Speech Contrast Research Articles

Neuroimaging Findings for the Overnight Consolidation of Learned Non-native Speech Sounds

Abstract Research over the past two decades has documented the importance of sleep to language learning. Sleep has been suggested to play a role in establishing new speech representations as well; however, the neural mechanisms corresponding to sleep-mediated effects on speech perception behavior are unknown. In this study, we trained monolingual English-speaking adults to perceive differences between the Hindi dental vs. retroflex speech contrast in the evening. We examined the blood oxygen level dependent signal using functional magnetic resonance imaging during perceptual tasks on both the trained talker and on an untrained talker shortly after training, and again the next morning. We also employed diffusion tensor imaging to determine if individual differences in white matter structure could predict variability in overnight consolidation. We found greater activity in cortical regions associated with language processing (e.g., left insula) on the second day. Fractional anisotropy values in the anterior thalamic radiation and the uncinate fasciculus was associated with the magnitude of overnight change in perceptual behavior on the generalization (untrained) talker, after controlling for differences in sleep duration and initial learning. Our findings suggest that speech-perceptual information is subject to an overnight transfer of information to the cortex. Moreover, neural structure appears to be linked to individual differences in efficiency of overnight consolidation.

Distributional Learning and Overnight Consolidation of Nonnative Tonal Contrasts by Tonal Language Speakers.

Previous studies have reported the success of distributional learning for adult speakers across segmental and suprasegmental categories immediately after training. On the other hand, second language (L2) perception models posit that the ease with which learners perceive a nonnative speech contrast depends on the perceptual mapping between the contrast and learners' first language (L1) categories. This study examined whether a difference in perceptual mapping patterns for different L2-Mandarin tonal contrasts might result in a difference in distributional learning effectiveness for tonal speakers and whether an interval of sleep enhanced the knowledge through consolidation. Following a pretest-training-posttest design, 66 L1-Cantonese participants with fewer than 9 years of Mandarin training were assigned to either the bimodal or unimodal distribution conditions. The participants of each group were asked to discriminate Mandarin level-falling (T1-T4) and level-rising (T1-T2) tone pairs on novel syllables in a within-subject design. All participants were trained in the evening, tested after training, and returned after 12 hr for overnight consolidation assessment. A significant distributional learning effect was observed for Mandarin T1-T4, but only after sleep. No significant distributional learning effect was observed for Mandarin T1-T2, either after training or after sleep. The findings may imply that distributional learning is contingent on perceptual mapping patterns of the target contrasts and that sleep may play a role in the consolidation of knowledge in an implicit statistical learning paradigm. https://doi.org/10.23641/asha.25970008.

Mismatch Negativity in Children with Deficits in Auditory Abilities.

Introduction Mismatch negativity (MMN) represents a negative component of event-related potentials, which is mentioned by guidelines as an important tool to provide measurable data regarding the functionality of the auditory system in acoustic processing. However, the literature still lacks reliable data that can support the clinical use of this potential in the complementary diagnosis of central auditory processing (CAP) disorder (CAPD). Objectives To analyze whether MMN assessment might be associated with the CAP behavioral test battery, as well as to assess the effects of auditory ability deficits on MMN responses in the pediatric population. Methods In total, 45 age-matched children participated in the study. They were submitted to the CAP behavior assessment and to MMN. The children were tested with a combination of speech contrast consisting of acoustic syllables [da] versus [ta], governed by the oddball paradigm. Results Mismatch negativity did not show a direct association with a single test but with the combination of the four tests used as a behavioral test battery to identify CAPD. The results also indicated that the auditory ability deficits influenced the measurement of MMN latency ( p = 0.003*), but not the amplitude ( p = 0.857) or the area ( p = 0.577). Conclusion Mismatch negativity was shown to be statistically associated with the battery of tests used to identify deficits in auditory abilities in the studied sample rather than with a single behavioral test. The deficits in auditory abilities were observed in the MMN latency. Mismatch negativity can be used to assess children with CAPD.

Enhancement of laryngeal contrasts in non-native English clear speech: a comparison between L2-immersed sequential bilinguals and L1-immersed speakers.

Clear speech, a speaking style used to mitigate communicative circumstances affecting the transmission or decoding of speech signal, often involves the enhancement of language-specific phonological contrasts, including laryngeal contrasts. This study investigates the role of language dominance in the implementation of language-specific laryngeal contrasts in L2 clear speech. Two groups of Korean-English speakers (L1 Korean) were tested: a relatively less Korean-dominant L2-immersed group of sequential bilinguals (N = 30) and a strongly Korean-dominant L1-immersed group (N = 30), with dominance assessed based on the results of the Bilingual Language Profile. Participants read a set of English minimal pairs differing in the voicing of word-initial stops (e.g., tab vs. dab), and their acoustic enhancement strategies were compared with those of native English speakers (N = 20). As correlates of the English laryngeal contrast, voice onset time (VOT) and onset f0 were measured. Results showed that both bilingual groups enhanced English laryngeal contrast in clear speech via voiceless VOT lengthening, similarly to native English speakers, but to a smaller extent than native speakers. Both bilingual groups also implemented a greater degree of onset f0 difference between voiced and voiced English stops than native English speakers did, although no enhancement of this parameter was observed in their clear speech. Surprisingly, no significant differences were found between L2- and L1-immersed speakers, suggesting a lack of language immersion effect on the acoustic enhancement strategies in L2 clear speech. We discuss possible explanations for this finding and propose directions for future research.

SPEECH OPERATIONS IN THE PROCESS OF TRANSLATION

The primary method of showing contrast in spoken speech, according to the text, is through the use of antonyms. In antonymic relationships, polysemantic words that originated with this potential future meaning and may have an associated antonym may do so. By contrast, the semantics of various words can be determined by the meaning of a single word. The writers of the article demonstrated the reliance of derivative words of other parts of speech as well as the combination of antonyms generated by the method of word formation on the basis of antonyms.

Examining a new paradigm for simultaneous evaluation of mismatch response (MMR) and complex auditory brainstem response (cABR) for speech in MEG

The mismatch response (MMR) is a common neural signature, both in M/EEG, to evaluate neural sensitivity to sound change. Furthermore, the complex auditory brainstem response (cABR) has gained wide research interest recently as it is argued to reflect early sensory encoding of complex sounds, such as speech, along the auditory pathway. While both measures are important in infants as babies undergo rapid speech learning, they also share the crucial drawback that it takes many trials and thus long recording times, prohibiting a wide usage in infant population. Here, we investigate a new and more efficient recording paradigm to simultaneously assess both MMR and cABR for speech in MEG. Adult participants are recorded under this new paradigm using simultaneous M/EEG with previously published speech stimuli. For MMR, we aim to replicate previously published results that MMR for a native speech contrast is more concentrated than for a nonnative speech contrast. For cABR, we aim to extract a predominant spatiotemporal pattern from all MEG channels and examine its correlation with the EEG-recorded signal. Once the new paradigm can be validated in adults, it can be used in infant populations with much increased efficiency, opening the door for addressing new research questions.

Cortical processing of speech in high-school students with different sleeping habits

Sleep plays a critical role on cognitive function especially in the developing brain. However, sleep duration and sleep timing are marked by individual differences. It is currently unknown whether and how sleep habits modulate speech perception in the developing brain. This study examined the correlation between sleep duration and brain responses to speech contrast in high-schoolers. A passive-listening oddball paradigm was used to deliver the speech contrast, and electroencephalogram (EEG)/Event-related potentials (ERPs) were used to collect cortical responses. Preliminary results indicated that there is a negative correlation between mismatch negativity responses and sleep duration in high-schoolers. The implication of the study will be discussed.

Longitudinal trajectories of electrophysiological mismatch responses in infant speech discrimination differ across speech features

Infants rapidly advance in their speech perception, electrophysiologically reflected in the transition from an immature, positive-going to an adult-like, negative-going mismatch response (MMR) to auditory deviancy. Although the MMR is a common tool to study speech perception development, it is not yet completely understood how different speech contrasts affect the MMR’s characteristics across development. Thus, a systematic longitudinal investigation of the MMR’s maturation depending on speech contrast is necessary. We here longitudinally explored the maturation of the infant MMR to four critical speech contrasts: consonant, vowel, vowel-length, and pitch. MMRs were obtained when infants (n = 58) were 2, 6 and 10 months old. To evaluate the maturational trajectory of MMRs, we applied second-order latent growth curve models. Results showed positive-going MMR amplitudes to all speech contrasts across all assessment points that decreased over time towards an adult-like negativity. Notably, the developmental trajectories of speech contrasts differed, implying that infant speech perception matures with different rates and trajectories throughout the first year, depending on the studied auditory feature. Our results suggest that stimulus-dependent maturational trajectories need to be considered when drawing conclusions about infant speech perception development reflected by the infant MMR.

Development of infants’ neural speech processing and its relation to later language skills: A MEG study

The ‘sensitive period’ for phonetic learning (∼6–12 months) is one of the earliest milestones in language acquisition where infants start to become specialized in processing speech sounds in their native language. In the last decade, advancements in neuroimaging technologies for infants are starting to shed light on the underlying neural mechanisms supporting this important learning period. The current study reports on a large longitudinal dataset with the aim to replicate and extend on two important questions: 1) what are the developmental changes during the ‘sensitive period’ for native and nonnative speech processing? 2) how does native and nonnative speech processing in infants predict later language outcomes? Fifty-four infants were recruited at 7 months of age and their neural processing of speech was measured using Magnetoencephalography (MEG). Specifically, the neural sensitivity to a native and a nonnative speech contrast was indexed by the mismatch response (MMR). They repeated the measurement again at 11 months of age and their language development was further tracked from 12 months to 30 months of age using the MacArthur-Bates Communicative Development Inventory (CDI). Using an a priori Region-of-Interest (ROI) approach, we observed significant increases for the Native MMR in the left inferior frontal region (IF) and superior temporal region (ST) from 7 to 11 months, but not for the Nonnative MMR. Complementary whole brain comparison revealed more widespread developmental changes for both contrasts. However, only individual differences in the left IF and ST for the Nonnative MMR at 11 months of age were significant predictors of individual vocabulary growth up to 30 months of age. An exploratory machine-learning based analysis further revealed that whole brain time series for both Native and Nonnative contrasts can robustly predict later outcomes, but with very different underlying spatial-temporal patterns. The current study extends our current knowledge and suggests that native and nonnative speech processing may follow different developmental trajectories and utilize different mechanisms that are relevant for later language skills.

Cortical plasticity for speech processing in English & Mandarin-speaking adolescents: The effect of transcranial direct current stimulation

Language experience and brain maturation both shape speech processing at the cortical level. To examine whether transcranial direction stimulation (tDCS) shows any effect on automaticity of neural speech processing in relation to language experience in adolescents, we recorded event-related potentials (ERP) to a speech contrast both before and after administering tDCS. The participants were adolescents (14–19 years old) from monolingual English-speaking households and bilingual English-Mandarin speaking households. We used a passive listening oddball paradigm and recorded ERP responses before and after 10 minutes of tDCS. The mismatch negativity (MMN) and late negativities (LN) were examined. Both groups showed clear neural discrimination. We observed language group differences in the amplitudes of MMN and stimulus condition differences in the amplitudes of LN. The preliminary analyses of ERP responses before and after tDCS suggest that one short session of tDCS does not influence neural discrimination of speech in typically-developing adolescents.

Neural-Behavioral Relation in Phonetic Discrimination Modulated by Language Background.

It is a well-demonstrated phenomenon that listeners can discriminate native phonetic contrasts better than nonnative ones. Recent neuroimaging studies have started to reveal the underlying neural mechanisms. By focusing on the mismatch negativity/response (MMN/R), a widely studied index of neural sensitivity to sound change, researchers have observed larger MMNs for native contrasts than for nonnative ones in EEG, but also a more focused and efficient neural activation pattern for native contrasts in MEG. However, direct relations between behavioral discrimination and MMN/R are rarely reported. In the current study, 15 native English speakers and 15 native Spanish speakers completed both a behavioral discrimination task and a separate MEG recording to measure MMR to a VOT-based speech contrast (i.e., pre-voiced vs. voiced stop consonant), which represents a phonetic contrast native to Spanish speakers but is nonnative to English speakers. At the group level, English speakers exhibited significantly lower behavioral sensitivity (d’) to the contrast but a more expansive MMR, replicating previous studies. Across individuals, a significant relation between behavioral sensitivity and the MMR was only observed in the Spanish group. Potential differences in the mechanisms underlying behavioral discrimination for the two groups are discussed.

A Clash of Worlds: A Stylistic Analysis of Imrana’s ‘Imagine Say’

The study explores creativity and innovation in the song (music video) ‘Imagine Say,’ by Imrana, a young Ghanaian musician. Adopting various theories and principles of Stylistics, the study identifies such creativity and innovation as parallelism, deviation, contrast, and other figures of speech, and what they foreground, in order to examine how effectively they contribute to the overall meaning and message of the song. The result indicates that the artiste adopts multimodality to express the meaning and message of the song. The diction, background scenes and chorus, sound effects, personification, repetition Parallelism, deviation, metaphor, and other figures of speech highlight the theme and meaning of the song, and thus help the audience to get the message – Discrimination and injustice against those who come from the streets (the poor and vulnerable) must cease. It is not by choice that they come from the streets; coming from the street does not make one a criminal; if any street person can be charged for any crime s/he must be given a fair hearing at a court of competent jurisdiction, rather than subjecting him/her to mob/instant justice.

Overnight changes to dual-memory processes reflected in speech-perceptual performance.

Adults' ability to attain and retain nonnative speech sound categories vary substantially among individuals. While we know that speech-perceptual skills play a role, we know less about how consolidation-related changes in acoustic-phonetic memory contribute to perceptual tasks. The goal of this investigation was to examine contributions of memory and perceptual skills to the perceptual performance on a trained nonnative speech contrast over two days. Twenty-one adult participants (ages 18-24) completed four different experiments. Three of these assessed learning and memory: visual statistical learning (implicit), visual object recognition (explicit), and nonnative (Hindi dental-retroflex) speech-sound training. Participants completed the learning tasks around 8 p.m., and performance was measured shortly after learning and again 12 hours later. On a separate day, participants completed a categorical perception task on a native (/a/-/e/) vowel continuum. Nonnative speech perception was associated with implicit learning performance when both were assessed shortly after learning, and associated with the retention of explicit memory when both were assessed after an overnight delay. Native speech-sounds were at least marginally associated with nonnative speech perception performance on both days, but with a stronger association observed with performance assessed on Day 2. These findings provide preliminary support for the interpretation that speech-sounds are encoded by at least two memory systems in parallel, but that perceptual performance may reflect acoustic-phonetic knowledge learned by different memory systems over time since exposure. Moreover, performance on speech perception tasks in both native and nonnative speech-sounds may rely on similar retrieval mechanisms for long-term storage of speech-sound information.

Speech token detection and discrimination in individual infants using functional near-infrared spectroscopy

Speech detection and discrimination ability are important measures of hearing ability that may inform crucial audiological intervention decisions for individuals with a hearing impairment. However, behavioral assessment of speech discrimination can be difficult and inaccurate in infants, prompting the need for an objective measure of speech detection and discrimination ability. In this study, the authors used functional near-infrared spectroscopy (fNIRS) as the objective measure. Twenty-three infants, 2 to 10 months of age participated, all of whom had passed newborn hearing screening or diagnostic audiology testing. They were presented with speech tokens at a comfortable listening level in a natural sleep state using a habituation/dishabituation paradigm. The authors hypothesized that fNIRS responses to speech token detection as well as speech token contrast discrimination could be measured in individual infants. The authors found significant fNIRS responses to speech detection in 87% of tested infants (false positive rate 0%), as well as to speech discrimination in 35% of tested infants (false positive rate 9%). The results show initial promise for the use of fNIRS as an objective clinical tool for measuring infant speech detection and discrimination ability; the authors highlight the further optimizations of test procedures and analysis techniques that would be required to improve accuracy and reliability to levels needed for clinical decision-making.

Is talker variability a critical component of effective phonetic training for nonnative speech?

The current investigation adopted high variability phonetic training with additional audiovisual input and adaptive acoustic exaggeration to examine the role of talker variability. Sixty native Chinese-speaking adults were randomly assigned to a multiple-talker (MT) training group, a single-talker (ST) training group, and a control (CTRL) group without training. The target sounds were the English /i/-/ɪ/ contrast, delivered in 7 sessions using minimal pair word lists. Pre- and post-tests employed natural word identification, synthetic phoneme identification, and word production. Unlike the CTRL group, both training groups showed significant identification improvements, and the effects generalized to novel talkers and new phonetic contexts. Although training did not improve speech intelligibility, there was a significant gain in the use of the primary spectral cues and a decrease in the secondary durational cue. No differences were observed between the MT and ST groups. By removing the “enhancement” features, however, the training program with independent samples was able to verify the advantages of MT over ST training. These results provide the first evidence for the efficacy of other facilitative training features, independent of talker variability, in retuning second language learners’ attention to critical acoustic cues for the target speech contrast and producing transfer of learning.

PRAUTOCAL corpus: a corpus for the study of Down syndrome prosodic aspects

Oral productions of speakers with Down syndrome exhibit special characteristics that have been the target of study for decades. In spite of this attention, the availability of rich resources for its analysis is still scarce. In this paper, we present the definition and compiling procedure of a corpus of semi-controlled oral productions of speakers with Down syndrome that aims to allow the analysis of how these speakers with these speakers produce functional and linguistic aspects of speech. The PRAUTOCAL corpus has been recorded while using a video game for training oral competences. Utterances are related to well defined communicative tasks recorded by both speakers with Down syndrome and typically developing speakers. We present the procedure for human experts to evaluate the recordings and the transcription criteria followed for enriching the utterances of the corpus. PRAUTOCAL permits the analysis of the clear contrast in voice and speech between individuals with Down syndrome and typically developing speakers, taking into account the high heterogeneity of the speech problems characteristic of the syndrome. This material allows the analysis of the speech problems in Down syndrome, with applications to the generation of knowledge that could be used in future works for therapists to prepare specific training or enriching diagnosis regarding possible speech and language disorders.

Mismatched response predicts behavioral speech discrimination outcomes in infants with hearing loss and normal hearing.

Children with hearing loss (HL) remain at risk for poorer language abilities than normal hearing (NH) children despite targeted interventions; reasons for these differences remain unclear. In NH children, research suggests speech discrimination is related to language outcomes, yet we know little about it in children with HL under the age of 2years. We utilized a vowel contrast, /a-i/, and a consonant-vowel contrast, /ba-da/, to examine speech discrimination in 47 NH infants and 40 infants with HL. At Mean age=3months, EEG recorded from 11 scalp electrodes was used to compute the time-frequency mismatched response (TF-MMRSE ) to the contrasts; at Mean age=9months, behavioral discrimination was assessed using a head turn task. A machine learning (ML) classifier was used to predict behavioral discrimination when given an arbitrary TF-MMRSE as input, achieving accuracies of 73% for exact classification and 92% for classification within a distance of one class. Linear fits revealed a robust relationship regardless of hearing status or speech contrast. TF-MMRSE responses in the delta (1-3.5Hz), theta (3.5-8Hz), and alpha (8-12Hz) bands explained the most variance in behavioral task performance. Our findings demonstrate the feasibility of using TF-MMRSE to predict later behavioral speech discrimination.

Increased speech contrast induced by sensorimotor adaptation to a nonuniform auditory perturbation.

When auditory feedback is perturbed in a consistent way, speakers learn to adjust their speech to compensate, a process known as sensorimotor adaptation. Although this paradigm has been highly informative for our understanding of the role of sensory feedback in speech motor control, its ability to induce behaviorally relevant changes in speech that affect communication effectiveness remains unclear. Because reduced vowel contrast contributes to intelligibility deficits in many neurogenic speech disorders, we examine human speakers' ability to adapt to a nonuniform perturbation field that was designed to affect vowel distinctiveness, applying a shift that depended on the vowel being produced. Twenty-five participants were exposed to this "vowel centralization" feedback perturbation in which the first two formant frequencies were shifted toward the center of each participant's vowel space, making vowels less distinct from one another. Speakers adapted to this nonuniform shift, learning to produce corner vowels with increased vowel space area and vowel contrast to partially overcome the perceived centralization. The increase in vowel contrast occurred without a concomitant increase in duration and persisted after the feedback shift was removed, including after a 10-min silent period. These findings establish the validity of a sensorimotor adaptation paradigm to increase vowel contrast, showing that complex, nonuniform alterations to sensory feedback can successfully drive changes relevant to intelligible communication.NEW & NOTEWORTHY To date, the speech motor learning evoked in sensorimotor adaptation studies has had little ecological consequences for communication. By inducing complex, nonuniform acoustic errors, we show that adaptation can be leveraged to cause an increase in speech sound contrast, a change that has the capacity to improve intelligibility. This study is relevant for models of sensorimotor integration across motor domains, showing that complex alterations to sensory feedback can successfully drive changes relevant to ecological behavior.

Language learning as a function of infant directed speech (IDS) in Spanish: Testing neural commitment using the positive-MMR

Spanish-English bilingual families (N = 17) were recruited to assess the association between infant directed speech (IDS) in Spanish and their degree of neural commitment to the Spanish language. IDS was assessed by extracting the caregivers’ Vowel Space Area (VSA) from recordings of a storybook reading task done at home. Infants’ neural commitment was assessed by extracting the positive mismatch brain response (positive-MMR), an Event-Related Potential (ERP) thought to be indicative of higher attentional processes and early language commitment. A linear mixed model analysis demonstrated that caregivers’ VSA predicted the amplitude of the positive-MMR in response to a native speech contrast (Spanish), but not to a non-native speech contrast (Chinese), even after holding other predictors constant (i.e., socioeconomic status, infants’ age, and fundamental frequency). Our findings provide support to the view that quality of language exposure fosters language learning, and that this beneficial relationship expands to the bilingual population.

Mismatch Negativity in children with Phonological Disorders

Objective: to characterize the latency, amplitude and area variables of the Mismatch Negativity (MMN) elicited with verbal stimuli in children with PD, in addition to assessing whether this potential can be a useful tool in capturing auditory perception and discrimination deficits related to this disorder. Methods: MMN was recorded using a combination of speech contrast consisting of acoustic syllables [da vs ta], as the standard and deviant stimuli, in 34 children aged between 5 and 8 years. 14 children of the sample were already diagnosed with Phonological Disorder (PD) while 19 were characterized with typical development. Results: No statistically significant differences were observed for the MMN responses recorded between children with PD and their typically developed peers. Conclusion: The results suggest that the MMN may not be the most suitable procedure to assess auditory perception and discrimination deficits that could potentially be related to PD.