Biomedical subjects

P H van Lieshout

Publications and source records attributed to P H van Lieshout.

6 recordsLinked to original sources

PubMed2001

Lip movement in patients with a history of unilateral cleft lip.

OBJECTIVE: The influence of a repaired cleft lip on the stability of coordination between upper and lower lip in nonspeech and speech tasks was investigated. DESIGN: First, we looked at the effects of a secondary cleft lip repair in three individuals. Second, we compared subjects with a history of repaired unilateral cleft lip and subjects with no history of cleft lip (controls). Lip coordination was measured using continuous estimates of relative phase. PARTICIPANTS: Subjects were nine children and adolescents with a primary unilateral cleft lip and palate repair and 4 participants without cleft matched for age across different age categories. RESULTS: In general, the averaged relative phase angle (RPA) angle values were smaller than 180 degrees, indicating an upper lip lead for lip closure. Controls showed a tendency toward a more symmetric type of coordination (close to 180 degrees), compared with subjects with a repaired unilateral cleft lip. The controls also showed less variation in coordination between the lips. For the more complex speech tasks, a general increase in variability of the RPA values for all subjects was observed, most likely suggesting a more flexible type of coordination. Regarding the effect of a secondary cleft lip repair, only one of the three patients showed a clearly less symmetric and less stable type of coordination, compared with preoperation results. CONCLUSIONS: There appear to be differences in lip coordination between speakers without and speakers with a repaired unilateral cleft lip. Furthermore, it seems that the stability of lip coordination tends to increase with age.

Adolescent↗

PubMed1998

The stability of pen-joint and interjoint coordination in loop writing.

This study is concerned with pen-joint and interjoint coordination in handwriting. In particular, it focuses on the stability of coordination as a means to find the locus of coordination control in the arm-pen effector system. Twelve subjects generated loop sequences of varying length at various positions on the baseline of writing. Joint excursions and pen-tip displacements were recorded by means of a 3D-motion tracking system. The coordination stability of 15 pairs of 6 mechanical degrees of freedom (d.f.s) of the arm-pen effector system was investigated by means of relative phase analyses. Pen-joint coordination between horizontal pen-tip displacements and wrist excursions was found to be most stable; that between vertical pen-tip displacements and finger excursions was considerably less stable. Interjoint coordination was generally less stable than pen-joint coordination, and most stable between the wrist and the elbow. Sequence length and its position on the line differentially affected the coordination stability of the d.f. combinations. The results are discussed in relation to assumptions about joint coordination in writing as expressed by computational handwriting models.

Adult↗

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

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↗