing, including identifying and discriminating questions and statements (Jiang et al., 2015), distinguishing lexical stress contrasts (Paul et al., 2005), as well as encoding lexical tones (Lau et al., 2021;Wang et al., 2017). Given that semantic and prosodic information play a crucial role in speech communication and interaction, this atypical pitch processing in speech may hinder language acquisition and development in ASD (Schreibman et al., 1986). ...
... However, these apparently contradictory findings can be further explained by considering the complex and multi-stage aspects of pitch processing (Germain et al., 2019;Haesen et al., 2011), whose facets may be differently recruited and exposed depending on task demands, thus leading to various conclusions about the impact of ASD on pitch processing across studies. Specifically, a wide range of stimuli (e.g. from pure tone to natural speech utterance or musical melody) and task complexity (e.g. from simple tone discrimination to local temporal deviant analysis in complex sequences) have been explored in pitch-processing studies in ASD, with a fundamental question remaining unresolved; that is, why low-level pitch sensitivity can be mismatched with performance on musical or linguistic pitch-processing tasks (Jiang et al., 2015;Lau et al., 2021;Paul et al., 2005;Wang et al., 2017). We hypothesized that the mismatched extrapolations may have higher-level origins, given that in contrast to bottomup sensory processing for simple detection tasks, discriminating complex speech or musical sequences recruit top-down processing (Germain et al., 2019;Haesen et al., 2011). ...
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Lay abstract: As a key auditory attribute of sounds, pitch is ubiquitous in our everyday listening experience involving language, music and environmental sounds. Given its critical role in auditory processing related to communication, numerous studies have investigated pitch processing in autism spectrum disorder. However, the findings have been mixed, reporting either enhanced, typical or impaired performance among autistic individuals. By investigating top-down comparisons of internal mental representations of pitch contours in speech and music, this study shows for the first time that, while autistic individuals exhibit diverse profiles of pitch processing compared to non-autistic individuals, their mental representations of pitch contours are typical across domains. These findings suggest that pitch-processing mechanisms are shared across domains in autism spectrum disorder and provide theoretical implications for using music to improve speech for those autistic individuals who have language problems.
... However, due to differences in early social interactions compounded by later atypical interactions with others (e.g., Crompton et al., 2020), autistic people show different neural patterns when processing speech (Wang et al., 2017;Yu et al., 2015), and altered perceptual flexibility during speech processing and word recognition (e.g., Happé & Frith, 2014;Stewart et al., 2018;Stewart & Ota, 2008). For instance, adults with elevated autistic traits are less likely to show evidence of top-down lexical processing during speech perception, leading to a reduced "Ganong effect" (Stewart et al., 2018;Stewart & Ota, 2008). ...
... To date, it is still unclear exactly how the phonological systems of autistic people are formed (and/or retuned), whether they are marked by a limited number of prototypes, or whether atypicalities stem from underlying sensory-processing mechanisms unique to the autistic perceptual endophenotype. In autistic people, atypical perceptual organization of phonemic prototypes (Wang et al., 2017;Yu et al., 2015) and altered processing of voice and speech sounds have previously been contributed to variances in phonological acquisition patterns (Boucher & Anns, 2018) resulting in altered neural plasticity and, in consequence, reduction of phonetic flexibility (Kissine et al., 2021), of categorical precision (You et al., 2017) and of specialization for native speech sound categories (DePape et al., 2012;Stewart et al., 2018). Weakened incorporation of lower-level with higherlevel processing in the autistic group may therefore be explained by atypicalities in flexible perceptual processing set out within the Bayesian framework (Pellicano & Burr, 2012). ...
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The automatic retuning of phoneme categories to better adapt to the speech of a novel talker has been extensively documented across various (neurotypical) populations, including both adults and children. However, no studies have examined auditory perceptual learning effects in populations atypical in perceptual, social, and language processing for communication, such as populations with autism. Employing a classic lexically‐guided perceptual learning paradigm, the present study investigated perceptual learning effects in Australian English autistic and non‐autistic adults. The findings revealed that automatic attunement to existing phoneme categories was not activated in the autistic group in the same manner as for non‐autistic control subjects. Specifically, autistic adults were able to both successfully discern lexical items and to categorize speech sounds; however, they did not show effects of perceptual retuning to talkers. These findings may have implications for the application of current sensory theories (e.g., Bayesian decision theory) to speech and language processing by autistic individuals. Lexically guided perceptual learning assists in the disambiguation of speech from a novel talker. The present study established that while Australian English autistic adult listeners were able to successfully discern lexical items and categorize speech sounds in their native language, perceptual flexibility in updating speaker‐specific phonemic knowledge when exposed to a novel talker was not available. Implications for speech and language processing by autistic individuals as well as current sensory theories are discussed.
... However, this conclusion was mainly drawn from data collected from ASD individuals speaking English or other non-tonal languages, where syllable-level prosodic variations (or lexical tones) do not distinguish lexical meaning. For tonal language speakers with autism, atypical perception of lexical tones and vowel exaggeration has been observed [187,188], which indicates impairment in grammatical-prosodic processing in addition to their pragmatic difficulties [189]. Therefore, whether grammatical functions of prosody are impaired among the ASD population is disputed and is likely to differ, due to the influence of language backgrounds, so the design of future VR-based practice should take into consideration this language-specific problem and be tailored to ASD individuals according to their language backgrounds. ...
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Virtual reality (VR) technology gains theoretical support from rehabilitation and pedagogical theories and offers a variety of capabilities in educational and interventional contexts with affordable products. VR is attracting increasing attention in the medical and healthcare industry as it provides fully interactive three-dimensional simulations of real-world settings and social situations, which are particularly suitable for cognitive and performance training including social and interaction skills. The worldwide rising trend in the prevalence of autism spectrum disorder calls for innovative and efficacious techniques for assessment and treatment. The article offers a summary of current perspectives and evidence-based applications of VR technology as an educational and intervention tool for individuals with autism spectrum disorder, with a primary focus on social communication including social functioning, emotion recognition, and speech and language. Technology- and design-related limitations as well as the disputes over the application of virtual reality to autism research and therapy are discussed and future directions of this emerging field are highlighted with regards to application expansion and improvement, technology enhancement, and the development of brain-based research and theoretical models.
... Moreover, LNR enhancement to hum was more marked in the autism group than in the NT group. These observations indicate enhanced neural processing of the phoneme-free nonspeech signal in autism, which agree with the studies that tapped cross-domain auditory processing of speech and nonspeech Järvinen-Pasley & Heaton, 2007;Wang et al., 2017;Yu et al., 2015). For example, in Yu et al., (2015), native Chinese-speaking schoolage children with autism displayed diminished mismatch negativities (MMN) to pitch contrasts embedded in speech (i.e., lexical tones) compared to their NT peers, whereas the MMN was enhanced for pitch contrasts carried by pure tones and hum (Yu et al., 2015). ...
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Children with autism often show atypical brain lateralization for speech and language processing, however, it is unclear what linguistic component contributes to this phenomenon. Here we measured event-related potential (ERP) responses in 21 school-age autistic children and 25 age-matched neurotypical (NT) peers during listening to word-level prosodic stimuli. We found that both groups displayed larger late negative response (LNR) amplitude to native prosody than to nonnative prosody; however, unlike the NT group exhibiting left-lateralized LNR distinction of prosodic phonology, the autism group showed no evidence of LNR lateralization. Moreover, in both groups, the LNR effects were only present for prosodic phonology but not for phoneme-free prosodic acoustics. These results extended the findings of inadequate neural specialization for language in autism to sub-lexical prosodic structures.
... Thus, the deficits of speech motor planning skills in children with ASD may degrade their performances on sequencing the articulatory movements that are necessary for the aspirated sounds. Thirdly, the perceptual deficit in children with ASD (Huang et al., 2018;Wang et al., 2017;You et al., 2017;Yu et al., 2015) may also limit their ability to perceive others' speech and adjust their speech production to ensure an intelligible and appropriate speech production. ...
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Impaired speech sound production adds difficulties to social communication in children with Autism Spectrum Disorder (ASD), while a limited attempt has been made to figure out the speech sound production among Mandarin-speaking children with ASD. The current study conducted both auditory-perceptual scoring and quantitative acoustic analysis of speech sound imitated by 27 Mandarin-speaking children with ASD (3.33–7.00 years) and 30 chronological-age matched typically developing (TD) children. Auditory-perceptual scoring showed significantly lower scores for aspirated/unaspirated consonants and monophthongs in children with ASD. Moreover, the correlation between the developmental age of language and production accuracy in children with ASD emphasised the importance of language assessment. The quantitative acoustic analysis further indicated that the ASD group produced a much shorter voice onset time for aspirated consonants and showed a reduced vowel space than the TD group. Early interventions focusing on these production patterns should be introduced to improve the speech sound production in Mandarin-speaking children with ASD.
... Indeed, previous acoustic analyses only reported utterance-level f0 differences across ASD and TD groups in English [17-19, 21, 22] but not Cantonese [35], consistent with our classification patterns using f0-based features across Models 1 and 2. It is possible that the prolific usage of linguistic pitch in tone languages provides a compensatory effect ameliorating intonational differences in ASD. In the perception domain, pitch processing differences found in tone language-speaking children with ASD [78][79][80][81] were surprisingly not evident in their adult peers [82], potentially due to a longer exposure to the native tone language. This possibility, i.e., that extensive pitch experience may ameliorate intonational differences in ASD, highlights pitch and intonation as a fruitful target for speech interventions in ASD for those who do not speak a tone language, where targeting this potentially more malleable factor could lead to therapeutic gains and help to advance more global speech and language characteristics. ...
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Differences in speech prosody are a widely observed feature of Autism Spectrum Disorder (ASD). However, it is unclear how prosodic differences in ASD manifest across different languages that demonstrate cross-linguistic variability in prosody. Using a supervised machine-learning analytic approach, we examined acoustic features relevant to rhythmic and intonational aspects of prosody derived from narrative samples elicited in English and Cantonese, two typologically and prosodically distinct languages. Our models revealed successful classification of ASD diagnosis using rhythm-relative features within and across both languages. Classification with intonation-relevant features was significant for English but not Cantonese. Results highlight differences in rhythm as a key prosodic feature impacted in ASD, and also demonstrate important variability in other prosodic properties that appear to be modulated by language-specific differences, such as intonation.
... However, this conclusion was mainly drawn from data collected from ASD individuals speaking English or other non-tonal languages, where syllable-level prosodic variations (or lexical tones) do not distinguish lexical meaning. For tonal language speakers with autism, atypical perception of lexical tones and vowel exaggeration has been observed [187,188], which indicates impairment in grammatical-prosodic processing in addition to their pragmatic difficulties [189]. Therefore, whether grammatical functions of prosody are impaired among the ASD population is disputed and is likely to differ, due to the influence of language backgrounds, so the design of future VR-based practice should take into consideration this language-specific problem and be tailored to ASD individuals according to their language backgrounds. ...
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The worldwide rising trend of autism spectrum disorder (ASD) calls for innovative and efficacious techniques for assessment and treatment. Virtual reality (VR) technology gains support from rehabilitation and pedagogical theories and offers a variety of capabilities in educational and interventional contexts with affordable products. VR is attracting increasing attention in the medical and healthcare industry, as it provides fully interactive three-dimensional simulations of real-world settings and social situations, which are particularly suitable for cognitive and performance training, including social and interaction skills. This review article offers a summary of current perspectives and evidence-based VR applications for children with ASD, with a primary focus on social communication, including social functioning, emotion recognition, and speech and language. Technology- and design-related limitations, as well as disputes over the application of VR to autism research and therapy, are discussed, and future directions of this emerging field are highlighted with regards to application expansion and improvement, technology enhancement, linguistic diversity, and the development of theoretical models and brain-based research.
... Previous research on auditory and language-related deficits in ASD has also indicated that observation in the ASD population who are native speakers of nontonal languages cannot be adapted directly to those speaking a tonal language (Russo et al., 2008;Yu et al., 2015). As the majority of languages in the world are tonal languages (Yip, 2002), recent findings about domain-specific deficits for lexical tone processing in Chinese children with ASD (Wang et al., 2017;Yu et al., 2015) would naturally raise a question about the potential cross-channel influences of pitch information for linguistic and emotional processing. In this regard, current knowledge on multichannel processing of emotion in ASD is very limited and incomprehensive. ...
Article
Purpose Numerous studies have identified individuals with autism spectrum disorder (ASD) with deficits in unichannel emotion perception and multisensory integration. However, only limited research is available on multichannel emotion perception in ASD. The purpose of this review was to seek conceptual clarification, identify knowledge gaps, and suggest directions for future research. Method We conducted a scoping review of the literature published between 1989 and 2021, following the 2005 framework of Arksey and O'Malley. Data relating to study characteristics, task characteristics, participant information, and key findings on multichannel processing of emotion in ASD were extracted for the review. Results Discrepancies were identified regarding multichannel emotion perception deficits, which are related to participant age, developmental level, and task demand. Findings are largely consistent regarding the facilitation and compensation of congruent multichannel emotional cues and the interference and disruption of incongruent signals. Unlike controls, ASD individuals demonstrate an overreliance on semantics rather than prosody to decode multichannel emotion. Conclusions The existing literature on multichannel emotion perception in ASD is limited, dispersed, and disassociated, focusing on a variety of topics with a wide range of methodologies. Further research is necessary to quantitatively examine the impact of methodological choice on performance outcomes. An integrated framework of emotion, language, and cognition is needed to examine the mutual influences between emotion and language as well as the cross-linguistic and cross-cultural differences. Supplemental Material https://doi.org/10.23641/asha.19386176
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Enhanced pitch perception has been identified in autistic individuals, but it remains understudied whether such enhancement can be observed in the lexical tone perception of language-delayed autistic children. This study examined the categorical perception of Mandarin lexical tones in 23 language-delayed autistic children and two groups of non-autistic children, with one matched on chronological age ( n = 23) and the other on developmental age in language ability ( n = 23). The participants were required to identify and discriminate lexical tones. A wider identification boundary width and a lower between-category discrimination accuracy were found in autistic children than their chronological-age-matched non-autistic peers, but the autistic group exhibited seemingly comparable performance to the group of developmental-age-matched non-autistic children. While both non-autistic groups displayed a typical categorical perception pattern with enhanced sensitivity to between-category tone pairs relative to within-category ones, such a categorical perception pattern was not observed in the autistic group. These findings suggest among language-delayed autistic children with a developmental age around 4, categorical perception is still developing. Finally, we found categorical perception performance correlated with language ability, indicating autistic children’s language disability might be predictive of their poor categorical perception of speech sounds. Lay abstract Some theories suggested that autistic people have better pitch perception skills than non-autistic people. However, in a context where pitch patterns are used to differentiate word meanings (i.e. lexical tones), autistic people may encounter difficulties, especially those with less language experience. We tested this by asking language-delayed autistic children to identify and discriminate two Mandarin lexical tones (/yi/ with Tone 1, meaning ‘clothes’; /yi/ with Tone 2, meaning ‘aunt’; /yi/: the standard romanization of Mandarin Chinese). On average, these autistic children were 7.35 years old, but their developmental age in language ability was 4.20, lagging behind 7-year-old non-autistic children in terms of language ability. Autistic children’s performance in identifying and discriminating lexical tones was compared with two groups of non-autistic children: one group was matched with the autistic group on age, and the other was matched based on language ability. Autistic children performed differently from the non-autistic children matched on age, while autistic and non-autistic children matched on language ability exhibited seemingly similar performance. However, both the non-autistic groups have developed the perceptual ability to process lexical tones as different categories, but this ability was still developing in autistic children. Finally, we found autistic children who performed worse in identifying lexical tones had poorer language ability. The results suggest that language disability might have adverse influence on the development of skills of speech sound processing.
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