SEARCH · PubMed Health

Results for “visual feedback”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources

PubMed1994

Women but not men exhibit a positive correlation between complex partial epileptic-like signs and tactile-visual cross-modal matching: implications for hemispheric intercalation.

16 right-handed men and 19 women were asked to feel various sized wooden cubes with the dominant hand for 2 sec. (without visual feedback) and then to select this cube from a random visual arrangement of cubes (tactile-visual matching) after a brief delay. The accuracy for men and women for this task did not differ significantly; however, the accuracy was significantly correlated (rho = 0.61) with a history of complex partial epileptic-like signs for the women but not for the men. The results support the hypothesis that elevated scores for complex partial epileptic-like signs in right-handed women enhance their capacity to associate different perceptual domains of the same stimuli because there is elevated activity within the (multimodal) hippocampal-amygdaloid system (sensory-limbic hyperconnectionism) and the correlative enhanced intercalation between the right and left temporoparietal lobes.

Adolescent↗

PubMedDate not supplied

Heart rate decrease: a comparison of feedback modalities and biofeedback with other procedures.

Sixty subjects were divided into six groups in a comparison of heart rate (HR) decreases obtained with (1) visual feedback, (2) auditory biofeedback, (3) combined visual and auditory biofeedback, (4) instructions to decrease HR without biofeedback, (5) sitting quietly, (6) abbreviated relaxation training, and, as a comparison, a group of 10 experienced mediators were also studied. Biofeedback stimuli were pulsed signals generated by the R-wave of the heartbeat. The results indicated that (a) there was no differential advantage on a HR decrease task to subjects receiving visual, auditory or combined biofeedback; and (b) all groups showed evidence of some decline in HR over the testing session. The mediation group showed the greatest overall decline.

Adolescent↗

PubMed1996

The horizontal vertical illusion: evidence for strategic factors in feedback-induced illusion decrement.

This study assessed whether feedback would improve performance on a horizontal vertical illusion task and whether such improvement would transfer to different forms of the illusion. Subjects shortened the extended vertical line of small, medium, and large inverted-T figures to be equal in length to the horizontal line before and after being shown a correctly adjusted medium-sized figure (visual feedback). Next, they were tested on three alternate forms of the illusion; a production task (drawing 1-in. lines in the horizontal and vertical planes), an adjustment task using L figures, and a task requiring them to choose which of several sailboat drawings had mast height equal to hull length. Prior to feedback, vertical lines were adjusted shorter than the horizontal lines on each size inverted-T figure. After feedback on the medium-size figure, experimental subjects were more accurate than the controls on each size inverted-T figure. The results suggest that transfer of illusion decrement was also obtained for the boat-selection and, to a lesser extent, the L-figure adjustment tasks but not to the line-production task. These findings are consistent with the notion that improvement after feedback is not due to structural changes in visual processing or to simple feedback-induced compensation in performance but involves some strategic or cognitive change in judging line length.

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↗

PubMed1997

Eye-hand interactions during goal-directed pointing movements.

Saccadic eye and hand movements made to step displacements in target position were measured under conditions designed to dissociate the output of the ocular and manual motor systems. This was accomplished by having subjects look and point, either with or without vision of the hand (closed or open loop, respectively) at peripheral targets starting from independent initial positions. The results showed that the amplitude of open loop pointing responses increased in size when accompanied by saccades that were larger than the required hand movement. Providing the subject with visual feedback of the hand during the response or asking them to visually fixate caused this effect to disappear. Taken together, this pattern of results suggests that when vision of the hand is unavailable the programming of saccade metrics influences the control of simultaneously produced pointing movements in an on-line manner.

Adult↗

PubMed1982

Balance performance under varied conditions of sensory cues.

43 junior-high-school girls performed three trials on a dynabilometer on each of seven days. After learning the balance task with all sensory cues available, subjects were tested under three conditions of partial feedback occlusion, i.e., with earphones, blindfold, and combination of earphone and blindfold. When visual feedback was absent, performance deteriorated significantly. Such deterioration did not occur when hearing was occluded.

Adolescent↗

PubMed1988

Control of isometric finger force in patients with cerebellar disease.

Control of isometric forces during grasping or handling of objects is an essential feature of all skilled manual performances. Previous studies of hand function in cerebellar patients were restricted to movements; force control was only investigated under isotonic conditions in combination with movements. Control of isometric forces during voluntary contraction of finger muscles was investigated in 31 patients with chronic cerebellar disease and in 20 normal controls. Eight patients with Friedreich's ataxia were considered to be typical for a disease affecting the afferents to the cerebellum; 4 patients with anterior lobe atrophy, which affects leg movements to a greater extent than finger movements, were compared with 3 patients with hemisphere lesions; 16 patients suffered from diffuse cerebellar atrophy. Using a recently developed microcomputer system for the continuous measurement of finger force, control of isometric force was studied in several tasks within the same subjects. The tasks included the maintenance of constant force output at different force levels with and without visual feedback, fast repetitive force changes, tracking of a sinusoidal target presented visually, and measurement of maximum grip force. The amount of voluntary contraction in terms of muscular power was normal in all patients; in all other tasks clear deficits were observed. The extent of the disturbances was highly variable between patients even within the same clinical subgroup. The detailed analysis of force traces revealed a great variety in types of disturbance. The frequently observed slowing of the speed in repetitive force changes can be attributed to different components in different patients and not only to difficulties at turning points as might be predicted from comparable movement studies. In addition, performance deficits across different tasks were not uniform, indicating dissociation of impairment. Deficits in maintaining force, which may be interpreted as dysmetria or due to tremor, do not necessarily imply an abnormality in diadochokinesis, as measured in fast repetitive force changes, nor does the converse apply.

Adolescent↗

PubMed2006

Functional alignment of feedback effects from visual cortex to thalamus.

Following from the classical work of Hubel and Wiesel, it has been recognized that the orientation and the on- and off-zones of receptive fields of layer 4 simple cells in the visual cortex are linked to the spatial alignment and properties of the cells in the visual thalamus that relay the retinal input. Here we present evidence showing that the orientation and the on- and off-zones of receptive fields of layer 6 simple cells in cat visual cortex that provide feedback to the thalamus are similarly linked to the alignment and properties of the receptive fields of the thalamic cells they contact. However, the pattern of influence linked to on- and off-zones is phase-reversed. This has important functional implications.

Action Potentials↗

PubMed2004

Functional properties of grasping-related neurons in the dorsal premotor area F2 of the macaque monkey.

We investigated the properties of neurons located in the distal forelimb field of dorsal premotor area F2 of macaque monkey using a behavioral paradigm for studying the neuronal discharge during observation (object fixation condition) and grasping of different 3-dimensional objects with and without visual guidance of the movement (movement in light and movement in dark conditions, respectively). The main result is that almost all studied neurons were selective for both the type of prehension and the wrist orientation required for grasping an object. Three categories of neurons were found: purely motor, visually modulated, and visuomotor neurons. The discharge of purely motor neurons was not affected by either object presentation or by the visual feedback of the hand approaching to and interacting with the object. Visually modulated neurons presented a different discharge in the 2 movement conditions, this determining a decrease in selectivity for the grip and wrist orientation in the movement in dark condition. Visuomotor neurons typically discharged during the object fixation task even in the absence of any grasping movement. Nine of them also displayed a different discharge rate between the 2 movement conditions. Congruence was observed between the neuron response during the most effective type of prehension and the neuron response during observation of the object requiring that particular prehension. These results indicate an important role of F2 in the control of goal-related hand movements.

Animals↗

PubMedDate not supplied

The effects of static friction and backlash on extended physiological proprioception control of a powered prosthesis.

In general, externally powered prostheses do not provide proprioceptive feedback and thus require the user to rely on cognitively expensive visual feedback to effectively control the prosthesis. Applying the concept of extended physiological proprioception (EPP) to externally powered prostheses provides direct feedback to the user's proprioceptive system regarding the position, velocity, and forces applied to the prosthesis. However, electric elbows with EPP controllers developed at the Northwestern University Prosthetics Research Laboratory have exhibited unexplained "jerky" behavior in both clinical fittings and bench-top operation. In addition, the development of limit cycles, a specific type of constant-amplitude oscillation, had been observed in bench-top use of these elbows. Backlash and static friction within the EPP system were found to be primarily responsible for the development of limit cycles. Reducing static friction and backlash improved the system's performance. These results suggest that to most effectively implement EPP, prosthesis manufacturers should design prosthetic components that minimize static friction and backlash.

Arm↗

PubMed1985

Vestibular and visual rotational stimulation as treatment for attention deficit and hyperactivity.

Previously published studies report an improvement in hyperactivity following exposure to vestibular semicircular canal stimulation under eyes-open, lights-on conditions (conditions that provide visual feedback). To separate the effectiveness of vestibular stimulation from that of visual stimulation, 30 primary school children who met the criteria for having attention deficit disorder with hyperactivity were enrolled in a split-sample Latin square crossover study. The effects of just vestibular stimulation and of just visual stimulation were compared with the effect of combined vestibular and visual stimulation. Behavior ratings showed significant improvement at the end of the last treatment and at follow-up one year later; this is not easily explained by statistical regression, history, or the placebo effect. The most improvement was with solitary vestibular stimulation, which showed large effect sizes; however, differences from the other two conditions failed to reach significance at traditional p levels.

Acoustic Stimulation↗

PubMed2005

Evaluation of scanning methodology in bimanual coordination.

A major component of a dynamical paradigm involves a "scanning" procedure in an attempt to determine an individual's intrinsic coordination tendencies before learning, as well as subsequent changes in the coordination landscape after practice. The purpose of the present study was to evaluate two methods of the scanning procedure. Scans were performed before and after 75 trials of a 90 degrees bimanual-coordination pattern and were compared with early and late acquisition trials. Four groups of participants performed scanning and acquisition trials using a combination of either concurrent visual feedback in the form of Lissajous figures, paced by an auditory metronome, or visual metronomes in the form of flashing stimuli. Analyses revealed that all groups improved performance of the 90 degrees pattern with practice. As predicted by the theory of practice specificity, scanning via the same method as acquisition appears to be valid. Scanning via Lissajous figures when the acquisition procedure was flashing squares was also found to be valid, but not the opposite condition. Reasons for this unidirectional transfer are given with these results suggesting that the sensitivity of a given scanning method might be influenced by the method of acquiring the coordination pattern.

Acoustic Stimulation↗

PubMed2006

V4 receptive field dynamics as predicted by a systems-level model of visual attention using feedback from the frontal eye field.

Visual attention is generally considered to facilitate the processing of the attended stimulus. Its mechanisms, however, are still under debate. We have developed a systems-level model of visual attention which predicts that attentive effects emerge by the interactions between different brain areas. Recent physiological studies have provided evidence that attention also alters the receptive field structure. For example, V4 receptive fields typically shrink and shift towards the saccade target around saccade onset. We show that receptive field dynamics are inherently predicted by the mechanism of feedback in our model. According to the model an oculomotor feedback signal from an area involved in the competition for the saccade target location, e.g. the frontal eye field, enhances the gain of V4 cells. V4 receptive field dynamics can be observed after pooling the gain modulated responses to obtain a certain degree of spatial invariance. The time course of the receptive field dynamics in the model resemble those obtained from macaque V4.

Animals↗

PubMed1992

Neonatal eye growth and emmetropisation--a literature review.

The refractive development of the neonatal eye has been the subject of much study and debate. In this paper the hypothetical mechanisms of emmetropisation and their relationship to the development of refractive errors will be reviewed. The evidence supporting visual feedback control of eye growth will be described, and the role of ocular accommodation will be discussed.

Accommodation, Ocular↗

PubMed1999

Experimental grinding in healthy subjects: a model for postexercise jaw muscle soreness?

AIMS: Pain in some bruxers has been suggested to represent a state of postexercise muscle soreness. This study examined the effect of voluntary, controlled grinding movements on the development of pain and soreness in the masticatory system. METHODS: Twelve healthy men (21 to 42 years old) without signs or symptoms of temporomandibular disorders (TMD) participated. Nine trials of 5 minutes of repeated grinding from the intercuspal position to the right canine-canine position (0.5 Hz) were performed on the first day. During the lateral excursions, the electromyographic (EMG) activity of the right masseter muscle was kept above 50% of maximal voluntary occlusal force (MVOF) with the use of visual feedback. The subjects rated pain intensity, unpleasantness, and soreness on 100-mm visual analogue scales (VAS); other pain measures, including the McGill Pain Questionnaire, were also used. Before and after the exercise trials, the MVOF was determined, and pain detection thresholds (PDT) to pressure stimuli were measured at 9 different sites on the masseter muscles. The subjects returned to the laboratory the 3 following days, where VAS, PDT, and MVOF were measured. RESULTS: Immediately following the last grinding trial, there was a significant increase in VAS and MPQ scores of pain intensity, unpleasantness, and soreness, as compared to baseline values (analysis of variance, P < 0.001). There was still a significant effect from grinding on the VAS score of muscle soreness on the following days, with a peak the first day after the exercise (Tukey test, P < 0.023). Pain was frequently (in 7 of 12 subjects) reported in or around the temporomandibular joint. There was a significant effect from grinding on PDT at both masseter muscles (analysis of variance, P < 0.043), with significantly lower PDT the first day after the grinding exercise (Tukey test, P < 0.046). There were no effects from grinding on MVOF. CONCLUSION: These findings suggest that significant but low levels of postexercise muscle soreness can be elicited by standardized grinding movements in the masticatory system of healthy subjects.

Adult↗

PubMed1977

Sensory feedback therapy in patients with brain insult.

Brain insults, regardless of etiology, may disrupt the CNS servosystems concerned with patterned voluntary movements and result in disorders of such movement. To aid functional recovery, we applied in these patients oscilloscopic display of digitally integrated EMG, monitored from malfunctioning primary movers, during attempted execution of movement (sensory feedback therapy). Such display provided the patient with an immediate and continuous visual feedback loop reflecting the events underlying the movement and occuring in the monitored muscle (force, displacement and rate). This information is essential for motor control of patterned voluntary movement. Coupled with auditory reward for optimal performance, such feedback also assumed reinforcing qualities and motivated the patient to execute voluntary movements with progressive improvement. Sixty patients with longstanding CNS insult, resulting in motor impairment, were treated and followed for periods of four months to four years. One half of these patients learned and retained voluntary movements that significantly improved their functional capabilities. Temporary substitution of feedback information about fundamental events in dysfunctional muscles can apparently be of lasting value in treatment of some patients with brain insult.

Adolescent↗

PubMed1984

Audio-ocular response: saccadic programming.

The eye movements elicited by auditory stimuli--the audio-ocular response (AOR)--differ from those made in response to a visual target. The movements consist of both monosaccadic and multiple saccadic refixations (MSR). In visual refixation, monosaccadic refixations are always accurate; in AOR, they rarely are. In MSR, many strategies were used in the attempt to find the target but they were not always successful. However, final amplitudes of the total refixation were quite accurate in both MSR and monosaccadic refixations. Velocity profiles of the AOR showed such anomalies as discrete decelerations and multiple, closely-spaced saccades. These data suggest that, without visual feedback, the location of acoustic targets is difficult. In the absence of visual afference, when vigilance may be decreased by the lack of arousal, the velocity profiles also became abnormal, even at small amplitudes. Thus, for cockpit warning devices, a combination of auditory and visual indicators should be used.

Acoustic Stimulation↗

PubMed1994

The role of the striatum in motor learning: dissociations between isometric motor control processes in Parkinson's disease.

Studies of Parkinson's disease (PD) have been used to support the hypothesis that the striatum serves procedural learning but interpretation of the results is confounded by extra-striate pathology and coincidental non-procedural cognitive deficits. The motor deficit of PD involves particularly internally cued movement, without visual feedback, because of disruption to frontostriatal circuits. Thus, we used a non-visual isometric task as a sensitive measure of motor learning in early non-demented patients with PD and examined the effects of dopamine replacement. The PD group showed disproportionate under-shooting of the target but normal motor learning. Learning correlated with some cognitive measures but not clinical motor disability or depression. Treatment had no effect on performance, despite clinical improvement. The results indicate dissociations between motor control processes resulting from striatal pathology. Putaminal circuits are involved in force generation and prediction but not critically in motor learning.

Basal Ganglia↗