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Biomedical subjects

M Fleury

Publications and source records attributed to M Fleury.

At least 55 records · Page 3Linked to original sources
PubMed1995

Contribution of proprioception for calibrating and updating the motor space.

The absence of muscular proprioception, whether at a segmental or at a central level, impairs performance in several ways. The contribution of proprioception to movement control and learning is not easily dissociated from that of other sources of sensory information (e.g., vision). Therefore, the rare clinical cases of extensive neuropathy, depriving the brain massively and permanently of its presumed main sources of dynamogenic information from skin and muscles, are of very special interest. Two such patients and controls were tested in experiments investigating (i) force production, (ii) amplitude coding, (iii) spatial reference frames in pointing, and (iv) prismatic adaptation. Overall, our results highlight the key role of proprioceptive afferents for calibrating the spatial motor frame of reference, and the powerful substitutive properties of the central nervous system.

Adult↗
PubMed1995

Is proprioception important for the timing of motor activities?

This study tested whether a deafferented patient demonstrates impaired timing ability compared with four control subjects. By comparing normal subjects with the deafferented patient, some insight was expected on the importance of proprioception in timing of motor behavior. The protocol was set to enhance the strategy of the subjects in using feedbacks. Subjects had to synchronize finger taps with a sound produced at regular intervals. Once synchronized, the bips were muted and the subjects had to continue the tapping at the same pace. Interresponse interval (IRI) variability was measured under two feedback conditions: with and without vision and auditory feedback. The Wing and Kristofferson model (A.M. Wing and A.B. Kristofferson. Percept. Psychophys. 13(3): 455-460, 1973) was used to segment IRI variance into separate components: a central clock and a peripheral motor delay. When the deafferented patient saw and heard the outcome of her tapping movements, there was a greater variability in successive intervals between taps than when vison and hearing were blocked. We interpret this variability as indicating that the subject used auditory and visual feedback to maintain a correct overall rhythm. The patient may easily substitute visual and (or) auditory feedback for her defective proprioception for movement timing. However, this substitution proved to be inefficient in the limited training period provided in this experiment. The results suggest that the proprioceptive contribution to the time-keeping mechanism presumably depends on the presence of an efference copy signal.

Efferent Pathways↗
PubMed1995

Postural stability in diabetic polyneuropathy.

OBJECTIVE: To examine whether sensory changes in lower limbs associated with diabetic sensory polyneuropathy compromise postural stability in different visual sensory conditions. RESEARCH DESIGN AND METHODS: The presence and severity of sensory neuropathy was evaluated with a clinical scale and measures of nerve conduction velocity in the lower limbs. Balance control was evaluated by testing subjects' postural stability (with a force platform) with vision, without vision, and during a recovery period after being without vision. RESULTS: Neuropathic patients showed larger ranges of sway, a faster sway speed, and a greater dispersion of sway than control subjects in all conditions. They also exhibited similar or less stable postural performance with vision than that of control subjects without vision. There was a strong relationship between the severity of the neuropathy and the postural stability. CONCLUSIONS: This experiment highlights that even with vision, the postural stability of neuropathic patients is impaired and may put them at higher risk of falling when performing more challenging daily tasks.

Aged↗
PubMed1994

Production of short timing responses: a comparative study with a deafferented patient.

How far can proprioception contribute to time keeping? To answer this question, a deafferented patient and neurologically normal subjects produced 1- or 5-sec durations in a sustained (continuous finger press) or discrete (two successive finger taps) manner, with and without Knowledge of Results. The findings were that: (1) proprioceptive afferents contribute to timing regulation in motor production of short durations; (2) this role can be rapidly compensated by Knowledge of Results; (3) the proprioceptive contribution is more important for sustained than for discrete performances; (4) stable performances are produced even when KR is withdrawn, suggesting familiarization with KR leads to the establishment of a mnemonic trace.

Adult↗
PubMed1994

Resolving power of the perceptual- and sensorimotor systems in 6- to 10-year-old children.

Children aged 6 to 10 were tested on their ability to move accurately and to perceptually evaluate their motor response. Subjects performed a directional and an amplitude visuo-manual aiming task without vision of their moving limb. They were asked to correct their error, after completion of their movements, only if they felt they were not accurate. Terminal aiming errors and correction responses (adjustments) were analyzed, and threshold detection was determined relative to terminal aiming error. Action accuracy and evaluation of action accuracy are two abilities that do not develop synchronously. Moreover, the relationship between these abilities depends on whether accuracy and direction or amplitude are required. Amplitude undergoes more corrections than direction, suggesting that the spatial system of reference involved depends more upon the coding of the final position than on direction. Two spatial comparators, operating on the basis of two types of evaluation, seem to have a variably distinct contribution to movement and perception accuracy, according to age.

Journal Article↗
PubMed1994

Local steroid therapy and bacterial skin flora in atopic dermatitis.

A double-blind, randomized trial was conducted to determine the influence of topical steroid therapy on atopic skin flora. The bacteriological and clinical effects of desonide (Locapred), compared with those of its excipient, were studied in 40 children. Clinical scoring and bacteriological sampling were performed before the start of the trial and after 7 days of once-daily topical treatment. Before treatment, no differences in clinical score or Staphylococcus aureus colonization were noted between the two groups. After treatment, the clinical score improved (P < 0.001) in the desonide group, and S. aureus density decreased dramatically (P < 0.001). In the excipient group, no significant differences in clinical score or S. aureus density were noted. A comparison of the two groups demonstrated statistically significant differences with regard to clinical score (P < 0.001) and S. aureus density (P < 0.05). These results show the efficacy of topical corticosteroid treatment alone on S. aureus colonization in atopic skin, and confirm the critical role of inflammation in bacterial colonization.

Adolescent↗
PubMed1994

Age, cognitive style, and traffic signs.

This study assessed the efficiency with which young and older adults of varying field dependence extract information from traffic signs. It also identified some visual attributes of signs which affect recognition time. Two experiments were conducted. In Exp. 1, digitized signs, embedded in rural and urban backgrounds, were presented on a computer monitor. Subjects indicated on which side a target sign had appeared. Analysis showed that recognition times were dependent on age and field-dependence scores. Also, visual backgrounds and spatial frequency of pictographs affected RTs. In Exp. 2, recognition RT to 2 signs with redesigned pictographs was measured as well as time taken to detect signs. The signs showing reduced spatial frequency were the fastest to recognize, although no effect was noticed during detection. The subjects who showed the worst performance when facing the original signs benefitted the most from the modifications.

Adult↗
PubMed1993

Reference systems for coding spatial information in normal subjects and a deafferented patient.

To produce accurate goal-directed arm movements, subjects must determine the precise location of target object. Position of extracorporeal objects can be determined using: (a) an egocentric frame of reference, in which the target is localized in relation to the position of the body; and/or (b) an allocentric system, in which target position is determined in relation to stable visual landmarks surrounding the target (Bridgeman 1989; Paillard 1991). The present experiment was based on the premise that (a) the presence of a structured visual environment enables the use of an allocentric frame of reference, and (b) the sole presence of a visual target within a homogeneous background forces the registration of the target location by an egocentric system. Normal subjects and a deafferented patient (i.e., with an impaired egocentric system) pointed to visual targets presented in both visual environments to evaluate the efficiency of the two reference systems. For normals, the visual environment conditions did not affect pointing accuracy. However, kinematic parameters were affected by the presence or absence of a structured visual surrounding. For the deafferented patient, the presence of a structured visual environment permitted a decrease in spatial errors when compared with the unstructured surrounding condition (for movements with or without visual feedback of the trajectory). Overall, results support the existence of an egocentric and an allocentric reference system capable of organizing extracorporeal space during arm movements directed toward visual targets.

Adult↗
PubMed1993

Attentional demands for static and dynamic equilibrium.

Upright standing and walking tasks require the integration of several sources of sensory information. In a normal and highly predictable environment, locomotor synergies involving several muscles may take place at lower spinal levels with neural circuitry tuned by local loops of assistance or self-organizing processes generated in coordinative networks. When ongoing regulation of gait is necessary (obstacles, changes in direction) supraspinal involvement is necessary to perform movements adapted to the environment. Using a classical information processing framework and a dual-task methodology, it is possible to evaluate the attentional demands for performing static and dynamic equilibrium tasks. The present experiment evaluates whether the attentional requirements for a control sitting condition and for standing and walking conditions vary with the intrinsic balance demands of the tasks. The results show that standing and walking conditions required more attention than sitting in a chair. The attentional cost for walking was also significantly greater than for standing. For the walking task, reaction times when subjects were in single-support phase (small base of support) were significantly longer than those in double-support phase, suggesting that the attentional demands increased with an increase in the balance requirements of the task. Balance control requires a continuous regulation and integration of sensory inputs; increasing balance demands loads the higher level cognitive system.

Adult↗
PubMed1993

The role of proprioceptive information for the production of isometric forces and for handwriting tasks.

A patient showing a total loss of all the large sensory myelinated fibers but intact peripheral motor system produced simple isometric force pulses and more complex tasks like handwriting and drawing. Overall, the patient was able to perform the isometric force task with an accuracy that approached that of normal subjects. The writing tasks, however, proved to be more challenging. In absence of vision, the different forms and cursive trajectories forming letters (morphocinetic components) were preserved but their localization within the constraints of the graphic space (topocinetic components) were severely impaired. These results demonstrate that, in absence of visual information, proprioceptive information is necessary to calibrate the hand in space.

Adult↗
PubMed1993

Directional control of rapid arm movements: the role of the kinetic visual feedback system.

Vision has long been considered as a single feedback system providing information about the static and the dynamic features of motor behaviors and of the environment where they take place. However, recent models for oculo-manual movements have included multi-channeling of visual cues (Goodale & Milner, 1992; Jeannerod, 1981; 1984; Paillard, 1980, 1982). According to Paillard's model, a kinetic system, mostly sensitive to dynamic cues, provides directional information of the movement in the rapid distance-covering phase, and a static system, highly sensitive to position cues, provides positional signal errors. The present experiment gives kinematic evidence for the significant contribution of vision during the initial phase of rapid pointing movements when this phase is under the control of the kinetic channel. Movements having directional requirements were more accurate (directional precision) when vision of the initial portion of the trajectory was available. Times-to-peak acceleration and velocity were all shorter and their respective amplitudes were generally higher when vision was available for the first third of the trajectory than when it was not. Further, vision of the entire trajectory did not yield better precision then when vision was available for the initial phase of the movements only. Overall, the data support the existence of two corrective visual feedback systems.

Adult↗
PubMed1993

Determining movement onsets from temporal series.

With the advent of recent measurement techniques, kinematic and kinetic measures commonly are used to describe events over time. Often, the central and peripheral nature of the control processes involved are derived from these temporal series. For example, movement onset often arbitrarily defines the end of the central and the beginning of the peripheral processes. Because of its critical temporal location, we examined whether response dynamics (average movement velocity) affects the determination of movement onset. Interactive graphics and numerical methods of determining movement onsets from temporal series were evaluated on various kinematic signals. Variations in the initial rate of change in a given signal significantly affected the determination of movement onset. Consequently, measurements of component latency must be regarded with caution. A cursory description of related problems elucidated in previous research is discussed, and procedures that can minimize these artifacts are suggested.

Journal Article↗
PubMed1993

On-line versus off-line control of rapid aiming movements.

Recent studies have shown the importance of visual feedback during the rapid initial phase of aiming movements for the control of direction (e.g., Bard, Paillard, Fleury, Hay, & Larue, 1990; Blouin, Teasdale, Bard, & Fleury, in press; Teasdale, Blouin, Bard, & Fleury, 1991). In most of these studies, visual feedback conditions were presented in blocked sessions. Consequently, higher-order processes (e.g., feedforward and/or learning processes), along with on-line processing of visual feedback, might have contributed to the better accuracy found when subjects had visual feedback of only the initial portion of the movements (compared with movements without visual feedback). To test this possibility, we studied subjects' performance of rapid arm movements under different types of presentation (random, precued, and blocked) of the visual feedback conditions of the trajectory (no vision, initial portion only, and vision of the entire trajectory). Directional errors were larger in the no-vision condition than in both conditions with visual feedback. There were no differences among the presentation conditions, suggesting that on-line processing of visual information contributed to the control of the arm movements.

Journal Article↗
PubMed1992

Role of afferent information in the timing of motor commands: a comparative study with a deafferented patient.

The accuracy of the motor system in synchronizing simultaneous movements initiations was tested in two conditions: (1) when the motor commands were triggered by an external signal (reactive condition), and (2) when subjects self-paced their movement onsets (self-paced condition). The task consisted of initiating simultaneously ipsilateral finger extension and heel raising. Eight normal subjects and a deafferented patient were tested. In the reactive condition, both normal subjects and the deafferented patient exhibited a precession of finger initiation over heel raising. This delay corresponds to the difference observed in the reaction time of the two limbs when measured independently. It reflects the difference in conduction times of the efferent pathways, as if the two motor commands were released simultaneously through a common triggering signal in the motor cortex. In contrast, in the self-paced condition normal subjects showed precession of heel over finger onsets, suggesting that synchrony is based upon the evaluation of afferent information. Unlike normal subjects, the patient showed no heel precession in the self-paced condition. These findings suggest that reactive and self-paced responses are produced through two different control modes and that afferent information contributes to the timing of motor commands in the self-paced mode.

Adult↗
PubMed1992

Mirror drawing in a deafferented patient and normal subjects: visuoproprioceptive conflict.

Results on a mirrow drawing task showed that a deafferented patient had no problem completing the pattern, whereas normal subjects needed more than four trials to attain a similar performance. The results suggest the presence of integrated visual and proprioceptive maps. The inversion of visual coordinates requires the need for a recalibration. Without proprioception, the task is more like a simple visual tracking task.

Adult↗
PubMed1992

Comparative effects of two topical antiseptics (chlorhexidine vs KMn04) on bacterial skin flora in atopic dermatitis.

In order to determine the efficacy and tolerance of two topical antiseptics, chlorhexidine vs KMn04 (diluted at 1:20,000), we compared their bacteriological and clinical effects in a randomized trial on 20 children with Atopic Dermatitis (AD) treated with topical steroids (desonide). After treatment, a clinical improvement was noted in the two groups, though without statistical differences. In vivo: Before treatment, Staphylococcus aureus (S.A.) density was high and predominant in both groups. After treatment, the decrease in S.A. was greater in the chlorhexidine group than in the KMn04 group, without significant difference. In vitro: At the clinical dilution used, there was a statistical difference (p < 0.05) between the number of killed bacteria in the chlorhexidine group (-3 log) and the number in the KMn04 group (-1 log). This study confirms the role and importance of the choice of a topical antiseptic in the treatment of AD.

Administration, Cutaneous↗
PubMed1992

[Attentional requirements for preparing to return a serve in tennis].

Recent studies demonstrated that athletes use more efficient strategies than novices in sports with high perceptual requirements (Abernethy and Russel, 1984; Goulet et al., 1989; Starkes, 1987b). The aim of the present study was to investigate the attentional cost of information processing preceding action in tennis players of different calibers. The dual-task paradigm was used. The primary task consisted of identifying the type of serve (flat, slice, or top-spin) presented on 16-mm file. The secondary task was a manual response to an auditory probe. Results demonstrated that attentional requirements during information processing do not differ between experts and novices. Nevertheless, the experts' results on the primary task are significantly higher than those of novices, whether the primary task is performed alone or simultaneously with the secondary task. The attentional cost of information processed during the ritual phase of the serve is significantly higher than the costs for processing information from the preparation and execution of the serve. It appears, therefore, that attentional input effort is maximal before identification of the most important cues necessary for adequate performance.

Adult↗