Voice dysfunction in dysarthria: application of the Multi-Dimensional Voice Program.

Phonatory dysfunction is a frequent component of dysarthria and often is a primary feature noted in clinical assessment. But the vocal impairment can be difficult to assess because (a). the analysis of voice disorder of any kind can be challenging, and (b). the voice disorder in dysarthria often occurs along with other impairments affecting articulation, resonance, and respiration. A promising assessment tool is multi-parameter acoustic analysis, such as the Multi-Dimensional Voice Program (MDVP). Part 1 of this paper recommends procedures and standards for the acoustic analysis of voice, including (1). selection of the sample to be analyzed, (2). signal quality requirements, (3). availability of normative data for both genders and different ages of speakers, (4). reliability of analysis, and (5). correlation of acoustic results with results from other methods of analysis. In Part 2, acoustic data are reviewed for the dysarthria associated with Parkinson disease (PD), cerebellar disease, amyotrophic lateral sclerosis (ALS), traumatic brain injury (TBI), unilateral hemispheric stroke, and essential tremor. Tentative profiles of voice disorder are described for these conditions. These profiles may serve as hypotheses for future research. Although several issues remain to be resolved in the acoustic analysis of voice disorder in dysarthria, steps can be taken now to promote the reliability, validity, and clinical utility of such analyses. (1). As a result of this activity, the participant will be able to describe ways in which an optimal multi-dimensional analysis of voice can be performed with modern acoustic analysis systems. (2). As a result of this activity, the participant will be able to apply multi-dimensional acoustic analysis of voice to individuals who have a dysarthria-related voice disorder. (3). As a result of this activity, the participant will be able to identify major sources of normative data on the Multi-Dimensional Voice Program.

Clinicoanatomic studies in dysarthria: review, critique, and directions for research.

More than 30 years ago, Darley, Aronson, and Brown (1969) proposed clinicoanatomic correlations for seven perceptual types of dysarthria. These correlations have not been systematically re-examined even though imaging technologies developed in recent years provide the means to do so. This review considers data from published imaging studies as well as data from selected medical interventions to evaluate the current state of knowledge that relates lesion site to the nature of a speech disturbance. Although the extant data are not sufficient to allow a complete evaluation of the seven types of dysarthria described by Darley et al., relevant information has been reported on lesions of the pyramidal pathway, extrapyramidal pathway, and cerebellum. In general, the results are best explained by an equivalence mode of brain-behavior relationship in which a type of dysarthria is associated with a lesion in one of two or more brain structures. Criteria also are proposed for future studies of clinicoanatomic relationships in neurogenic communication disorders.

Acoustic and intelligibility characteristics of sentence production in neurogenic speech disorders.

The purpose of this study was to examine the relationship between scaled speech intelligibility and selected acoustic variables in persons with dysarthria. Control speakers and speakers with amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD) produced sentences which were analyzed acoustically and perceptually. The acoustic variables included total utterance durations, segment durations, estimates of the acoustic vowel space, and slopes of formant transitions; the perceptual variables included scaled speech intelligibility and severity of speech involvement. Results indicated that the temporal variables typically differentiated the ALS group, but not the PD group, from the controls, and that vowel spaces were smaller for both neurogenic groups as compared to controls, but only significantly so for the ALS speakers. The relation of these acoustic measures to scaled speech intelligibility is shown to be complex, and the composite results are discussed in terms of sentence vs. single-word intelligibility estimates and their underlying acoustic bases.

Ataxic dysarthria.

Although ataxic dysarthria has been studied with various methods in several languages, questions remain concerning which features of the disorder are most consistent, which speaking tasks are most sensitive to the disorder, and whether the different speech production subsystems are uniformly affected. Perceptual and acoustic data were obtained from 14 individuals (seven men, seven women) with ataxic dysarthria for several speaking tasks, including sustained vowel phonation, syllable repetition, sentence recitation, and conversation. Multidimensional acoustic analyses of sustained vowel phonation showed that the largest and most frequent abnormality for both men and women was a long-term variability of fundamental frequency. Other measures with a high frequency of abnormality were shimmer and peak amplitude variation (for both sexes) and jitter (for women). Syllable alternating motion rate (AMR) was typically slow and irregular in its temporal pattern. In addition, the energy maxima and minima often were highly variable across repeated syllables, and this variability is thought to reflect poorly coordinated respiratory function and inadequate articulatory/voicing control. Syllable rates tended to be slower for sentence recitation and conversation than for AMR, but the three rates were highly similar. Formant-frequency ranges during sentence production were essentially normal, showing that articulatory hypometria is not a pervasive problem. Conversational samples varied considerably across subjects in intelligibility and number of words/ morphemes in a breath group. Qualitative analyses of unintelligible episodes in conversation showed that these samples generally had a fairly well-defined syllable pattern but subjects differed in the degree to which the acoustic contrasts typical of consonant and vowel sequences were maintained. For some individuals, an intelligibility deficit occurred in the face of highly distinctive (and contrastive) acoustic patterns.

Research on speech motor control and its disorders: a review and prospective.

This paper reviews issues in speech motor control and a class of communication disorders known as motor speech disorders. Speech motor control refers to the systems and strategies that regulate the production of speech, including the planning and preparation of movements (sometimes called motor programming) and the execution of movement plans to result in muscle contractions and structural displacements. Traditionally, speech motor control is distinguished from phonologic operations, but in some recent phonologic theories, there is a deliberate blurring of the boundaries between phonologic representation and motor functions. Moreover, there is continuing discussion in the literature as to whether a given motor speech disorder (especially apraxia of speech and stuttering) should be understood at the phonologic level, the motoric level, or both of these. The motor speech disorders considered here include: the dysarthrias, apraxia of speech, developmental apraxia of speech, developmental stuttering, acquired (neurogenic and psychogenic) stuttering, and cluttering.

Effect of speaking rate manipulations on acoustic and perceptual aspects of the dysarthria in amyotrophic lateral sclerosis.

The current study explored the acoustic and perceptual effects of speaking rate adjustments in persons with amyotrophic lateral sclerosis (ALS) and in neurologically normal individuals. Sentence utterances were obtained from the participants at two self-selected speaking rates: habitual and fast. Total utterance durations, segment durations, and vowel formant frequencies comprised the acoustic measures, whereas magnitude estimates of speech intelligibility and severity of speech involvement were the perceptual measures. Results showed that participants in both the neurologically normal and ALS groups were able to increase their speaking rate when asked to do so, but that the participants with ALS were significantly slower than the neurologically normal participants at both rates. Both groups of participants also showed compression of the acoustic vowel space with increased speaking rate, with the vowel spaces of participants with ALS generally being more compressed than the vowel spaces of neurologically normal participants, at either rate. Most importantly, the perceptual measures failed to show any effect of the speaking rate adjustment on scaled intelligibility or severity, for either group. These findings are discussed relative to the general issue of slow habitual speaking rates among many speakers with dysarthria, and possible explanations for the slowness. The lack of an effect of increased rate on the perception of the speech deficit among speakers with ALS argues against the idea that the habitually slow rates are a form of compensation to reduce the complexity of speech production.

An auditory-feedback-based neural network model of speech production that is robust to developmental changes in the size and shape of the articulatory system.

The purpose of this article is to demonstrate that self-produced auditory feedback is sufficient to train a mapping between auditory target space and articulator space under conditions in which the structures of speech production are undergoing considerable developmental restructuring. One challenge for competing theories that propose invariant constriction targets is that it is unclear what teaching signal could specify constriction location and degree so that a mapping between constriction target space and articulator space can be learned. It is predicted that a model trained by auditory feedback will accomplish speech goals, in auditory target space, by continuously learning to use different articulator configurations to adapt to the changing acoustic properties of the vocal tract during development. The Maeda articulatory synthesis part of the DIVA neural network model (Guenther et al., 1998) was modified to reflect the development of the vocal tract by using measurements taken from MR images of children. After training, the model was able to maintain the 11 English vowel targets in auditory planning space, utilizing varying articulator configurations, despite morphological changes that occur during development. The vocal-tract constriction pattern (derived from the vocal-tract area function) as well as the formant values varied during the course of development in correspondence with morphological changes in the structures involved with speech production. Despite changes in the acoustical properties of the vocal tract that occur during the course of development, the model was able to demonstrate motor-equivalent speech production under lip-restriction conditions. The model accomplished this in a self-organizing manner even though there was no prior experience with lip restriction during training.

Task-based profiles of the dysarthrias.

The dysarthrias are associated with a variety of motor disturbances distributed over several motor systems of speech production. The features of a given dysarthria often vary with the speaking task, and this task-dependency affords insights into the responsible neural lesion and its effects on the motor regulation of speech. Each task also is amenable to quantitative analyses with acoustic or physiologic methods, and these analyses may redefine the value of these speaking tasks. This article considers task-based analyses for the dysarthrias associated with Parkinson's disease, cerebellar disease, and stroke.

Perceptuo-acoustic assessment of prosodic impairment in dysarthria.

Dysprosody was studied in four groups of male subjects: subjects with amyotrophic lateral sclerosis (ALS) and mild intelligibility impairment, subjects with ALS and a more severe intelligibility loss, subjects with cerebellar disease, and neurologically normal controls. Dysprosody was assessed with perceptual ratings and acoustic measures pertaining to the regulation of duration, ƒ(0), and intensity within tone units of conversational samples. Intelligibility reduction and prosodic disturbance were not necessarily equally impaired in all subjects, and it is concluded that these are complementary indices of severity of dysarthria. Compared to the neurologically normal control group, the clinical groups tended to decrease the overall duration of tone units, produce fewer words in a tone unit, and use smaller variations in ƒ(0). Recommendations are offered for the assessement of.

Magnetic resonance imaging procedures to study the concurrent anatomic development of vocal tract structures: preliminary results.

The vocal tract structures undergo drastic anatomic restructuring during the course of development from infancy to adulthood. This study demonstrates the feasibility of using MRI to examine the growth processes of the vocal tract. This method affords precise and detailed visualization of the soft tissues in the oro-pharyngeal region, while also providing images of related bony and cartilaginous structures. Information on anatomic restructuring contributes to the understanding of how speech emerges and develops, and it also establishes normative information that can be used in the assessment of developmental anomalies. This paper describes the method used to measure and examine the concurrent anatomic development of the various vocal tract structures during early childhood. Preliminary results from two pediatric subjects indicate that there is synchrony of growth in the different structures-both soft and hard tissues-, and that such synchronous growth appears to persist during periods of growth spurts.

Acoustic studies of dysarthric speech: methods, progress, and potential.

EDUCATIONAL OBJECTIVES: (1) The reader will be able to describe the major types of acoustic analysis available for the study of speech, (2) specify the components needed for a modern speech analysis laboratory, including equipment for recording and analysis, and (3) list possible measurements for various aspects of phonation, articulation and resonance, as they might be manifest in neurologically disordered speech.

Self-organizing map for the classification of normal and disordered female voices.

The goal of this research was to train a self-organizing map (SOM) on various acoustic measures (amplitude perturbation quotient, degree of voice breaks, rahmonic amplitude, soft phonation index, standard deviation of the fundamental frequency, and peak amplitude variation) of the sustained vowel /a/ to enhance visualization of the multidimensional nonlinear regularities inherent in the input data space. The SOM was trained using 30 spasmodic dysphonia exemplars, 30 pretreatment functional dysphonia exemplars, 30 post-treatment functional dysphonia exemplars, and 30 normal voice exemplars. After training, the classification performance of the SOM was evaluated. The results indicated that the SOM had better classification performance than that of a stepwise discriminant analysis over the original data. Analysis of the weight values across the SOM, by means of stepwise discriminant analysis, revealed the relative importance of the acoustic measures in classification of the various groups. The SOM provided both an easy way to visualize multidimensional data, and enhanced statistical predictability at distinguishing between the various groups (over that conducted on the original data set). We regard the results of this study as a promising initial step into the use of SOMs with multiple acoustic measures to assess phonatory function.

DECTalk and MacinTalk speech synthesizers: intelligibility differences for three listener groups.

This study examined word level intelligibility differences between DECTalk and MacinTalk speech synthesizers using the Modified Rhyme Test in an open format transcription task. Three groups of listeners participated: inexperienced, speech-language pathologists, and speech synthesis experts. Results for between-subjects ANOVA showed that the expert group correctly identified a significantly higher number of words than each of the other listener groups. For the within-subjects factor of voice, simple effects ANOVA and post hoc contrasts within each group showed that listeners had higher intelligibility scores for the DECTalk male voice, Perfect Paul, than for the MacinTalk male voice, Bruce. No other pairwise gender/age-matched differences were found between the two synthesizers.

Neuroimaging studies of brain activation for language, with an emphasis on functional magnetic resonance imaging: a review.

Neuroimaging studies have greatly enhanced the potential to understand brain-behavior relationships in complex behaviors such as language. The method of functional magnetic resonance imaging (fMRI) is one of the newest tools for neuroimaging, and it will in all likelihood contribute substantially to new knowledge about brain activation for language processing. This review summarizes basic information about fMRI, including principles of operation, experimental pitfalls and examples of application to language.

A speaking task analysis of the dysarthria in cerebellar disease.

Cerebellar disease affects a number of skilled movements, including those in speech. Ataxic dysarthria, the speech disorder that typically accompanies cerebellar disease, was studied by acoustic methods. Control subjects and subjects with ataxic dysarthria were recorded while performing a number of speaking tasks, including sustained vowel phonation, syllable repetition, monosyllabic word production (intelligibility test), sentence recitation, and conversation. Acoustic data derived from the speech samples confirmed the hypothesis that temporal dysregulation is a primary component of the speech disorder. The data also show that the nature of the disorder varies with the speaking task. This result agrees with observations on other motor systems in subjects with cerebellar disease and may be evidence of a dissociation of impairments. Suggestions are offered on the selection of measures for a given task and on the role of the cerebellum in the regulation of speaking.

Formoffa: An automated formant, moment, fundamental frequency, amplitude analysis of normal and disordered speech.

A system for semi-automatic, multi-parameter acoustic analysis is described. The system, called FORMOFFA (For = FORmants, Mo = MOments, FF = Fundamental Frequency, A = Amplitude), operates on a PC microcomputer by adaptations of commercially available software. Data displays include a deterministic time record of instantaneous values, and an ergodic time-compressed distribution. In this report the technique is developed with a one-word example, and some measurement and reliability issues are described. The analysis possibilities are then illustrated with several applications: (1) segmental analysis of normal speech, (2) acoustic assessment of the effects of a progressive neurological disease (amyotrophic lateral sclerosis) on sentence production, (3) acoustic study of palatal lift management of a patient with traumatic brain injury, and (4) phonetic assessment of word production by a subject with dysarthria. Although the current technique is recommended as a research tool, this kind of analysis promises several advantages for clinical application, including semi-automaticity, efficiency, parsimony, and relevance to both segmental and suprasegmental levels of analysis.

Vocal tract acoustics.

This paper considers the topic of vocal tract acoustics from the three perspectives: (a) the acoustic theory of speech production; (b) contemporary laboratory methods for acoustic analysis, and (c) measurement of the acoustic signal of speech. Linear source-filter theory is the standard acoustic theory of speech production and is the foundation for remarkable advances in the analysis and synthesis of speech. Digital signal processing, the dominant laboratory method for speech analysis, enables the acquisition and recording of the acoustic speech signal but also implements quantitative algorithms largely based on linear source-filter theory. Measurements of the acoustic signal reflect the acoustic theory of speech production, laboratory methods for signal analysis, and principles of experimental phonetics. Basic issues in the three domains of theory, laboratory methods, and measurement are summarized as they pertain to the interests of the voice scientist, voice clinician, and voice teacher.

Speaking rate and speech movement velocity profiles.

The effects of speaking rate on the velocity profiles of movements of the lower lip and tongue tip during the production of stop consonants were examined using an x-ray microbeam system. Five young adults used a magnitude production task to produce five speaking rates that ranged from very fast to very slow. Results indicated that changes in speaking rate were associated with changes in the topology of the speech movement velocity-time function. Specifically, the velocity profile changed from a symmetrical, single-peaked function at the fast speaking rates to an asymmetrical and multi-peaked function at the slow speaking rates. This variation in velocity profile shape is interpreted as support for the view that alterations in speaking rate are associated with changes in motor control strategies. In particular, the control strategy for speech gestures produced at fast speaking rates appears to involve unitary movements that may be predominantly preprogrammed, whereas gestures produced at slow speaking rates consist of multiple submovements that may be influenced by feedback mechanisms.

Quantitative description of the dysarthria in women with amyotrophic lateral sclerosis.

Speech intelligibility and its phonetic and acoustic correlates were studied in a group of 10 women with amyotrophic lateral sclerosis (ALS). Intelligibility assessment with a word-identification test indicated that the most disrupted phonetic features pertained to velopharyngeal valving, lingual function for consonant contrasts of place and manner, and syllable shape. An acoustic signature analysis based on trajectories of the first and second formants in selected monosyllabic test words revealed that the mean slope of the second formant (F2) was reduced compared with that of a normal geriatric control group. This F2 slope reduction is interpreted to reflect loss of lingual motoneurons. Acoustic measures of phonatory function for sustained vowel prolongation demonstrated abnormalities in fundamental frequency, perturbations of frequency (jitter) and amplitude (shimmer), and signal-to-noise ratio. The data for women with ALS are compared with data for a normal geriatric control group of women and with data for a group of 25 men with ALS (Kent et al., 1990). Although the overall ranking of errors was similar for males and females with ALS, men were more likely to have impairments of voicing in syllable-initial position.