Jerald B. Moon

An Anatomic Study of the Tensor Veli Palatini and Dilatator Tubae Muscles in Relation to Eustachian Tube and Velar Function

In a gross anatomic study of 20 sides in 16 human head specimens, the tensor veli palatini, the dilatator tubae, and the tensor tympani muscles were studied. The tensor veli palatini was observed to insert onto the anterior one-third of the pterygoid hamulus, whereas the dilatator tubae rounded the middle one-third of the pterygoid hamulus without an insertion. Thus, the dilatator tubae, not the tensor veli palatini, could serve to tense the anterior velum. An insertion from the superior pharyngeal constrictor muscle onto the posterior one-third of the hamulus could provide a curbing function for the dilatator tubae muscle. Adipose tissue, located at the hamulus, could provide lubrication for the tendinous fibers of the dilatator tubae as they round the hamulus. The dilatator tubae was observed to attach to the hook of the eustachian tube and is accepted as the tubal dilator. Observed on 13 of 20 sides in 11 specimens, the bulk of the dilatator tubae remained distinct from the tensor veli palatini despite a connective tissue alliance and intermingling of some muscle fibers. On 5 of 20 sides in 5 specimens, fibers of the dilatator tubae intermingled extensively with the tensor veli palatini. Of the 20 dilatator tubae muscles dissected, 2 were observed to be deficient. The tensor veli palatini was observed to be continuous with the tensor tympani. Full color versions of the figures are available at the following website: http://www.shc.uiowa.edu/papers/tensor/.

Coordination of Velopharyngeal Muscle Activity during Positioning of the Soft Palate

The relative contributions of the levator veli palatini, palatoglossus, and palatopharyngeus muscles were assessed relative to a range of positions of the velopharynx during production of the vowels [a] and [i] by four normal adult speakers. The results indicate that velopharyngeal positioning is determined by the relative contributions of the levator veli palatini, palatoglossus, and palatopharyngeus muscles. There was an increase in coefficients of determination (i.e., amount of closure level variability explained) when activity levels of all three muscles are included in the statistical model compared to activity in any one muscle analyzed independently. Both consistent and inconsistent relations among activity levels in the three velopharyngeal muscles studied were observed across speaker and vowel produced.

Measurement of velopharyngeal closure force during vowel production

The purposes of this study were to (a) design and test a new velopharyngeal closure force sensing bulb, and (b) use the closure force bulb to gather additional information on the variations in closure force associated with different vowels. The closure force sensing bulb possessed a flat frequency response to 30 Hz. Its output was highly linear relative to applied gram force. Reliable placement of the bulb in human subjects was achieved following prescribed placement criteria. The bulb was sensitive to small variations in velopharyngeal closure force. In agreement with some previous reports, high vowels were associated with greater velopharyngeal closure forces than low vowels. The results of this investigation support the notion that articulatory goals are specified for vowels. This vowel specificity was observed during production in both isolation and in context.

A finite element model of the soft palate

OBJECTIVE As a step toward better understanding of normal and abnormal velar control, a finite element model of the soft palate was developed. DESIGN A static two-dimensional midsagittal model of the velum was given physical dimensions to match that of a 10-year-old boy. Biomechanical properties of the tissues were inferred based on previous histologic studies. Velar movements were induced by the influence of three extrinisic velar muscles: the levator veli palatini, the palatoglossus, and the palatopharyngeus, which were simulated as external forces acting on the velar model. RESULTS AND CONCLUSIONS Velopharyngeal opened and closed positions were simulated as well as a variety of intermediate steps between the two configurations. Velopharyngeal closure was also simulated in a manner appropriate for both high and low vowels. Future extensions of the model will incorporate the muscles as an intrinsic component of the model and will include a full time-dependent implementation, including inertial effects. Future studies will compare model predictions with experimental data from the laboratory, including both kinematic data and velopharyngeal closure forces.

What can nonspeech tasks tell us about speech motor disabilities

Abstract This paper considers the possible role of nonspeech tasks in theassessment of individuals with motor speech disorders. The difficulties in the definition and isolation of both speech and nonspeech tasks are discussed. A primary point is that an inability to control the movements of the speech structures may be separate from an inability or ability to use the processes that code meaning in the construction of linguistic messages. It may be possible to design nonspeech tasks that provide insight into an individuals ability or inability to control speech movements, but are separate from his or her ability to use language.

Air pressure regulation during speech productiona)

Vocal tract pressures during speech tend to be maintained in the face of airway leaks that might be encountered by individuals with repaired palatal clefts. This study tested the hypothesis that such constant pressures can be explained as a consequence of constant pressure source characteristics of the respiratory system during speech production. This conceptualization differs from pressure regulation theories [e.g., D. Warren, Cleft Palate J. 23, 251–260 (1986)] which posit that active reflexive compensatory responses occur to regulate air pressure during speech. Four experiments were conducted to (a) confirm the distinction between constant flow versus constant pressure sources using a plastic vocal tract model, (b) compare air pressure and flow patterns associated with airway leaks in normal speakers to model data, (c) study the effects of gas density in the vocal tract model on air pressure and air flow patterns predicted by a nonreflexive constant pressure source hypothesis, and (d) compare air press...

Effects of Gravity on Velopharyngeal Muscle Activity During Speech

Assessment of the role of gravitational forces in the motor control of the velopharyngeal mechanism was the focus of this study. Specifically, the effect of gravity on activation levels of the levator veli palatini and palatoglossus muscles was assessed. Nineteen volunteers repeated a CV syllable in upright and supine body positions. Overall, lower peak activation levels of levator veli palatini were observed in the supine body position. The results suggest that less muscle activity was seen in the levator veli palatini in the supine body posture, where gravitational effects worked in the same direction (i.e., toward closure). No statistically significant group effects were seen in muscle activation levels of palatoglossus across the two body postures, although clear gravity effects were observed in some subjects. The implications of these findings from a speech motor control perspective are discussed in relation to normal and disordered velopharyngeal function.

Induced Velopharyngeal Fatigue Effects in Speakers With Repaired Palatal Clefts

Objective: To address whether speakers with cleft palate exhibit velopharyngeal mechanism fatigue and are more susceptible to muscle fatigue than are speakers without cleft palate. Methods: Six adults with repaired palatal clefts and mild-moderate hypernasality served as subjects. Velopharyngeal closure force and levator veli palatini muscle activity were recorded. Subjects were asked to repeat /si/ 100 times while an external load consisting of air pressure (0, 5, 15, 25, 35 cm H2O) was applied via a mask to the nasal side of the velopharyngeal mechanism. Fatigue was defined as a reduction in velopharyngeal closure force across the series of /si/ productions, as evidenced by a negatively sloped regression line fit to the closure force data. Results: Absolute levels of velopharyngeal closure force were much lower than those observed previously in speakers without palatal clefts. All subjects showed evidence of fatigue. Furthermore, all subjects demonstrated exhaustion, where they were unable to close the velopharyngeal port against the nasal pressure load. This occurred at pressure load levels lower than those successfully completed by speakers without cleft palate. Conclusions: In speakers with a repaired palatal cleft, the velopharyngeal closure muscles may not possess the same strength and/or endurance as in normal speakers. Alternatively, muscles may possess adequate strength, but not be positioned optimally within the velopharynx following cleft palate repair or may be forced to move velopharyngeal structures that are stiffer as a result of surgical scarring.

Muscle Fiber Type Distribution in the Normal Human Levator Veli Palatini Muscle

OBJECTIVE This study examined the muscle fiber type distribution within the normal adult levator veli palatini muscle. METHODS Levator veli palatini muscle tissue was harvested from the palates of 12 (seven female, five male) adult noncleft cadavers. Adjacent sections were stained for adenosine triphosphatase at pH 10.4 or 4.2. After mounting, magnifying, and photographing, Type I versus Type II fiber types were differentiated by the intensity of, or by the inhibition of, staining of matched fibers at each pH level. Type I fibers stained light at pH 10.4 and dark at pH 4.2, while Type II fibers stained light at pH 4.2 and dark at pH 10.4. MAIN OUTCOME MEASURES The number of fibers counted for each specimen ranged from 60 to 616. The numbers of Type I and Type II stained fibers appearing in each muscle tissue sample were determined and expressed as a percentage of the total number of fibers identified. A few identified fibers could not be labelled as either Type I or Type II. RESULTS The overall proportion of Type I fibers, averaged across all specimens, was 59.8%. Male specimens had 67.4% Type I fibers and 31.8% Type II fibers, while female specimens had 54.4% Type I fibers and 44.4% Type II fibers. CONCLUSIONS Observed fiber type distributions were similar to those reported for other articulatory muscles, but differed slightly from previously reported distributions for normal levator veli palatini. The distributions observed in this study provide a baseline against which to relate fiber type data from the levator veli palatini of cleft palates to the functional status of the velopharyngeal mechanism.

The effects of auditory feedback on the regulation of intraoral air pressure during speech

Previous experimental evidence has been interpreted as support for regulation of both acoustics and aerodynamics during speech production. One recent perspective is that although speech acoustics may be manipulated, regulation of aerodynamics is a central component of the processes that produce speech. From this perspective, it has been suggested that aerodynamic regulation is given priority over perceptual accuracy. The experiment attempted to test this hypothesis by forcing speakers into a choice between aerodynamic and acoustic regulation. The intensity level of frication (embedded in a carrier phrase) was selectively amplified or attenuated and fed back to the speaker on line. Intraoral air pressure was recorded in order to assess whether or not perturbed auditory feedback would result in aerodynamic compensation. Although compensatory changes in peak intraoral air pressure, pressure duration, and pressure curve area were seen in response to 30-dB alterations of frication, no systematic effects were seen for smaller auditory manipulations. Further, the compensations were less than what one might expect from a system controlling auditory output. Explanations of these findings and their implications for the control of speech production are offered.