Articulatory Coordination Research Articles

Motor coordination of articulators depends on the place of articulation

Although the sounds/p/and/k/are both voiceless plosives, they have different places of articulation: bilabial and velar, respectively. The purpose of this study was to determine the relationship among articulators in plosives with reference to their place of articulation. Ten healthy subjects repeated bilabial and velar plosives in synchronization with magnetic resonance scanning. Each run was measured using a gradient echo sequence. Several linear and angular variables were defined to delineate the individual movements of articulators and to determine the temporal relationships among articulators. These variables showed distinctive changes depending on the place of articulation. In addition, movement of the velum was significantly correlated with that of the lips and the anterior part of the tongue in the bilabial plosive and with the posterior part of the tongue in the velar plosive. We conclude that unitary motor coordination of articulators depends on the place of articulation.

Prosodic effects on articulatory coordination in initial consonant clusters in German

This study examines how articulatory coordination in heterorganic initial consonant clusters is modulated by prosodic condition. Extending the paradigm of articulatory strengthening at domain edges to clusters, we provide EPG data of 7 speakers as well as EMA data of two speakers including domain-initial clusters (/kl/, /kn/ and /sk/) in different prosodic positions, varying the strength of the preceding boundary and the position of lexical stress. (e.g. 'Claudia vs. Klau'sur, i.e. stressed vs. unstressed target cluster). The results show that C1 was consistently lengthened at higher boundaries, but only if the cluster was preceded by a clear pause. C2 was only weakly and inconsistently affected. There were no effects on the spatial domain at all. No consistent effects of lexical stress were found for either C1 or C2. Regarding overlap of C1 and C2 there was a tendency, albeit quite weak, in the direction of more overlap at the lower boundary levels and in unstressed condition. However, differences in timing between segmentally different clusters were consistent and much larger than boundary and stress effects. Especially for /kl/ vs. /kn/ we find that the lateral's timing to /k/ is much closer than the nasal's.

Influences of manner and voicing on articulatory coordination in German and French initial consonant clusters

This study aims for improved understanding of whether and how coordination patterns of supraglottal gestures in complex syllable onsets are driven by competing demands of motor economy for the speaker and high recoverability for the listener. Specifically, EMA data for four German and three French speakers was acquired for C1C2 clusters where manner of articulation was varied for C2 (/l/ vs. /n/) and voicing for C1 (/p/ vs. /b/, /k/ vs. /g/). Results (1): A robust effect of less overlap of the constriction gesture for C1 and C2 when C2 is nasal. Clusters with nasal C2 may require less overlap in order to avoid compromising the acoustic characteristics of the C1 burst by early velar lowering. Interestingly, such clusters appear to be less stable diachronically and may be less favoured for the formation of complex onsets because of reduced scope for efficient parallel transmission of segmental information. Results (2): For German, a consistent effect of less overlap for voiceless compared to voiced C1. Discussion here will centre on whether possible cross‐language differences between German and French can be related to differences in timing of voice onset and resulting differences in the acoustic properties of the C1‐C2 transitions.

Articulatory coordination in German and English onset and coda clusters

Articulatorily, onset consonants differ from coda consonants in their spatial as well as their temporal characteristics in that onsets exhibit greater spatial displacement and are generally less variable than codas. As to their temporal organization, it has been claimed that onsets, but not codas exhibit a so-called c-center organization in which all consonant gestures of a cluster are organized as a single complex structure with respect to the vowel, while consonant clusters in codas have been hypothesized to be organized sequentially [Browman & Goldstein 1988 Phonetica]. While some studies have confirmed the c-center hypothesis for onsets but not codas, others found a c-center organization for both onset and coda consonants. The current study uses German and English onset and coda clusters to test systematically the c-center hypothesis on the basis of EMA data. Results for both languages indicate that a c-center organization may be observed in both onset and coda position, yet it does not appear consistently for all clusters. Also cross word-boundary clusters may exhibit c-center organization, possibly indicating resyllabification.

Articulatory coordination and real-time spoken word recognition

This study investigates how listeners use information regarding articulatory timing in consonant sequences during lexical access. Research in spoken word recognition of assimilated consonant sequences has shown that listeners make use of detailed variation in the acoustic signal and knowledge of systematic phonological variability [e.g., Gaskell and Marslen‐Wilson (1996), Gow and McMurray (to appear)]. However, no earlier work has reported on real‐time processing of consonant sequences for which articulatory data is available. This study combines articulator movement‐tracking with real‐time eye‐movement monitoring to relate the articulatory timing properties associated with assimilation with use of the resulting acoustic signal in word recognition. Using magnetometry, words to be used as stimuli in an eye‐tracking task are recorded. These contain consonant sequences with a continuum of intergestural overlap obtained by varying prosody and speech rate. In the eye‐tracking experiment, listeners hear two‐word stimuli such as ‘‘bad ban,’’ some of which are perceived with an assimilated final consonant in the first word, and select a picture that matches the stimulus. The recorded eye movements provide a window into real‐time processing [see Altmann and Kamide (2004)], allowing us to investigate listener behavior in using articulatory timing cues for lexical access. [Supported by NIH.]

Nasal consonant production in Broca’s and Wernicke’s aphasics: Speech deficits and neuroanatomical correlates

The present study investigated the articulatory implementation deficits of Broca’s and Wernicke’s aphasics and their potential neuroanatomical correlates. Five Broca’s aphasics, two Wernicke’s aphasics, and four age-matched normal speakers produced consonant–vowel–(consonant) real word tokens consisting of [m, n] followed by [i, e, a, o, u]. Three acoustic measures were analyzed corresponding to different properties of articulatory implementation: murmur duration (a measure of timing), amplitude of the first harmonic at consonantal release (a measure of articulatory coordination), and murmur amplitude over time (a measure of laryngeal control). Results showed that Broca’s aphasics displayed impairments in all of these parameters, whereas Wernicke’s aphasics only exhibited greater variability in the production of two of the parameters. The lesion extent data showed that damage in either Broca’s area or the insula cortex was not predictive of the severity of the speech output impairment. Instead, lesions in the upper and lower motor face areas and the supplementary motor area resulted in the most severe implementation impairments. For the Wernicke’s aphasics, the posterior areas (superior marginal gyrus, parietal, and sensory) appear to be involved in the retrieval and encoding of lexical forms for speech production, resulting in increased variability in speech production.

Phonotactics and Articulatory Coordination Interact in Phonology: Evidence from Nonnative Production

A core area of phonology is the study of phonotactics, or how sounds are linearly combined. Recent cross-linguistic analyses have shown that the phonology determines not only phonotactics but also the articulatory coordination or timing of adjacent sounds. In this article, I explore how the relation between coordination and phonotactics affects speakers producing nonnative sequences. Recent experimental results (Davidson 2005, 2006) have shown that English speakers often repair unattested word-initial sequences (e.g., /zg/, /vz/) by producing the consonants with a less overlapping coordination. A theoretical account of the experimental results employs Gafos's (2002) constraint-based grammar of coordination. In addition to Gafos's Alignment constraints establishing temporal relations between consonants, a family of Release constraints is proposed to encode phonotactic restrictions. The interaction of Alignment and Release constraints accounts for why speakers produce nonnative sequences by failing to adequately overlap the articulation of the consonants. The optimality theoretic analysis also incorporates floating constraints to explain why speakers are not equally accurate on all unattested clusters.

Speech motor coordination in Dutch-speaking children with DAS studied with EMMA

Developmental apraxia of speech (DAS) is generally classified as a ‘speech motor’ disorder. Direct measurement of articulatory movement is, however, virtually non-existent. In the present study we investigated the coordination between articulators in children with DAS using kinematic measurements. The results of articulatory coordination in CCV and CVC syllable productions showed systematic effects of place of articulation in the relative phase values in normally speaking children. Deviant and more variable relative phase values as found in the children with DAS are an indication of coordination problems. The relative phase values are discussed with respect to phonological vs. motoric involvement.

The elastic phrase: modeling the dynamics of boundary-adjacent lengthening

This work examines the relation between phrasal structure and the control and coordination of articulation within a dynamical systems model of speech production. In this context, we review how speakers modulate the spatiotemporal organization of articulatory gestures as a function of their phrasal position. We present computational simulations that capture several important qualitative properties of these phrase boundary effects, such as prosodically-induced local slowing. This slowing is generated by dynamical effects on the activation timecourse of articulatory gestures and is controlled by prosodic gestures or π-gestures, which share much with the familiar dynamical description of constriction gestures. Prosodic gestures, however, function at boundaries purely to temporally stretch or shrink gestural activation trajectories. This modulation of the “clock-rate” that controls the temporal unfolding of an utterance near junctures is such that the clock slows increasingly as the boundary is approached and speeds up again as the boundary recedes. Viewing phrase boundaries as warping the temporal fabric of an utterance represents a promising confluence of the fields of prosody and of speech dynamics.

Articulatory coordination by muscle-linkage during bilabial utterances

Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology,4259, Nagatsudacho, Midori, Yokohama, 226–8503 Japan(Received 5 March 2003, Accepted for publication 27 March 2003)Keywords: Muscle stiffness, Lip-jaw model, Compensatory movement, Asymmetrical propertyPACS number: 43.70.Aj, 43.70.Bk [DOI: 10.1250/ast.24.391]1. IntroductionPrevious studies [1–4] showed that the upper lip com-pensatory movement against the downward perturbation to thejaw is effective in maintaining labial constriction or inattaining labial contact for the production of bilabial utter-ances. We measured the stiffness of the muscle-linkagebetween the upper lip and jaw and proposed a model in whichthe muscle-linkage plays key role in coordinating articulatorsduring speech [2]. To further examine the compensatorymechanism using muscle-linkage, we here investigate thecoordination change of the lip-jaw system under the upwardperturbation condition, and examine the directional differencebetween the upward and downward perturbation. Based on theexperimental observations, we propose an extended lip-jawmodel, which could explain the directional difference.2. Experiment and results2.1. EXP1: Downward perturbationFour subjects (all males, Japanese native speakers: A, B,C and D) participated in this experiment. They were instructedto say a carrier sentence ‘‘kono =a a a= mitai’’ for each trialwith the assistance of beeps. Articulatory movements [upperlip (UL), lower lip + jaw (LL+J) and jaw (J)] were measuredby using a three-dimensional optical position sensor (OPTO-TRAK 3020). The subject’s jaw was connected to a jawmanipulandum [2], which can disturb or assist jaw movement.Note that this connection did not interfere very much withspeech movements under unperturbed condition. A downwardperturbation, which was stepwise in shape (4.0N), disturbedthe jaw movement by suddenly acting in the jaw-opendirection and was triggered 0, 30, 60, 90, or 120ms (P

Real-time MRI and articulatory coordination in speech

This paper describes the real-time MRI technique and its use for the study of speech production. The two major problems, ( i) the simultaneous recording of the MR images and the speech signal and ( ii) the synchronisation of the images and of the speech signal, are addressed. Measurement accuracy on real-time images is evaluated by comparison with similar measurements on static MR images.

Kinematics of compensatory vowel shortening: Intra and interarticulatory timing

The acoustic shortening of vowels has been demonstrated to occur across a variety of contextual variations. The current study examined the kinematic adjustments involved in vowel shortening, as a function of speaking rate and coda composition (singleton consonants versus consonant clusters). Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in a carrier phrase, across three distinct speaking rates (slow, normal, and fast). Changes in the timing of the jaw-closing gesture for post-vocalic bilabial production, and in the upper lip–jaw timing relationship (measured via phase angles), were examined. The onset of the jaw-closing gesture typically shifted earlier in the cycle of jaw movement for consonant cluster productions, across all speaking rates. Subject-specific modifications of interarticulator timing were observed, with some speakers adjusting upper lip movement in order to maintain constant timing with the jaw, while others tended to dissociate the upper lip and jaw. Both coda composition and speaking-rate manipulations resulted in substantial intersubject variability in the lip–jaw timing relationship. These findings suggest that, in order to achieve the intended acoustic-perceptual goals, articulatory coordination may not be absolutely invariant, but rather, systematically and individually organized across task manipulations. [Work supported by CRDF-University of Pittsburgh and NSERC.]

A cinefluorographic study of the temporal organization of articulator gestures: Examples from Greenlandic

Movement data on articulator gestures in West Greenlandic are presented in order to elucidate principles of articulator coordination, especially the domain of coarticulation (as distinct from the domain of assimilation), the handling of conflicting demands on articulators, and the relation of vowels to consonants. The present data are consistent with results previously obtained from Swedish and Bulgarian. The Greenlandic informant varied his domain of coarticulation by up to two phonemes either side of the current phoneme; potential gesture conflicts were resolved in accordance with the model of Kozhevnikov and Chistovich, oncoming gestures being delayed when they were antagonistic to ongoing gestures; finally, articulator gestures were organized according to the same principles for both vowels and consonants.

Investigating the ‘‘trough:’’ Vowel dynamics and aerodynamics

Articulatory coordination in vowel–consonant–vowel utterances (V=/i a/, C=/p b/) was studied in 5 Swedish, 3 English, 2 German, and 3 French speakers. Electropalatographic records showed that the amount of transconsonantal V-to-V coarticulation was greater in German and French than in Swedish and English. For the symmetrical utterances /ipi/ and /ibi/, the EPG patterns displayed a marked ‘‘trough’’ (a temporary reduction of tongue height) associated with the stop closure in the Swedish and English, but not in the German and French speakers; the Swedish and English trough patterns were, however, differently timed. These observations are consistent with dynamic vowel features characteristic of the respective languages. In a second experiment, using a wider voice onset time range, three Swedish speakers produced words containing CV syllables (C=/p b t d k g/, V=/i o/ a ■ u/). VOT was controlled in terms of voicing, stress, word length, and position in the word. Formant data showed that the amount of F2 locus-to-target assimilation decreased as a function of voicing lag. This suggests that aerodynamic factors associated with aspiration affect anticipatory coarticulation patterns; specifically, it may affect trough patterns in symmetrical VCVs.

Temporal coordination of articulator gestures.

Movement data are analyzed to elucidate principles of articulator coordination. Procedures for tracking articulator gestures from x‐ray motion films, and results obtained from Swedish and Bulgarian work are reported in Wood [J. Phon. 19, 281–292 (1991), Proc. 3rd Congress I.C.P.L.A., 191‐200, Helsinki (1994), Proc. 13th I.C.Ph.Sc., Vol. 1, 392–395, Stockholm (1995), J. Phon. (in press)]. Coarticulation and gesture conflict have been studied. The domain of coarticulation has been seen variously as a between‐target transition, or comprising of one or two phonemes on either side. These are usually presented as rival solutions, but the present data show speakers using all three schemes. The pertinent question is how does a speaker select one of them. For gesture conflict, there are two approaches. The one feeds all gestures to the musculature where conflicts are resolved by summing rival forces. The second modifies motor input by queuing antagonistic gestures in order to avoid conflicts. All potential gesture conflicts in the present data were resolved by queuing gestures. The data to be reported here include Eskimo to provide a further test on the universality of these principles for articulator coordination. [Work supported by Swedish Research Council for Humanities and Social Sciences.]

Timing relationships of the upper lip and jawacross changes in speaking rate

Select patterns of stability across changes in speaking rate have beendocumented in the relative timing of articulatory events. However, contradictory evidence regarding the presence of such invariance has been presented. The current study investigated the stability of the angle on the jaw phase plane at which the upper lip began its downward movement toward bilabial closure. This phase angle was examined as speaking rate was manipulated across a wide range of speaker-selected rates. Results indicated that five of eight subjects evidenced significant changes in phase angle across changes in speaking rate, with two other subjects demonstrating similar trends. However, the direction of phase angle change varied with individual speakers. There findings suggest that, in order to achieve the intended acoustic-perceptual goals, articulatory coordination for speech may not be absolutely invariant, but rather, systematically and individually organized across changes in speaking rate.

Adults Who Stutter

The purpose of this study was to investigate the effects of speed and cognitive stress on the articulatory coordination abilities of adults who stutter. Cardiovascular (heart rate, systolic blood pressure, and diastolic blood pressure), behavioral (dysfluencies, errors, speech rate, and response latency), and acoustic (word duration, vowel duration, consonant-vowel transition duration/extent, and formant center frequency) measures for nine stutterers and nine nonstutterers were collected during performance of the Stroop Color Word task, a well-established and highly stressful cognitive task. Significant differences were found between the two groups for heart rate, word duration, vowel duration, speech rate, and response latency. In addition, stutterers produced more dysfluencies under speed plus cognitive stress versus speed stress or a self-paced reading task. These findings demonstrate that the presence of cognitive stress resulted in greater temporal disruptions and more dysfluencies for stutterers than for nonstutterers. However, similar spatial impairments were not evident. The potential contributions of the Stroop paradigm to stuttering research as well as the need for further research on autonomic correlates of stuttering are also discussed.

Hot topics in speech communication

In speech perception, the issues emphasized are related to long-term representation of speech units, language-specific differences in speech perception by infants and adults, and some new results from cochlear implant and other hearing research relating to the auditory coding of speech cues. New results on the question of prototypes for speech units and how speaker and contextual variability affect listeners’ behavior are reviewed. Next, there is a survey of recent findings on the effect of language background on infants’ and adults’ perception of speech. Finally, results from perceptual studies of cochlear implant patients involving systematically designed stimulus sets are summarized. In speech production, focus is on the applications of instrumentation, on numerical simulation, and on sensory feedback. There is discussion of measuring instruments that are beginning to provide data on motor compensation and coproduction, and sophisticated numerical simulations that are being developed to answer questions about vibratory mechanisms, air flow, and their relation to sound output. Finally, there is a discussion on the roles of receptor and auditory feedback on articulatory coordination and timing. In speech processing, stress is placed on the progress made in auditory representations, in computational models of language, and in statistical methods for text-to-speech synthesis. In auditory-based representations, 100- to 200-ms speech segments may serve as a basis for distance measures for speech coding that reflect perceptual acceptability of acoustic distortions, and as speech-recognition features that capture dynamic aspects of speech production. In spoken-language processing, the gap between stochastic models of speech (e.g., HMM’s and more traditional models of language structure (syntax) and content (semantics) is being bridged. Finally, text-to-speech synthesis is moving, albeit slowly, from hand-tuned to automatically trained systems.

Characteristics of articulatory coordination during Japanese VCV sequences: Observations using optical and marker-tracking systems.

We examined the influence of context on the articulatory positions of the tongue, lips, and mandible using optical and marker-tracking systems and speculated articulatory coordination during the production of Japanese VCV sequence from the standpoint of current theories of speech production. The primary articulator for the consonant was comparatively invariant in the context. The secondary articulator was variant in the context. Influence of the preceding vowel on the secondary articulators for the con-sonant decreased monotonically and the influence of the following vowel increased in the same way. Thus, movements during the Japanese VCV sequence seem to consist of basic vowel-to-vowel gestures and comparatively invariant movement for the relevant consonant articulator.

Interactive coordination of articulation and prosody in Japanese: A chronotopographic observation of laryngeal EMG.

It is widely accepted that the cricothyroid (CT) plays a predominant role in accentual rise of F0 while the strap muscle, particularly the sternohyoid (SH), exhibits a supplementary function in F0 fall. Antagonistic activity has often been observed between these muscles in typical Japanese accent types. However, the activity of SH is usually less consistent with F0 of overall utterances, mainly because the strap muscle is also involved in articulatory control for jaw opening. Therefore, the interaction should be observed between articulatory and prosody controls. This study is aimed at examining the coordination of jaw articulation and prosody production in Japanese words, using a noninvasive technique to record EMG from the CT and the strap. The signals from arrays of miniature surface electrodes attached on the neck surface are processed to form a chronotopographic EMG, i.e., the place versus time display of neck surface electrical potential. The EMG of the CT is extracted by removing signals from the superficial muscles. The activity of the SH either to lower F0 or to lower the jaw tends to vary with overall F0 of utterances: the SH becomes active when the utterance is produced in low F0. The results suggest a complicated relationship between jaw articulation and prosody control: SH activity and the degree of jaw opening are slightly reduced when high F0 is maintained due to sandhi, and F0 rise tends to be suppressed at jaw lowering in some accent kernels of focused words.