Nonspeech Movements Research Articles

Speech apraxia without oral apraxia: can normal brain function explain the physiopathology?

Apraxia of speech, usually associated with stroke, refers to the inability to perform speech motor movements typically with an intact ability to execute non-speech oral movements. It is uncertain whether apraxia of speech results from damage affecting the insula or the inferior frontal gyrus. The controversy started because of conflicting results from studies investigating patients with disrupted brain structure, when dysfunction of both sites can coexist. We conducted a functional magnetic resonance imaging study of individuals without neurological disorders comparing speech and non-speech movements. Speech movements did not recruit the insula, but activated the left inferior frontal gyrus, suggesting that Broca's area, but not the insula, is critical for speech articulation.

Motor Cortex Dynamics in Visuomotor Production of Speech and Non-speech Mouth Movements

We investigated timing and hemispheric balance of motor cortex activation when kinetically similar speech and non-speech mouth movements and sequences of such movements were triggered by visually presented letter- and symbol-strings. As an index of motor cortex activation, we used magnetoencephalographic recording of task-related change of precentral 20 Hz (16-24 Hz) activity. Suppression of the 20 Hz rhythm revealed pre-movement activation in the face representation areas that was tied to visual instruction, not movement onset. The 20 Hz rhythm remained suppressed throughout the preparation and execution of mouth movements and was followed by post-movement rebound. Left hemisphere preceded the right at the onset and offset of the suppression, similarly for isolated and sequential speech and non-speech movements. Pattern of task-related change in 20 Hz activity was otherwise symmetrical. In the face areas, the overall modulation of 20 Hz activity increased with sequence length and motor demands. Hand representation areas showed also weak reactivity, with systematically larger modulation of 20 Hz activity for non-speech than speech movements. Our results suggest an active role for the motor cortex in cognitive control of visually triggered mouth movements, not limited to movement execution.

Imaging speech production using fMRI

Human speech is a well-learned, sensorimotor, and ecological behavior ideal for the study of neural processes and brain-behavior relations. With the advent of modern neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), the potential for investigating neural mechanisms of speech motor control, speech motor disorders, and speech motor development has increased. However, a practical issue has limited the application of fMRI to issues in spoken language production and other related behaviors (singing, swallowing). Producing these behaviors during volume acquisition introduces motion-induced signal changes that confound the activation signals of interest. A number of approaches, ranging from signal processing to using silent or covert speech, have attempted to remove or prevent the effects of motion-induced artefact. However, these approaches are flawed for a variety of reasons. An alternative approach, that has only recently been applied to study single-word production, uses pauses in volume acquisition during the production of natural speech motion. Here we present some representative data illustrating the problems associated with motion artefacts and some qualitative results acquired from subjects producing short sentences and orofacial nonspeech movements in the scanner. Using pauses or silent intervals in volume acquisition and block designs, results from individual subjects result in robust activation without motion-induced signal artefact. This approach is an efficient method for studying the neural basis of spoken language production and the effects of speech and language disorders using fMRI.

Kinematic analyses of speech, orofacial nonspeech, and finger movements in stuttering and nonstuttering adults.

This work investigated the hypothesis that neuromotor differences between individuals who stutter and individuals who do not stutter are not limited to the movements involved in speech production. Kinematic data were obtained from gender- and age-matched stuttering (n = 10) and nonstuttering (n = 10) adults during speech movements, orofacial nonspeech movements, and finger movements. All movements were performed in 4 conditions differing in sequence length and location of the target movement within the sequence. Results revealed statistically significant differences between the stuttering and nonstuttering individuals on several measures of lip and jaw closing (but not opening) movements during perceptually fluent speech. The magnitude of these differences varied across different levels of utterance length (larger differences during shorter utterances) and across different locations of the target movement within an utterance (larger differences close to the beginning). Results further revealed statistically significant differences between the stuttering and nonstuttering groups in finger flexion (but not extension) movement duration and peak velocity latency. Overall, findings suggest that differences between stuttering and nonstuttering individuals are not confined to the sensorimotor processes underlying speech production or even movements of the orofacial system in general. Rather, it appears that the groups show generalized differences in the duration of certain goal-directed movements across unrelated motor systems.

Review

Background : This work was motivated by recent attempts at explaining apraxia of speech as a general motor disorder which involves both speech and nonspeech movements (Ballard, Granier, & Robin, 2000). It also relates to some more recent theoretical accounts of the diagnostic value of nonspeech tasks, which postulate that such tasks may help to isolate single motor components and examine their individual contributions to a complex motor speech impairment (e.g., Folkins et al., 1995; Robin, Solomon, Moon, & Folkins, 1997). These approaches are implicitly based on a model which assumes that motor control of the organs implicated in speaking is independent of the particular motor task that is imposed on them. Aims : Two alternative models are discussed: a task-independent model of motor control, which postulates a universal sensory-motor system controlling all motor functions of the speech apparatus, irrespective of their purpose, and a task-dependent model, which postulates different sensory-motor control systems for vegetative functions, emotional expression, and speech. The motor subsystems distinguished in the task-dependent model are considered separate in the sense that (1) they involve distinct sensory-motor patterns, (2) they are based on distinct and specialised neural circuitries, and (3) their impairments through brain lesions are dissociated from each other and from impairments of the nonspeech voluntary motor functions of the same musculature. Main Contribution : Evidence for the task-dependent model is provided in three major sections: a section on vegetative motor functions, a section on emotional expressive motor functions, and a section on voluntary nonspeech motor activities. In each section, clinical and experimental dissociations between speech and nonspeech tasks are reviewed and the physiological and neuro-anatomical underpinnings of these observations are discussed. In a general discussion, the nature of speech as a learned motor skill and the relation of speech motor control to an auditory reference frame are highlighted. Conclusions : It is claimed that both the dysarthrias and apraxia of speech should be considered disorders of a sensory-motor system specialised for speaking. Impairments of speech and nonspeech movements should be kept separate.

The effects of masseter tendon vibration on nonspeech oral movements and vowel gestures.

The role of proprioception in speech and oral motor control was investigated by applying tendon vibration to the masseter during vowel production and nonspeech oral movements. Measures were made of peak jaw-opening amplitude, jaw-opening velocity, and movement time in both vibration and nonvibration conditions. Generally, the tendon vibration caused a consistent and marked reduction in the amplitude and velocity of jaw-opening movements for each subject in both tasks. Movement time remained consistent across the vibration conditions for both tasks. These results indicate that masseter tendon vibration causes significant changes in jaw kinematics during simple speech gestures and nonspeech movements. These findings are consistent with the documented effects of tendon vibration on limb movements. The study demonstrates that tendon vibration is a potent tool for investigating proprioception in speech and oral motor control.

Understanding the nature of apraxia of speech: Theory, analysis, and treatment

Researchers have interpreted the behaviours of individuals with acquired apraxia of speech (AOS) as impairment of linguistic phonological processing, motor control, or both. Acoustic, kinematic, and perceptual studies of speech in more recent years have led to significant advances in our understanding of the disorder and wide acceptance that it affects phonetic - motoric planning of speech. However, newly developed methods for studying nonspeech motor control are providing new insights, indicating that the motor control impairment of AOS extends beyond speech and is manifest in nonspeech movements of the oral structures. We present the most recent developments in theory and methods to examine and define the nature of AOS. Theories of the disorder are then related to existing treatment approaches and the efficacy of these approaches is examined. Directions for development of new treatments are posited. It is proposed that treatment programmes driven by a principled account of how the motor system learns to produce skilled actions will provide the most efficient and effective framework for treating motorbased speech disorders. In turn, well controlled and theoretically motivated studies of treatment efficacy promise to stimulate further development of theoretical accounts and contribute to our understanding of AOS.

Neuromotor control in stuttering: Speech, orofacial nonspeech, and finger movements

Neuromotor control in stuttering: Speech, orofacial nonspeech, and finger movements

Can a model with gestural phonological repre-sentations account for acquired phonological and articulatory impairments? Two case studies

AbstractThis study investigated the errors of speech sound production made by a woman (NC) with Dementia of the Alzheimer Type, and a man (HO) with cerebrovascular etiology. Five tasks were used to investigate the participants' phonological retrieval in picture naming, reading and repetition; ability to preserve phonological contrast in one-syllable minimal pair production; articulatory execution in vowel production and diadochokinesis; and non-speech orofacial movements. Both speakers made speech sound production errors in all single word production tasks, but had greater difficulty retrieving spoken word forms in naming than reading or repetition. Both preserved phonological contrast in one-syllable minimal pairs. HO was impaired at vowel production and diadochokinesis and NC showed a lesser degree of impairment in diadochokinesis. In the orofacial praxis tasks, HO showed impaired laryngeal control and NC was unimpaired. These results suggest that both speakers had difficulty in the phasing, scaling and...

Hemispheric contributions for speech and nonspeech facial movements

Hemispheric contributions for speech and nonspeech facial movements

No place for motor speech acts in the assessment of dysphagia? Intelligibility and swallowing difficulties in stroke and Parkinson's disease patients.

Speech and language therapists are increasingly being asked to treat dysphagic patients. Concern has been expressed and surveys have confirmed that radiological assessment procedures are rarely available. Consequently, patients must often be assessed and their treatment planned on the basis of bedside examinations. Despite evidence that swallowing disorders need not be related to problems of articulation, recommendations on the procedure of such examinations frequently include an evaluation of speech and non-speech articulatory movements. A study is reported of patients who exhibit both dysphagia and dysarthria as a result of either stroke or Parkinson's disease. Assessments of the intelligibility of their speech and of their swallowing problems were found to be unrelated. The implications of this finding for the assessment of dysphagia are discussed.

Evidence of Common Timing Processes in the Control of Manual, Orofacial, and Speech Movements.

Recent investigations of timing in motor control have been interpreted as support for the concept of brain modularity. According to this concept, the brain is organized into functional modules that contain mechanisms responsible for general processes. Keele and colleagues (Keele & Hawkins, 1982; Keele & Ivry, 1987; Keele, Ivry, & Pokorny, 1987; Keele, Pokorny, Corcos, & Ivry, 1985) demonstrated that the within-subject variability in. cycle duration of repetitive movements is correlated across finger, forearm, and foot movements, providing evidence in support of a general timing module. The present study examines the notion of timing modularity of speech and nonspeech movements of the oral motor system as well as the manual motor system. Subjects produced repetitive movements with the finger, forearm, and jaw. In addition, a fourth task involved the repetition of a syllable. All tasks were to be produced with a 400-ms cycle duration; target duration was established with a pacing tone, which then was removed. For each task, the within-subject variability of the cycle duration was computed for the unpaced movements over 20 trials. Significant correlations were found between each pair of effectors and tasks. The present results provide evidence that common timing processes are involved not only in movements of the limbs, but also in speech and nonspeech movements of oral structures.

Cerebral Averaged Potentials Preceding Oral Movement

The "readiness potential" is an event-related potential that shows increasing negativity at vertex and motor strip scalp recording sites prior to voluntary, unilateral limb movements. Though speech involves movement on both sides of the midline, recent recordings of prespeech potentials suggest a pattern of bilateral activation that lateralizes to the dominant hemisphere just prior to the onset of articulatory movement. To determine whether this pattern of dominant hemisphere activation is present prior to a stereotyped, nonspeech movement of the mouth, the averaged potentials preceding a lip protrusion task were recorded at the cranial vertex and over the right and left motor cortex. Results were compared to potentials preceding a right finger extension task performed by the same subjects. Both the finger and the lip movements were initially preceded by slow negative potentials. Prior to the finger extension task, the negative amplitude became greatest over the left motor cortex, contralateral to the side of movement. Prior to the lip protrusion task, the amplitude of the potential remained even over the right and left motor cortices. The results suggest that, for this nonspeech movement of a midline structure, bilateral cortical control takes place. Control of lip movement is apparently not necessarily a dominant hemisphere function, though dominance may become part of the motor control strategy for more complex movements such as those used during speech.

Articulatory coding in prose reading: Evidence from braille on changes with skill

The role of speech-based strategies in prose reading was tested in two experiments with braillists at different levels of proficiency. Subjects read prose texts in silent and oral control conditions, under articulatory suppression, and while making non-speech movements during silent and oral reading, respectively. Experiment 1 used relatively difficult braille texts and showed that articulatory suppression reduced comprehension significantly compared to the other conditions. Speed (syllables per minute) was not significantly reduced under articulatory suppression, although two subjects were unable to read at all in that condition. Experiment 2 used easy texts and included beginning readers. Proficiency levels interacted significantly with experimental conditions for both speed and comprehension. The best readers showed no effect of articulatory suppression on either speed or comprehension with easy tests. Beginners showed significantly reduced speed and comprehension (or failed to score at all) under articulatory suppression, despite good comprehension in control conditions. For subjects in the middle groups, articulatory suppression had some effect on comprehension but speeded rather than slowed reading, if anything. The results suggest that articulatory suppression can affect input strategies as well as comprehension, but that the strategies which underly it vary with skill and test conditions. It was argued that suppression taps important but changing strategies in prose reading.

The relation between oral movement control and speech

A large series of neurological patients, selected solely on the basis that they had damage restricted to one hemisphere of the brain, was given a variety of tests of basic speech and praxic function. Within the left-damaged group, patients were further identified as aphasic or nonaphasic, based on preexisting standard tests of aphasia. Subgroups of aphasics were studied on the basis of lesion location, rather than on the basis of aphasia type. The focus of the study was the relation between the production of speech and nonspeech oral movements, particularly across anterior and posterior lesions. Reproduction of single nonverbal oral movements and of single isolated speech sounds was found to be very highly correlated, and both depended selectively on the left anterior region of the brain. This same region was critically important for rapid repeated articulation of a syllable, suggesting that it mediates control at some “unit” level of movement, in a phenomenological sense, for both speech and nonspeech movements. Other “speech” regions in the left hemisphere appeared to be dispensable for the production of single oral movements, whether these were verbal or nonverbal movements. However, for most aphasic patients, an area in the left posterior region was inferred to be essential for production of multiple oral movements, whether nonverbal or verbal, suggesting a critical role in the accurate selection of movements. Within the posterior region, there was further differentiation for multisyllabic speech into a parietal system, which appeared to mediate primarily praxic function, and a temporal system, which appeared to mediate verbal-echolalic function. Aphasias from anterior and posterior lesions resembled “Broca's” and “Wernicke's” aphasia only insofar as they differed in fluency, with anterior aphasics clearly less fluent. Tests of speech comprehension did not differentiate the groups. It is suggested that classifying aphasic patients via lesion location rather than aphasic typology might yield a view of functional subsystems different from those commonly accepted.

New technique for acquiring three-dimensional orofacial nonspeech movements.

A new video-based motion analysis system is described that permits acquisition of kinematic patterns from multiple structures (upper lip, lower lip, and jaw), movement patterns to be captured in three dimensions, and acquisition of non-speech orofacial movement patterns without restricting natural head motion. The importance of acquiring three-dimensional lip and jaw movements during nonspeech (e.g., oral opening-closing and chewing motions) movements is emphasized.

Neuromuscular specialization of the mandibular motor system: Speech versus non-speech movements

A number of EMG studies have provided significant contributions to our understanding of the mandibular muscle system. Nevertheless, little is known about the organization of the action patterns of the jaw muscles during movements underlying speech production, in relation to those of other functional activities. In the present study, the activity patterns of the mandibular elevator muscle system were investigated for speech and non-speech gestures for the purpose of determining the possibility of neuromuscular specialization for speech in relation to other mandibular functions. The activity of eight muscles were recorded along with the displacement of the incisal point of the jaw in three-dimensional space. These signals were recorded from three adult American-English subjects during the production of speech at different rates, and for non-speech movements. Results indicated that jaw space for speech was the most restricted of any mandibular function and jaw movements for speech were generally produced by the most simple muscle action patterns. Chewing and functional jaw movements are presumably neurophysiologically distinct. In addition, individual differences exist in the selection of a given muscle or muscle system for a specific function and/or utterance and in the coordination of muscle activity patterns for different gestures.

Mandible movements during increasingly rapid articulations of single syllables: preliminary observations.

A previous study of mandible movements in normal speech [W.L. Nelson, J. Acoust. Soc. Am. Suppl. 1 68, S32 (1980)] suggested that the speech motor control process resulted in a relationship between movement time, distance, and peak velocity which implied (1) some adaptation to the physical effort required for the movement, and (2) that the force limit effective during speech was considerably below that which the mandibular muscles are capable of producing. In the present study, mandible movements were measured during maximally rapid opening and closing tasks, and during increasingly rapid repetitions of a spoken syllable and a nonspeech "syllable." The results indicate that (1) peak acceleration levels for the repeated mandible movements were less than half of those for the maximally rapid single mandible movements, and (2) a rather different mode of control is used for the repeated speech movements as compared to the nonspeech movements.

Relation between finger reaction time and voice reaction time in stuttering and nonstuttering children and adults.

Nine stutterers and nine nonstutterers at each of three age levels (5 years, 9 years, and 18 years and above) responded to the onset of 21 1-kHz tones by depressing the index finger of their preferred hand on a response key. Finger reaction times (FRTs) were measured to the nearest millisecond and compared to the voice reaction times (VRTs) obtained from the same subjects. Increased speed and stability of the finger reaction times were observed as an inverse function of age for both groups. The stutterers, as a group, exhibited mean FRTs which were significantly longer and more variable than those of the nonstutterers at each of the three age levels. High correlations also were found between the finger and voice reaction scores for both the stutterers and the nonstutterers. Results support the inference that some stutterers may exhibit difficulty in the consistent execution of motor control strategies common to both speech and nonspeech movements.

The effects of varying lower-lip displacement on upper-lip movements: implications for the coordination of speech movements.

Upper-lip and lower-lip movements were transduced in the inferior-superior dimension in five normal-speaking subjects during four tasks. In task 1 visual feedback was used to manipulate the maximum displacement of the lower lip during speech. The upper lip elevated significantly less for the opening gesture when the amount of opening from the lower lip was increased. The upper lip moved to significantly lower positions for bilabial closure when the distance to be moved by the lower lip was increased. In task 2 the same procedures were followed with a bite block between the teeth. The bite block did not significantly change the interactions between lips for the opening gesture. The interactions were larger for bilabial closure with the bite block. In task 3 different vowels instead of visual feedback were used to manipulate lower-lip displacement. The relations between lips were similar to those found in task 1. In task 4 it was shown that these relations between lips are not found in nonspeech lower-lip movements. The interactions between lips are discussed in relation to models of speech motor control, including spatial targets, mass-spring systems, and planned trajectories.