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Biomedical subjects

C W Starkweather

Publications and source records attributed to C W Starkweather.

11 recordsLinked to original sources
PubMed1995

Effects of linguistic correlates of stuttering on Emg activity in nonstuttering speakers.

In this study changes in upper lip and lower lip integrated electromyographic (IEMG) amplitude and temporal measures related to linguistic factors known for their influence on stuttering were investigated. Nonstuttering subjects first read and then verbalized sentences of varying length (sentence length factor), in which meaningless but phonologically appropriate character strings were varied in their position within the sentence (word position factor) and their size (word size factor). It was hypothesized that the production of stressed, vowel-rounding gestures of words in initial position, longer words, and words in longer sentences would be characterized by specific changes in IEMG amplitude that would reflect an increase in speech motor demands, intuitively defined as articulatory effort. Basically, the findings corroborated our assumptions, showing that words in sentence initial position have shorter word and vowel durations in combination with an increase in IEMG activity. Similarly, we found shorter vowel durations for longer words, and in sentence final position an increase in IEMG activity. For longer sentences we found a clear increase in speech rate, but contrary to our expectations a decrease in IEMG activity. It was speculated that this might relate to the use of a movement reduction strategy to allow higher speech rates with increased coarticulation. These findings were discussed both for their implications in normal speech production, as well as for their possible implications for explaining stuttering behavior. To this end our data can illustrate both why stutterers might run a higher risk of stuttering at these linguistic loci of stuttering, and why they might come up with a strategic solution to decrease the motor demands in speech production. The basic outcome of this study shows that higher order (linguistic) specifications can have clear effects on speech motor production.

Adolescent↗
PubMed1993

Physiological differences between stutterers and nonstutterers in perceptually fluent speech: EMG amplitude and duration.

Electromyograph (EMG) signals of the m. orbicularis oris inferior evoked by lip-rounding gestures were analyzed to see whether stutterers in their perceptually fluent speech had higher levels of EMG and longer EMG durations. The relationship between levels of EMG and durations of elevated muscle activity was investigated, and a search for the best discriminating EMG measure was made. In contrast to some previous studies on the EMG signals of stutterers, a relatively large group of stutterers (n = 15) and control speakers (n = 20), matched for age and gender, was examined. Both groups took part in a reaction time experiment using verbal items of different length (syllables, words, and sentences) in two time-stress conditions. Measures were taken for lip muscle activity during lip-rounding gestures for the Dutch /o/ sound. Only perceptually fluent trials were analyzed. The results showed that stutterers had significantly higher EMG levels at the moment of speech onset and during speech production than nonstutterers. A much larger difference between the two groups, however, was found for the EMG peak latency measure, which proved to be a very powerful distinctive feature in differentiating stutterers from nonstutterers. The results were discussed with respect to previous findings and recent theories about (speech) motor control strategies.

Adult↗
PubMed1989

Acoustic and physiological reaction times of stutterers and nonstutterers.

This study investigates reaction times in the fluent speech utterances of stutterers and nonstutterers under several experimental conditions. Twenty adult stutterers and twenty matched controls produced utterances of three lengths--one syllable words, polysyllabic words, and sentences--in two conditions of time pressure (high and low) and two conditions of preparation (delayed and immediate responding) in a reaction-time paradigm. Recordings were made of EMG signals from the orbicularis oris inferior and from the extrinsic laryngeal area, as well as electroglottographic and acoustic signals. Measures were made of the duration of intervals between the stimulus, the acoustical onset of voicing, the onset of laryngeal EMG activity, and the onset of lip EMG activity. The durations of subintervals between the stimulus, the three physiological signals, and the acoustic signal were also measured. The results suggest that the reaction times of stutterers and nonstutterers are both increased by longer utterances, and that the effect is proportionally greater for the stutterers. The requirement to respond with minimal preparation produced longer reaction times in both groups, particularly for longer utterances, but this finding was stronger for stutterers than for nonstutterers, particularly in the prelaryngeal subintervals. The high time-pressure condition produced an unusual pattern of responding in many subjects. The analysis of subintervals indicated that the additional time taken by stutterers in responding was located in the earlier parts of the response, particularly when the utterances were longer. The results are interpreted as suggesting that stutterers may have difficulty in the motor programming of speech behavior.

Adult↗
PubMed1984

Vocal and finger reaction times in stutterers and nonstutterers: differences and correlations.

The purposes of this study were (a) to assess whether the slower reaction times of stutterers are related to the etiology of the disorder or whether they are a by-product of it, and (b) to see if previously reported correlations between vocal and manual reaction times resulted from large numbers of trials. Fourteen adult stutterers and matched controls said "uh" or pressed a button in response to the offset of tones varying randomly in duration. Ten trials were used. The stutterers were significantly slower in both speech and nonspeech tasks, but the correlations between voice and manual reaction times were not significant. This suggested that stutterers' slower reaction times may be obtained without using large numbers of trials and that the correlation between the two tasks may depend on the number of trials used. The stutterers showed a significantly larger difference between vocal and manual reaction times than the nonstutterers. This suggested that the slower reaction times of stutterers are not entirely a by-product of the disorder.

Adolescent↗
PubMed1984

Language alive!

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Humans↗
PubMed1982

Floppy structure.

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Phonetics↗
PubMed1977

Disorders of nonverbal communication.

The idea that nonverbal communication can be disordered is explored, and several types of nonverbal communication disorders are described. The characteristics of these disorders and a number of possible explanations for their acquisition are offered. Finally, suggestions for therapeutic procedures are made.

Avoidance Learning↗
PubMed1976

Latency of vocalization onset: stutterers versus nonstutterers.

Eleven stutterers and matched controls were asked to produce as quickly as possible each of 26 different syllables following a visual stimulus. Three trials were given for each syllable. Responses were filtered to remove supraglottally produced sounds, and the time between the visual stimulus and the onset of vocalization was measured by a voice-operated relay and a computer's internal clock. The results suggested that stutterers are slower in initiating vocalization across a wide variety of syllables, and the difference averages about 65 msec. Furthermore, when phonologic conditions delayed voice onset by a comparable amount, the stutterers gained enough time so that no significant differences were observed between the two groups. The results are interpreted as suggesting that auditory dysfunction cannot be a cause for slower vocalization reaction time in stutterers but that either vocal dysfunction or a lack of cerebral dominance may be responsible for these differences.

Adult↗