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R Netsell

Publications and source records attributed to R Netsell.

At least 19 recordsLinked to original sources
PubMed1998

Vowel-related differences in laryngeal articulatory and phonatory function.

The purpose of this investigation was to study the interaction between the supralaryngeal and laryngeal components of the speech mechanism by examining vowel-related effects for a variety of vocal fold articulatory and phonatory measures. Secondary issues were to determine if vowel-related differences were influenced by the nature of the speaking task or gender. Between-vowel differences in estimated subglottal air pressure, peak oral air flow, mean phonatory air flow, air flow near the termination of the vowel, electroglottograph cycle width (EGGW), fundamental frequency, and voice onset time were examined for men and women during syllable repetitions and sentence productions. Significant vowel-related differences were found for all of the measures except mean phonatory air flow, and generally were not influenced by speaking task or gender. Vowel-related effects for estimated subglottal air pressure, peak oral air flow, fundamental frequency, and VOT were consistent with some earlier studies. New findings included vowel-related differences in EGGW and air flow near the termination of the vowel. We propose a model that includes the contribution of mechanical forces, reflexive neural activity, and learned neural activity to explain vowel-related effects. When vowel height is varied, changes in laryngeal cartilage positioning and vocal fold and vocal tract tension appear to influence laryngeal articulatory and phonatory function.

Adult↗
PubMed1994

Developmental patterns of laryngeal and respiratory function for speech production.

Estimates of subglottal air pressure, laryngeal airflow, and laryngeal airway resistance from syllable repetitions of children and adults were used in describing developmental changes in these variables and in hypothesizing corresponding changes in respiratory function. A trend was found for pressure and resistance to decrease with increases in flow from preschool age through adulthood. These patterns could be explained by the smaller size of laryngeal airway structures and increased expiratory muscle forces during speech in the younger subjects. When the subglottal air pressures were combined with published data on air volume expired during speech and recoil pressures of the respiratory system, hypothetical functions were derived for respiratory muscle forces and the work of speech breathing. These functions predict (a) a developmental shift from the use of net expiratory muscle force in the speech of preschool children to the adult patterns of combined inspiratory and expiratory muscle forces, and (b) the expiratory work of speech breathing is greater in preschool children than in older children and adults.

Adult↗
PubMed1994

Aerodynamic and electroglottographic measures of normal voice production: intrasubject variability within and across sessions.

The purpose of this investigation was to quantify the normal intrasubject performance variability of four measures of phonatory function within and across sessions. Two different speaking tasks, syllable series and sentence production, were used to determine if more natural speaking tasks resulted in greater intrasubject variability. Vowel type ([i] versus [a]) also was varied. Estimated subglottal air pressure, mean phonatory air flow, abduction quotient, and fundamental frequency were derived from aerodynamic and electroglottographic signals obtained from 11 normally speaking men and 10 normally speaking women on four different days. Relative intrasubject variability was compared across speaking task, gender, and vowel type. Average across-session intrasubject variability was 5% for fundamental frequency and abduction quotient, 8% for estimated subglottal air pressure, and 15% for mean phonatory air flow during syllable repetition. There was significantly greater intrasubject variability for mean phonatory air flow and abduction quotient for the sentence repetition task. There were no significant differences in intrasubject variability across gender and vowel type. The data were used to compute cutoff values that represent the amount of variability that would be considered within normal limits. These normal data can be used for comparison when assessing and monitoring the phonatory abilities of individuals with voice disorders.

Adult↗
PubMed1992

Vocalizations in the cat: behavioral methodology and spectrographic analysis.

Attempts to understand the neural mechanisms underlying mammalian vocal behaviors, including speech, require study of the neural activity and anatomy of vocalization-controlling brain structures. Such studies necessitate the application of invasive neurobiological techniques in animal models. In the current study, cats are used in the development of an animal model of vocal tract control. The animals are instrumentally conditioned to vocalize for food reward. Acquisition of this task can occur within a few minutes, although additional training generally is required to solidly establish the behavior and to train subjects to produce consistently high rates of vocalization for prolonged periods of time. Following training, animals can generally sustain a rate of two calls per minute for a period of over two hours. Optimal task performance is partly dependent on motivation level. Although there is considerable variation between animals, the vocalizations produced have an average duration of 600 ms and a fundamental frequency of around 500 Hz. In addition, during a typical vocalization, there are dynamic variations of about 150 Hz for fundamental frequency and 17 dB for sound intensity. These variations provide opportunities for relating neural and muscular activity to different aspects of the vocal behavior they control. Based on a number of considerations, the model and techniques discussed here probably are most applicable to studying the neurobiology of sub-cortical nuclei subserving vocal control. Similar mechanisms might well be present in other species, including humans. Thus, data obtained from study of this model may be applicable to understanding the processes underlying vocal tract control during human speech.

Animals↗
PubMed1992

Factors influencing neural activity in parabrachial regions during cat vocalizations.

The parabrachial nucleus in mammals is intimately connected with other vocalization controlling brainstem structures. It, along with ventromedially adjacent structures, also has been identified as the pneumotaxic center, and as such shows strong respiratory related activity in the anesthetized cat. The current study examines the neuronal activity in cat parabrachial regions during production of instrumentally conditioned vocalizations. Most of the units in our sample show considerable activity during periods between vocalizations. For many units, firing rate fluctuates during the respiratory cycle, although apparently not as strongly as reported in the decerebrate cat. Also, there is often strong phasic activity during periods where animals are licking to ingest their food rewards. During the peri-vocalization period, various neural activity patterns can be recorded. Most common is an activity increase during the vocalization itself. Moreover, in some units, this activity increase has an auditory component. A smaller number of units show other activity patterns, including a suppression of activity during vocalization and activity increases preceding the vocalization. Overall, our results suggest that the parabrachial region's involvement in vocal control is quite complex, involving convergence of respiratory, acoustic, vocalization-related, and perhaps somatosensory influences.

Acoustic Stimulation↗
PubMed1987

Phonetic development in identical twins differing in auditory function.

The subjects of this report are identical (monozygotic) twin boys who differ in auditory function. One has normal hearing; the other has a profound hearing loss bilaterally. These boys offered a rare opportunity to study the effects of hearing loss on vocal development with reasonable control over environmental and genetic factors. This initial report focuses on their vocal development over the sampled ages of 8, 12, and 15 months. Acoustic-phonetic differences in the babbling of the two boys were evident in the 8-month sample (the first recording opportunity), and some differences between them became greater over the succeeding samples at 12 and 15 months. The major differences were in the formant patterns of vocalic elements; the frequency of occurrence of fricatives, affricates, and trills; histograms of syllable type; and variation in vowel usage. The data hold implications for the early identification of infants at risk for communication disorder and for the understanding of auditory-motor processes in phonetic development during infancy.

Child Language↗
PubMed1986

Differential fine force control of the upper and lower lips.

From a review of the literature, it was hypothesized that the upper lip and lower lip are differentially controlled by separate, but interacting, neuronal connectivities. A normal data base was developed for select measures of fine force control occurring within physiologic levels presumably involved in speech production. Fine force control in the lower lip was found to be significantly more stable, and recruited at higher rates than the upper lip. Explanations are presented for the lower lip superiority on these measures and observations are made concerning the use of these rudimentary physiologic measures in studies of the dysarthrias.

Adolescent↗
PubMed1986

Pediatric videonasoendoscopy for speech and voice evaluation.

Many otolaryngologists and speech clinicians have found videofiberoptic evaluations to be invaluable for assessment of velopharyngeal and laryngeal function in adults. However, many professionals question the feasibility of routine use of these procedures in the pediatric population. This article describes a method for successful completion of videonasoendoscopic speech and voice evaluations of children as young as 3 years of age. The importance of the ENT/speech team is emphasized in both the collection and interpretation of data. In addition, contributions of videonasoendoscopic observations to diagnosis, medical treatment, and therapy for speech and voice disorders are discussed.

Child↗
PubMed1979

Acoustic characteristics of dysarthria associated with cerebellar disease.

The speech of five individuals with cerebellar disease and ataxic dysarthria was studied with acoustic analyses of CVC words, words of varying syllabic structure (stem, stem plus suffix, stem plus two suffixes), simple sentences, the Rainbow Passage, and conversation. The most consistent and marked abnormalities observed in spectrograms were alterations of the normal timing pattern, with prolongation of a variety of segments and a tendency toward equalized syllable durations. Vowel formant structure in the CVC words was judged to be essentially normal except for transitional segments. The greater the severity of the dysarthria, the greater the number of segments lengthened and the degree of lengthening of individual segments. The ataxic subjects were inconsistent in durational adjustments of the stem syllable as the number of syllables in a word was varied and generally made smaller reductions than normal subjects as suffixes were added. Disturbances of syllable timing frequently were accompanied by abnormal contours of fundamental frequency, particularly monotone and syllable-falling patterns. These dysprosodic aspects of ataxic dysarthria are discussed in relation to cerebellar function in motor control.

Aged↗
PubMed1979

Dysarthria in adults: physiologic approach to rehabilitation.

A case study is used to illustrate a physical approach to the speech rehabilitation of adults with dysarthria. The approach emphasizes the component-by-component analysis of the peripheral speech mechanism, where the selection and sequencing of treatment procedures follow directly from the physiologic nature and severity of involvement in each component. The selection and sequencing of procedures also are conditioned by the inherent physical interdependencies of these component parts. Several biofeedback procedures of our own are incorporated that have not been reported previously. The case illustration is of a young man injured in an auto accident whose speech intelligibility improves from approximately 5-10% to 95% during the rehabilitation period. Effects of treatment upon individual components of the speech mechanism are illustrated.

Adult↗
PubMed1978

Articulatory abnormalities in athetoid cerebral palsy.

This report presents cinefluorographic data on the articulation of isolated vowels, VCV nonsense utterances, and short sentences by five subjects with athetoid cerebral palsy. Articulatory abnormalities were identified from tracings of vocal tract shapes and from displacement-by-time plots of articulatory events. The most frequent abnormalities were large ranges of jaw movement, inappropriate positioning of the tongue for various phonetic segments (especially because of a reduced range of tongue movement in the anteroposterior dimension), intermittency of velopharyngeal closure caused by an instability of velar elevation, prolonged transition times for articulatory movements, and retrusion of the lower lip. The speech disorder associated with athetosis is considered with respect to a model of motor learning.

Adult↗
PubMed1976

Paroxysmal ataxic dysarthria.

This report reviews 13 cases in which a dysarthria appeared, remitted, and reappeared within seconds. The speech pattern of each case was characteristic of ataxic dysarthria. A cinefluorographic film for one of the subjects provided a rare opportunity to study the articulatory dynamics of this disorder. Multiple sclerosis either was given as a diagnosis or was strongly suspected in each case, and carbamazepine has been an effective treatment. Speculations concerning the origin of the paroxysmal and ataxic character of the dysarthria are presented along with a preliminary checklist for identifying the disorder.

Acoustics↗
PubMed1976

A new technique for measuring velopharyngeal orifice area during sustained vowel production: an application of aerodynamic forced oscillation principles.

A new technique for measuring velopharyngeal orifice area during sustained vowel production is described. The technique is based on a simple oscillatory flow balancing procedure between two aerodynamic branches, a mechanical model of the human upper airway and the subject's upper airway. The area of the velopharyngeal orifice in the model is adjusted until identical oscillatory flows traverse it and the subject's velopharyngeal orifice in response to a common forced oscillatory pressure. When identical oscillatory flows are observed, the area of the adjusted orifice is taken as a measure of the area of the subject's velopharyngeal orifice.

Humans↗
PubMed1975

A case study of an ataxic dysarthric: cineradiographic and spectrographic observations.

Cineradiographic and spectrographic analyses were performed to study the speech production of a subject who presented the classical neurologic signs of cerebellar lesion and who had speech characteristics like those that have been reported for ataxic dysarthria. These analyses were conducted with special attention to the deviant perceptual dimensions that have been described for ataxic speech. Examination of the cineradiographic and spectrographic records revealed conspicuous abnormalities in speaking rate, stress patterns, articulatory placements for both vowels and consonants, velocities of articulator movements, and fundamental frequency contours. In general, our physiological and acoustic observations of ataxic dysarthria were compatible with existing perceptual descriptions of this condition. The data for the subject are discussed in the light of current hypotheses concerning cerebellar participation in the regulation of skilled movement. Particular suggestions are made concerning the nature of the neuromuscular abnormalities that may underlie the aberrant motorics of ataxic dysarthria.

Cerebellar Ataxia↗