Effects of gravity on velopharyngeal muscle activity during speech

Tongue Postures and Tongue Centers: A Study of Acoustic-Articulatory Correspondences Across Different Head Angles

Recent research on body and head positions has shown that postural changes may induce varying degrees of changes on acoustic speech signals and articulatory gestures. While the preservation of formant profiles across different postures is suitably accounted for by the two-tube model and perturbation theory, it remains unclear whether it is resulted from the accommodation of tongue postures. Specifically, whether the tongue accommodates the changes in head angle to maintain the target acoustics is yet to be determined. The present study examines vowel acoustics and their correspondence with the articulatory maneuvers of the tongue, including both tongue postures and movements of the tongue center, across different head angles. The results show that vowel acoustics, including pitch and formants, are largely unaffected by upward or downward tilting of the head. These preserved acoustics may be attributed to the lingual gestures that compensate for the effects of gravity. Our results also reveal that the tongue postures in response to head movements appear to be vowel-dependent, and the tongue center may serve as an underlying drive that covariates with the head angle changes. These results imply a close relationship between vowel acoustics and tongue postures as well as a target-oriented strategy for different head angles.

Speech and Language Issues in the Cleft Palate Population: The State of the Art

Objective

State-of-the-art activity demands a look back, a look around, and, importantly, a look into the new millennium. The area of speech and language has been an integral part of cleft palate care from the very beginning. This article reviews the development and progression of our knowledge base over the last several decades in the areas of speech; language; anatomy and physiology of the velopharynx; assessment of velopharyngeal function; and treatment, both behavioral and physical, for velopharyngeal problems.

Method

The clear focus is on the cleft palate condition. However, much of what is reviewed applies to persons with other craniofacial disorders and with other underlying causes of velopharyngeal impairment. A major challenge in the next several years is to sort through speech disorders that have a clear anatomic underpinning, and thus are more amenable to physical management, versus those that may be treated successfully using behavioral approaches. Speech professionals must do a better job of finding and applying ways of treating individuals with less severe velopharyngeal impairment, thus avoiding the need for physical management in these persons or ignoring the speech problem altogether.

Conclusion

Early and aggressive management for speech and language disorders should be conducted. For most individuals born with cleft conditions, a realistic goal should be normal speech and language usage by the time the child reaches the school-age years.

Detecting Nasal Vowels in Speech Interfaces Based on Surface Electromyography

Nasality is a very important characteristic of several languages, European Portuguese being one of them. This paper addresses the challenge of nasality detection in surface electromyography (EMG) based speech interfaces. We explore the existence of useful information about the velum movement and also assess if muscles deeper down in the face and neck region can be measured using surface electrodes, and the best electrode location to do so. The procedure we adopted uses Real-Time Magnetic Resonance Imaging (RT-MRI), collected from a set of speakers, providing a method to interpret EMG data. By ensuring compatible data recording conditions, and proper time alignment between the EMG and the RT-MRI data, we are able to accurately estimate the time when the velum moves and the type of movement when a nasal vowel occurs. The combination of these two sources revealed interesting and distinct characteristics in the EMG signal when a nasal vowel is uttered, which motivated a classification experiment. Overall results of this experiment provide evidence that it is possible to detect velum movement using sensors positioned below the ear, between mastoid process and the mandible, in the upper neck region. In a frame-based classification scenario, error rates as low as 32.5% for all speakers and 23.4% for the best speaker have been achieved, for nasal vowel detection. This outcome stands as an encouraging result, fostering the grounds for deeper exploration of the proposed approach as a promising route to the development of an EMG-based speech interface for languages with strong nasal characteristics.

Effects of Gravity on the Velopharyngeal Structures in Children Using Upright Magnetic Resonance Imaging

Objective

The influence of gravity on the velopharyngeal structures in children is unknown. The purpose of this study is to compare the velopharyngeal mechanism in the upright and supine positions while at rest and during sustained speech production in children between 4 and 8 years old.

Methods

A 0.6 Tesla open-type, multipositional magnetic resonance imaging scanner was used to image subjects in the upright and supine positions. The scanning protocol included a T2 fluid attenuation inversion recovery and an oblique coronal turbo spin echo scan with short scanning durations (7.9 seconds) to enable visualization of the velopharyngeal anatomy during rest and production of sustained /i/ and /s/.

Results

The magnetic resonance imaging protocol used for this study enabled successful visualization of the velopharyngeal anatomy in the sagittal and oblique coronal planes at rest and during sustained phonation of /i/ and /s/. Positional differences demonstrated a small nonsignificant ( P > .05) variation for velar measures (length, thickness, and height), retrovelar space, and levator veli palatini measures (length and angles of origin).

Conclusions

Gravity had a negligible effect on velar length, velar thickness, velar height, retrovelar space, levator muscle length, and levator angles of origin. Supine imaging data can be translated to an upright activity such as speech. This is the first study to provide normative levator muscle lengths for children between 4 and 8 years old. Upright imaging may be a promising tool for difficult-to-test populations.

Videofluoroscopic investigation of body position on articulatory positioning

PURPOSE

To quantitatively examine the effects of body position on the positioning of the epiglottis, tongue, and velum at rest and during speech.

METHOD

Videofluoroscopic data were obtained from 12 healthy adults in the supine and upright positions at rest and during speech while the participants produced 12 VCV sequences. The effects of body position, target sounds, and adjacent sounds on structural positioning and vowel formant structure were investigated.

RESULTS

Velar retropositioning in the supine position was the most consistent pattern observed at rest. During speech, all structures, with varying degrees of adjustment, appeared to work against the gravitational pull, resulting in no significant narrowing in the oro- and nasopharyngeal regions while in the supine position. Minimal differences in the formant data between the body positions were also observed. Overall, structural positioning was significantly dependent on the target and adjacent sounds regardless of body position.

CONCLUSIONS

The present study demonstrated that structural positioning in response to gravity varied across individuals based on the type of activities being performed. With varying degrees of positional adjustment across different structures, fairly consistent articulatory positioning in the anterior-posterior dimension was maintained in different body positions during speech.

Influences of swallowing volume and viscosity on regulation of levator veli palatini muscle activity during swallowing

This study examined the aspect of the regulation of velum movement in the transition from the oral to pharyngeal phases of swallowing in relation to changes in the swallowing volume and viscosity by means of measurment of levator veli palatini muscle activity. The subjects were nine normal adults, ranging in age from 24 to 30 years. The swallowing volume was set at 1/4, 1/2 and 1 volume of the optimum volume of green tea for swallowing determined in each subject, and the viscosity was adjusted to 0, 2·0 and 4·6 Pa·s by mixing with thickener. Nine test foods were prepared in total. The electromyographic activity of the levator veli palatini muscle was monitored using bipolar hooked wire electrodes. The levator veli palatini muscle activity was defined as the integrated electromyographic wave. The mean in swallowing each test food was determined in each subject. The levator veli palatini muscle activity increased with the swallowing volume for all subjects (P < 0·05) and decreased inversely with the viscosity for six subjects (P < 0·05), but no change with the increase in the viscosity was noted for three subjects. This study clarified the aspect of the regulation of velar movement with regard to the involvement of the levator veli palatini muscle in swallowing activity with changes in the swallowing volume and viscosity.

Variations in velopharyngeal structures between upright and supine positions using upright magnetic resonance imaging

OBJECTIVE

No studies have used MRI to compare the dimensional changes of the velopharyngeal musculature between upright and supine positions. The purpose of this study is to provide a comparison between structures of the velopharyngeal mechanism while in the supine and upright positions during rest and sustained speech productions of four female subjects.

METHODS

Four healthy white female subjects between 30 and 36 years of age (mean, 32.5 ± 1.75 years) were imaged using a 0.6-tesla open-type multi-position MRI scanner. Subjects produced two speech tasks (/i/ and /s/) in the two body positions.

RESULTS

Velar measures (length, thickness, and height), pharyngeal measures (retrovelar and retrolingual), and levator muscle measures (length and angles of origin) demonstrated a small variation between upright and supine positions. Differences in velar height during production of /i/ between the two positions was significant for all subjects. In most cases, the velar thickness remained nearly the same (group mean difference was between -0.2 and 1.2 mm). Group means demonstrated an average levator muscle shortening from upright to supine of 2.8 mm at rest, 2.0 mm during /i/ production, and 2.3 mm during /s/ production. Percentage of levator shortening were 17% for /i/ production and 21% for /s/ production, which were independent of body position.

CONCLUSIONS

Overall, gravity had a minimal effect on velar thickness, velar length, velar height, levator muscle length, angles of origin, and pharyngeal dimensions. Differences between the two body positions (upright and supine) were not significant during rest or during production of /i/ and /s/, with the exception of velar height during /i/ production.

Characteristics of Movement of the Lips, Tongue and Velum during a Bilabial Plosive

Objective: To obtain dynamic images of articulators using a magnetic resonance imaging (MRI) movie and to clarify the relationships among the articulators.

Materials and Methods: The subjects consisted of 10 volunteers. Custom-made circuitry was connected to an MRI apparatus to enable an external trigger pulse to control the timing of the scanning sequence and to provide an auditory cue for synchronization of the subject's utterance. The subject repeated a bilabial plosive, and the run was measured using a gradient echo sequence with a repetition time of 30 ms. Several variables were defined to delineate the individual movements of articulators and to determine the temporal relationships among them.

Results: It was found that (1) the change in these variables showed distinctive waveforms; (2) mean values of the standard deviations for these variables were relatively small; and (3) the movement of the velum was significantly correlated with those of the lips and the anterior part of the tongue, but not with the posterior part of the tongue.

Conclusions: These results suggest that (1) articulatory movements were clearly recorded using an MRI movie, and (2) there seems to be a central mechanism for controlling articulators, and the level of coupling may be associated with the place of articulation.

Change in Palatoglossus Muscle Activity in Relationto Swallowing Volume During the Transition from the Oral Phaseto the Pharyngeal Phase

The purpose of this study was to examine whether the palatoglossus (PG) muscle is involved in the regulation of function during the transition from the oral to the pharyngeal phase. Seven normal adults participated in the study. Smoothed electromyography (EMG) signals of the PG muscle and levator veli palatini (LVP) muscle were collected. Each subject swallowed water at five different volumes: 12.5%, 25%, 50%, 100%, and 150% (or 200%) of his/her optimum swallowing volume. PG muscle waveform showed two patterns of activity: one of a single peak and the other of two peaks. There was no significant difference (p < 0.01) in the timing of emergence between the single peak and the second peak of the two-peak pattern. There were two patterns of PG muscle activity in response to a change in swallowing volume, i.e., one was a pattern in which the activity was correlated to the change in swallowing volume, the other was a pattern in which the activity was not changed but almost at the maximum activity level, irrespective of swallowing volume. We conclude that the PG muscle could be involved in the regulation of swallowing from the oral to the pharyngeal phase. The activity could be influenced by swallowing volume.

Change in levator veli palatini muscle activity for patients with cleft palate in association with placement of a speech-aid prosthesis

OBJECTIVE

The purpose of this study was to examine whether a speech-aid prosthesis normalizes the activity of the levator veli palatini muscle for patients with cleft palate who exhibit velopharyngeal incompetence.

DESIGN

Each subject was instructed to produce repetitions of /mu/, /u/, /pu/, /su/, and /tsu/ and to blow with maximum possible effort. Electromyographic (EMG) activity of the levator veli palatini muscle was recorded with and without a hybrid speech-aid prosthesis in place.

PARTICIPANTS

The participants were five patients with repaired cleft palate who were routinely wearing a hybrid speech-aid prosthesis.

RESULTS

With the prosthesis in place, the mean value of levator activity changed positively in relation to oral air-pressure change during blowing. Differences in levator activity in relation to speech samples were similar to those in normal speakers. With the prosthesis in place, levator activity for speech tasks was less than 50% of the maximum levator activity for all subjects. The findings were similar to those reported previously for normal speakers.

CONCLUSION

Placement of the prosthesis changed EMG activity levels of the levator veli palatini muscle to levels that are similar to normal speakers. It is possible that, with the increase in the differential levator activity between speech and a maximum force task, the velopharyngeal mechanism has a greater reserve capacity to maintain velopharyngeal closure compared with the no-prosthesis condition.

Change in levator veli palatini muscle activity of normal speakers in association with elevation of the velum using an experimental palatal lift prosthesis

OBJECTIVE

The purpose of this study was to examine whether mechanical elevation of the velum can directly affect the levator veli palatini muscle (LVP) activity using normal speakers as subjects.

DESIGN

Each subject was instructed to produce /mu/, /u/, /pu/, /su/, and /tsu/ in a speech task and to blow with maximum possible effort. Smoothed electromyographic activity of the LVP was recorded with an experimental palatal lift prosthesis (PLP) both in place and removed.

PARTICIPANTS

Four normal speakers were used as subjects.

RESULTS

LVP activity for all tasks was significantly smaller (p <.001; Student's t test) with the PLP in place than without the PLP for all subjects. An analysis of variance (p <.001) clarified that activity ranges of the LVP were significantly different between the removal and placement conditions for all the subjects.

CONCLUSION

The result was similar to that previously obtained for patients with velopharyngeal incompetence wearing a PLP. It is possible that the decrease in the LVP activity in association with placement of a PLP is caused by the direct effect of mechanical elevation, which decreases the distance the velopharyngeal mechanisms must travel for complete closure of the velopharynx.

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.