PubMed Health⌕ Search

Biomedical subjects

L Proteau

Publications and source records attributed to L Proteau.

At least 19 recordsLinked to original sources
PubMed2001

On the role of static and dynamic visual afferent information in goal-directed aiming movements.

Movement planning has been shown to be optimized when the participant is permitted to see his or her hand resting on the starting base prior to movement initiation. However, this proposition is opposed by contradictory results. In the present study, we wanted to determine whether these conflicting results were caused by procedural differences. The results showed that seeing one's hand on the starting base did not result in more accurate aiming movement than when this information was not available. However, lower aiming errors were found when one was asked to foveate the starting base and then the target prior to movement initiation, but only when no dynamic visual information was available during movement. When an aiming movement was performed while one's hand was visible in visual periphery, foveating the starting base or not prior to movement initiation did not modify aiming accuracy. These results suggest that gazing at the starting base and then at the target provides an eye-based representation of the movement to be performed that can be used by the CNS to plan a manual aiming movement. Information for better planning of the direction--but not the extent--dimension of an upcoming movement can also be derived from dynamic visual information available in peripheral vision.

Adult↗
PubMed2001

A distance effect in a manual aiming task to remembered targets: a test of three hypotheses.

It has been noted that manual aiming error and variability when pointing to remembered targets increase as a function of target eccentricity. In the present study we evaluated which one of three hypotheses (target localization, motor, or movement duration) best explains this 'distance effect'. In experiment 1, older and younger participants aimed with their unseen hand at the remembered location of targets distributed between 129 and 309 mm from the starting base. Target presentation time was of either 50 or 500 ms and aiming movements could be initiated following either a 100- or a 10,000-ms recall delay. Participants had either no constraints concerning movement time or were asked to reach the near target in a longer movement time than the farther targets. The results revealed a significant distance effect when no time constraints were imposed but showed a significantly reversed distance effect when the instructions were to reach the near targets in a longer movement time than the far targets. The same results were obtained regardless of target presentation time, recall delay, or age of the participants. These results supported a movement duration interpretation of the distance effect. In experiment 2, a distance effect was replicated when pointing with one's unseen hand toward a remembered target but did not take place when pointing to visible targets. Taken together these results suggest that prolonged movement execution interferes with the stored egocentric target representation.

Adult↗
PubMed2001

Specificity of practice in a ball interception task.

Learning of an aiming task has been shown to be specific to the sources of afferent information available during practice. However, this has not been the case when a one-hand ball-catching task has been used. The goal of the present study was to determine the cause of these conflicting results. Participants practiced an interception task in either a normal vision condition or a ball-only condition. They were all then transferred to the ball-only condition, using either the same ball trajectories as in acquisition or different ones. Being transferred from a normal vision condition to a ball-only condition resulted in a significant increase in spatial interception errors, thus supporting the specificity of practice hypothesis. Using new ball trajectories in transfer caused a significant increase in error for all participants. The pattern of errors observed when new ball trajectories were used suggests that participants had difficulty correlating information about the location of their arm via proprioception and a combination of retinal and extra-retinal information about the ball trajectory.

Analysis of Variance↗
PubMed2001

What causes specificity of practice in a manual aiming movement: vision dominance or transformation errors?

The withdrawal of vision of the arm during a manual aiming task has been found to result in a large increase in aiming error, regardless of the amount of practice in normal vision before its withdrawal. In the present study, the authors investigated whether the increase in error reflects the domination of visual afferent information over the movement representation developed during practice to the detriment of other sources of afferent information or whether it reflects only transformation errors of the location of the target from an allocentric to an egocentric frame of reference. Participants (N = 40) performed aiming movements with their dominant or nondominant arm in a full-vision or target- only condition. The results of the present experiment supported both of those hypotheses. The data indicated that practice does not eliminate the need for visual information for optimizing movement accuracy and that learning is specific to the source or sources of afferent information more likely to ensure optimal accuracy during practice. In addition, the results indicated that movement planning in an allocentric frame of reference might require simultaneous vision of the arm and the target. Finally, practice in a target-only condition, with knowledge of results, was found to improve recoding of the target in an egocentric frame of reference.

Adult↗
PubMed2001

Development of multiple movement representations with practice: specificity versus flexibility.

The question addressed in the present experiment was whether an individual who practices a task under different conditions of afferent information develops different movement representations, each of which is based on the most accurate source of afferent information for movement control. In Experiment 1, participants (N = 23) performed a manual aiming movement in a target-only condition for 520 trials before performing in a normal vision condition for an equivalent amount of practice. Control groups performed all practice trials in either a normal vision or a target-only condition. The results revealed that the movement representation developed in the initial (target-only) practice phase remained accessible for movement planning and control. The results of Experiment 2 indicated, however, that participants did not maintain such a representation when their initial practice in the target-only condition was reduced (40 or 160 trials) before they had extensive practice in normal vision. Those results indicate that extensive practice in a target-only and then in a normal vision condition enables an individual to plan and control his or her movement on the basis of the most efficient source of available afferent information. Because visual afferent information provides optimal information for ensuring movement accuracy, however, if initial practice in the target-only condition is only modest or moderate it is likely that that information source will progressively dominate all other sources of afferent information for movement planning and control.

Adult↗
PubMed2000

The role of scheduling in learning through observation.

In the 2 experiments reported in the present article, participants (N = 40, Experiment 1; N = 60, Experiment 2) learned to solve complex puzzles under different schedules of physical practice, observation, or a combination of the two. The results of both studies indicated that observation, in the absence of any physical practice, allows the development of an accurate but relatively nonfunctional cognitive representation. The data suggest that, even when the motor demands are minimal, the functional significance of the cognitive representation is not maximally realized until physical interaction with the task is possible. Thus, providing the participant with an interspersed practice schedule during acquisition enables that interaction to occur, thereby allowing the absolute number of physical practice trials to be reduced and replaced by observation trials, but leading to equivalent learning.

Cognition↗
PubMed2000

Exploring the limits of peripheral vision for the control of movement.

The role played by peripheral visual information in the control of aiming movements is not fully understood, as is indicated by the conflicting results reported in the literature. In the present study, the authors tested and confirmed the hypothesis that the source of the conflict lies in the portion of the visual peripheral field that has been under scrutiny in the different studies. Participants (N = 60) moved a computer mouse from a fixed starting position to 1 of 3 targets under varied vision conditions. The portion of the peripheral visual field that best ensured directional accuracy of a sweeping movement was found to be located between 20 degrees and 10 degrees of visual angle, whereas the area found to favor directional accuracy of an aiming movement comprised 30 degrees through 10 degrees of visual angle.

Humans↗
PubMed2000

On the cognitive basis of observational learning: development of mechanisms for the detection and correction of errors.

It has been proposed that observation of a model practising a motor skill results in the observer developing mechanisms for the detection and correction of errors that are similar to those acquired during physical practice. Results of a first experiment indicated that prior observation of a model permitted participants to estimate their errors as efficiently as those who had physically practised the task. Similarly, results of a second experiment indicated that observation of a model receiving biased knowledge of results during practice resulted in similarly biased reference and error detection/correction mechanisms for the observers and for the models. These results suggest that observation engages one in cognitive processes similar to those occurring during physical practice.

Adult↗
PubMed2000

Absence of interhemispheric transfer of unilateral visuomotor learning in young children and individuals with agenesis of the corpus callosum.

This study was undertaken to investigate the role of the corpus callosum in interhemispheric transfer of unilateral visuomotor learning. In the first experiment, the cross-manual performance of 4 callosal agenesis participants was compared to that of 4 age- and IQ-matched controls. In the second experiment, normal children of different ages (6-7 and 11-12 years) and adults were submitted to the same task to assess the impact of callosal maturation on interhemispheric transfer. Participants had to make aiming movements from a starting position toward either a central or a lateral target on the same side as the hand used, while maintaining central fixation. Prior to training, a pretest was performed with the hand contralateral to the hand used during learning. Participants were then submitted to a posttest with the untrained hand. All participants learned the unilateral aiming task in the learning phase, as evidenced by a reduction in spatial errors with an increasing number of practice trials. However, acallosal participants and children aged 6 to 7 years failed to transfer the acquired skill from the trained to the untrained hemisphere. These findings suggest that interhemispheric transfer of visuomotor skills cannot be assumed by other structures in the case of agenesis or morphological immaturity of the corpus callosum. The results further indicate that unilateral visuomotor learning leads to the formation of a single, unihemispheric engram in the absence, whether functional or anatomical, of the corpus callosum.

Adolescent↗
PubMed1999

The role of peripheral and central visual information for the directional control of manual aiming movements.

Seeing one's hand in visual periphery has been shown to optimize the directional accuracy of a sweeping hand movement, which is consistent with Paillard's (1980; Paillard & Amblard, 1985) two-channels model of visual information processing. However, contrary to this model, seeing one's hand in central vision, even for a brief period of time, also resulted in optimal directional accuracy. One goal of the present study was to test two opposing hypotheses proposed to explain the latter finding. As a second goal, we wanted to determine whether additional support could be found for the existence of a visual kinetic channel. The results indicated that seeing one's hand in central vision, even for a very short delay, resulted in the same accuracy as being permitted to see one's hand for the duration of the whole movement. This suggests that seeing one's hand around the target might enable one to code its location and that of the target within a single frame of reference and, thus, facilitate movement planning. In addition, the results of the present study indicated that seeing one's hand in motion while in visual periphery permitted a better directional accuracy than when this information was not available. This suggests that the movement vector, which is planned prior to movement initiation, can be quickly updated following movement initiation.

Adult↗
PubMed1997

Evidence Supporting the Importance of Peripheral Visual Information for the Directional Control of Aiming Movement.

The focus of the present study was on determining whether the high level of directional accuracy found in aiming studies in which the subjects can see their hand in the visual periphery supports the existence of a kinetic visual channel or, rather, the advantage of binocular over monocular vision for movement directional control. The limits of this kinetic visual channel were also explored. The results of the 1st experiment indicated that seeing one's hand in the visual periphery is sufficient to ensure optimal directional aiming accuracy. Further, no differences in aiming accuracy were noted between monocular and binocular vision. These results supported the existence of a visual kinetic channel. In the 2nd experiment, whether this kinetic visual channel would operate with movements slower (55°/s) than those usually used in studies that had proved its existence (over 110°/s) was determined. The results indicated that this visual kinetic channel was operative even at relatively slow movement velocities. Central vision of the hand seemed to be used for on-line directional control of relatively slow movements.

binocular vision↗
PubMed1997

Visual perception modifies goal-directed movement control: supporting evidence from a visual perturbation paradigm.

It is well known that dynamic visual information influences movement control, whereas the role played by background visual information is still largely unknown. Evidence coming mainly from eye movement and manual tracking studies indicates that background visual information modifies motion perception and might influence movement control. The goal of the present study was to test this hypothesis. Subjects had to apply pressure on a strain gauge to displace in a single action a cursor shown on a video display and to immobilize it on a target shown on the same display. In some instances, the visual background against which the cursor moved was unexpectedly perturbed in a direction opposite to (Experiment 1), or in the same direction as (Experiment 2) the cursor controlled by the subject. The results of both experiments indicated that the introduction of a visual perturbation significantly affected aiming accuracy. These results suggest that background visual information is used to evaluate the velocity of the aiming cursor, and that this perceived velocity is fed back to the control system, which uses it for on-line corrections.

Adult↗
PubMed1996

Effects of task instructions and oscillation frequency on bimanual coordination.

Increases in the oscillation frequency of bimanual movements produce a switch from an antiphase (180 degrees relative phase) to an in-phase (0 degrees relative phase) coordination pattern. This finding is observed when subjects are instructed not to intervene when they feel themselves slipping out of the anti-phase pattern. The question addressed in this study concerned how performance would be affected if subjects were instructed to try to maintain the pattern at all times. This issue was addressed using two separate groups of subjects: one group was given the "do not intervene" instructions, the other group was told to try to stay with the pattern at all times. Forearm rotations were tested in 15 s trials, paced by an auditory metronome set at 1.0, 1.5, 2.0, 2.5, and 3.0 Hz. Frequency distributions of the point estimates of relative phase were analyzed. The Do not Intervene group replicated previous findings, as indicated by the development of a bimodal histogram of relative phase distributions with increases in oscillation frequency. However, a very different pattern of findings emerged with increases in oscillation frequency for the group told to stay with the anti-phase pattern. Rather than a bimodal distribution being developed, the data maintained 180 degrees as its central tendency--no secondary distribution developed around 0 degrees relative phase. These data suggest that volitional control can override the inherent dynamical tendencies of the motor system.

Adult↗
PubMed1996

Aging and motor control.

The goal of the two experiments of the present study was to determine whether in an aiming task performed within a relatively long movement time (MT) bandwidth, older adults make similar use of visual information for motor control as younger adults. Older and younger subjects practiced a manual aiming task toward one (Experiment 1), or one of many (Experiment 2) small target(s) while only the target to be reached was visible (proprioception only: P) or under normal lighting condition (proprioception+vision: PV). Following practice, all subjects were transferred to the P conditions. The results of both experiments indicate that the older subjects were, during practice, as accurate as the younger ones in the PV condition. Moreover, both groups suffered a large and similar increase in aiming error in the transfer condition. This underlines that a useful source of sensory information, namely vision, has been withdrawn in transfer. This result is different from those of earlier studies in which a shorter target MT had been used (Chaput & Proteau, 1996; Proteau, Charest, & Chaput, 1994). This suggests that older adults process the sensory information available in that type of task similarly to younger subjects but at a lower speed. However, when the temporal constraints of the task are stringent, older adults might rely more on modes of control in which sensory information plays a minimal role when compared to younger subjects. Finally, the results of the second experiment suggest that, when multiple targets are used, older adults appear to program a response which is optimally suited for a "central" target.

Aged↗
PubMed1995

Effects of stationary and moving textured backgrounds on the visuo-oculo-manual tracking in humans.

We investigated the effects of stationary and moving textured backgrounds on ocular and manual pursuit of a discrete target that suddenly starts to move at constant speed (ramp motion). When a stationary textured background was superimposed to the target displacement, the gain of the steady-state eye smooth pursuit velocity was significantly reduced, while the latency of pursuit initiation did not vary significantly, as compared to a dark background condition. The initial velocity of the eye smooth pursuit was also lowered. Both the initial acceleration and the steady-state manual tracking angular velocity were slightly, but not significantly, lowered when compared to a dark background condition. Detrimental effects of the stationary textured background were of comparable amplitude (approximately 10%) for ocular and manual pursuit. In a second condition, we compared ocular and manual pursuit when the textured background was either stationary or drifting. Initial and steady-state eye velocities increased when the textured background moved in the same direction as the target. Conversely, when the background moved in the opposite direction, both velocities were decreased. Eye displacement gain remained however close to unity due to an increase in the occurrence of catch-up corrective saccades. The effects of the moving backgrounds on the initial and steady-state forearm velocities were inverse to that reported for smooth pursuit eye movements. Neither manual nor ocular smooth pursuit latencies were affected.

Adult↗
PubMed1995

Sensory integration in the learning of an aiming task.

Results of recent research on motor control indicate that in an aiming task, visual information remains of primary importance for optimal accuracy even after extended practice. One of the points that is yet unclear is whether it is solely the dynamic visual information about the moving limb that is important for movement control. To shed some light on this issue, subjects practiced an oscilloscope aiming task. In a transfer test, the dynamic information regarding the displacement of the to-be-moved object could be withdrawn without altering the static visual information that had been available during the learning of the task. The results indicated that, after 200 trials of practice, withdrawing dynamic visual information regarding the displacement of the to-be-moved object produced a deterioration in the accuracy of the subjects' responses. This indicates that the role played by the dynamic visual information for aiming control does not diminish with practice. Moreover, although visual cues available before or after movement execution have been shown to help better plan an upcoming movement, the static cues available during movement execution do not appear to play an important role in the movement representation thought to develop through practice.

Adult↗
PubMed1994

The effects of the amount and variability of practice on the learning of a multi-segmented motor task.

Since the Shea, J.B. and Morgan (1979) study, investigators have repeatedly shown that the learning of a set of movement patterns (as evaluated in a retention test) is enhanced when acquisition occurred under a random rather than a blocked schedule of practice. Supposedly, this is the case because a random schedule of practice necessitates more elaborate cognitive activities than a blocked schedule before each acquisition trial can be initiated. Our main objective was to determine whether the advantage for learning found for random practice increases as a function of the number of acquisition trials. During acquisition, the results indicated a general tendency for smaller movement reproduction errors under a blocked rather than a random schedule of practice. However, this effect disappeared with larger amount of acquisition trials. In retention, larger errors were observed when acquisition occurred under a blocked rather than a random schedule of practice. Finally, the disadvantage for learning observed for the blocked schedule of practice disappeared under a block-repeated condition in which each movement pattern was first practiced under a blocked schedule which was then repeated a second time. The results are discussed in terms of the so-called contextual interference effect and indicates some of its limitations.

Humans↗