Speech Production In Adults Research Articles

First-language interference without bilingualism? Evidence from second language vowel production in international adoptees

Abstract The ability to acquire the speech sounds of a second language has consistently been found to be constrained with increasing age of acquisition. Such constraints have been explained either through cross-linguistic influence in bilingual speakers or as the result of maturational declines in neural plasticity with age. Here, we disentangle these two explanations by investigating speech production in adults who were adopted from China to Sweden as toddlers, lost their first language, and became monolingual speakers of the second language. Although we find support for predictions based on models of bilingual language acquisition, these results cannot be explained by the bilingual status of the learners, indicating instead a long-term influence of early specialization for speech that is independent of bilingual language use. These findings are discussed in light of first-language interference and the theory of maturational constraints for language acquisition.

Subsegmental representation in child speech production: structured variability of stop consonant voice onset time in American English and Cantonese.

Voice onset time (VOT) of aspirated stop consonants is marked by variability and systematicity in adult speech production. The present study investigated variability and systematicity of voiceless aspirated stop VOT from 161 two- to five-year-old talkers of American English and Cantonese. Overall, many aspects of child VOT productions parallel adult patterns, the analysis of which can help inform our understanding of early speech production. For instance, VOT means were comparable between children and adults, despite greater variability. Further, across children in both languages, talker-specific VOT means were strongly correlated between [th] and [kh]. This correlation may reflect a constraint of "target uniformity" that minimizes variation in the phonetic realization of a shared distinctive feature. Therefore findings suggest that target uniformity is not merely a product of a mature grammar, but may instead shape speech production representations in children as young as two years of age.

Neural activity during solo and choral reading: A functional magnetic resonance imaging study of overt continuous speech production in adults who stutter.

Previous neuroimaging investigations of overt speech production in adults who stutter (AWS) found increased motor and decreased auditory activity compared to controls. Activity in the auditory cortex is heightened, however, under fluency-inducing conditions in which AWS temporarily become fluent while synchronizing their speech with an external rhythm, such as a metronome or another speaker. These findings suggest that stuttering is associated with disrupted auditory motor integration. Technical challenges in acquiring neuroimaging data during continuous overt speech production have limited experimental paradigms to short or covert speech tasks. Such paradigms are not ideal, as stuttering primarily occurs during longer speaking tasks. To address this gap, we used a validated spatial ICA technique designed to address speech movement artifacts during functional magnetic resonance imaging (fMRI) scanning. We compared brain activity and functional connectivity of the left auditory cortex during continuous speech production in two conditions: solo (stutter-prone) and choral (fluency-inducing) reading tasks. Overall, brain activity differences in AWS relative to controls in the two conditions were similar, showing expected patterns of hyperactivity in premotor/motor regions but underactivity in auditory regions. Functional connectivity of the left auditory cortex (STG) showed that within the AWS group there was increased correlated activity with the right insula and inferior frontal area during choral speech. The AWS also exhibited heightened connectivity between left STG and key regions of the default mode network (DMN) during solo speech. These findings indicate possible interference by the DMN during natural, stuttering-prone speech in AWS, and that enhanced coordination between auditory and motor regions may support fluent speech.

Effect of word phonetic properties on stuttering anticipation and speech production in adults who stutter

PurposeStuttering anticipation is a significant factor in an individual’s stuttering experience. People who stutter have reported words and sounds that they anticipate stuttering on. Attempts at understanding the association between stuttering anticipation and stuttering outcomes and the impact of phonetic properties on stuttering anticipation and overt stuttering have been insufficiently examined. This study aims to address these important issues. MethodsData were collected as part of a larger brain imaging study. Twenty adults who stutter rated a 414 word-list on stuttering anticipation. Participant-specific ‘high’ and ‘low’ anticipated words were selected. Twelve of the 20 participants returned for a second session 2–11 weeks later, during which they read the selected words again and stuttering occurrence was recorded. ResultsAmong the 20 participants, three sub-groups with “high” (N = 6), “moderate” (N = 5) and “low” (N = 9) stuttering anticipation were identified. Significant “high stuttering” anticipation was found on consonants, plosives, bilabials and alveolars, as well as labials and coronals. In 5 of the 8 participants who stuttered during session 2, more than 80 % of words stuttered were previously rated with high anticipation. Consonants, plosives, bilabials and alveolars, and labials and coronals were the most frequently stuttered (>27 %). ConclusionWhile not all adults who stutter demonstrate high word-specific stuttering anticipation, we found that more than half anticipated this to a high degree. Furthermore, both word-specific phonetic properties and stuttering anticipation impact stuttering occurrence. The inclusion of word-specific stuttering anticipation ratings may increase the likelihood of stuttering in experimental studies and improve treatment outcomes through individualized intervention.

What anticipatory coarticulation in children tells us about speech motor control maturity.

PurposeThis study aimed to evaluate the role of motor control immaturity in the speech production characteristics of 4-year-old children, compared to adults. Specifically, two indices were examined: trial-to-trial variability, which is assumed to be linked to motor control accuracy, and anticipatory extra-syllabic vowel-to-vowel coarticulation, which is assumed to be linked to the comprehensiveness, maturity and efficiency of sensorimotor representations in the central nervous system.MethodAcoustic and articulatory (ultrasound) data were recorded for 20 children and 10 adults, all native speakers of Canadian French, during the production of isolated vowels and vowel-consonant-vowel (V1-C-V2) sequences. Trial-to-trial variability was measured in isolated vowels. Extra-syllabic anticipatory coarticulation was assessed in V1-C-V2 sequences by measuring the patterns of variability of V1 associated with variations in V2. Acoustic data were reported for all subjects and articulatory data, for a subset of 6 children and 2 adults.ResultsTrial-to-trial variability was significantly larger in children. Systematic and significant anticipation of V2 in V1 was always found in adults, but was rare in children. Significant anticipation was observed in children only when V1 was /a/, and only along the antero-posterior dimension, with a much smaller magnitude than in adults. A closer analysis of individual speakers revealed that some children showed adult-like anticipation along this dimension, whereas the majority did not.ConclusionThe larger trial-to-trial variability and the lack of anticipatory behavior in most children—two phenomena that have been observed in several non-speech motor tasks—support the hypothesis that motor control immaturity may explain a large part of the differences observed between speech production in adults and 4-year-old children, apart from other causes that may be linked with language development.

Speech Production From a Developmental Perspective.

PurposeCurrent approaches to speech production aim to explain adult behavior and so make assumptions that, when taken to their logical conclusion, fail to adequately account for development. This failure is problematic if adult behavior can be understood to emerge from the developmental process. This problem motivates the proposal of a developmentally sensitive theory of speech production. The working hypothesis, which structures the theory, is that feedforward representations and processes mature earlier than central feedback control processes in speech production.MethodTheoretical assumptions that underpin the 2 major approaches to adult speech production are reviewed. Strengths and weaknesses are evaluated with respect to developmental patterns. A developmental approach is then pursued. The strengths of existing theories are borrowed, and the ideas are resynthesized under the working hypothesis. The speech production process is then reimagined in developmental stages, with each stage building on the previous one.ConclusionThe resulting theory proposes that speech production relies on conceptually linked representations that are information-reduced holistic perceptual and motoric forms, constituting the phonological aspect of a system that is acquired with the lexicon. These forms are referred to as exemplars and schemas, respectively. When a particular exemplar and schema are activated with the selection of a particular lexical concept, their forms are used to define unique trajectories through an endogenous perceptual–motor space that guides implementation. This space is not linguistic, reflecting its origin in the prespeech period. Central feedback control over production emerges with failures in communication and the development of a self-concept.

A preliminary study on the neural oscillatory characteristics of motor preparation prior to dysfluent and fluent utterances in adults who stutter

PurposeRecent literature on speech production in adults who stutter (AWS) has begun to investigate the neural mechanisms characterizing speech-motor preparation prior to speech onset. Compelling evidence has suggested that stuttering is associated with atypical processing within cortical and sub-cortical motor networks, particularly in the beta frequency range, that is effective before speech production even begins. Due to low stuttering frequency in experimental settings, however, the literature has so far predominantly reported on fluent speech production in AWS. Consequently, we have limited understanding of the way in which fluent speech processing in AWS is disturbed leading to a dysfluency. This preliminary study aims to characterize neural motor preparation prior to stuttered utterances in AWS. MethodsEight AWS participated in the study. A total of 336 stuttered utterances were compared to the participants’ own fluent utterance productions. Beta oscillatory activity was analyzed with magnetoencephalography (MEG) and localized using minimum-variance beamforming. ResultsPreparation for speech production induced beta suppression in the bilateral premotor and motor cortex prior to speech onset. Although the data revealed some interesting trends, no significant differences between fluent and stuttered utterances were present. This may be due to a relatively low and variable number of stuttered trials analyzed in individual subjects. ConclusionWhile the lack of significant differences may have resulted from the relatively low numbers of stuttered utterances across subjects, the observed trends demonstrated that the proposed methodology and experimental paradigm is a promising approach for future studies aiming to characterize differences between stuttered and fluent speech.

Orthography and Modality Influence Speech Production in Adults and Children.

The acquisition of literacy skills influences the perception and production of spoken language. We examined if orthography influences implicit processing in speech production in child readers and in adult readers with low and high reading proficiency. Children (n = 17), adults with typical reading skills (n = 17), and adults demonstrating low reading proficiency (n = 18) repeated or read aloud nonwords varying in orthographic transparency. Analyses of implicit linguistic processing (segmental accuracy and speech movement stability) were conducted. The accuracy and articulatory stability of productions of the nonwords were assessed before and after repetition or reading. Segmental accuracy results indicate that all 3 groups demonstrated greater learning when they were able to read, rather than just hear, the nonwords. Speech movement results indicate that, for adults with poor reading skills, exposure to the nonwords in a transparent spelling reduces the articulatory variability of speech production. Reading skill was correlated with speech movement stability in the groups of adults. In children and adults, orthography interacts with speech production; all participants integrate orthography into their lexical representations. Adults with poor reading skills do not use the same reading or speaking strategies as children with typical reading skills.

Effects of blindness on production–perception relationships: Compensation strategies for a lip-tube perturbation of the French [u

ABSTRACTThe impact of congenital visual deprivation on speech production in adults was examined in an ultrasound study of compensation strategies for lip-tube perturbation. Acoustic and articulatory analyses of the rounded vowel /u/ produced by 12 congenitally blind adult French speakers and 11 sighted adult French speakers were conducted under two conditions: normal and perturbed (with a 25-mm diameter tube inserted between the lips). Vowels were produced with auditory feedback and without auditory feedback (masked noise) to evaluate the extent to which both groups relied on this type of feedback to control speech movements. The acoustic analyses revealed that all participants mainly altered F2 and F0 and, to a lesser extent, F1 in the perturbed condition – only when auditory feedback was available. There were group differences in the articulatory strategies recruited to compensate; while all speakers moved their tongues more backward in the perturbed condition, blind speakers modified tongue-shape parameters to a greater extent than sighted speakers.

The effects of autonomic arousal on speech production in adults who stutter: A preliminary study

The purpose of this study was to investigate the influence of autonomic system reactivity and response on the speech production of people who stutter. Participants included three adults who stutter (AWS) and three who did not (AWNS). An aversive acoustic stimulus was paired with a set of neutral pictures to condition an autonomic system response as measured by skin conductance response (SCR). Speech production probes were placed in trials where a conditioned autonomic response was expected in order to record fundamental frequency (F0) and temporal acoustic measures of segments of speech from utterances at different levels of autonomic arousal. Analyses of SRC indicated that AWS had a significantly greater autonomic response to the aversive stimulus compared to AWNS. All of the AWS, but none of the AWNS, acquired a conditioned response. In addition, AWS exhibited F0, voice onset time, and frication durations that were positively correlated with SCR. This study provides evidence that AWS show a greater susceptibility to classical conditioning, along with higher autonomic reactivity and related changes in speech production than AWNS. Findings are discussed as they pertain to risk factors in the development of stuttering.

Is Tongue Strength an Important Influence on Rate of Articulation in Diadochokinetic and Reading Tasks?

The purpose of this study was to assess the relationship between tongue strength and rate of articulation in 2 speech tasks, diadochokinetic rates and reading aloud, in healthy men and women between 20 and 78 years of age. Diadochokinetic rates were measured for the syllables /p/, /t/, /k/, and /ptk/, and articulation rates were calculated for a reading of the Rainbow Passage for 57 adult volunteers. The Iowa Oral Performance Instrument (LLC Northwest) was used to obtain maximum tongue pressure, tongue pressure exerted during production of /t/, and tongue endurance. Correlation analyses were performed to determine the relation among articulation rate and tongue pressure and endurance measures. Maximum tongue pressure, the pressure used to produce /t/, the proportion of maximum pressure used to produce /t/, and tongue endurance were poor predictors of diadochokinetic rates and articulation rate in reading for healthy speakers. Discussion Focus must remain on factors beyond strength, such as movement precision and coordination, to improve researchers' understanding of normal and disordered speech production in adults.

Computer-mediated assessment of intelligibility in aphasia and apraxia of speech

Background: Previous work indicates that single-word intelligibility tests developed for dysarthria are sensitive to segmental production errors in aphasic individuals with and without apraxia of speech. However, potential listener learning effects and difficulties in adapting elicitation procedures to coexisting language impairments limit their applicability to left hemisphere stroke survivors. Aims: The main purpose of this study was to examine basic psychometric properties for a new monosyllabic intelligibility test developed for individuals with aphasia and/or AOS. A related purpose was to examine clinical feasibility and potential to standardise a computer-mediated administration approach. Methods & Procedures: A 600-item monosyllabic single-word intelligibility test was constructed by assembling sets of phonetically similar words. Custom software was used to select 50 target words from this test in a pseudo-random fashion, and to elicit and record production of these words by 23 speakers with aphasia and 20 neurologically healthy participants. To evaluate test–retest reliability, two identical sets of 50-word lists were elicited by requesting repetition after a live speaker model. To examine the effect of a different word set and auditory model, an additional set of 50 different words was elicited with a pre-recorded model. The recorded words were presented to normal-hearing listeners for identification via orthographic and multiple-choice response formats. To examine construct validity, production accuracy for each speaker was estimated via phonetic transcription and rating of overall articulation. Outcomes & Results: Recording and listening tasks were completed in less than 6 minutes for all speakers and listeners. Aphasic speakers were significantly less intelligible than neurologically healthy speakers and displayed a wide range of intelligibility scores. Test–retest and inter-listener reliability estimates were strong. No significant difference was found in scores based on recordings from a live model versus a pre-recorded model, but some individual speakers favoured the live model. Intelligibility test scores correlated highly with segmental accuracy derived from broad phonetic transcription of the same speech sample and a motor speech evaluation. Scores correlated moderately with rated articulation difficulty. Conclusions: We describe a computerised, single-word intelligibility test that yields clinically feasible, reliable, and valid measures of segmental speech production in adults with aphasia. This tool can be used in clinical research to facilitate appropriate participant selection and to establish matching across comparison groups. For a majority of speakers, elicitation procedures can be standardised by using a pre-recorded auditory model for repetition. This assessment tool has potential utility for both clinical assessment and outcomes research.

Associations Between Key Language-Related Measures in Typically Developing School-Age Children

Associations Between Key Language-Related Measures in Typically Developing School-Age Children

Articulatory and acoustic characteristics of English /l/ in children’s speech production

English /l/ is one of the later-developing sounds in language acquisition. It has syllable-based allophones (e.g., light l in initial, dark l in final) and comprises multiple articulatory gestures (e.g., tongue tip fronting and raising, tongue dorsum backing, lateral dipping) with different coordination in timing and magnitude in syllable position (e.g., synchronicity in initial, tongue tip delay in final with greater reduction in magnitude). Using ultrasound, this study examined how articulatory characteristics of /l/ are presented in children’s speech production. Replicating previous articulatory studies in adult speech production, /l/ words in isolation and combination were collected from eight monolingual children aged 3;11 to 5;9. Although some children produced more similar to adult /l/, children produced /l/ using different articulatory properties. /l/ was produced with less detail and more variations than in the adults’ speech as movements of the tongue were simplified or modified. While articulatory performance varied across subjects as well as syllable positions, acoustic analysis of formants (F1, F2, F3) of sample tokens showed similar patterns for all subjects. This study suggests that the tendency toward late acquisition of /l/ is due directly to the articulatory as well as motor complexity.

The effects of cognitive demand on speech production in adults who stutter

The effects of cognitive demand on speech production in adults who stutter

Prosodic Structure in Young Children's Language Production

Research in prosodic phonology, as well as experiments on adult speech production, suggest that segmental and suprasegmental processes in language are not governed directly by syntactic structure. Rather these processes reflect an independent prosodic structure, which includes prosodic categories such as metrical foot, prosodic word, and phonological phrase. Five experiments examined English-speaking two-year-olds' omissions of object articles in different prosodic structures. The data indicate that children omit unfooted syllables and that foot boundaries, in turn, are influenced by prosodic word and phonological phrase boundaries. Thus, it appears that children create prosodic structures remarkably similar to those proposed in theories of prosodic phonology.*

Phonetic coding and reading in college students with and without learning disabilities.

This study examined whether adult speech production and oral reading were related independent of auditory short-term memory and vocabulary. Forty-four university students served as subjects for the study. They ranged in age from 17 to 28 years old; 26 were men and 18 were women; 11 were students with learning disabilities and 33 were students without disabilities. All subjects were tested individually on tasks requiring multisyllabic pseudoword repetition, oral reading, memory for digits, and vocabulary. In both groups--with and without learning disabilities--significant correlations were found between pseudoword repetition accuracy and reading, suggesting that poor readers also have more inaccurate speech production. The correlations remained significant after controlling for both memory and vocabulary. A scatter plot of the speech-reading relationship showed performance overlap between groups, as well as within-group heterogeneity. Significance of the findings is discussed, and issues for future research are identified.

The effect of Trigeminal Nerve Block on the Articulatory Emg Activity of Facial Muscles

The effect of blocking trigeminal afferent fibres was studied with reference to the EMG activity of facial muscles during speech production. Normal-speaking subjects were investigated without and with mandibular anaesthesia, and patients with trigeminal neuralgia before and after blockade of the Gasserian ganglion. No audible difference was detected between the non-anaesthetized and the uni-or bilaterally anaesthetized. The most consistent and salient finding was a general increase in the amount of prespeech and background activity as well as, in particular, the amount of articulatory activity. This increase often appeared symmetrically on both sides even with unilateral anaesthesia and was localized to the muscles that are best adapted for the production of the speech sounds in question, while the cocontractive activity of the antagonistic muscles decreased. The increase was often associated with an earlier onset of articulatory activity. The context dependence of the EMG activity was obviously impaired for the production of vowels but not of consonants. These EMG observations are discussed in relation to previous reports by other authors on the effects of de-afferentation of the limb and intercostal musculature. It is concluded that the EMG changes observed after blocking of afferent activity in the trigeminal nerve cannot be explained by a disturbed peripheral closed-loop feedback, similar to the muscle spindle-gamma efferent system, which therefore does not seem to be crucial for adult speech production. However, the findings could be accounted for by a disturbed positional sense. To compensate for this disturbance, the control of articulatory activity, which is not normally conscious, may be referred to a higher level of the central nervous system. Such a more conscious motor control might explain the overshooting muscle activation and the lack of context dependence of the EMG activity.