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Biomedical subjects

W Hulstijn

Publications and source records attributed to W Hulstijn.

At least 37 records · Page 2Linked to original sources
PubMed1998

Manual dexterity and keyboard use in spastic hemiparesis: a comparison between the impaired hand and the 'good' hand on a number of performance measures.

OBJECTIVE: To assess the functional deficits in tapping performance of subjects with spastic hemiparesis. DESIGN: In a pilot study, typing performance on a computer keyboard was examined on a number of performance measures. SETTING: Department of Research and Development at the Werkenrode Institute. SUBJECTS: Four subjects (mean age 16.4 years, standard deviation 1.8 years) with cerebral palsy and diagnosed as having spastic hemiparesis. INTERVENTIONS: Subjects had to type a sequence of one or more keys as quickly as possible within an 8 second period with the fingers of both hands separately. MAIN OUTCOME MEASURES: The average number of good and false responses were calculated. Within the false response category, four, mutually exclusive, types of errors were distinguished; wrong key, repetition, registrations under 75 ms and holding. Speed and regularity of the typing responses were also established. RESULTS: The 'good' hand outperformed the impaired hand on all performance measures except on the amount of repetition errors made. The holding error was only present for the impaired hand, and there was an increase in holding errors from the index to the little finger in this hand. In addition, the impaired hand performed the task with a slower speed and in a more irregular fashion. CONCLUSIONS: The results are discussed with reference to keyboard design. It is concluded that the standard 'QWERTY' keyboard hampers typing performance extensively, especially for subjects with left spastic hemiparesis. A learning method is presented in which the role of an external pacer (e.g. metronome) is discussed. This device can initially be used to decrease movement variability and, eventually, for increasing movement speed.

Adolescent↗
PubMed1998

The timing of prehensile movements in subjects with cerebral palsy.

In this study, a paradigm is presented for the assessment of manual dexterity in subjects with cerebral palsy (CP) that divides the prehensile action into a 'time-to-contact' phase and a 'time-in-contact' phase. Two experiments were performed that determined the effect of object weight on the timing of both phases for the impaired hand and non-impaired hand of subjects with spastic hemiparesis (N = 14). In the first experiment, subjects had to reach for and lift a tube at their own preferred speed. The results showed that the prehensile deficit of the impaired limb is to a large degree manifested by a longer time spent in contact with the object before it was lifted. The time-in-contact phase was decreased after repeated lifts, suggesting that subjects with CP can control and modify force output in advance based on weight information from preceding lifts. In the second experiment speed of movement execution was stressed to examine whether the observed timing pattern of the first experiment is characteristic of prehensile movements of the paretic arm or represents a movement strategy adapted to the disorder. The results of the second experiment showed that subjects could comply with the instruction by reducing the absolute duration of both phases of the prehensile movement. Furthermore, the anticipation effects were eliminated to a large degree. In both experiments the time-in-contact phase was longer for the impaired limb. These results indicate a pathological constant in the time-in-contact phase for the impaired limb. This assumption is discussed in relation to the application of grip and lift forces during this phase. It is concluded that the paradigm is well suited for use in a practical setting as a simple and broad clinical test to assess the prehensile decrements of subjects with CP.

Adolescent↗
PubMed1997

Depressive retardation and treatment with fluoxetine: assessment of the motor component.

Changes in motor slowing between the start and end of treatment were studied in 22 inpatients with a Major Depressive Episode and 22 normal, healthy control persons. The degree and pattern of motor slowing were measured and analysed using computer-aided simple drawing tasks that did not require any higher order cognitive processing. The patients were treated with fluoxetine 20 mg/day for 6 weeks. Tests took place after 1 week (T0) and 6 weeks (T1). At T0 patients showed marked slowing, apparent in longer movement times and lower velocities than their controls. The differences between groups increased as the size of the movement increased or the accuracy demands increased. In all the trials, patients showed clear initiation difficulties. At T1 the motor slowing of the depressed patients had improved, but not disappeared. Significant differences remained between the two groups.

Adolescent↗
PubMed1996

Changes in fine motor retardation in depressed patients treated with fluoxetine.

Changes in psychomotor slowing were studied in 21 inpatients with a Major Depressive Episode. Fine motor retardation was measured and analysed using computer-aided drawing and figure-copying tasks at T0 (the start of 6 weeks treatment with fluoxetine 20 mg/day) and 5 weeks later (T1). The differences in reaction time between the patients and a group of healthy, matched controls at T0 had disappeared at T1. The initial motor deficit, expressed in longer movement times, had not improved at T1. These findings combined with the effect of manipulation of cognitive and motor demands, suggested that only cognitive processes had accelerated.

Adolescent↗
PubMed1996

Bimanual movement coordination in spastic hemiparesis.

A Fitts' task was used to examine whether the large movement asymmetry in subjects with spastic hemiparesis can be reduced or eliminated when both limbs are required to perform functionally equivalent tasks. Furthermore, it was determined whether any such benefit was expressed as mutual accommodation, or whether one hand "slaves" the other. Finally, the effect of increased task constraints on the magnitude of the asymmetry was considered. A group of ten students served as controls. Subjects had to grasp small balls and subsequently place them into holes. As expected, large total response time differences were present between the hands of the hemiparetic subjects in the unimanual conditions. However, 92% of the difference between hands was eliminated in the bimanual conditions. It is argued that the observed temporal invariance, or time locking, between hands in the bimanual conditions might be facilitated through the activity of bilateral controls exerted from each hemisphere and neural crosstalk at different levels of the central nervous system. Still, an asymmetric tendency remained in the bimanual conditions: a tendency existed for the impaired hand to reach the "target" later in time compared with the dominant hand. This tendency was enlarged as the asymmetry in task demands for the two limbs increased.

Adolescent↗
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

Changes in motor planning during the acquisition of movement patterns in a continuous task.

Changes in the planning and execution of movements were studied as a function of practice on a continuous motor task. Twelve subjects learned to move a pen through a cut-out square and maze patterns with their eyes closed. Maze patterns consisted of six, eight, ten, or twelve segments that were connected by intersections. Task performance was studied during six blocks. Although the mazes could be traced continuously in a clockwise direction, selecting a wrong turn at an intersection resulted in coming to a dead end. Performance at intersections was analyzed by determining the number of correct (and incorrect) turns following mechanically forced stops and the number of correctly planned and executed turns without any halt. In addition, movement time and pause duration were analyzed. With practice an increase in the number of correctly executed turns indicated that subjects gradually learned to group segments into chunks of increasing size. It was found that up to eight segments could be organized and executed as a single unit. Finally, with practice a non-linear performance improvement was found, suggesting that the learning process proceeded through qualitatively different learning stages. It is concluded that within five minutes subjects gradually changed their movement strategy from a sequential, trial-and-error mode in which planning and execution occurred segment by segment, to a mode in which concurrent planning was realized, i.e. in which the planning of oncoming segments occurred concurrently with the execution of segments.

Adult↗
PubMed1993

The effects of motor complexity and practice on initiation time in writing and drawing.

A large number of reaction-time studies have shown that more complex movements require more advance programming than simpler movements, thereby increasing initiation time. In handwriting experiments, however, increases in initiation time as a function of the number of strokes tend to be very small or nonexistent. This may be caused by the well-practiced nature of letter writing and the level of advance programming. To investigate this, we conducted an experiment in which subjects had to copy, as quickly as possible, stimuli consisting of three categories. Not only letters but also figures and patterns were used, consisting of familiar figures and novel nonsense (unfamiliar) patterns which were both rarely or never drawn before. These stimuli were presented on a computer screen; writing and drawing movements were recorded by means of an XY-tablet. Initiation time was found to increase linearly with the number of strokes--which varied from four to ten--but the effect was much larger for figures and patterns than for letters, and rapidly decreased with practice (successive presentations). In order to try to eliminate a difference in initiation time on account of perceptual processing, the same stimuli were presented again, but had to be written and drawn in another style, which differed only in motor complexity (the number of strokes had to be doubled by requiring the subject to draw each line twice). Drawing double lines increased initiation time with increasing number of strokes significantly for the figures and patterns. For letters, the increase was irrespective of the number of strokes. These results suggest that the planning of a movement sequence involves several levels and that the amount of preprogramming is highly influenced by the amount of motor practice.

Adult↗
PubMed1993

Figure drawing and psychomotor retardation: preliminary report.

Psychomotor retardation, a general slowing of activity which is one of the central characteristics of depression, was investigated by measuring reaction time and movement duration in drawing tasks. Twenty depressive patients and 20 normal controls participated in two tasks in which either simple or more complex figures had to be copied as fast as possible on a digitizer. In general, patients needed more time to complete the drawing tasks than controls, and they performed them differently. Six patients, who could be tested before and after treatment, showed changes in drawing speed that correlated with clinical improvement. These results suggest that psychomotor retardation might be fruitfully studied by measuring the kinematic aspects of drawing and might provide objective parameters to measure progress in therapy.

Adult↗
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↗
PubMed1992

Influence of the type of anaesthesia on post-operative subjective physical well-being and mental function in elderly patients.

Standardized behavioural observations were used to establish the influence of the type of anaesthesia on the mental function and the subjective physical well-being in 60 patients, all men, following urological surgery. The patients were randomized to two groups, receiving spinal or general anaesthesia. For evaluation of the influence of pre-operative physical condition on post-operative mental function, a supplementary group of 34 patients with pre-existing cardiovascular and/or pulmonary disorders was included in the study. These patients all received spinal anaesthesia. The patients were observed from the day before surgery until 4 weeks after. In all patients a short-lasting temporary decline in mental function was observed. The outcome was not influenced by the type of anaesthesia. In the two groups receiving spinal anaesthesia the decline in post-operative mental function and subjective sense of well-being was most pronounced in patients with a compromised physical condition pre-operatively. Four weeks after surgery, no signs of mental deterioration were present; however, the subjective sense of physical well-being had not fully returned.

Aged↗
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↗
PubMed1986

EMG feedback and the restoration of motor control. A controlled group study of 12 hemiparetic patients.

A controlled group study involving 12 patients was performed with the purpose of comparing the effects of EMG feedback in the (re-)learning of motor control to the effects of a conventional physical therapy procedure (NDT). The therapy was focussed on the improvement of the dorsiflexion function of the foot. Special attention was given to the measurement and evaluation of functional parameters (range of motion and gait). The results indicated no significant differences between the two methods. The implications of the results for the employment of EMG feedback and other therapeutic procedures in motor rehabilitation are discussed.

Adult↗
PubMed1985

Sensory feedback in the learning of a novel motor task.

The role of different forms of feedback is examined in learning a novel motor task. Five groups of ten subjects had to learn the voluntary control of the abduction of the big toe, each under a different feedback condition (proprioceptive feedback, visual feedback, EMG feedback, tactile feedback, force feedback). The task was selected for two reasons. First, in most motor learning studies subjects have to perform simple movements which present hardly any learning problem. Second, studying the learning of a new movement an provide useful information for neuromuscular reeducation, where patients often also have to learn movements for which no control strategy exists. The results show that artificial sensory feedback (EMG feedback, force feedback) is more powerful than "natural" (proprioceptive, visual, and tactile) feedback. The implications of these results for neuromuscular reeducation are discussed.

Journal Article↗