Attenuated brain responses to speech sounds in moderate preterm infants at term age

Recent findings have revealed that very preterm neonates already show the typical brain responses to place of articulation changes in stop consonants, but data on their sensitivity to other types of phonetic changes remain scarce. Here, we examined the impact of 7–8 weeks of extra‐uterine life on the automatic processing of syllables in 20 healthy moderate preterm infants (mean gestational age at birth 33 weeks) matched in maturational age with 20 full‐term neonates, thus differing in their previous auditory experience. This design allows elucidating the contribution of extra‐uterine auditory experience in the immature brain on the encoding of linguistically relevant speech features. Specifically, we collected brain responses to natural CV syllables differing in three dimensions using a multi‐feature mismatch paradigm, with the syllable/ba/ as the standard and three deviants: a pitch change, a vowel change to/bo/ and a consonant voice‐onset time (VOT) change to/pa/. No significant between‐group differences were found for pitch and consonant VOT deviants. However, moderate preterm infants showed attenuated responses to vowel deviants compared to full terms. These results suggest that moderate preterm infants' limited experience with low‐pass filtered speech prenatally can hinder vowel change detection and that exposure to natural speech after birth does not seem to contribute to improve this capacity. These data are in line with recent evidence suggesting a sequential development of a hierarchical functional architecture of speech processing that is highly sensitive to early auditory experience.     

The role of production abilities in the perception of consonant category in infants

The influence of motor knowledge on speech perception is well established, but the functional role of the motor system is still poorly understood. The present study explores the hypothesis that speech production abilities may help infants discover phonetic categories in the speech stream, in spite of coarticulation effects. To this aim, we examined the influence of babbling abilities on consonant categorization in 6‐ and 9‐month‐old infants. Using an intersensory matching procedure, we investigated the infants’ capacity to associate auditory information about a consonant in various vowel contexts with visual information about the same consonant, and to map auditory and visual information onto a common phoneme representation. Moreover, a parental questionnaire evaluated the infants’ consonantal repertoire. In a first experiment using /b/–/d/ consonants, we found that infants who displayed babbling abilities and produced the /b/ and/or the /d/ consonants in repetitive sequences were able to correctly perform intersensory matching, while non‐babblers were not. In a second experiment using the /v/–/z/ pair, which is as visually contrasted as the /b/–/d/ pair but which is usually not produced at the tested ages, no significant matching was observed, for any group of infants, babbling or not. These results demonstrate, for the first time, that the emergence of babbling could play a role in the extraction of vowel‐independent representations for consonant place of articulation. They have important implications for speech perception theories, as they highlight the role of sensorimotor interactions in the development of phoneme representations during the first year of life.     

Parallel processing of auditory and phonetic information in speech discrimination

Recent experiments using a variety of techniques have suggested that speech perception involves separate auditory and phonetic levels of processing. Two models of auditory and phonetic processing appear to be consistent with existing data: (a) a strictserial model in which auditory information would be processed at one level, followed by the processing of phonetic information at a subsequent level; and (b) aparallel model in which auditory and phonetic processing could proceed simultaneously. The present experiment attempted to distinguish empirically between these two models. Ss identified either an auditory dimension (fundamental frequency) or a phonetic dimension (place of articulation of the consonant) of synthetic consonant-vowel syllables. When the two dimensions varied in a completely correlated manner, reaction times were significantly shorter than when either dimension varied alone. This “redundancy gain” could not be attributed to speed-accuracy trades, selective serial processing, or differential transfer between conditions. These results allow rejection of a completely serial model, suggesting instead that at least some portion of auditory and phonetic processing can occur in parallel.     

Sing that tune: Infants’ perception of melody and lyrics and the facilitation of phonetic recognition in songs

To better understand how infants process complex auditory input, this study investigated whether 11-month-old infants perceive the pitch (melodic) or the phonetic (lyric) components within songs as more salient, and whether melody facilitates phonetic recognition. Using a preferential looking paradigm, uni-dimensional and multi-dimensional songs were tested; either the pitch or syllable order of the stimuli varied. As a group, infants detected a change in pitch order in a 4-note sequence when the syllables were redundant (experiment 1), but did not detect the identical pitch change with variegated syllables (experiment 2). Infants were better able to detect a change in syllable order in a sung sequence (experiment 2) than the identical syllable change in a spoken sequence (experiment 1). These results suggest that by 11 months, infants cannot “ignore” phonetic information in the context of perceptually salient pitch variation. Moreover, the increased phonetic recognition in song contexts mirrors findings that demonstrate advantages of infant-directed speech. Findings are discussed in terms of how stimulus complexity interacts with the perception of sung speech in infancy.     

The role of distinctive features in the dichotic perception of vowels

A dichotic listening experiment was conducted to determine if vowel perception is based on phonetic feature extraction as is consonant perception. Twenty normal right-handed subjects were given dichotic CV syllables contrasting in final vowels. It was found that, unlike consonants, the perception of dichotic vowels was not significantly lateralized, that the dichotic perception of vowels was not significantly enhanced by the number of phonetic features shared, and that the occurrence of double-blend errors was not greater than chance. However, there was strong evidence for the use of phonetic features at the level of response organization. It is suggested that the differences between vowel and consonant perception reflect the differential availability of the underlying acoustic information from auditory store, rather than differences in processing mechanisms.     

Perception of syllable-final stop consonants by 2-month-old infants

Previous research has shown that infants are capable of perceiving many phonetic distinctions between initial segments of syllables. The present study demonstrates that 2-month-old infants have the ability to distinguish syllables differing only in their final segments. Infants were found to be sensitive to place-of-articulation differences for stop consonants in final segments of both consonant-vowel-consonant (CVC) and vowel-consonant (VC) syllable pairs. Contrary to previous reports for older infants (Shvachkin, 1973), there was no indication that 2-month-olds have any more difficulty with contrasts of final-stop consonant:3 than they do with initial ones.     

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.     

Identification times for phonemic components of graded complexity and for spelling of speech

Identification time was measured for targets in speech in terms of the number of phonemes occurring between the target and response. Auditory targets in the mam experiment were at three levels of phonetic complexity; (1) monosyllabic words or nonsense syllables, each containing four phonemes; (2) clusters (vowel + consonant) consisting of the second and third phonemes within these syllables; (3) individual phonemes within these clusters. Identification time was always shorter for (1) than for (2) or (3). The effect of semantic and grammatical context upon identification was small. Plosive consonants which did not begin a syllable generally could not be identified as isolated phonemic targets, although they could be identified readily as part of a cluster. Letter targets corresponding to the spelling of the auditory stimulus permitted identification of plosive consonants, and in general followed different rules than the phonemic targets. Additional observations concerning individual targets were made.     

An investigation of young infants' perceptual representations of speech sounds

The present study examined the ability of newborns and 2-month-olds to detect phonetic differences between syllables. By relying on the modified high-amplitude sucking procedure, which did not permit the infants to use a simple same-different response, the present experiments tapped the perceptual representations of the speech sounds. Infants as young as a few days old displayed some capacity to represent differences in a set of syllables varying in their phonetic composition, although there was no convincing evidence that their representations were structured in terms of phonetic segments. Finally, evidence of developmental changes in speech processing were noted for the first time with infants in this age range. The change noted was a tendency from global toward more specific representations on the part of the older infants.     

塞辅音范畴通达的时间进程：来自语境效应的证据

采用语境效应范式,以汉语听者为被试,在三个实验中考察了塞辅音声学信息和语音信息激活的时间进程。实验1语境刺激是/ta/、/ka/音节和/ta/、/ka/塞音段的声学模拟音,目标刺激是/ta/-/ka/对比连续体,结果发现,塞音声学信息激活没有产生语境效应。实验2语境刺激是/ta/、/ka/音节和/ta/、/ka/塞音段,结果发现塞音语音信息激活产生了显著的对比语境效应。实验3变化塞音段和目标刺激之间的间隔,系统考察塞音范畴通达的时间进程,结果发现,塞音知觉中听觉加工阶段向语音加工阶段的转变约发生于刺激加工后120 ms。实验结果揭示了塞辅音知觉中音位范畴通达的时间进程。     

Perceptual-motor processing of phonetic features in speech

Some reaction time experiments are reported on the relation between the perception and production of phonetic features in speech. Subjects had to produce spoken consonant-vowel syllables rapidly in response to other consonant-vowel stimulus syllables. The stimulus syllables were presented auditorily in one condition and visually in another. Reaction time was measured as a function of the phonetic features shared by the consonants of the stimulus and response syllables. Responses to auditory stimulus syllables were faster when the response syllables started with consonants that had the same voicing feature as those of the stimulus syllables. A shared place-of-articulation feature did not affect the speed of responses to auditory stimulus syllables, even though the place feature was highly salient. For visual stimulus syllables, performance was independent of whether the consonants of the response syllables had the same voicing, same place of articulation, or no shared features. This pattern of results occurred in cases where the syllables contained stop consonants and where they contained fricatives. It held for natural auditory stimuli as well as artificially synthesized ones. The overall data reveal a close relation between the perception and production of voicing features in speech. It does not appear that such a relation exists between perceiving and producing places of articulation. The experiments are relevant to the motor theory of speech perception and to other models of perceptual-motor interactions.     

Atypical central auditory speech-sound discrimination in children who stutter as indexed by the mismatch negativity

PurposeRecent theoretical conceptualizations suggest that disfluencies in stuttering may arise from several factors, one of them being atypical auditory processing. The main purpose of the present study was to investigate whether speech sound encoding and central auditory discrimination, are affected in children who stutter (CWS).MethodsParticipants were 10 CWS, and 12 typically developing children with fluent speech (TDC). Event-related potentials (ERPs) for syllables and syllable changes [consonant, vowel, vowel-duration, frequency (F0), and intensity changes], critical in speech perception and language development of CWS were compared to those of TDC.ResultsThere were no significant group differences in the amplitudes or latencies of the P1 or N2 responses elicited by the standard stimuli. However, the Mismatch Negativity (MMN) amplitude was significantly smaller in CWS than in TDC. For TDC all deviants of the linguistic multifeature paradigm elicited significant MMN amplitudes, comparable with the results found earlier with the same paradigm in 6-year-old children. In contrast, only the duration change elicited a significant MMN in CWS.ConclusionsThe results showed that central auditory speech-sound processing was typical at the level of sound encoding in CWS. In contrast, central speech-sound discrimination, as indexed by the MMN for multiple sound features (both phonetic and prosodic), was atypical in the group of CWS. Findings were linked to existing conceptualizations on stuttering etiology.Educational objectives: The reader will be able (a) to describe recent findings on central auditory speech-sound processing in individuals who stutter, (b) to describe the measurement of auditory reception and central auditory speech-sound discrimination, (c) to describe the findings of central auditory speech-sound discrimination, as indexed by the mismatch negativity (MMN), in children who stutter.     

Cognitive influences on cross-language speech perception in infancy

Previous research has shown that young infants can discriminate both native and nonnative phonetic contrasts with ease. By 10 to 12 months of age, however, infants—like adults—typically have difficulty discriminating consonant contrasts that are not used to distinguish meaning in their native language. Although the timing of this change in speech perception has been firmly established, little is currently known about the processes or mechanisms involved in this selective and adaptive reorganization in nonnative phonetic discrimination. This study was designed to determine if there is a relation between age-related changes in speech perception performance and other developing cognitive abilities. A total of 40 8- to 10-month-old infants were tested on a nonnative consonant discrimination task and then on two additional tasks (a visual categorization task and an object search task) in an attempt to determine whether changes in nonnative consonant perception coincide with changes in these other areas of cognitive/perceptual functioning. The results indicate that changes in task performance occur in synchrony across all three tasks, and that this synchrony is not explained by simple age effects. These findings suggest that domain-general cognitive/perceptual competencies may influence developmental changes in speech perception by the end of the 1st year of life.     

Phonetic segmentation in prereaders: Effect of corrective information

This study is focused on the capacity of preliterate children to learn explicit phonetic segmentation. In Experiment 1, subjects were induced through examples to delete the initial consonant in consonant-vowel-consonant (CVC) utterances. Performance was very poor at the beginning of the test but large improvements were observed in 5-year-olds when corrective feedback was provided. Four-year-olds did not on the average show a similar effect of feedback, but when tested again in Experiment 2 with a free segmentation procedure the majority proved capable of decomposing CVC syllables into smaller units and also displayed significant transfer from the earlier experience. In Experiment 3, fresh groups of children, aged four and five, were tested for either initial or final consonant deletion with immediate feedback. Improvements were observed at both ages and for both manipulations, although performance on initial consonant deletion was poorer than on final consonant deletion. Most children as young as 4 years can thus learn new segmentation games quite rapidly. The finding is discussed in relation to the notion that phonetic analysis is an important stumbling block in reading acquisition.     

Brain potentials to native and non-native speech contrasts in 7- and 11-month-old American infants

Abstract Behavioral data establish a dramatic change in infants' phonetic perception between 6 and 12 months of age. Foreign-language phonetic discrimination significantly declines with increasing age. Using a longitudinal design, we examined the electrophysiological responses of 7- and 11-month-old American infants to native and non-native consonant contrasts. Analyses of the event-related potentials (ERP) of the group data at 7 and at 11 months of age demonstrated that infants' discriminatory ERP responses to the non-native contrast are present at 7 months of age but disappear by 11 months of age, consistent with the behavioral data reported in the literature. However, when the same infants were divided into subgroups based on individual ERP components, we found evidence that the infant brain remains sensitive to the non-native contrast at 11 months of age, showing differences in either the P150-250 or the N250-550 time window, depending upon the subgroup. Moreover, we observed an increase in infants' responsiveness to native language consonant contrasts over time. We describe distinct neural patterns in two groups of infants and suggest that their developmental differences may have an impact on language development.     

Dichotic interactions of speech sounds and phonetic feature processing

Identification of CV syllables was studied in a backward masking paradigm in order to examine two types of interactions observed between dichotically presented speech sounds: the feature sharing effect and the lag effect. Pairs of syllables differed in the consonant, the vowel, and their relative times of onset. Interference between the two dichotic inputs was observed primarily for pairs which contrasted on voicing. Performance on pairs that shared voicing remained excellent under all three conditions. The results suggest that the interference underlying the lag effect and the feature sharing effect for voicing occur before phonetic analysis where both auditory inputs interact.     

声调在汉语音节感知中的作用

探讨超音段(如声调)与音段信息的共同作用机制, 对口语词汇识别研究具有重要的理论意义。有研究探讨了声调在口语词汇语义通达阶段的作用, 但在相对早期的音节感知阶段, 声调与声母、韵母的共同作用机制还缺乏系统的认识。本研究采用oddball实验范式, 通过两个行为实验考察了声调在汉语音节感知中的作用。实验1发现检测声调和声母变化的时间没有差异, 均比检测韵母变化的时间长, 表明在汉语音节感知中对声调的敏感性不及韵母。实验2发现声母和韵母的组合并没有明显优于对韵母的觉察, 但声调与声母或韵母的同时变化都促进了被试对偏差刺激的觉察, 表明声调通过与声母、韵母的结合来共同影响汉语音节的感知加工。研究结果在认知行为层面为声调在音节感知中的作用机制提供了直接的实验证据, 为进一步探讨超音段与音段信息共同作用的认知神经机制提供了基础。     

Phonotactic acquisition in healthy preterm infants

Previous work has shown that preterm infants are at higher risk for cognitive/language delays than full‐term infants. Recent studies, focusing on prosody (i.e. rhythm, intonation), have suggested that prosodic perception development in preterms is indexed by maturational rather than postnatal/listening age. However, because prosody is heard in‐utero, and preterms thus lose significant amounts of prenatal prosodic experience, both their maturation level and their prosodic experience (listening age) are shorter than that of full‐terms for the same postnatal age. This confound does not apply to the acquisition of phonetics/phonotactics (i.e. identity and order of consonants/vowels), given that consonant differences in particular are only perceived after birth, which could lead to a different developmental pattern. Accordingly, we explore the possibility that consonant‐based phonotactic perception develops according to listening age. Healthy French‐learning full‐term and preterm infants were tested on the perception of consonant sequences in a behavioral paradigm. The pattern of development for full‐term infants revealed that 7‐month‐olds look equally at labial‐coronal (i.e. /pat/) compared to coronal‐labial sequences (i.e. /tap/), but that 10‐month‐olds prefer the labial‐coronal sequences that are more frequent in the French lexicon. Preterm 10‐month‐olds (having 10 months of phonetic listening experience but 7 months of maturational age) behaved as full‐term 10‐month‐olds. These results establish that preterm developmental timing for consonant‐based phonotactic acquisition is based on listening age (experience with input). This questions the interpretation of previous results on prosodic acquisition in terms of maturational constraints, and raises the possibility that different constraints apply to the acquisition of different phonological subcomponents.     

Extending formant transitions may not improve aphasics'' perception of stop consonant place of articulation

Synthetic speech stimuli were used to investigate whether aphasics' ability to perceive stop consonant place of articulation was enhanced by the extension of initial formant transitions in CV syllables. Phoneme identification and discrimination tests were administered to 12 aphasic patients, 5 fluent and 7 nonfluent. There were no significant differences in performance due to the extended transitions, and no systematic pattern of performance due to aphasia type. In both groups, discrimination was generally high and significantly better than identification, demonstrating that auditory capacity was retained, while phonetic perception was impaired; this result is consistent with repeated demonstrations that auditory and phonetic processes may be dissociated in normal listeners. Moreover, significant rank order correlations between performances on the Token Test and on both perceptual tasks suggest that impairment on these tests may reflect a general cognitive rather than a language-specific deficit.     

Two‐month‐old infants match phonetic information in lips and voice

Infants aged 4.5 months are able to match phonetic information in the face and voice ( Kuhl & Meltzoff, 1982 ; Patterson & Werker, 1999 ); however, the ontogeny of this remarkable ability is not understood. In the present study, we address this question by testing substantially younger infants at 2 months of age. Like the 4.5‐month‐olds in past studies, the 2‐month‐old infants tested in the current study showed evidence of matching vowel information in face and voice. The effect was observed in overall looking time, number of infants who looked longer at the match, and longest look to the match versus mismatch. Furthermore, there were no differences based on male or female stimuli and no preferences for the match when it was on the right or left side. These results show that there is robust evidence for phonetic matching at a much younger age than previously known and support arguments for either some kind of privileged processing or particularly rapid learning of phonetic information.