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Biomedical subjects

H F Peters

Publications and source records attributed to H F Peters.

14 recordsLinked to original sources
PubMed1996

Speech production in people who stutter: testing the motor plan assembly hypothesis.

The main purpose of the present study was to test the hypothesis that persons who stutter, when compared to persons who do not stutter, are less able to assemble abstract motor plans for short verbal responses. Subjects were adult males who stutter and age- and sex-matched control speakers, who were tested on naming pictures and words, using a choice-reaction time paradigm for both tasks. Words varied in the number of syllables (1, 2, and 3 syllables) and, for the bisyllabic words, also in the number of consonants (one or more) at the onset of the second syllable. Measurements consisted of speech reaction times, word durations, and measures of relative timing of specific motor events in the respiratory, phonatory, and articulatory subsystems. Results indicated that, in spite of longer speech reaction times for persons who stutter in comparison to control speakers, there was no interaction with word size, a finding that does not lend support to the abovementioned hypothesis. Word durations were found to be longer for persons who stutter, and, in addition, there was an interaction of group with word size. Both findings were associated with longer delays for persons who stutter in the onset of upper lip integrated electromyographic (IEMG) activity and thoracic compression, and a group effect on the order of upper lip and lower lip IEMG onset. Findings are taken to suggest the possibility that persons who stutter may use different motor control strategies to compensate for a reduced verbal motor skill, and although the nature of this reduced skill is unknown, it is speculated that it relates to the processes involved in the integration of sensory-motor information.

Adult↗
PubMed1996

From planning to articulation in speech production: what differentiates a person who stutters from a person who does not stutter?

The main purpose of the present study was to differentiate between people who stutter and control speakers regarding their ability to assemble motor plans and to prepare (and execute) muscle commands. Adult males who stutter, matched for age, gender, and educational level with a group of control speakers, were tested on naming words and symbols. In addition, their ability to encode and retrieve memory representations of combinations of a symbol and a word, was tested in a recognition task, using manual reaction times and sensitivity scores, as defined in signal detection theory, as performance measures. Group differences in muscle command preparation were assessed from electromyographic recordings of upper lip and lower lip. Results indicated no interaction between group and word size effects in choice reaction times or a group effect in the ability to recognize previously learned symbol-word combinations. However, they were significantly different in the timing of peak amplitudes in the integrated electromyographic signals of upper lip and lower lip (IEMG peak latency). Findings question the claim that people who stutter have problems in creating abstract motor plans for speech. In addition, it is argued that the group differences in IEMG peak latency that were found in the present study might be better understood in terms of motor control strategies than in terms of motor control deficits.

Adult↗
PubMed1995

Perceptual rating instrument for speech evaluation of stuttering treatment.

A rating instrument is described that can be used to assess the results of stuttering treatments. The instrument is designed for use with naive listeners. It yields a comprehensive and detailed description of the speech quality in terms of articulation, phonation, pitch, and loudness; in addition, it includes a naturalness scale. Analysis of ratings obtained with the instrument show that naturalness is a multidimensional characteristic. Moreover, the speech characteristics that determine the naturalness ratings appear to be different pretreatment, posttreatment, and at follow-up treatment. The psychometric characteristics of the instrument are analyzed in detail. It is concluded that mixing of samples of stutterers and nonstutterers in one rating experiment may artificially inflate the reliability of the ratings. Also, ratings on equal-appearing interval scales cannot be interpreted in an absolute sense. Solutions for this methodological problem are suggested.

Adolescent↗
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↗
PubMed1989

The pupillary light reflex in diabetes mellitus: evaluation of a newly developed infrared light reflection method.

Pupillary light reflexes were measured in 18 diabetic patients without clinical signs of neuropathy and in 18 control subjects, using a newly developed infrared light reflection technique called IRIS. This method has some important advantages. Apart from being non traumatic, it enables the recording of dynamic pupillary light reflexes simultaneously in both eyes. Furthermore, it has a large amplitude and time resolution (1 ms), permitting accurate determination of latency values. It was found that 78% of the diabetic patients show a significantly prolonged latency of the constriction reaction, while 39% of the diabetic patients show an abnormally prolonged dilatation latency. All patients with an abnormally prolonged dilatation latency also show a prolonged constriction latency. This finding suggests that in diabetes mellitus the parasympathetic system is affected before abnormalities of the sympathetic nervous system can be demonstrated. Assessment of the pupillary light reflex, using the sensitive IRIS method, is an easily applicable and reliable method for detection of subclinical autonomic nervous system dysfunction associated with diabetes mellitus. The method may also provide an objective tool for the assessment of therapy results in diabetic neuropathy.

Adult↗
PubMed1988

Coordination of aerodynamic and phonatory processes in fluent speech utterances of stutterers.

It has often been suggested that there is a close relation between problems in the coordination of respiratory, phonatory, and articulatory processes and dysfluencies in speech production. However, empirical support for this hypothesis is scarce, because most studies of speech behavior have been restricted to a single motor process. The present investigation examines the interactions of respiration (specifically the build up of subglottal pressure), phonation, and articulation. Pressure build-up patterns preceding the onset of phonation were studied in 573 fluent utterances of 10 stutterers and in 552 utterances of 7 control subjects. Stutterers evidenced deviant patterns of subglottal pressure build-up much more often than did control speakers. Electroglottographic records of voice onset were classified as either abrupt or gentle and with respect to the presence or absence of gross irregularities in amplitude (shimmer) and period duration (jitter). Stutterers evidenced abrupt voice onsets significantly more often than did controls. The occurrence of jitter and shimmer, however, did not differ significantly across the groups. Acoustic measures of abruptness of voice onset, first syllable duration, and average syllable duration were also obtained, but they failed to differ significantly between the two groups. This study corroborates previous findings that perceptually fluent utterances of stutterers may differ, on a physiological level, from the speech of nonstutterers.

Adult↗
PubMed1986

Perceptual judgment of abruptness of voice onset in vowels as a function of the amplitude envelope.

Four experienced speakers were trained to produce isolated vowels with different degrees of abruptness of voice onset while keeping the maximum sound level and the duration of the sounds constant. A total of 420 vowel tokens were rated for abruptness of voice onset by 11 trained speech scientists in order to study the reliability of the ratings, which was found to be moderately high (r1,1 = .74 with an extremely large range of the stimuli). Next a number of simple descriptions of the rising slope of the amplitude envelope are developed. It appears that the logarithm of the time needed for the amplitude envelope to rise from 10% to 90% of its eventual maximum level is the best predictor of perceived abruptness of voice onset of the measures examined in this study. Based on this result, an inexpensive instrument is described that can help the speech-language pathologist in assessing abruptness of voice onset in clinical practice.

Adult↗
PubMed1984

Phloem Unloading of Amino Acids at the Site of Attachment of Cuscuta europaea.

By washing out (14)C-solutes or (3)H-solutes in 0.5 mm CaSO(4) during a period of 5 to 6 hours, the release of amino acids by excised stem segments of broad bean (Vicia faba L. cv Witkiem) was studied. Three hours after pulse labeling with l-valine, l-asparagine, or alpha-aminoisobutyric acid (AIB), hollow stem segments were excised from the plant and incubated in a washout solution.In experiments with valine and asparagine, stem segments parasitized by Cuscuta europaea released a higher percentage of labeled solutes into the bathing medium than control segments. This can be ascribed to enhanced phloem unloading at the site of attachment of Cuscuta. At low temperature (0 degrees C) and after addition of p-chloromercuribenzene sulfonate to the bathing medium, parasitized segments did not release an enhanced percentage of labeled solutes, in comparison with control segments. These data suggest a metabolic control of the phenomenon of enhanced phloem unloading of amino acids. In experiments with AIB, an enhanced release of labeled solutes could not clearly be observed, but at the site of attachment of Cuscuta an accumulation of labeled solutes was measured. Accumulation of AIB in parenchyma cells, before the start of a washout experiment, will tend to obscure the phenomenon of enhanced phloem unloading.

Journal Article↗
PubMedDate not supplied

Recent developments in speech motor research into stuttering.

This paper discusses recent speech motor research into stuttering within the framework of a speech production model. There seems to be no support for the claim that stutterers differ from nonstutterers in assembling motor plans for speech. However, physiological data suggest that stutterers may at least have different ways of initiating and controlling speech movements. It is hypothesized that stuttering may be the result of a deficiency in speech motor skill. Furthermore, objections to the use of stuttering frequency as a severity index are formulated and future developments in the assessment of speech motor behavior in stuttering are described.

Humans↗