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PubMed1997

Adaptation to gradual as compared with sudden visuo-motor distortions.

If visual feedback is discordant with movement direction, the visuo-motor mapping is disrupted, but can be updated with practice. In this experiment subjects practiced discrete arm movements under conditions of visual feedback rotation. One group was exposed to 10 degree-step increments of visual feedback rotation up to a total of 90 degrees, a second group to a 90 degree visual feedback rotation throughout the experiment. After the first group reached the 90 degree visual feedback rotation, its subjects performed faster, with less spatial error, and showed larger aftereffects than the subjects who practiced constantly under the 90 degree visual feedback rotation condition. Results suggest that gradually increasing feedback distortion allows more complete adaptation than a large, sudden distortion onset.

Adaptation, Physiological↗

PubMed1976

A biofeedback study of postural sway.

An experiment was performed to control postural sway under auditory and visual feedback signals using a new apparatus. The subjects of 52 healthy high school girls were divided into 13 small groups. Each small group had four subjects who were assigned to one of the following four groups; 1) visual feedback group, 2) auditory feedback group, 3) auditory and visual feedback group, and 4) control group. Comparisons were made as to the duration of the green lamp being on, which indicated sway stayed around the initial central gravity. The results showed that auditory and visual feedback groups had a significant increase in the duration as compared to other three groups. With regard to the changes in the areas of postural sway, the largest increase was seen in the auditory and visual group. While the three feedback groups showed downward curves, the control group showed an upward one. Thus it is suggested that postural sway can be voluntarily controlled by a combination of an auditury feedback procedure and a visual feedback procedure, but not be either of them independently.

Adolescent↗

PubMed1976

A biofeedback study of postural sway.

An experiment was performed to control postural sway under auditory and visual feedback signals using a new apparatus. The subjects of 52 healthy high school girls were divided into 13 small groups. Each small group had four subjects who were assigned to one of the following four groups; 1) visual feedback group, 2) auditory feedback group, 3) auditory and visual feedback group, and 4) control group. Comparisons were made as to the duration of the green lamp being on, which indicated sway stayed around the initial central gravity. The results showed that auditory and visual feedback groups had a significant increase in the duration as compared to other three groups. With regard to the changes in the areas of postural sway, the largest increase was seen in the auditory and visual group. While the three feedback groups showed downward curves, the control group showed an upward one. Thus it is suggested that postural sway can be voluntarily controlled by a combination of an auditory feedback procedure and a visual feedback procedure, but not by either of them independently.

Adolescent↗

PubMed2003

Comparison of performance on memory-guided saccade and delayed spatial match-to-sample tasks in monkeys.

To investigate the sources of spatial error in memory-guided saccades (MGS), we have trained monkeys on two different tasks: a MGS task and a delayed spatial match-to-sample (MTS) task. We first tested the effect of introducing a post-saccadic visual feedback on the accuracy of MGS. We found that visual feedback had a pronounced effect on the systematic saccade error, but less of an effect on the variable error. Visual feedback can improve the accuracy of saccadic eye movements over several days, while feedback removal can decrease accuracy in a reversible way. These effects also depend both on target eccentricity and the duration of the memory delay. To test whether saccade error is due to the accuracy of spatial memory storage or arises downstream from that memory, we measured behavioral performance on a spatial MTS task both before and after training with visual feedback. The results showed no significant difference in performance of the MTS task before and after feedback training despite significant changes in MGS accuracy. The results suggest that the accuracy of spatial memory is not the source of the systematic errors that accompany MGS.

Analysis of Variance↗

PubMed2003

Guiding movements with internal representations: a reach-and-grasp task.

We investigated participants' ability to use internal representations of the environment to guide prehensile movements, when visual feedback was not available. Reaching and grasping performed with concurrent visual feedback was compared to conditions in which participants actively formed spatial images and passively encoded images from visual presented information. Movement times, the proportion of time spent after peak velocity and peak apertures, were greater when concurrent visual feedback was unavailable. Movement times increased as a function of premovement occlusion length, with passively encoded images resulting in shorter movement durations than actively formed images. The findings indicated that participants adapted their movement trajectories to compensate for the degradation of stored spatial information, when concurrent visual feedback was not available.

Adolescent↗

PubMed1990

Computer-displayed eye position as a visual aid to pulmonary nodule interpretation.

Approximately 30% of nodules are missed during the initial reading of chest radiographs. Eye-position recordings have shown that most nodules that are missed receive prolonged visual attention. A computer algorithm was developed that uses eye-position and gaze-duration times to identify locations on the chest image likely to contain missed nodules. These locations are highlighted on the displayed image to give visual feedback. The current study tested whether visual feedback was an effective aid to nodule detection. Six radiology residents searched 40 chest images for nodules while their eye-position and gaze-duration times were recorded. Half received displayed visual feedback and half were given a second view without feedback. Two months later the two groups returned and viewed the images in the opposite condition to counterbalance for possible practice effects. Performance of readers who were given feedback showed an average of 16% improvement as measured by the alternative free response operating characteristic (AFROC) curve area, A1. Performance of the same readers given a second look without feedback did not improve.

Algorithms↗

PubMed1977

Role of feedback in the development and maintenance of complex skill.

Three experiments examined the role of various sources of feedback in the development and maintenance of a complex ballistic skill, dart throwing, using extended practice. Even a brief delay of visual feedback initially affected accuracy and consistency adversely, though with practice performance gradually recovered. A total absence of visual feedback impelled subjects to use subtle cues such as crude auditory localization. When these cues were available, accuracy suffered to the same extent as with delayed visual feedback, but consistency in this case was unaffected. When all external feedback was removed, with subjects throwing in the dark at a luminous dot without hearing the dart land, consistency remained unimpaired, but accuracy suffered. However, on returning to full visual feedback both accuracy and consistency were found to have improved when compared to a control group. The independence of accuracy and consistency is discussed in terms of fixed and variable parameters of the skill. The effect of delayed visual feedback is attributed to the failure to integrate visual information with the fading proprioceptive trace. Central importance is attached to improvement in compentence when no external feedback is available, and possible underlying mechanisms for this improvement are described.

Auditory Perception↗

PubMed1986

The formation of finger grip during prehension. A cortically mediated visuomotor pattern.

The pattern of finger grip formation during natural prehension movements was described in normal subjects with the help of a quantified film technique. Movements were studied in one condition with visual feedback from the moving hand available, and one condition without visual feedback. The studied parameters, including the maximum size of the anticipatory grip and the final size of the grip before contact with the object, were not affected by shifting from one condition of visual feedback to the other. The same technique was applied to a group of patients with cerebral lesions. In two patients with unilateral lesions involving the motor cortex, grip formation with the hand contralateral to the lesion, was found to be severely affected, in that fingers and particularly the index finger, remained stretched until contact with the object was made. In two patients with unilateral lesions in the posterior parietal cortex, grip formation of the contralateral hand was absent specifically in the no-visual feedback condition. The same result was obtained in two other patients with a lesion (subcortical in one case, cortical in the other) of somatosensory pathways corresponding to one hand. These results are interpreted as evidence for the role of cerebral cortex in the control of finger grip formation during prehension of visual objects. Integration at cortical level of visual and somatosensory cues from the involved hand is a necessary condition for grip formation to be adapted to the grasp.

Adult↗

PubMed1992

Effect of changing feedback delay on spontaneous oscillations in smooth pursuit eye movements of monkeys.

1. Our goal was to discriminate between two classes of models for pursuit eye movements. The monkey's pursuit system and both classes of model exhibit oscillations around target velocity during tracking of ramp target motion. However, the mechanisms that determine the frequency of oscillations differ in the two classes of model. In "internal feedback" models, oscillations are controlled by internal feedback loops, and the frequency of oscillation does not depend strongly on the delay in visual feedback. In "image motion" models, oscillations are controlled by visual feedback, and the frequency of oscillation does depend on the delay in visual feedback. 2. We measured the frequency of oscillation during pursuit of ramp target motion as a function of the total delay for visual feedback. For the shortest feedback delays of approximately 70 ms, the frequency of oscillation was between 6 and 7 Hz. Increases in feedback delay caused decreases in the frequency of oscillation. The effect of increasing feedback delay was similar, whether the increases were produced naturally by dimming and decreasing the size of the tracking target or artificially with the computer. We conclude that the oscillations in eye velocity during pursuit of ramp target motion are controlled by visual inputs, as suggested by the image motion class of models. 3. Previous experiments had suggested that the visuomotor pathways for pursuit are unable to respond well to frequencies as high as the 6-7 Hz at which eye velocity oscillates in monkeys. We therefore tested the response to target vibration at an amplitude of +/- 8 degrees/s and frequencies as high as 15 Hz. For target vibration at 6 Hz, the gain of pursuit, defined as the amplitude of eye velocity divided by the amplitude of target velocity, was as high as 0.65. We conclude that the visuomotor pathways for pursuit are capable of processing image motion at high temporal frequencies. 4. The gain of pursuit was much larger when the target vibrated around a constant speed of 15 degrees/s than when it vibrated around a stationary position. This suggests that the pursuit pathways contain a switch that must be closed to allow the visuomotor pathways for pursuit to operate at their full gain. The switch apparently remains open for target vibration around a stationary position. 5. The responses to target vibration revealed a frequency at which eye velocity lagged target velocity by 180 degrees and at which one monkey showed a local peak in the gain of pursuit.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1963

Motor-sensory feedback and the geometry of visual space.

Normal surroundings appear curved when viewed through wedge prism eyeglasses. But prolonged viewing of uniformly curved lines makes them appear less curved. An environment specially patterned to prevent the appearance of curvature when viewed through a prism made possible the demonstration of change in apparent curvature wholly dependent upon the visual feedback accompanying self-produced movement of the prism-wearer.

Feedback, Sensory↗

PubMed2006

Sensory integration does not lead to sensory calibration.

One generally has the impression that one feels one's hand at the same location as one sees it. However, because our brain deals with possibly conflicting visual and proprioceptive information about hand position by combining it into an optimal estimate of the hand's location, mutual calibration is not necessary to achieve such a coherent percept. Does sensory integration nevertheless entail sensory calibration? We asked subjects to move their hand between visual targets. Blocks of trials without any visual feedback about their hand's position were alternated with blocks with veridical visual feedback. Whenever vision was removed, individual subjects' hands slowly drifted toward the same position to which they had drifted on previous blocks without visual feedback. The time course of the observed drift depended in a predictable manner (assuming optimal sensory combination) on the variable errors in the blocks with and without visual feedback. We conclude that the optimal use of unaligned sensory information, rather than changes within either of the senses or an accumulation of execution errors, is the cause of the frequently observed movement drift. The conclusion that seeing one's hand does not lead to an alignment between vision and proprioception has important consequences for the interpretation of previous work on visuomotor adaptation.

Adaptation, Physiological↗

PubMed1994

The role of proprioception in the control of prehension movements: a kinematic study in a peripherally deafferented patient and in normal subjects.

In this study we investigated the role of proprioception in the control of prehension movements, with particular reference to the grasp component. Grasp and transport kinematics were studied in a peripherally deafferented patient and in five healthy subjects. Two experiments were carried out: the prehension experiment and the grasp perturbation experiment. In the prehension experiment both the patient and the control subjects were required to reach and grasp three objects of different size, located at three different distances, both with and without visual feedback. In the grasp perturbation experiment a mechanical perturbation was applied to the fingers during prehension movements, again executed with and without visual feedback. In the prehension experiment temporal parameters of the patient's movements were generally slowed, with greater variability on some measures. However, over the first phase of the movement the pattern of the patient's hand opening and transport acceleration, scaled to object size and distance, was the same as that of controls, both with and without visual feedback. On the contrary, during the final phase of the movement (the finger closure phase and deceleration) the patient's performance differed significantly from the controls. These phases were abnormally lengthened and frequent movement adjustments were observed. In the grasp perturbation experiment the patient was not able to compensate for the perturbations applied to the fingers, even with visual feedback. The data allowed us to investigate also the respective contribution of proprioception and of vision of the hand in the control of prehension. We compared prehension kinematics in two conditions: (a) with visual but no proprioceptive feedback (in the patient) and (b) with proprioceptive but no visual feedback (in the controls). In both experiments proprioceptive control was more efficient than visual control. The results of this study are interpreted in favour of the strict dependence of prehension control on proprioception. The first phase of the movement, however, can be appropriately planned and executed without the necessity of either proprioceptive or visual information about the hand.

Adult↗

PubMed2003

Visual and haptic matching of perceived orientations of lines.

In this study we investigated the perception and production of line orientations in a vertical plane. Previous studies have shown that systematic errors are made when participants have to match oblique orientations visually and haptically. Differences in the setup for visual and haptic matching did not allow for a quantitative comparison of the errors. To investigate whether matching errors are the same for different modalities, we asked participants to match a visually presented orientation visually, haptically with visual feedback, and haptically without visual feedback. The matching errors were the same in all three matching conditions. Horizontal and vertical orientations were matched correctly, but systematic errors were made for the oblique orientations. The errors depended on the viewing position from which the stimuli were seen, and on the distance of the stimulus from the observer.

Feedback, Psychological↗

PubMed2004

Disturbances in programming goal-directed arm movements in children with ADHD.

We investigated in children with attention-deficit-hyperactivity disorder (ADHD) the ability to programme and execute goal-directed arm movements. The sample consisted of 25 males with ADHD (mean age 11 years 6 months, SD 1 year 11 months, range 8 to 15 years) and 25 age-matched typically developing males. The children moved a cursor on a screen by moving a hand-held indicator on a horizontal digitizing tablet. Start and target positions on the screen were always visible during the movement. The screen cursor, however, could either be visible throughout the movement (visual feedback) or blanked at movement initiation (without visual feedback). Analysis showed that movement control was impaired in children with ADHD and that their problems were especially pronounced during the without-visual-feedback condition. In this condition, the children with ADHD exhibited large end-point errors and prolonged movement durations. As there can be no visual corrections of the movement during this condition, results indicate poorer motor programming in children with ADHD. Moreover, children with ADHD performed jerky movements and showed a reduced capacity to select a movement speed that met with the accuracy demands of the movement.

Adolescent↗

PubMed1982

The role of visual monitoring in observational learning of action patterns: making the unobservable observable.

The present experiment tested the hypothesis that concurrent visual feedback enhances observational learning of a novel action pattern that normally would be unobservable. Subjects repeatedly enacted a modeled action pattern with visual monitoring of their reproductions throughout enactments, during only early or late phases of enactment, or not at all. At periodic intervals the adequacy of their conception of the modeled pattern was also measured. Visual feedback during ongoing performance enhanced accurate reproduction of the modeled pattern; the facilitative effect was most pronounced for reproduction of complex response components. The superiority of subjects who had enacted these difficult response components with visual feedback was maintained even when both the model and feedback were withdrawn. Visual feedback did not facilitate accurate enactment of the modeled pattern before development of an adequate cognitive representation of it. The results support the social learning view that observationally-learned behaviors are cognitively represented and that visual monitoring serves to decrease discrepancies between conception and action.

Journal Article↗

PubMed1999

A study of shoulder motions as a control source for adolescents with C4 level SCI.

This study quantitatively examined and compared the shoulder motions of C4 level spinal cord injury (SCI), C5 level SCI, and able-bodied persons as a command source. The study was motivated by both the success of shoulder control in functional electrical stimulation (FES) systems designed for C5 level SCI people and the lack of quantitative information on the shoulder motion of persons with C4 level SCI. A dual-axis transducer was used to monitor the elevation/depression and protraction/retraction angles of each subject's shoulder while they performed three experimental sections which examined: the range of active shoulder motion; the ability to move incrementally to discrete positions with the aid of visual feedback; and the ability to hold discrete shoulder positions for an extended period without visual feedback. Results indicated that each group had the largest average shoulder displacements (abled = 23 degrees +/- 4 degrees, C5's = 14 degrees +/- 3 degrees, and C4's = 9 degrees +/- 3 degrees) while attempting to elevate and that on average the C4 group had the smallest range of active shoulder motion. No statistically significant differences between the groups were found in either the accuracy or stability of reaching discrete positions with the aid of visual feedback or in the accuracy of holding discrete shoulder positions for an extended period without visual feedback. The results suggest that within their limited range of motion the individuals with C4 level SCI retained shoulder control sufficient for use as an neuroprosthetic command interface.

Adolescent↗

PubMed2004

Perception of non-voluntary brief contractions in normal subjects and in a deafferented patient.

The accuracy of force perception by human subjects in the absence of voluntary motor command was evaluated by exploring how they perceived isometric twitches of wrist extensor muscles produced by external stimulation. Twelve normal subjects and a well-known patient lacking large-diameter afferent fibres (GL) performed estimation, production and reproduction tasks. Magnetic stimulation of the radial nerve and, in normal subjects, transcranial magnetic stimulation (TMS) of the motor cortex were used to produce weak brief non-voluntary twitches. In estimation tasks, the subjects had to ascribe verbal marks on a 1-5 scale to the forces of stimulation-induced twitches. Loose covariations of marks and forces were observed, while directions of force variations between successive twitches were relatively well detected. GL did less well than normal subjects in detecting directions of force variations. In production tasks, subjects had to produce twitches matching verbal command marks in a 1-5 range, with or without visual feedback. Performances of normal subjects and GL resembled those of estimation tasks and were not improved by visual feedback. In reproduction tasks, subjects had to duplicate stimulation-induced test twitches: first without visual feedback, second with and third again without. Large errors were observed but all subjects did better with visual feedback. In the third step, improvement with respect to the first one was significantly more marked with TMS than with peripheral stimulation. GL improved her performance in the third step, possibly because she could use information provided by group III and group IV afferents still present in her nerves. Altogether, for normal subjects (1) the performances in estimation tasks are consistent with the known behaviour of Golgi tendon organs as observed in animal experiments, and (2) results observed in reproduction tasks suggest that cortical stimulation might elicit, in addition to corticospinal activation of motoneurones, collateral discharges that could be stored as a memory of motor command.

Adult↗

PubMed1985

Control of children's observing responses by information feedback during visual discrimination learning.

Four experiments examined the control of observing responses by information feedback during visual discrimination learning. Second-grade children participated in Experiment 1; kindergarten, second-, and fifth-grade children were subjects in Experiments 2 and 3, and grade 5 and adult subjects were tested in Experiment 4. In order to view the stimuli, subjects in Experiments 1, 2, and 3 activated lights in viewing boxes; in Experiment 4, stimulus fixations were measured using a corneal reflection technique. Fifth graders and adults observed the discriminative stimuli for longer times on trials following negative feedback than on trials following positive feedback; in contrast, kindergartener's observing was not affected by type of feedback. Second graders showed smaller and less reliable reactions to type of feedback than did older subjects. These results support the view that visual observing is controlled by cognitive processes associated with hypothesis testing.

Child↗