Neural coding of formant-exaggerated speech in the infant brain

Age and Sex Differences in Infants' Neural Sensitivity to Emotional Prosodies in Spoken Words: A Multifeature Oddball Study

PURPOSE

This study aimed to investigate infants' neural responses to changes in emotional prosody in spoken words. The focus was on understanding developmental changes and potential sex differences, aspects that were not consistently observed in previous behavioral studies.

METHOD

A modified multifeature oddball paradigm was used with emotional deviants (angry, happy, and sad) presented against neutral prosody (standard) within varying spoken words during a single electroencephalography recording session. The reported data included 34 infants (18 males, 16 females; age range: 3-12 months, average age: 7 months 26 days).

RESULTS

Infants exhibited distinct patterns of mismatch responses (MMRs) to different emotional prosodies in both early (100-200 ms) and late (300-500 ms) time windows following the speech onset. While both happy and angry prosodies elicited more negative early MMRs than the sad prosody across all infants, older infants showed more negative early MMRs than their younger counterparts. The distinction between early MMRs to angry and sad prosodies was more pronounced in younger infants. In the late time window, angry prosody elicited a more negative late MMR than the sad prosody, with younger infants showing more distinct late MMRs to sad and angry prosodies compared to older infants. Additionally, a sex effect was observed as male infants displayed more negative early MMRs compared to females.

CONCLUSIONS

These findings demonstrate the feasibility of the modified multifeature oddball protocol in studying neural sensitivities to emotional speech in infancy. The observed age and sex effects on infants' auditory neural responses to vocal emotions underscore the need for further research to distinguish between acoustic and emotional processing and to understand their roles in early socioemotional and language development.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.27914553.

Electrophysiological auditory measures to identify potential cortical markers of tinnitus

Tinnitus, or the perception of a sound in the absence of an external acoustic stimulus, is a common condition that cannot yet be objectively diagnosed. Current diagnostic tests of tinnitus consist of case history and behavioral measures that rely on subjective responses. This study examined electrophysiological measures, specifically the auditory late response (ALR), mismatch negativity (MMN), and P300 as potential neural biomarkers of tinnitus in both a tinnitus and non-tinnitus control group while utilizing the pitch-matched tinnitus frequencies as the test stimuli. Results of this study found differences in MMN amplitudes and area under the curve, and in P300 topographic maps between tinnitus and control subjects. The differences in MMN responses across groups suggest that dysfunctional processing of acoustic stimuli located near the tinnitus frequency in individuals with tinnitus manifests as soon as 200 ms after initial onset of the stimulus. In addition, results from a global field power analysis and differences in spatial distributions on topographical maps indicate that deficits persist through higher levels of cortical processing. A secondary goal of this study was to determine if electrophysiological measures correlated with reported tinnitus severity on questionnaires. This analysis indicated that P2 latency was a significant predictor of Tinnitus Reaction Questionnaire, Tinnitus Handicap Inventory, and percent of the time participant's tinnitus was considered bothersome, suggesting that this measure could potentially be used to assess the efficacy of treatment programs for tinnitus.

Theta activity and cognitive functioning: Integrating evidence from resting-state and task-related developmental electroencephalography (EEG) research

The theta band is one of the most prominent frequency bands in the electroencephalography (EEG) power spectrum and presents an interesting paradox: while elevated theta power during resting state is linked to lower cognitive abilities in children and adolescents, increased theta power during cognitive tasks is associated with higher cognitive performance. Why does theta power, measured during resting state versus cognitive tasks, show differential correlations with cognitive functioning? This review provides an integrated account of the functional correlates of theta across different contexts. We first present evidence that higher theta power during resting state is correlated with lower executive functioning, attentional abilities, language skills, and IQ. Next, we review research showing that theta power increases during memory, attention, and cognitive control, and that higher theta power during these processes is correlated with better performance. Finally, we discuss potential explanations for the differential correlations between resting/task-related theta and cognitive functioning, and offer suggestions for future research in this area.

Ten-month-old infants' neural tracking of naturalistic speech is not facilitated by the speaker's eye gaze

Eye gaze is a powerful ostensive cue in infant-caregiver interactions, with demonstrable effects on language acquisition. While the link between gaze following and later vocabulary is well-established, the effects of eye gaze on other aspects of language, such as speech processing, are less clear. In this EEG study, we examined the effects of the speaker's eye gaze on ten-month-old infants' neural tracking of naturalistic audiovisual speech, a marker for successful speech processing. Infants watched videos of a speaker telling stories, addressing the infant with direct or averted eye gaze. We assessed infants' speech-brain coherence at stress (1-1.75 Hz) and syllable (2.5-3.5 Hz) rates, tested for differences in attention by comparing looking times and EEG theta power in the two conditions, and investigated whether neural tracking predicts later vocabulary. Our results showed that infants' brains tracked the speech rhythm both at the stress and syllable rates, and that infants' neural tracking at the syllable rate predicted later vocabulary. However, speech-brain coherence did not significantly differ between direct and averted gaze conditions and infants did not show greater attention to direct gaze. Overall, our results suggest significant neural tracking at ten months, related to vocabulary development, but not modulated by speaker's gaze.

Real-time monitoring of infant theta power during naturalistic social experiences

Infant-directed speech and direct gaze are important social cues that shape infant's attention to their parents. Traditional methods for probing their effect on infant attention involve a small number of pre-selected screen-based stimuli, which do not capture the complexity of real-world interactions. Here, we used neuroadaptive Bayesian Optimization (NBO) to search a large 'space' of different naturalistic social experiences that systematically varied in their visual (gaze direct to averted) and auditory properties (infant directed speech to nonvocal sounds). We measured oscillatory brain responses (relative theta power) during episodes of naturalistic social experiences in 57 typically developing 6- to 12-month-old infants. Relative theta power was used as input to the NBO algorithm to identify the naturalistic social context that maximally elicited attention in each individual infant. Results showed that individual infants were heterogeneous in the stimulus that elicited maximal theta with no overall stronger attention for direct gaze or infant-directed speech; however, individual differences in attention towards averted gaze were related to interpersonal skills and greater likelihood of preferring speech and direct gaze was observed in infants whose parents showed more positive affect. Our work indicates NBO may be a fruitful method for probing the role of distinct social cues in eliciting attention in naturalistic social contexts at the individual level.

Language Experience Modulates the Visual N200 Response for Disyllabic Chinese Words: An Event-Related Potential Study

Prior event-related potential (ERP) research on how the brain processes non-alphabetic scripts like Chinese has identified an N200 component related to early visual processing of Chinese disyllabic words. An enhanced N200 response was observed when similar prime-target pairs were presented, but it was not elicited when native Chinese speakers read Korean Hangul, a script resembling Chinese characters. This led to the proposal that N200 was not a universal marker for orthographic processing but rather specific and unique to Chinese. However, there was uncertainty due to the absence of Korean participants in the previous research. The impact of language experience on N200 remains unclear. To address this, the present pilot ERP study included three adult groups (totaling 30 participants) with varying language proficiency levels. The participants judged if randomly presented words were Chinese or Korean, while the ERP responses were recorded. The behavioral data showed high accuracy across the groups. The reaction times differed between the groups with the native speakers responding faster. The N200 patterns varied across the groups. Both Chinese native speakers and Chinese-as-second-language learners showed stronger N200 responses for Chinese words compared to Korean words regardless of whether an adaptive or a fixed-time window was used for the N200 quantification, but this was not the case for Korean native speakers. Our cross-linguistic study suggests that N200 is not exclusive to Chinese orthography. Instead, it reflects general visual processing sensitive to both orthographic features and learning experience.

Does musicianship influence the perceptual integrality of tones and segmental information?

This study investigated the effect of musicianship on the perceptual integrality of tones and segmental information in non-native speech perception. We tested 112 Cantonese musicians, Cantonese non-musicians, English musicians, and English non-musicians with a modified Thai tone AX discrimination task. In the tone discrimination task, the control block only contained tonal variations, whereas the orthogonal block contained both tonal and task-irrelevant segmental variations. Relative to their own performance in the control block, the Cantonese listeners showed decreased sensitivity index (d') and increased response time in the orthogonal block, reflecting integral perception of tones and segmental information. By contrast, the English listeners performed similarly across the two blocks, indicating independent perception. Bayesian analysis revealed that the Cantonese musicians and the Cantonese non-musicians perceived Thai tones and segmental information equally integrally. Moreover, the English musicians and the English non-musicians showed similar degrees of independent perception. Based on the above results, musicianship does not seem to influence tone-segmental perceptual integrality. While musicianship apparently enhances tone sensitivity, not all musical advantages are transferrable to the language domain.

How infant-directed actions enhance infants' attention, learning, and exploration: Evidence from EEG and computational modeling

When teaching infants new actions, parents tend to modify their movements. Infants prefer these infant-directed actions (IDAs) over adult-directed actions and learn well from them. Yet, it remains unclear how parents' action modulations capture infants' attention. Typically, making movements larger than usual is thought to draw attention. Recent findings, however, suggest that parents might exploit movement variability to highlight actions. We hypothesized that variability in movement amplitude rather than higher amplitude is capturing infants' attention during IDAs. Using EEG, we measured 15-month-olds' brain activity while they were observing action demonstrations with normal, high, or variable amplitude movements. Infants' theta power (4-5 Hz) in fronto-central channels was compared between conditions. Frontal theta was significantly higher, indicating stronger attentional engagement, in the variable compared to the other conditions. Computational modelling showed that infants' frontal theta power was predicted best by how surprising each movement was. Thus, surprise induced by variability in movements rather than large movements alone engages infants' attention during IDAs. Infants with higher theta power for variable movements were more likely to perform actions successfully and to explore objects novel in the context of the given goal. This highlights the brain mechanisms by which IDAs enhance infants' attention, learning, and exploration.

Neural responses to affective speech, including motherese, map onto clinical and social eye tracking profiles in toddlers with ASD

Affective speech, including motherese, captures an infant's attention and enhances social, language and emotional development. Decreased behavioural response to affective speech and reduced caregiver-child interactions are early signs of autism in infants. To understand this, we measured neural responses to mild affect speech, moderate affect speech and motherese using natural sleep functional magnetic resonance imaging and behavioural preference for motherese using eye tracking in typically developing toddlers and those with autism. By combining diverse neural-clinical data using similarity network fusion, we discovered four distinct clusters of toddlers. The autism cluster with the weakest superior temporal responses to affective speech and very poor social and language abilities had reduced behavioural preference for motherese, while the typically developing cluster with the strongest superior temporal response to affective speech showed the opposite effect. We conclude that significantly reduced behavioural preference for motherese in autism is related to impaired development of temporal cortical systems that normally respond to parental affective speech.

Language development in infants with hearing loss: Benefits of infant-directed speech

The majority of infants with permanent congenital hearing loss fall significantly behind their normal hearing peers in the development of receptive and expressive oral communication skills. Independent of any prosthetic intervention ("hardware") for infants with hearing loss, the social and linguistic environment ("software") can still be optimal or sub-optimal and so can exert significant positive or negative effects on speech and language acquisition, with far-reaching beneficial or adverse effects, respectively. This review focusses on the nature of the social and linguistic environment of infants with hearing loss, in particular others' speech to infants. The nature of this "infant-directed speech" and its effects on language development has been studied extensively in hearing infants but far less comprehensively in infants with hearing loss. Here, literature on the nature of infant-directed speech and its impact on the speech perception and language acquisition in infants with hearing loss is reviewed. The review brings together evidence on the little-studied effects of infant-directed speech on speech and language development in infants with hearing loss, and provides suggestions, over and above early screening and external treatment, for a natural intervention at the level of the carer-infant microcosm that may well optimize the early linguistic experiences and mitigate later adverse effects for infants born with hearing loss.

Setting the Stage for Speech Production: Infants Prefer Listening to Speech Sounds With Infant Vocal Resonances

PURPOSE

Current models of speech development argue for an early link between speech production and perception in infants. Recent data show that young infants (at 4-6 months) preferentially attend to speech sounds (vowels) with infant vocal properties compared to those with adult vocal properties, suggesting the presence of special "memory banks" for one's own nascent speech-like productions. This study investigated whether the vocal resonances (formants) of the infant vocal tract are sufficient to elicit this preference and whether this perceptual bias changes with age and emerging vocal production skills.

METHOD

We selectively manipulated the fundamental frequency (f₀ ) of vowels synthesized with formants specifying either an infant or adult vocal tract, and then tested the effects of those manipulations on the listening preferences of infants who were slightly older than those previously tested (at 6-8 months).

RESULTS

Unlike findings with younger infants (at 4-6 months), slightly older infants in Experiment 1 displayed a robust preference for vowels with infant formants over adult formants when f₀ was matched. The strength of this preference was also positively correlated with age among infants between 4 and 8 months. In Experiment 2, this preference favoring infant over adult formants was maintained when f₀ values were modulated.

CONCLUSIONS

Infants between 6 and 8 months of age displayed a robust and distinct preference for speech with resonances specifying a vocal tract that is similar in size and length to their own. This finding, together with data indicating that this preference is not present in younger infants and appears to increase with age, suggests that nascent knowledge of the motor schema of the vocal tract may play a role in shaping this perceptual bias, lending support to current models of speech development.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.17131805.

Investigating Heritage Language Processing: Meaning Composition in Chinese Classifier-Noun Phrasal Contexts

The aim of the present study was to investigate how Chinese-Malay bilingual speakers with Chinese as heritage language process semantic congruency effects in Chinese and how their brain activities compare to those of monolingual Chinese speakers using electroencephalography (EEG) recordings. To this end, semantic congruencies were manipulated in Chinese classifier-noun phrases, resulting in four conditions: (i) a strongly constraining/high-cloze, plausible (SP) condition, (ii) a weakly constraining/low-cloze, plausible (WP) condition, (iii) a strongly constraining/implausible (SI) condition, and (iv) a weakly constraining/implausible (WI) condition. The analysis of EEG data focused on two event-related potential components, i.e., the N400, which is known for its sensitivity to semantic fit of a target word to its context, and a post-N400 late positive complex (LPC), which is linked to semantic integration after prediction violations and retrospective, evaluative processes. We found similar N400/LPC effects in response to the manipulations of semantic congruency in the mono- and bilingual groups, with a gradient N400 pattern (WI/SI > WP > SP), a larger frontal LPC in response to WP compared to SP, SI, and WI, as well as larger centro-parietal LPCs in response to WP compared to SI and WI, and a larger centro-parietal LPC for SP compared to SI. These results suggest that, in terms of event-related potential (ERP) data, Chinese-Malay early bilingual speakers predict and integrate upcoming semantic information in Chinese classifier-noun phrase to the same extent as monolingual Chinese speakers. However, the global field power (GFP) data showed significant differences between SP and WP in the N400 and LPC time windows in bilinguals, whereas no such effects were observed in monolinguals. This finding was interpreted as showing that bilinguals differ from their monolingual peers in terms of global field power intensity of the brain by processing plausible classifier-noun pairs with different congruency effects.

Neurophysiological Correlates of Asymmetries in Vowel Perception: An English-French Cross-Linguistic Event-Related Potential Study

Behavioral studies examining vowel perception in infancy indicate that, for many vowel contrasts, the ease of discrimination changes depending on the order of stimulus presentation, regardless of the language from which the contrast is drawn and the ambient language that infants have experienced. By adulthood, linguistic experience has altered vowel perception; analogous asymmetries are observed for non-native contrasts but are mitigated for native contrasts. Although these directional effects are well documented behaviorally, the brain mechanisms underlying them are poorly understood. In the present study we begin to address this gap. We first review recent behavioral work which shows that vowel perception asymmetries derive from phonetic encoding strategies, rather than general auditory processes. Two existing theoretical models-the Natural Referent Vowel framework and the Native Language Magnet model-are invoked as a means of interpreting these findings. Then we present the results of a neurophysiological study which builds on this prior work. Using event-related brain potentials, we first measured and assessed the mismatch negativity response (MMN, a passive neurophysiological index of auditory change detection) in English and French native-speaking adults to synthetic vowels that either spanned two different phonetic categories (/y/vs./u/) or fell within the same category (/u/). Stimulus presentation was organized such that each vowel was presented as standard and as deviant in different blocks. The vowels were presented with a long (1,600-ms) inter-stimulus interval to restrict access to short-term memory traces and tap into a "phonetic mode" of processing. MMN analyses revealed weak asymmetry effects regardless of the (i) vowel contrast, (ii) language group, and (iii) MMN time window. Then, we conducted time-frequency analyses of the standard epochs for each vowel. In contrast to the MMN analysis, time-frequency analysis revealed significant differences in brain oscillations in the theta band (4-8 Hz), which have been linked to attention and processing efficiency. Collectively, these findings suggest that early-latency (pre-attentive) mismatch responses may not be a strong neurophysiological correlate of asymmetric behavioral vowel discrimination. Rather, asymmetries may reflect differences in neural processing efficiency for vowels with certain inherent acoustic-phonetic properties, as revealed by theta oscillatory activity.

Neural coding of formant-exaggerated speech and nonspeech in children with and without autism spectrum disorders

The presence of vowel exaggeration in infant-directed speech (IDS) may adapt to the age-appropriate demands in speech and language acquisition. Previous studies have provided behavioral evidence of atypical auditory processing towards IDS in children with autism spectrum disorders (ASD), while the underlying neurophysiological mechanisms remain unknown. This event-related potential (ERP) study investigated the neural coding of formant-exaggerated speech and nonspeech in 24 4- to 11-year-old children with ASD and 24 typically-developing (TD) peers. The EEG data were recorded using an alternating block design, in which each stimulus type (exaggerated/non-exaggerated sound) was presented with equal probability. ERP waveform analysis revealed an enhanced P1 for vowel formant exaggeration in the TD group but not in the ASD group. This speech-specific atypical processing in ASD was not found for the nonspeech stimuli which showed similar P1 enhancement in both ASD and TD groups. Moreover, the time-frequency analysis indicated that children with ASD showed differences in neural synchronization in the delta-theta bands for processing acoustic formant changes embedded in nonspeech. Collectively, the results add substantiating neurophysiological evidence (i.e., a lack of neural enhancement effect of vowel exaggeration) for atypical auditory processing of IDS in children with ASD, which may exert a negative effect on phonetic encoding and language learning. LAY SUMMARY: Atypical responses to motherese might act as a potential early marker of risk for children with ASD. This study investigated the neural responses to such socially relevant stimuli in the ASD brain, and the results suggested a lack of neural enhancement responding to the motherese even in individuals without intellectual disability.

The Role of Affectionate Caregiver Touch in Early Neurodevelopment and Parent-Infant Interactional Synchrony

Though rarely included in studies of parent–infant interactions, affectionate touch plays a unique and vital role in infant development. Previous studies in human and rodent models have established that early and consistent affectionate touch from a caregiver confers wide-ranging and holistic benefits for infant psychosocial and neurophysiological development. We begin with an introduction to the neurophysiological pathways for the positive effects of touch. Then, we provide a brief review of how affectionate touch tunes the development of infant somatosensory, autonomic (stress regulation), and immune systems. Affective touch also plays a foundational role in the establishment of social affiliative bonds and early psychosocial behavior. These touch-related bonding effects are known to be mediated primarily by the oxytocin system, but touch also activates mesocorticolimbic dopamine and endogenous opioid systems which aid the development of social cognitive processes such as social learning and reward processing. We conclude by proposing a unique role for affectionate touch as an essential pathway to establishing and maintaining parent-infant interactional synchrony at behavioral and neural levels. The limitations of the current understanding of affectionate touch in infant development point to fruitful avenues for future research.

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.

Acoustic features of infant-directed speech to infants with hearing loss

This study investigated the effects of hearing loss and hearing experience on the acoustic features of infant-directed speech (IDS) to infants with hearing loss (HL) compared to controls with normal hearing (NH) matched by either chronological or hearing age (experiment 1) and across development in infants with hearing loss as well as the relation between IDS features and infants' developing lexical abilities (experiment 2). Both experiments included detailed acoustic analyses of mothers' productions of the three corner vowels /a, i, u/ and utterance-level pitch in IDS and in adult-directed speech. Experiment 1 demonstrated that IDS to infants with HL was acoustically more variable than IDS to hearing-age matched infants with NH. Experiment 2 yielded no changes in IDS features over development; however, the results did show a positive relationship between formant distances in mothers' speech and infants' concurrent receptive vocabulary size, as well as between vowel hyperarticulation and infants' expressive vocabulary. These findings suggest that despite infants' HL and thus diminished access to speech input, infants with HL are exposed to IDS with generally similar acoustic qualities as are infants with NH. However, some differences persist, indicating that infants with HL might receive less intelligible speech.

Intention to imitate: Top-down effects on 4-year-olds' neural processing of others' actions

From early in life, we activate our neural motor system when observing others' actions. In adults, this so-called mirroring is modulated not only by the saliency of an action but also by top-down processes, like the intention to imitate it. Yet, it remains unknown whether neural processing of others' actions can be modulated by top-down processes in young children who heavily rely on learning from observing and imitating others but also still develop top-down control skills. Using EEG, we examined whether the intention to imitate increases 4-year-olds' motor activation while observing others' actions. In a within-subjects design, children observed identical actions preceded by distinct instructions, namely to either imitate the action or to name the toy's color. As motor activation index, children's alpha (7-12 Hz) and beta (16-20 Hz) power over motor cortices was analyzed. The results revealed more motor activity reflected by significantly lower beta power for the Imitation compared to the Color-naming Task. The same conditional difference, although differently located, was detected for alpha power. Together, our results show that children's neural processing of others' actions was amplified by their intention to imitate the action. Thus, already at age 4 top-down attention to others' actions can modulate neural action processing.

The rhythm of learning: Theta oscillations as an index of active learning in infancy

Active learning is a critical component of human development, however, the mechanisms supporting it are not fully understood. Given that early learning experiences may affect both infants' immediate learning success, as well as their motivation to learn, it is particularly important to investigate the mechanisms of active learning in this period, when the foundations of learning habits and curiosity are built. Traditional behavioural approaches of studying infant learning face challenges that emerging tools from neuroscience may help relieve. We introduce one such tool, EEG theta oscillations, and propose this neural marker has great potential for offering novel insights into active learning. Theta activity, recorded prior to or during learning, has been shown to be predictive of learning success. We argue that this involvement in memory formation, combined with theta activity's tight association with reward processing, makes theta oscillations a uniquely suited tool for the investigation of motivational mechanisms underlying active learning. We outline research questions as well as methodological approaches pertinent to infant learning and suggest how and why theta oscillations may offer complementary insights. As such, we aim to bridge the gap between cognitive and neural approaches, and advance our knowledge of active learning in development more broadly.

Investigating Influences of Medial Olivocochlear Efferent System on Central Auditory Processing and Listening in Noise: A Behavioral and Event-Related Potential Study

This electrophysiological study investigated the role of the medial olivocochlear (MOC) efferents in listening in noise. Both ears of eleven normal-hearing adult participants were tested. The physiological tests consisted of transient-evoked otoacoustic emission (TEOAE) inhibition and the measurement of cortical event-related potentials (ERPs). The mismatch negativity (MMN) and P300 responses were obtained in passive and active listening tasks, respectively. Behavioral responses for the word recognition in noise test were also analyzed. Consistent with previous findings, the TEOAE data showed significant inhibition in the presence of contralateral acoustic stimulation. However, performance in the word recognition in noise test was comparable for the two conditions (i.e., without contralateral stimulation and with contralateral stimulation). Peak latencies and peak amplitudes of MMN and P300 did not show changes with contralateral stimulation. Behavioral performance was also maintained in the P300 task. Together, the results show that the peripheral auditory efferent effects captured via otoacoustic emission (OAE) inhibition might not necessarily be reflected in measures of central cortical processing and behavioral performance. As the MOC effects may not play a role in all listening situations in adults, the functional significance of the cochlear effects of the medial olivocochlear efferents and the optimal conditions conducive to corresponding effects in behavioral and cortical responses remain to be elucidated.

Hypnotizability-Related Effects of Pain Expectation on the Later Modulation of Cortical Connectivity

This study examined hypnotizability-related modulation of the cortical network following expected and nonexpected nociceptive stimulation. The electroencephalogram (EEG) was recorded in 9 high (highs) and 8 low (lows) hypnotizable participants receiving nociceptive stimulation with (W1) and without (noW) a visual warning preceding the stimulation by 1 second. W1 and noW were compared to baseline conditions to assess the presence of any later effect and between each other to assess the effects of expectation. The studied EEG variables measured local and global features of the cortical connectivity. With respect to lows, highs exhibited scarce differences between experimental conditions. The hypnotizability-related differences in the later processing of nociceptive information could be relevant to the development of pain-related individual traits. Present findings suggest a lower impact of nociceptive stimulation in highs than in lows.

Toward the Understanding of Topographical and Spectral Signatures of Infant Movement Artifacts in Naturalistic EEG

Electroencephalography (EEG) is perhaps the most widely used brain-imaging technique for pediatric populations. However, EEG signals are prone to distortion by motion. Compared to adults, infants' motion is both more frequent and less stereotypical yet motion effects on the infant EEG signal are largely undocumented. Here, we present a systematic assessment of naturalistic motion effects on the infant EEG signal. EEG recordings were performed with 14 infants (12 analyzed) who passively watched movies whilst spontaneously producing periods of bodily movement and rest. Each infant produced an average of 38.3 s (SD = 14.7 s) of rest and 18.8 s (SD = 17.9 s) of single motion segments for the final analysis. Five types of infant motions were analyzed: Jaw movements, and Limb movements of the Hand, Arm, Foot, and Leg. Significant movement-related distortions of the EEG signal were detected using cluster-based permutation analysis. This analysis revealed that, relative to resting state, infants' Jaw and Arm movements produced significant increases in beta (∼15 Hz) power, particularly over peripheral sites. Jaw movements produced more anteriorly located effects than Arm movements, which were most pronounced over posterior parietal and occipital sites. The cluster analysis also revealed trends toward decreased power in the theta and alpha bands observed over central topographies for all motion types. However, given the very limited quantity of infant data in this study, caution is recommended in interpreting these findings before subsequent replications are conducted. Nonetheless, this work is an important first step to inform future development of methods for addressing EEG motion-related artifacts. This work also supports wider use of naturalistic paradigms in social and developmental neuroscience.

Neural Coding of Syllable-Final Fricatives with and without Hearing Aid Amplification

BACKGROUND

Cortical auditory event-related potentials are a potentially useful clinical tool to objectively assess speech outcomes with rehabilitative devices. Whether hearing aids reliably encode the spectrotemporal characteristics of fricative stimuli in different phonological contexts and whether these differences result in distinct neural responses with and without hearing aid amplification remain unclear.

PURPOSE

To determine whether the neural coding of the voiceless fricatives /s/ and /ʃ/ in the syllable-final context reliably differed without hearing aid amplification and whether hearing aid amplification altered neural coding of the fricative contrast.

RESEARCH DESIGN

A repeated-measures, within subject design was used to compare the neural coding of a fricative contrast with and without hearing aid amplification.

STUDY SAMPLE

Ten adult listeners with normal hearing participated in the study.

DATA COLLECTION AND ANALYSIS

Cortical auditory event-related potentials were elicited to an /ɑs/-/ɑʃ/ vowel-fricative contrast in unaided and aided listening conditions. Neural responses to the speech contrast were recorded at 64-electrode sites. Peak latencies and amplitudes of the cortical response waveforms to the fricatives were analyzed using repeated-measures analysis of variance.

RESULTS

The P2' component of the acoustic change complex significantly differed from the syllable-final fricative contrast with and without hearing aid amplification. Hearing aid amplification differentially altered the neural coding of the contrast across frontal, temporal, and parietal electrode regions.

CONCLUSIONS

Hearing aid amplification altered the neural coding of syllable-final fricatives. However, the contrast remained acoustically distinct in the aided and unaided conditions, and cortical responses to the fricative significantly differed with and without the hearing aid.

Interpersonal Neural Entrainment during Early Social Interaction

Currently, we understand much about how children's brains attend to and learn from information presented while they are alone, viewing a screen - but less about how interpersonal social influences are substantiated in the brain. Here, we consider research that examines how social behaviors affect not one, but both partners in a dyad. We review studies that measured interpersonal neural entrainment during early social interaction, considering two ways of measuring entrainment: concurrent entrainment (e.g., 'when A is high, B is high' - also known as synchrony) and sequential entrainment ('changes in A forward-predict changes in B'). We discuss possible causes of interpersonal neural entrainment, and consider whether it is merely an epiphenomenon, or whether it plays an independent, mechanistic role in early attention and learning.

Perception of audiovisual infant directed speech

Infant perception often deals with audiovisual speech input and a first step in processing this input is to perceive both visual and auditory information. The speech directed to infants has special characteristics and may enhance visual aspects of speech. The current study was designed to explore the impact of visual enhancement in infant-directed speech (IDS) on audiovisual mismatch detection in a naturalistic setting. Twenty infants participated in an experiment with a visual fixation task conducted in participants' homes. Stimuli consisted of IDS and adult-directed speech (ADS) syllables with a plosive and the vowel /a:/, /i:/ or /u:/. These were either audiovisually congruent or incongruent. Infants looked longer at incongruent than congruent syllables and longer at IDS than ADS syllables, indicating that IDS and incongruent stimuli contain cues that can make audiovisual perception challenging and thereby attract infants' gaze.

The Role of Temporal Acoustic Exaggeration in High Variability Phonetic Training: A Behavioral and ERP Study

High variability phonetic training (HVPT) has been found to be effective in helping adult learners acquire non-native phonetic contrasts. The present study investigated the role of temporal acoustic exaggeration by comparing the canonical HVPT paradigm without involving acoustic exaggeration with a modified adaptive HVPT paradigm that integrated key temporal exaggerations in infant-directed speech (IDS). Sixty native Chinese adults participated in the training of the English /i/ and /i/ vowel contrast and were randomly assigned to three subject groups. Twenty were trained with the typical HVPT paradigm (the HVPT group), twenty were trained under the modified adaptive approach with acoustic exaggeration (the HVPT-E group), and twenty were in the control group. Behavioral tasks for the pre- and post- tests used natural word identification, synthetic stimuli identification, and synthetic stimuli discrimination. Mismatch negativity (MMN) responses from the HVPT-E group were also obtained to assess the training effects in within- and across- category discrimination without requiring focused attention. Like previous studies, significant generalization effects to new talkers were found in both the HVPT group and the HVPT-E group. The HVPT-E group, by contrast, showed greater improvement as reflected in larger progress in natural word identification performance. Furthermore, the HVPT-E group exhibited more native-like categorical perception based on spectral cues after training, together with corresponding training-induced changes in the MMN responses to within- and across- category differences. These data provide the initial evidence supporting the important role of temporal acoustic exaggeration with adaptive training in facilitating phonetic learning and promoting brain plasticity at the perceptual and pre-attentive neural levels.

Theta oscillations in 4-year-olds are sensitive to task engagement and task demands

Top-down control processes are essential for guiding attention and working memory towards task-relevant information. Recently, theta oscillations were suggested as critical for these cognitive processes. Infant studies testing a mixture of bottom-up and top-down processes support adult theta findings. Yet, since infants cannot be instructed, it remains unclear to what extent theta oscillations are involved particularly in top-down control in early childhood. That is especially relevant towards school age when children need top-down control to solve the increasingly complex tasks. In this EEG study, we investigated whether theta-power in 4-year-olds is sensitive to task engagement and to different cognitive task demands. In a within-subjects design, children had three different instructions before watching videos including either no demands (No Task), language-related (Color-naming Task), or action-related (Imitation Task) demands. We analyzed children’s theta-power (3–6 Hz) in two contrasts: (1) Task vs. No Task and (2) Color-naming vs. Imitation Task. The findings revealed more frontomedial theta-power when children were engaged in a task and their frontomedial theta-power increased during their cognitive engagement. Theta-power was stronger over left fronto-temporal sites for language- compared to action-related demands. These findings support recent theoretical work highlighting theta oscillations in top-down control and extend this neurocognitive framework to preschoolers.

Infant-directed speech facilitates seven-month-old infants' cortical tracking of speech

This study assessed cortical tracking of temporal information in incoming natural speech in seven-month-old infants. Cortical tracking refers to the process by which neural activity follows the dynamic patterns of the speech input. In adults, it has been shown to involve attentional mechanisms and to facilitate effective speech encoding. However, in infants, cortical tracking or its effects on speech processing have not been investigated. This study measured cortical tracking of speech in infants and, given the involvement of attentional mechanisms in this process, cortical tracking of both infant-directed speech (IDS), which is highly attractive to infants, and the less captivating adult-directed speech (ADS), were compared. IDS is the speech register parents use when addressing young infants. In comparison to ADS, it is characterised by several acoustic qualities that capture infants' attention to linguistic input and assist language learning. Seven-month-old infants' cortical responses were recorded via electroencephalography as they listened to IDS or ADS recordings. Results showed stronger low-frequency cortical tracking of the speech envelope in IDS than in ADS. This suggests that IDS has a privileged status in facilitating successful cortical tracking of incoming speech which may, in turn, augment infants' early speech processing and even later language development.

Role of inter-trial phase coherence in atypical auditory evoked potentials to speech and nonspeech stimuli in children with autism

OBJECTIVE

This autism study investigated how inter-trial phase coherence (ITPC) drives abnormalities in auditory evoked potential (AEP) responses for speech and nonspeech stimuli.

METHODS

Auditory P1-N2 responses and ITPCs in the theta band (4-7 Hz) for pure tones and words were assessed with EEG data from 15 school-age children with autism and 16 age-matched typically developing (TD) controls.

RESULTS

The autism group showed enhanced P1 and reduced N2 for both speech and nonspeech stimuli in comparison with the TD group. Group differences were also found with enhanced theta ITPC for P1 followed by ITPC reduction for N2 in the autism group. The ITPC values were significant predictors of P1 and N2 amplitudes in both groups.

CONCLUSIONS

Abnormal trial-to-trial phase synchrony plays an important role in AEP atypicalities in children with autism. ITPC-driven enhancement as well as attenuation in different AEP components may coexist, depending on the stage of information processing.

SIGNIFICANCE

It is necessary to examine the time course of auditory evoked potentials and the corresponding inter-trial coherence of neural oscillatory activities to better understand hyper- and hypo- sensitive responses in autism, which has important implications for sensory based treatment.

The integration of audio-tactile information is modulated by multimodal social interaction with physical contact in infancy

Interaction between caregivers and infants is multimodal in nature. To react interactively and smoothly to such multimodal signals, infants must integrate all these signals. However, few empirical infant studies have investigated how multimodal social interaction with physical contact facilitates multimodal integration, especially regarding audio - tactile (A-T) information. By using electroencephalogram (EEG) and event-related potentials (ERPs), the present study investigated how neural processing involved in A-T integration is modulated by tactile interaction. Seven- to 8-months-old infants heard one pseudoword both whilst being tickled (multimodal 'A-T' condition), and not being tickled (unimodal 'A' condition). Thereafter, their EEG was measured during the perception of the same words. Compared to the A condition, the A-T condition resulted in enhanced ERPs and higher beta-band activity within the left temporal regions, indicating neural processing of A-T integration. Additionally, theta-band activity within the middle frontal region was enhanced, which may reflect enhanced attention to social information. Furthermore, differential ERPs correlated with the degree of engagement in the tickling interaction. We provide neural evidence that the integration of A-T information in infants' brains is facilitated through tactile interaction with others. Such plastic changes in neural processing may promote harmonious social interaction and effective learning in infancy.

Neural Correlates of Selective Attention With Hearing Aid Use Followed by ReadMyQuips Auditory Training Program

OBJECTIVES

The objectives of this study were to investigate the effects of hearing aid use and the effectiveness of ReadMyQuips (RMQ), an auditory training program, on speech perception performance and auditory selective attention using electrophysiological measures. RMQ is an audiovisual training program designed to improve speech perception in everyday noisy listening environments.

DESIGN

Participants were adults with mild to moderate hearing loss who were first-time hearing aid users. After 4 weeks of hearing aid use, the experimental group completed RMQ training in 4 weeks, and the control group received listening practice on audiobooks during the same period. Cortical late event-related potentials (ERPs) and the Hearing in Noise Test (HINT) were administered at prefitting, pretraining, and post-training to assess effects of hearing aid use and RMQ training. An oddball paradigm allowed tracking of changes in P3a and P3b ERPs to distractors and targets, respectively. Behavioral measures were also obtained while ERPs were recorded from participants.

RESULTS

After 4 weeks of hearing aid use but before auditory training, HINT results did not show a statistically significant change, but there was a significant P3a reduction. This reduction in P3a was correlated with improvement in d prime (d') in the selective attention task. Increased P3b amplitudes were also correlated with improvement in d' in the selective attention task. After training, this correlation between P3b and d' remained in the experimental group, but not in the control group. Similarly, HINT testing showed improved speech perception post training only in the experimental group. The criterion calculated in the auditory selective attention task showed a reduction only in the experimental group after training. ERP measures in the auditory selective attention task did not show any changes related to training.

CONCLUSIONS

Hearing aid use was associated with a decrement in involuntary attention switch to distractors in the auditory selective attention task. RMQ training led to gains in speech perception in noise and improved listener confidence in the auditory selective attention task.

A universal bias in adult vowel perception - By ear or by eye

Speech perceivers are universally biased toward "focal" vowels (i.e., vowels whose adjacent formants are close in frequency, which concentrates acoustic energy into a narrower spectral region). This bias is demonstrated in phonetic discrimination tasks as a directional asymmetry: a change from a relatively less to a relatively more focal vowel results in significantly better performance than a change in the reverse direction. We investigated whether the critical information for this directional effect is limited to the auditory modality, or whether visible articulatory information provided by the speaker's face also plays a role. Unimodal auditory and visual as well as bimodal (auditory-visual) vowel stimuli were created from video recordings of a speaker producing variants of /u/, differing in both their degree of focalization and visible lip rounding (i.e., lip compression and protrusion). In Experiment 1, we confirmed that subjects showed an asymmetry while discriminating the auditory vowel stimuli. We then found, in Experiment 2, a similar asymmetry when subjects lip-read those same vowels. In Experiment 3, we found asymmetries, comparable to those found for unimodal vowels, for bimodal vowels when the audio and visual channels were phonetically-congruent. In contrast, when the audio and visual channels were phonetically-incongruent (as in the "McGurk effect"), this asymmetry was disrupted. These findings collectively suggest that the perceptual processes underlying the "focal" vowel bias are sensitive to articulatory information available across sensory modalities, and raise foundational issues concerning the extent to which vowel perception derives from general-auditory or speech-gesture-specific processes.

Application of Linear Mixed-Effects Models in Human Neuroscience Research: A Comparison with Pearson Correlation in Two Auditory Electrophysiology Studies

Neurophysiological studies are often designed to examine relationships between measures from different testing conditions, time points, or analysis techniques within the same group of participants. Appropriate statistical techniques that can take into account repeated measures and multivariate predictor variables are integral and essential to successful data analysis and interpretation. This work implements and compares conventional Pearson correlations and linear mixed-effects (LME) regression models using data from two recently published auditory electrophysiology studies. For the specific research questions in both studies, the Pearson correlation test is inappropriate for determining strengths between the behavioral responses for speech-in-noise recognition and the multiple neurophysiological measures as the neural responses across listening conditions were simply treated as independent measures. In contrast, the LME models allow a systematic approach to incorporate both fixed-effect and random-effect terms to deal with the categorical grouping factor of listening conditions, between-subject baseline differences in the multiple measures, and the correlational structure among the predictor variables. Together, the comparative data demonstrate the advantages as well as the necessity to apply mixed-effects models to properly account for the built-in relationships among the multiple predictor variables, which has important implications for proper statistical modeling and interpretation of human behavior in terms of neural correlates and biomarkers.

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

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.

Infants' preferences for native speakers are associated with an expectation of information

Humans' preference for others who share our group membership is well documented, and this heightened valuation of in-group members seems to be rooted in early development. Before 12 mo of age, infants already show behavioral preferences for others who evidence cues to same-group membership such as race or native language, yet the function of this selectivity remains unclear. We examine one of these social biases, the preference for native speakers, and propose that this preference may result from infants' motivation to obtain information and the expectation that interactions with native speakers will provide better opportunities for learning. To investigate this hypothesis, we measured EEG theta activity, a neural rhythm shown to index active and selective preparation for encoding information in adults. In study 1, we established that 11-mo-old infants exhibit an increase in theta activation in situations when they can expect to receive information. We then used this neural measure of anticipatory theta activity to explore the expectations of 11-mo-olds when facing social partners who either speak the infants' native language or a foreign tongue (study 2). A larger increase in theta oscillations was observed when infants could expect to receive information from the native speaker, indicating that infants were preparing to learn information from the native speaker to a greater extent than from the foreign speaker. While previous research has demonstrated that infants prefer to interact with knowledgeable others, the current experiments provide evidence that such an information-seeking motive may also underpin infants' demonstrated preference for native speakers.

Mature neural responses to Infant-Directed Speech but not Adult-Directed Speech in Pre-Verbal Infants

Infant directed speech (IDS), the speech register adults use when talking to infants, has been shown to have positive effects on attracting infants' attention, language learning, and emotional communication. Here event related potentials (ERPs) are used to investigate the neural coding of IDS and ADS (adult directed speech) as well as their discrimination by both infants and adults. Two instances of the vowel /i/, one extracted from ADS and one from IDS, were presented to 9-month-old infants and adults in two oddball conditions: ADS standard/IDS deviant and IDS standard/ADS deviant. In Experiment 1 with adults, the obligatory ERPs that code acoustic information were different for ADS and IDS; and discrimination, indexed by mismatch negativity (MMN) responses, showed that IDS and ADS deviants were discriminated equally well; although, the P3a response was larger for IDS suggesting it captured adults' attention more than did ADS. In infants the obligatory responses did not differ for IDS and ADS, but for discrimination, while IDS deviants generated both a slow-positive mismatch response (MMR) as well as an adult-like MMN, the ADS deviants generated only an MMR. The presence of a mature adult-like MMN suggests that the IDS stimulus is easier to discriminate for infants.

Infant Directed Speech Enhances Statistical Learning in Newborn Infants: An ERP Study

Statistical learning and the social contexts of language addressed to infants are hypothesized to play important roles in early language development. Previous behavioral work has found that the exaggerated prosodic contours of infant-directed speech (IDS) facilitate statistical learning in 8-month-old infants. Here we examined the neural processes involved in on-line statistical learning and investigated whether the use of IDS facilitates statistical learning in sleeping newborns. Event-related potentials (ERPs) were recorded while newborns were exposed to12 pseudo-words, six spoken with exaggerated pitch contours of IDS and six spoken without exaggerated pitch contours (ADS) in ten alternating blocks. We examined whether ERP amplitudes for syllable position within a pseudo-word (word-initial vs. word-medial vs. word-final, indicating statistical word learning) and speech register (ADS vs. IDS) would interact. The ADS and IDS registers elicited similar ERP patterns for syllable position in an early 0-100 ms component but elicited different ERP effects in both the polarity and topographical distribution at 200-400 ms and 450-650 ms. These results provide the first evidence that the exaggerated pitch contours of IDS result in differences in brain activity linked to on-line statistical learning in sleeping newborns.

Perceptual Temporal Asymmetry Associated with Distinct ON and OFF Responses to Time-Varying Sounds with Rising versus Falling Intensity: A Magnetoencephalography Study

This magnetoencephalography (MEG) study investigated evoked ON and OFF responses to ramped and damped sounds in normal-hearing human adults. Two pairs of stimuli that differed in spectral complexity were used in a passive listening task; each pair contained identical acoustical properties except for the intensity envelope. Behavioral duration judgment was conducted in separate sessions, which replicated the perceptual bias in favour of the ramped sounds and the effect of spectral complexity on perceived duration asymmetry. MEG results showed similar cortical sites for the ON and OFF responses. There was a dominant ON response with stronger phase-locking factor (PLF) in the alpha (8–14 Hz) and theta (4–8 Hz) bands for the damped sounds. In contrast, the OFF response for sounds with rising intensity was associated with stronger PLF in the gamma band (30–70 Hz). Exploratory correlation analysis showed that the OFF response in the left auditory cortex was a good predictor of the perceived temporal asymmetry for the spectrally simpler pair. The results indicate distinct asymmetry in ON and OFF responses and neural oscillation patterns associated with the dynamic intensity changes, which provides important preliminary data for future studies to examine how the auditory system develops such an asymmetry as a function of age and learning experience and whether the absence of asymmetry or abnormal ON and OFF responses can be taken as a biomarker for certain neurological conditions associated with auditory processing deficits.

W, Parlato-Oliveira EM. Estratégias de percepção da língua materna: do nascimento até um ano de vida

RESUMO Bebês muito jovens demonstram habilidades linguísticas bastante refinadas, sendo capazes de perceber várias características na fala do adulto. A percepção da língua materna é, pois, imprescindível para a aquisição da linguagem. Esta revisão de literatura trata das habilidades de percepção de fala dos bebês a partir do nascimento até um ano de idade. Para tanto, foi realizada a busca bibliográfica em 7 bases de dados, nos idiomas inglês, francês, português e espanhol, no período de 2007 a 2014. Com esse levantamento bibliográfico foi possível reconhecer como a aquisição da linguagem ocorre de forma rápida e que bebês bem jovens são capazes de utilizar estratégias elaboradas para iniciar tal aquisição.

Neural indices of phonemic discrimination and sentence-level speech intelligibility in quiet and noise: A mismatch negativity study

Successful speech communication requires the extraction of important acoustic cues from irrelevant background noise. In order to better understand this process, this study examined the effects of background noise on mismatch negativity (MMN) latency, amplitude, and spectral power measures as well as behavioral speech intelligibility tasks. Auditory event-related potentials (AERPs) were obtained from 15 normal-hearing participants to determine whether pre-attentive MMN measures recorded in response to a consonant (from /ba/ to /bu/) and vowel change (from /ba/ to /da/) in a double-oddball paradigm can predict sentence-level speech perception. The results showed that background noise increased MMN latencies and decreased MMN amplitudes with a reduction in the theta frequency band power. Differential noise-induced effects were observed for the pre-attentive processing of consonant and vowel changes due to different degrees of signal degradation by noise. Linear mixed-effects models further revealed significant correlations between the MMN measures and speech intelligibility scores across conditions and stimuli. These results confirm the utility of MMN as an objective neural marker for understanding noise-induced variations as well as individual differences in speech perception, which has important implications for potential clinical applications.

Cortical processing of phonetic and emotional information in speech: A cross-modal priming study

The current study employed behavioral and electrophysiological measures to investigate the timing, localization, and neural oscillation characteristics of cortical activities associated with phonetic and emotional information processing of speech. The experimental design used a cross-modal priming paradigm in which the normal adult participants were presented a visual prime followed by an auditory target. Primes were facial expressions that systematically varied in emotional content (happy or angry) and mouth shape (corresponding to /a/ or /i/ vowels). Targets were spoken words that varied by emotional prosody (happy or angry) and vowel (/a/ or /i/). In both the phonetic and prosodic conditions, participants were asked to judge congruency status of the visual prime and the auditory target. Behavioral results showed a congruency effect for both percent correct and reaction time. Two ERP responses, the N400 and late positive response (LPR), were identified in both conditions. Source localization and inter-trial phase coherence of the N400 and LPR components further revealed different cortical contributions and neural oscillation patterns for selective processing of phonetic and emotional information in speech. The results provide corroborating evidence for the necessity of differentiating brain mechanisms underlying the representation and processing of co-existing linguistic and paralinguistic information in spoken language, which has important implications for theoretical models of speech recognition as well as clinical studies on the neural bases of language and social communication deficits.

Syllable Structure Universals and Native Language Interference in Second Language Perception and Production: Positional Asymmetry and Perceptual Links to Accentedness

The present study investigated how syllable structure differences between the first Language (L1) and the second language (L2) affect L2 consonant perception and production at syllable-initial and syllable-final positions. The participants were Mandarin-speaking college students who studied English as a second language. Monosyllabic English words were used in the perception test. Production was recorded from each Chinese subject and rated for accentedness by two native speakers of English. Consistent with previous studies, significant positional asymmetry effects were found across speech sound categories in terms of voicing, place of articulation, and manner of articulation. Furthermore, significant correlations between perception and accentedness ratings were found at the syllable onset position but not for the coda. Many exceptions were also found, which could not be solely accounted for by differences in L1-L2 syllabic structures. The results show a strong effect of language experience at the syllable level, which joins force with acoustic, phonetic, and phonemic properties of individual consonants in influencing positional asymmetry in both domains of L2 segmental perception and production. The complexities and exceptions call for further systematic studies on the interactions between syllable structure universals and native language interference with refined theoretical models to specify the links between perception and production in second language acquisition.

Effects of background noise on inter-trial phase coherence and auditory N1-P2 responses to speech stimuli

This study investigated the effects of a speech-babble background noise on inter-trial phase coherence (ITPC, also referred to as phase locking value (PLV)) and auditory event-related responses (AERP) to speech sounds. Specifically, we analyzed EEG data from 11 normal hearing subjects to examine whether ITPC can predict noise-induced variations in the obligatory N1-P2 complex response. N1-P2 amplitude and latency data were obtained for the /bu/syllable in quiet and noise listening conditions. ITPC data in delta, theta, and alpha frequency bands were calculated for the N1-P2 responses in the two passive listening conditions. Consistent with previous studies, background noise produced significant amplitude reduction and latency increase in N1 and P2, which were accompanied by significant ITPC decreases in all the three frequency bands. Correlation analyses further revealed that variations in ITPC were able to predict the amplitude and latency variations in N1-P2. The results suggest that trial-by-trial analysis of cortical neural synchrony is a valuable tool in understanding the modulatory effects of background noise on AERP measures.