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PubMed2006

Oculomotor rehabilitation for reading in acquired brain injury.

The purpose of this study was to assess reading-related oculomotor rehabilitation in individuals with acquired brain injury. Adults with either stroke (n=5) or traumatic brain injury (n=9) participated. Training paradigms included single-line and multiple-line simulated reading, as well as basic versional tracking (fixation, saccade, and pursuit), twice per week over an 8 week period. Training modes included normal internal oculomotor visual feedback either in isolation (4 weeks) or concurrent with external oculomotor auditory feedback (4 weeks). Training effects were assessed objectively using infrared eye movement recording technology for simulated and actual reading, with the assessments occurring before, midway, and after training. In addition, the individuals were assessed subjectively using a reading rating-scale questionnaire. All reported considerably improved reading ability, and this was confirmed by several of the objective oculomotor measures. There was a trend for improvement to be better with the combined visual and auditory oculomotor feedback. Reading-related oculomotor rehabilitation produced significant gains in both the subjective and objective domains. It is believed that rapid saccadic oculomotor adaptation, as well as the training of rhythmicity and automaticity, were involved in modifying eye movement behavior to produce a more systematic approach and resultant improved reading profile.

Acoustic Stimulation↗

PubMed2005

Effects of adaptation to altered display gain on the control of single aimed movements.

A display gain setting defines the mapping of a movement to the real-time visual display. In two experiments we investigated how the acquired adaptation to low and high display gain affected motor control of single aimed stylus movements. Experiments differed with respect to how gain was varied. In Experiment 1, gain was realized by manipulating the surface displacements with a constant display. The results show an expected linear decrease of movement time and spatial accuracy, which is in sharp contrast with the often-reported U-shaped relation. Experiment 2 was run to study the influence of visual feedback in low- and high-gain conditions. The manipulation of gain was realized by display variation with unaltered surface displacements. The linear increase of movement time and feedback processing with gain and the unaltered spatial accuracy across conditions, suggested that participants actively adapted to the displayed visual information in altered gain conditions.

Adaptation, Physiological↗

PubMed1997

Continuous concurrent feedback degrades skill learning: implications for training and simulation.

In two experiments we investigated the role of continuous concurrent visual feedback in the learning of discrete movement tasks. During practice the learner's actions either were or were not displayed on-line during the action; in both conditions the participant received kinematic feedback about errors afterward. Learning was evaluated in retention tests on the following day. We separated (a) errors in the fundamental spatial-temporal pattern controlled by the generalized motor program from (b) errors in scaling controlled by parameterization processes. During practice concurrent feedback improved parameterization but tended to decrease program stability. Based on retention tests, earlier practice with continuous feedback generally interfered with the learning of an accurate motor program and reduced the stability of time parameterization. Continuous feedback during acquisition degrades the learning of not only closed-loop processes in slower movements (as has been found in earlier studies) but also motor programs and their parameterization in more rapid tasks. Implications for feedback in training and simulation are discussed.

Analysis of Variance↗

PubMed2006

Visual proprioception in the timing of movements: evidence from deafferentation.

The present study investigated the control of movements in two patients with severe somatosensory deafferentation by systematically manipulating the visual information about the produced movements. In a synchronization task requiring the production of finger taps in synchrony with a regular auditory signal, participants controlled their movements under full vision or when the sight of the effector was partially or completely occluded. Results demonstrated large effects of visual feedback on the synchronization performance in the deafferented patients. Although the patients' performance differed substantially from that of unimpaired controls under partial or no feedback, their performance was comparable under full vision, the latter suggesting a compensation of the somatosensory loss by visual monitoring.

Adult↗

PubMed1981

Conditioning and recovery of functions lost by brain damage.

The muscle spindle is a receptor apparatus in striated muscle that is necessary for voluntary muscle movement. Paralysis victims lose the feedback of this receptor and cannot initiate motor responses. Four hemiplegic patients were trained to use auditory feedback from electromyographic recordings to initiate activity in paretic limbs. With the addition of visual feedback and the use of the auditory signal as a reinforcing stimulus, the patients' muscle activity was then shaped to approximate normal movement.

Adolescent↗

PubMed2004

The characteristics and neuronal substrate of saccadic eye movement plasticity.

Saccadic eye movements are shifts in the direction of gaze that rapidly and accurately aim the fovea at targets of interest. Saccades are so brief that visual feedback cannot guide them to their targets. Therefore, the saccadic motor command must be accurately specified in advance of the movement and continually modified to compensate for growth, injury, and aging, which otherwise would produce dysmetric saccades. When a persistent dysmetria occurs in subjects with muscle weakness or neural damage or is induced in normal primates by the surreptitious jumping of a target forward or backward as a saccade is made to acquire the target, saccadic amplitude changes to reduce the dysmetria. Adaptation of saccadic amplitude or direction occurs gradually and is retained in the dark, thus representing true motor plasticity. Saccadic adaptation is more rapid in humans than in monkeys, usually is incomplete in both species, and is slower and less robust for amplitude increases than decreases. Adaptation appears to be motor rather than sensory. In humans, adaptation of saccades that would seem to require more sensory-motor processing does not transfer to saccades that seem to require less, suggesting the existence of distributed adaptation loci. In monkeys, however, transfer from more simple to more complex saccades is robust, suggesting a common adaptation site. Neurophysiological data from both species indicate that the oculomotor cerebellum is crucial for saccadic adaptation. This review shows that the precise, voluntary behaviors known as saccadic eye movements provide an alternative to simple reflexes for the study of the neuronal basis of motor learning.

Adaptation, Physiological↗

PubMed1992

A sensorimotor basis for motor learning: evidence indicating specificity of practice.

Our previous work (Proteau, Marteniuk, Girouard, & Dugas, 1987) was concerned with determining whether with relatively extensive practice on a movement aiming task, as the skill theoretically starts becoming open-loop, there would be evidence for a decreasing emphasis on visual feedback for motor control. We eliminated vision of the moving limb after moderate and extensive practice and found that the movement became more dependent on this feedback with greater amounts of practice. In the present study, we wished to test the hypothesis, developed from our previous work, that at the base of movement learning is a sensorimotor representation that consists of integrated information from central processes and sensory feedback derived from previous experiences on the movement task. A strong test of this hypothesis would be the prediction that for an aiming task, the addition of vision, after moderate and relatively extensive practice without vision, would lead to an increasingly large movement decrement, relative to appropriate controls. We found good support for this prediction. From these and our previous results, and the idea of the sensorimotor representation underlying learning, we develop the idea that learning is specific to the conditions that prevail during skill acquisition. This has implications for the ideas of the generalized motor program and schema theory.

Feedback↗

PubMed1990

Use of augmented feedback for the modification of the pedaling mechanics of cyclists.

On-line computer representation of forces applied to the pedals during a 90-degree sector of the pedaling cycle were used to train a group of cyclists to alter their pattern of force application while they cycled on a stationary cycle. The subjects rode for 32 min each day for ten days. During these training rides, three cyclists were given augmented feedback on only their pedaling rate, while three other cyclists were presented with augmented, visual feedback on the magnitude of force application in the sector of interest as well as cadence. At the end of the training period it was noted that the experimental group showed significantly reduced pedal forces in the sector of interest while the control group did not. It was concluded that this technique of modifying a well-practised task was an effective one and that it could be used to explore various training modalities and other pedaling styles.

Adult↗

PubMed2004

Visually guided locomotion in the gerbil: a comparison of open- and closed-loop control.

Two experiments were conducted in order to explore the effects of visual feedback on control of locomotion in the gerbil. In the first experiment, gerbils were trained to run down an alleyway towards a visual target in order to obtain food reward. One group of animals was trained to run to a target whose size never varied while another group was trained to run to a target whose size varied randomly from trial to trial. On some trials, the target's size was changed dynamically during running to determine whether gerbils used this dynamic size change information to compute time to collision (tau). Results suggested that neither group used retinal image size information but both groups seemed able to compute tau. In a second experiment, gerbils were trained in the same way as in experiment 1, but on some trials the target was extinguished during the run. In this condition, probe trials showed that gerbils used retinal image size to compute target distance. Collectively, the results showed that gerbils were able to rapidly and flexibly utilize available information to complete a visually guided running task. The results are discussed in the context of the psychophysics of cue combination and its neural underpinnings.

Animals↗

PubMed1969

Visual reinforcement of nonnutritive sucking in human infants.

High-amplitude sucking was studied as a conditioned operant response reinforced by visual feedback in 4-and 12-month infants. Typicalresponse acquisition and extinction effects were obtained. With the 12-month infants the conditioned sucking rates were influenced by amounts of redundancy in the visual reinforcers.

Conditioning, Operant↗

PubMed2003

Efficiency of grip force adjustments for impulsive loading during imposed and actively produced collisions.

During object manipulation, both predictive feedforward and reactive feedback mechanisms are available to adjust grip force (GF) levels to compensate for the destabilizing effects of load force changes. During collisions, load force increases impulsively (< 20 ms). Thus, only predictive control of GF can be used to ensure grasp stabilization. A collision paradigm is here used to investigate the effects of practice and vision on the efficiency of the predictive control of GF. Subjects actively produced or received an imposed collision with a pendulum. Subjects were more efficient (used smaller GF for identical loads) when producing than when receiving the collisions. Effects of practice were evident in the active producing task only, with GF levels reducing over repetitions, suggesting that sensorimotor memory for the task was used to adjust GF more efficiently. With imposed collisions, GF levels did not reduce with repetition, which suggests that a direct relation between motor action and sensory feedback may be necessary to improve efficiency. Nevertheless, in this condition GF was lower with visual feedback, indicating potential for more efficient grip possibly associated with subjects degree of confidence. We discuss the implications of these results for accounts of the predictive and the reactive control of movement.

Adaptation, Physiological↗

PubMed2004

Enhanced accuracy in novel mirror drawing after repetitive transcranial magnetic stimulation-induced proprioceptive deafferentation.

When performing visually guided actions under conditions of perturbed visual feedback, e.g., in a mirror or a video camera, there is a spatial conflict between visual and proprioceptive information. Recent studies have shown that subjects without proprioception avoid this conflict and show a performance benefit. In this study, we tested whether deafferentation induced by repetitive transcranial magnetic stimulation (rTMS) can improve mirror tracing skills in normal subjects. Hand trajectory error during novel mirror drawing was compared across two groups of subjects that received either 1 Hz rTMS over the somatosensory cortex contralateral to the hand or sham stimulation. Mirror tracing was more accurate after rTMS than after sham stimulation. Using a position-matching task, we confirmed that rTMS reduced proprioceptive acuity and that this reduction was largest when the coil was placed at an anterior parietal site. It is thus possible, with rTMS, to enhance motor performance in tasks involving a visuoproprioceptive conflict, presumably by reducing the excitability of somatosensory cortical areas that contribute to the sense of hand position.

Adolescent↗

PubMed2002

Surgical simulation software for insertion of pedicle screws.

OBJECTIVE: As the first step toward finding noninvasive alternatives to the traditional methods of surgical training, we have developed a small, stand-alone computer program that simulates insertion of pedicle screws in different spinal vertebrae (T10-L5). METHODS: We used Delphi 5.0 and DirectX 7.0 extension for Microsoft Windows. This is a stand-alone and portable program. RESULTS: The program can run on most personal computers. It provides the trainee with visual feedback during practice of the technique. At present, it uses predefined three-dimensional images of the vertebrae, but we are attempting to adapt the program to three-dimensional objects based on real computed tomographic scans of the patients. The program can be downloaded at no cost from the web site: www.tums.ac.ir/downloads CONCLUSION: As a preliminary work, it requires further development, particularly toward better visual, auditory, and even proprioceptive feedback and use of the individual patient's data.

Bone Screws↗

PubMed2005

Role of visual context and oculomotor conditions in pointing accuracy.

Localizing a target in the extrapersonal space may rely on two types of spatial coordinate systems: egocentric or exocentric. Two experiments investigated the role of these systems in the accuracy of goal-directed movements. The accuracy of pointing movements performed without visual feedback of the hand was measured in two conditions of target presentation (darkness or within a visually structured background), and in two conditions of eye-hand coordination (eye fixed on a fixation point, or with a foveation saccade). The results showed (1) that pointing accuracy increased in the presence of a visual background, and (2) enhancement of this beneficial effect by a steady retinal image of target and background, that is without a foveation saccade. An object that has to be reached in the prehension space can be localized in two ways: (1) in relation to the body (egocentric), induced by the absence of a structured visual environment, (2) in relation to the external space (exocentric), favored by the presence of a visually structured background. We investigated the importance of the localizing mode in the accuracy of reaching movements, and how the two modes can be optimized. We found better reaching accuracy with exocentric than with egocentric localization, particularly when the retinal image of the goal and its environment was stabilized in the absence of eye movements.

Eye Movements↗

PubMed1991

Visual influence on postural reactions to sudden antero-posterior support surface movements.

Visual influence on force reactions to sudden antero-posterior (AP) translations of the support surface in 10 healthy men 23-58 years old (mean 36 years) were studied. Displacements ranged between 13 and 127 mm in both backwards and forwards directions. The experiment was conducted using a modified EquiTest dynamic posturography apparatus. An interactive menu-driven software enabled selection of a suitable translation pattern (i.e. square wave) in the AP direction. Data from four vertical force transducers were acquired and the position of centre of pressure (CP) in the AP direction was computed as function of time. The movement of CP in response to AP translation was characterized by the amplitude of the maximum CP displacement relative to the platform and the latency until maximum CP displacement occurred. The experiment unveiled that the latency to maximum CP displacement was larger for conditions with vision present. Furthermore, both the amplitude and latency to maximum CP deflection were increasing functions of translation amplitude. It is proposed that visual feedback influences the neural control on the postural reactions to sudden support surface translations. Absence of visual cues seems to cause a more rapid correction of the body position.

Adult↗

PubMed2002

Dynamic effects of the Ebbinghaus illusion in grasping: support for a planning/control model of action.

A distinction between planning and control can be used to explain the effects of context-induced illusions on actions. The present study tested the effects of the Ebbinghaus illusion on the planning and control of the grip aperture in grasping a disk. In two experiments, the illusion had an effect on grip aperture that decreased as the hand approached the target, whether or not visual feedback was available. These results are taken as evidence in favor of a planning/control model, in which planning is susceptible to context-induced illusions, whereas control is not. It is argued that many dissociations between perception and action may better be explained as dissociations between perception and on-line control.

Attention↗

PubMed1983

[Effects of evoking imagery on the control of peripheral skin temperature].

This study aimed to examine the effects of evoking imagery as a strategy to control the skin temperature with the biofeedback method. Subjects were 32 female nursing school students. Pair-matched by their ability to evoke imagery, they were assigned to either the I group that was instructed to evoke warm imagery or the NI group that did not receive such instruction. The experiment was consisted of four sessions: pre-test session, two feedback training sessions, and post-test session. All subjects were instructed to raise their finger skin temperature, and the visual feedback was presented to both groups only during the feedback training sessions. Results obtained were as follows: (a) Both groups were able to raise their skin temperature during the feedback training sessions. (b) In the post-test, however, the number of subjects who were able to raise their skin temperature were greater in the I group than the NI group. These results suggested that the subjects who had acquired a strategy could control their skin temperature more effectively if the feedback was taken off.

Autonomic Nervous System↗

PubMed2002

Modulation of slow cortical potentials by transcranial magnetic stimulation in humans.

We studied the effects of transcranial magnetic stimulation (TMS) on slow cortical potentials (SCPs) of the brain elicited during performance of a feedback and reward task. Ten healthy participants were trained to self-regulate their SCP amplitude using visual feedback and reward for increased or decreased amplitudes. Subjects participated in 27 runs (each comprising 70 trials) under three different conditions: single-pulse TMS delivered with the coil centered over Cz (vertex), over a lateral scalp position (LSP), which increased task difficulty, and in the absence of stimulation. Cz stimulation led to a non-significant enhancement of negative SCPs, while LSP stimulation led to a significant increase of positive SCPs. These results are consistent with the idea that enhanced task difficulty, as in LSP stimulation, enhances cognitive processing load leading to an increase of positive SCPs. Additionally, the data raise the hypothesis that TMS delivered to bilateral midcentral regions could modulate the amplitude of negative SCPs.

Adult↗