Interarticulator programming in VCV sequences: lip and tongue movements.

This study examined the temporal phasing of tongue and lip movements in vowel-consonant-vowel sequences where the consonant is a bilabial stop consonant /p, b/ and the vowels one of /i, a, u/; only asymmetrical vowel contexts were included in the analysis. Four subjects participated. Articulatory movements were recorded using a magnetometer system. The onset of the tongue movement from the first to the second vowel almost always occurred before the oral closure. Most of the tongue movement trajectory from the first to the second vowel took place during the oral closure for the stop. For all subjects, the onset of the tongue movement occurred earlier with respect to the onset of the lip closing movement as the tongue movement trajectory increased. The influence of consonant voicing and vowel context on interarticulator timing and tongue movement kinematics varied across subjects. Overall, the results are compatible with the hypothesis that there is a temporal window before the oral closure for the stop during which the tongue movement can start. A very early onset of the tongue movement relative to the stop closure together with an extensive movement before the closure would most likely produce an extra vowel sound before the closure.

On the registration of time and the patterning of speech movements.

In order to study speech coordination we frequently average kinematic and other physiological signals. The averages are assumed to be more representative of the underlying patterns of production than individual records. In this note we outline different approaches to averaging and present a new nonlinear normalization technique that offers better information than ensemble averaging, linear normalization, or feature alignment methods. We suggest that this technique provides a clear estimation of pattern shape while preserving information on the variation over time.

Lip and jaw kinematics in bilabial stop consonant production.

This paper reports two experiments, each designed to clarify different aspects of bilabial stop consonant production. The first one examined events during the labial closure using kinematic recordings in combination with records of oral air pressure and force of labial contact. The results of this experiment suggested that the lips were moving at a high velocity when the oral closure occurred. They also indicated mechanical interactions between the lips during the closure, including tissue compression and the lower lip moving the upper lip upward. The second experiment studied patterns of upper and lower lip interactions, movement variability within and across speakers, and the effects on lip and jaw kinematics of stop consonant voicing and vowel context. Again, the results showed that the lips were moving at a high velocity at the onset of the oral closure. No consistent influences of stop consonant voicing were observed on lip and jaw kinematics in five subjects, nor on a derived measure of lip aperture. The overall results are compatible with the hypothesis that one target for the lips in bilabial stop production is a region of negative lip aperture. A negative lip aperture implies that to reach their virtual target, the lips would have to move beyond each other. Such a control strategy would ensure that the lips will form an air light seal irrespective of any contextual variability in the onset positions of their closing movements.

Functional data analyses of lip motion.

The vocal tract's motion during speech is a complex patterning of the movement of many different articulators according to many different time functions. Understanding this myriad of gestures is important to a number of different disciplines including automatic speech recognition, speech and language pathologies, speech motor control, and experimental phonetics. Central issues are the accurate description of the shape of the vocal tract and determining how each articulator contributes to this shape. A problem facing all of these research areas is how to cope with the multivariate data from speech production experiments. In this paper techniques are described that provide useful tools for describing multivariate functional data such as the measurement of speech movements. The choice of data analysis procedures has been motivated by the need to partition the articulator movement in various ways: end effects separated from shape effects, partitioning of syllable effects, and the splitting of variation within an articulator site from variation from between sites. The techniques of functional data analysis seem admirably suited to the analyses of phenomena such as these. Familiar multivariate procedures such as analysis of variance and principal components analysis have their functional counterparts, and these reveal in a way more suited to the data the important sources of variation in lip motion. Finally, it is found that the analyses of acceleration were especially helpful in suggesting possible control mechanisms. The focus is on using these speech production data to understand the basic principles of coordination. However, it is believed that the tools will have a more general use.

Coarticulation of jaw movements in speech production: is context sensitivity in speech kinematics centrally planned?

Coarticulation in speech production is a phenomenon in which the articulator movements for a given speech sound vary systematically with the surrounding sounds and their associated movements. Although these variations may seem to be planned centrally, without explicit models of the speech articulators, the kinematic patterns that are attributable to central control cannot be distinguished from those that arise because of dynamics and are not represented in the underlying control signals. We address the origins of coarticulation by comparing the results of empirical and modeling studies of jaw motion in speech. The simulated kinematics of sagittal-plane jaw rotation and horizontal jaw translation are compared with the results of empirical studies in which subjects produce speech-like sequences at a normal rate and volume. The simulations examine both "anticipatory" and "carryover" coarticulatory effects. In both cases, the results show that even when no account is taken of context at the level of central control, kinematic patterns vary in amplitude and duration as a function of the magnitude of the preceding or following movement, in the same manner as that observed empirically in coarticulation. Because at least some coarticulatory effects may arise from muscle mechanics and jaw dynamics and not from central control, these factors must be considered before drawing inferences about control in coarticulation.

Articulatory organization of mandibular, labial, and velar movements during speech.

It has been shown that articulator movements during speech are adjusted along a number of spatiotemporal dimensions. For example, variations in the extent of lip, jaw, or tongue motion are associated with proportional changes in the respective articulators' peak velocity. Modifications in the timing of lip and jaw actions are apparently constrained, exhibiting relative timing covariation. Syllable prominence systematically affects some combination of the articular motion parameters, i.e., extent, speed, and duration. The present investigation is an attempt to extend observations of the spatiotemporal properties of articulator movement to include the velum. Lip, jaw, and velar kinematics were recorded optoelectronically and simultaneously with the acoustic signal during productions of the utterance/mabnab/. The spatial and temporal relations between the lips, the jaw, and the velum were examined and compared across articulators. For movements associated with each syllable, the velum displayed scaling pattern qualitatively similar to those of the lips and jaw. Moreover, velocity-displacement relations were more robust for the lowering than for the raising movements of the velum. There was evidence of interarticulator coupling between the velum and the jaw, and between the velum and the upper lip, although this coupling was not as strong as that observed among the oral articulators. Articulator specific differences in velocity-displacement correlations and degree of interarticulator cohesion for the various movement phases may be related to a combination of aerodynamic and phonetic factors, such as the phonologically noncontrastive nature of nasalization in English.

Speech motor coordination and control: evidence from lip, jaw, and laryngeal movements.

The movements of the lower lip, jaw, and larynx during speech were examined for two different speech actions involving oral closing for /p/ and oral constriction for /f/. The initial analysis focused on the manner in which the different speech articulators were coordinated to achieve sound production. It was found that the lip, jaw, and laryngeal movements were highly constrained in their relative timing apparently to facilitate their coordination. Differences were noted in the degree to which speech articulator timing covaried dependent on the functional characteristics of the action. Movements associated with coordinating multiple articulators for a single sound were more highly constrained in their relative timing than were movements associated with sequencing of individual sounds. The kinematic patterns for the different articulators were found to vary in a number of systematic ways depending on the identity of the sound being produced, the phonetic context surrounding the target sound, and whether one versus two consonants were produced in sequence. The results are consistent with an underlying organization reflecting the construct of the phoneme. It is suggested that vocal tract actions for the sounds of the language are stored in memory as motor programs and sequenced together into larger meaningful units during speaking. Speech articulator motion for the different vowel sounds was found to be influenced by the identity of the following consonant, suggesting that speech movements are modified in chunks larger than the individual phonetic segments. It appears that speech production is a hierarchical process with multiple levels of organization transforming cognitive intent into coherent and perceptually identifiable sound sequences.

Some organizational characteristics of speech movement control.

The neuromotor organization for a class of speech sounds (bilabials) was examined to evaluate the control principles underlying speech as a sensorimotor process. Oral opening and closing actions for the consonants /p/, /b/, and /m/ (C1) in /s V1 C1 V2 C2/ context, where V1 was either /ae/ or /i/, V2 was /ae/, and C2 was /p/, were analyzed from 4 subjects. The timing of oral opening and closing action was found to be a significant variable differentiating bilabial consonants. Additionally, opening and closing actions were found to covary along a number of dimensions implicating the movement cycle as the minimal unit of speech motor programming. The sequential adjustments of the lips and jaw varied systematically with phonetic context reflecting the different functional roles of these articulators in the production of consonants and vowels. The implication of these findings for speech production is discussed.

Tongue body kinematics in velar stop production: influences of consonant voicing and vowel context.

This study examines vertical and horizontal tongue body movements in VCV sequences, where the consonant is a voiced or voiceless velar stop. The movement data were recorded using a magnetic transduction technique in two subjects. Consistent with studies of lip and jaw kinematics, the duration of the tongue body raising movement towards closure for the consonant was longer for the voiced stop. In contrast to lip and jaw movements, peak velocity and amplitude of the raising movements were consistently higher for the voiced stop. The larger displacement of the closing movement for the voiced stop was due to a lower starting position of the movement during the preceding vowel. Examination of the tongue body lowering movement for the vowel preceding the velar stop showed it to be longer when the following stop was voiced. Also this lowering movement had a higher peak velocity and amplitude in the voiced environment. These results thus suggest that both the lowering and raising movements in the VC sequence are affected by the voicing status of the consonant. In addition, the second vowel in the VCV sequence showed reliable influences on tongue body movements for the first vowel and the consonant.

Effects of alterations in auditory feedback and speech rate on stuttering frequency.

This study investigated the effects of altered auditory feedback on stuttering frequency during speech production at two different speech rates, Nine stutterers, who exhibited at least 5% dysfluency during a reading task, served as subjects. They read eight different passages (each 300 syllables in length) while receiving four conditions of auditory feedback: nonaltered, masking, delayed, and frequency altered. For each auditory feedback condition, subjects read at both a normal and a fast rate. Results indicated that stuttering frequency was significantly decreased during conditions of delayed and frequency altered auditory feedback at both speech rates (p < 0.05). These findings refute the notion that a slowed speech rate is necessary for fluency enhancement under conditions of altered auditory feedback. Considering previous research and the results of this study, it is proposed that there may be two interdependent factors that are responsible for fluency enhancement: alteration of auditory feedback and modification of speech production.

Parkinsonian deficits in serial multiarticulate movements for speech.

Unlike the single joint arm movements so commonly the focus of Parkinson's disease (PD) studies, orofacial movements for speech are well-learned, complex motor sequences generated without visual guidance. The present study of upper lip, lower lip, and jaw movements during speech in PD was thus aimed at determining whether (1) PD speech kinematic deficits are comparable to those often observed in simpler limb movements; (2) coordination for multimovement actions such as speech is aberrant in PD, as recently claimed; and (3) the component muscle groups involved in this behaviour manifest uniform deficits. Results indicated that despite reduced amplitudes of jaw and upper lip displacement in PD subjects, all three of these oral movements were of normal duration. Secondly, PD lower lip movements manifested no deficits and bradykinesia (reduced velocity) was only found in movements of the jaw. Finally, there was an indication of movement coordination aberrations in these parkinsonian subjects. Overall, these results not only suggest a difference between orofacial and limb movement impairments in PD, but also document the need to broaden our perspectives on this movement disorder by examining a wider range of functional motor tasks.

Sensorimotor characteristics of speech motor sequences.

The present experiment focused on the characteristics of sequential speech movements. Subjects generated two successive lip and jaw closing movements associated with the two 'p's' in 'sapapple'. By selectively manipulating the lower lip perturbation it was possible to discern the role of somatic sensory interactions with the presumed sequential movement programming. Lower lip perturbation duration was manipulated to yield two different load conditions. In the Load On (LN) condition, the perturbation remained on for both closing movements. In the Load On/Off (LNF) condition, the perturbation was removed at variable times prior to the second closing movement. Analyses focused on comparing the EMG and resulting kinematic changes for the second "p" closure across the two load conditions relative to the normal control (no load) condition. The second "p" closure was differentially affected by the load conditions resulting in changes in the upper and lower lip compensations. Upper lip changes reflected consistent load duration differences; however, the magnitude of the lower lip EMG and kinematic adjustments did not mirror those of the upper lip. In contrast to the differential upper lip/lower lip changes observed for the magnitude adjustments, timing adjustments were similar for both upper lip and lower lip suggesting a separation between the specification of magnitude and timing of speech movements. Differential load effects were also observed for the timing of the second closing movements. For the LN condition, the onset of muscle activity and subsequent movement occurred earlier (re: control); for the LNF condition, load removal delayed the onset of muscle activity and the subsequent movement (re: control). Further, the opening movement preceding the second closing movement was modified for both load conditions suggesting that all movements in the sequence, not just closing movements, can be modified. The present results suggest that the programming of speech movement sequences is a dynamic process involving scaling and timing of motor commands relying on various degrees of sensory interaction. The apparent separation in the magnitude and timing specification of the movement sequences suggests the parallel influences of different neural systems. The consequence of this control scheme is that specification of movement parameters for sequential motor acts is a flexible real-time sensorimotor process interacting with less-flexible well-established central motor relations. Further, motor program for speech may reflect certain generalized movement actions (e.g., oral opening, oral closing) rather than individual words, syllables, or other linguistic categories programmed on a movement-to-movement basis.

Timing factors in the coordination of speech movements.

Speech movement coordination involves substantial timing adjustments among multiple degrees of muscles and movement freedom. The present investigation examined the kinematic and muscle timing adjustments associated with the production of select speech movements. For oral closing movements, the timing of the upper lip, lower lip, and jaw peak velocities were found to be tightly coupled, apparently reflecting a coordinative strategy. In contrast, oral opening movements demonstrated reduced temporal coupling and inconsistent sequencing across subjects. Overall, it appears that the temporal organization of speech movements varies with the specific movement goals. In order to evaluate the coordinative patterns for oral closing in detail, the temporal adjustments of multiple perioral muscles associated with the systematic closing peak velocity relations were examined. The relative timing of muscle onsets and peak EMG amplitudes was found to be predictably related to the peak velocity timing variations, suggesting that the motor commands are temporally scaled to generate changes in speaking conditions. It was also found that the mechanical properties of the speech articulators influence movement coordination and can be exploited to maximize movement efficiency. The systematic change in muscle timing characteristics for all synergistic muscles apparently reduces the degrees of freedom to control, thereby facilitating the coordination process.

Kinematic analysis of multiple movement coordination during speech in stutterers.

This study addresses the long-standing claim that stuttering reflects an impairment in the neuromotor coordination of multiple speech movements. Upper lip (UL), lower lip (LL), and jaw (J) kinematics for nonstuttered speech behaviours in stutterers and normal speakers were examined using quantitative indices of normal multiple movement coordination reported in recent studies of gait, reaching, grasping, and speech. While two measures of coordination--dynamic movement composition and intermovement motor equivalence--did not distinguish between stutterers and normals, stutterers manifested striking differences from normal on a third measure, the sequencing of UL, LL, and J movement onsets and velocity peaks. These findings suggest that, contrary to previous hypotheses, stutterers do not manifest general problems of coordination of speech movement. Instead, stuttering appears to be associated with a specific impairment in multiple movement coordination associated with sequencing of those movements.

Hypoglossal, trigeminal, and facial motoneuron involvement in amyotrophic lateral sclerosis.

Facial, trigeminal, and hypoglossal motoneuron involvement was quantified in 25 amyotrophic lateral sclerosis patients and in normal controls. Measures included (1) maximum voluntary contraction of the lower lip, mandible, and tongue using custom-designed force transducers, (2) clinical functions of each muscle group, and in some patients (3) orofacial mobility using videofluoroscopy. All measures indicated that the tongue muscles were most severely affected, even in patients who initially had symptoms in the extremities.

Central patterning of speech movements.

Previous speech kinematic studies have demonstrated systematic timing relations among the upper lip, lower lip, and jaw suggesting the operation of a central pattern generator (CPG). The present study evaluated the consistency of these timing relations following unanticipated perturbation of the lower lip. Using this approach, it was also possible to evaluate the influence of sensory information on the timing of motor output and subsequent coordination of the multiple speech movements. Perturbations were applied to the lower lip during the closing movement associated with the first "p" in "sapapple". Muscle activity and movements of the upper lip, lower lip, and jaw were obtained. Changes in movement displacement, velocity and duration, the timing and sequencing of peak velocities, EMG area, and EMG rise time were analyzed for the control and load conditions. Similar to previous perturbation results, significant magnitude compensations from the muscles and movements of the upper lip, lower lip, and jaw were observed. In contrast, movement durations and the sequencing of peak velocities were relatively unaffected by the lower lip load. The timing of peak EMG amplitude and consequently the timing of peak closing velocity for all structures (UL, LL, and J) occurred earlier relative to the preceding opening movement. These results are consistent with the interaction of phasic sensory input with centrally-driven commands resulting in a phase-advanced motor output. Further, as the timing of one structure is modified so were all the functionally-linked components thereby maintaining the necessary coordination. As in other rhythmic motor behaviors such as locomotion and chewing, there appears to be a centrally patterned framework for speech movement coordination.

Variant and invariant characteristics of speech movements.

Upper lip, lower lip, and jaw kinematics during select speech behaviors were studied in an attempt to identify potential invariant characteristics associated with this highly skilled motor behavior. Data indicated that speech motor actions are executed and planned presumably in terms of relatively invariant combined multimovement gestures. In contrast, the individual upper lip, lower lip, and jaw movements and their moment-to-moment coordination were executed in a variable manner, demonstrating substantial motor equivalence. Based on the trial-to-trial variability in the movement amplitudes, absolute positions, and velocities of the upper lip, lower lip, and jaw, it appears that speech motor planning is not formulated in terms of spatial coordinates. Seemingly, object-level planning for speech may be encoded in relation to the acoustic consequences of the movements and ultimately with regard to listener's auditory perceptions. In addition, certain temporal parameters among the three movements (relative times of movement onsets and velocity peaks) were related stereotypically, reflecting invariances characteristic of more automatic motor behaviors such as chewing and locomotion. These data thus appear to provide some additional insights into the hierarchy of multimovement control. At the top of the motor control hierarchy, the overall plan appears to be generated with explicit specification of certain temporal parameters. Subsequently, based upon the plan and within that stereotypic temporal framework, covariable adjustments among the individual movements are implemented. Given the results of previous perturbation studies, it is hypothesized that these covariable velocity and amplitude adjustments reflect the action of sensorimotor mechanisms.

Dynamic control of the perioral system during speech: kinematic analyses of autogenic and nonautogenic sensorimotor processes.

Afferent contributions to the motor control of speech were evaluated by applying unanticipated loads to the lower lip during the combined upper lip-lower lip gesture associated with the oral closing movements for a "b" sound. Loads were introduced randomly in approximately 15% of the trials to minimize subject anticipation or adaptation. A total of 490 load trials (in five naive subjects) were distributed within a restricted interval (100 ms) centered on the initiation of agonist muscle contraction associated with the lip-closing movements. Kinematic adjustments of the upper and lower lips to these perturbations were examined in detail. In all subjects, load-induced changes in upper and lower lip displacement, movement time, and closing velocity were statistically significant and observed the first time a perturbation was introduced. Load timing variations within the target interval resulted in systematic changes in the site of the compensatory adjustments (upper versus lower lip) and in the magnitude of the kinematic responses. These kinematic changes appeared to reflect the dynamic nature of underlying control processes and clearly contrasted the different response characteristics of autogenic (lower lip) and nonautogenic (upper lip) compensatory actions. Although both upper and lower lip adjustments contributed to perturbation compensations, autogenic responses were found to predominate when loads occurred 20-55 ms before muscle activation. For these early loads, autogenic responses provided approximately 75% of the total compensation. For later loads, when the evolving speech motor action was more time constrained, nonautogenic (open-loop) compensations predominated, providing approximately 65% of the total compensation. The variations in upper and lower lip compensatory response magnitude did not parallel the time course of facial muscle activation. Lower lip kinematic adjustments were reduced 10-15 ms prior to the onset of agonist muscle activation, whereas upper lip adjustments increased in magnitude 10-20 ms after agonist onset. Apparently the dynamic modulation of these responses is controlled independently from facial motoneuron excitation, possibly involving sensorimotor processing via supranuclear centers. Overall the compensatory movement displacements were highly related to the magnitude of the perturbation displacement, especially for loads introduced prior to agonist muscle onset, reflecting a well-calibrated readjustment.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional muscle partitioning during voluntary movement: facial muscle activity for speech.

Electromyographic activity was recorded from multiple intramuscular sites in the orbicularis oris muscle for a set of speech and other motor tasks. Because of its geometric heterogeneity and multiple functions, it was hypothesized that this muscle might be partitioned in a task-dependent manner. Comparison of the timing and amplitude of the EMG activity among the multiple recording sites supported this hypothesis. Because some facial motoneurons in primates, including humans, are monosynaptically activated from area 4 of the motor cortex, it is suggested that this task-dependent muscle partitioning may reflect an aspect of cortical organization.

Control of multimovement coordination: sensorimotor mechanisms in speech motor programming.

The present paper provides some hypotheses concerning the role of sensorimotor mechanisms in the coordination and programming of multimovement behaviors. The primary database is from experiments on the control of speech, a motor behavior that inherently requires multimovement coordination. From these data, it appears that coordination may be implemented by calibrated, sensorimotor actions which couple multiple movements for the accomplishment of common functional goals. The data from speech and select observations in other motor systems also reveal that these sensorimotor linkages are task-dependent and may underlie the intermovement motor equivalence that characterizes many natural motor behaviors. In this context, it is hypothesized also that motor learning may involve the calibration of these intermovement sensorimotor actions. These observations in turn provide some alternative perspectives on the concept of a motor program, primarily suggesting that individual movements and muscle contractions are not wholly prespecified, but shaped by sensorimotor adjustments.