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PubMedDate not supplied

Postural control measured by visual feedback posturography.

The objective was to study the applicability and repeatability of visual feedback posturography (VFP) in assessing postural control of 23 healthy subjects. The subjects had to move their center of gravity (COG) marker on a computer screen to chosen targets by leaning their body on the platform, and the accuracy, velocity, and side difference of these movements were measured. The intraclass correlation coefficients for all parameters during repeated tests were significant (r = 0.93 - 0.96; p < 0.01). Hold percentage within the targets and COG marker velocity to the targets did not change significantly during repeated tests. Balance index and hit delay were significantly smaller during the 4th and 5th than during the 1st test session (p < 0.05), but they did not change significantly between the other test sessions. The normative limit for side difference in postural control was 22%. VFP can be used to follow active postural control due to its high test-retest repeatability. However, learning effects in some parameters must be taken into account when applying VFP repeatedly in different patient populations to assess the progress in postural control.

Adolescent↗
PubMed1990

Delayed visual feedback and movement control in Parkinson's disease.

The dependence of movement on visual information was compared for healthy individuals and Stage II-III patients with Parkinson's disease (PD). A time delay (0-1400 ms) was introduced into a visually guided motor tracking task which required the subject to maintain constant index finger position relative to a stationary baseline on an oscilloscope. For healthy individuals, delayed visual feedback induced complex oscillations in finger displacement. Similar results were obtained for four of eight patients with PD. However, oscillations were not induced in four of eight patients with PD because of reduced gain and/or a higher tremor amplitude at zero delay which obscured the tracking error. These results suggest that some patients with PD are able to utilize visual information for controlling tracking in this motor task in the same manner as healthy individuals.

Adult↗
PubMedDate not supplied

[The effect of weightlessness on sensorimotor interaction during operator activity: visual feedback. Motor response latency time].

During the second joint French-Soviet space mission efficiency of compensating tracking was investigated in operator by velocity. It was shown that in spite of considerable changes in proprioceptive feedbacks, performance quality remained essentially as preflight. This evidences that visual feedback during operational activity is apt to offset losses in proprioceptive feedbacks.

Feedback↗
PubMed2003

A controlled pilot study of the utility of mirror visual feedback in the treatment of complex regional pain syndrome (type 1).

BACKGROUND: We assessed mirror visual feedback (MVF) to test the hypothesis that incongruence between motor output and sensory input produces complex regional pain syndrome (CRPS) (type 1) pain. METHODS: Eight subjects (disease duration > or =3 weeks to < or =3 yr) were studied over 6 weeks with assessments including two controls (no device and viewing a non-reflective surface) and the intervention (MVF). Pain severity and vasomotor changes were recorded. RESULTS: The control stages had no analgesic effect. MVF in early CRPS (< or =8 weeks) had an immediate analgesic effect and in intermediate disease (< or =1 yr) led to a reduction in stiffness. At 6 weeks, normalization of function and thermal differences had occurred (early and intermediate disease). No change was found in chronic CRPS. CONCLUSIONS: In early CRPS (type 1), visual input from a moving, unaffected limb re-establishes the pain-free relationship between sensory feedback and motor execution. Trophic changes and a less plastic neural pathway preclude this in chronic disease.

Adult↗
PubMed2006

Changing lanes: inertial cues and explicit path information facilitate steering performance when visual feedback is removed.

Can driver steering behaviors, such as a lane change, be executed without visual feedback? In a recent study with a fixed-base driving simulator, drivers failed to execute the return phase of a lane change when steering without vision, resulting in systematic final heading errors biased in the direction of the lane change. Here we challenge the generality of that finding. Suppose that, when asked to perform a lane (position) change, drivers fail to recognize that a heading change is required to make a lateral position change. However, given an explicit path, the necessary heading changes become apparent. Here we demonstrate that when heading requirements are made explicit, drivers appropriately implement the return phase. More importantly, by using an electric vehicle outfitted with a portable virtual reality system, we also show that valid inertial information (i.e., vestibular and somatosensory cues) enables accurate steering behavior when vision is absent. Thus, the failure to properly execute a lane change in a driving simulator without a moving base does not present a fundamental problem for feed-forward driving behavior.

Adolescent↗
PubMed1998

Sinusoidal forearm tracking with delayed visual feedback. I. Dependence of the tracking error on the relative delay.

During forearm tracking of a sinusoidally moving target matching of proprioceptive and visual feedback was altered by introducing different visual delays. In five normal subjects seven target frequencies were tested ranging from 0.3 to 1.5 Hz. For each target frequency nine different delays were used ranging from 0 to 120% of the cycle duration with target frequency and delay being varied randomly. Tracking error revealed a cyclic behaviour with an increase up to delays of about 50% of the target cycle duration and an improvement for delays larger than 50%. Modulation of response frequency was less pronounced compared with tracking error variation but also was dependent on relative phase. The response frequency matched the target frequency at delays of 0 and 100% of cycle duration and was slightly lower than the target frequency with relative delays of about 50%. The introduction of a visual delay during sinusoidal forearm tracking leads to a spatial in addition to the temporal mismatch between proprioception and vision. The temporal and the spatial incompatibility influence the tracking performance differentially.

Adult↗
PubMed1984

Smooth eye-movement control with secondary visual feedback.

A signal derived from continuous measurement of eye position is displayed on a visual frame of reference, thereby closing a secondary visual feedback (2VFB) loop. The distance between a target and the displayed gaze point provides the subject with an extra, artificial position error. Experiments show that subjects can use the 2VFB to generate smooth eye movements, even in the absence of any smoothly moving independent targets. Under these conditions, both direction and velocity can be brought under voluntary control by the subjects. As a control signal for the smooth-eye-movement mode, the 2VFB is robust and easily manipulated and provides an attractive means for the investigation of the smooth-movement control system in a variety of tasks and under different conditions.

Eye Movements↗
PubMed1991

The precision of motor control in human jaw and limb muscles during isometric contraction in the presence of visual feedback.

Experiments showed that the human capacity to maintain a particular isometric force in the presence of visual feedback during a force-level, pursuit-tracking experiment is less developed for the jaw-closing muscles than for the limb muscles. This finding may indicate that the projection on the trigeminal motoneurone pool from visual inputs is poor, or that the trigeminal effector system itself is less finely tuned.

Adult↗
PubMed1977

The effect of visual feedback of the hand on the reaching and retrieval behavior of young infants.

Reaching and retrieving, with and without visual feedback of the hand, were observed in 50 infants ranging in age from 2 1/2 to 6 1/2 months. Failure, to see the hand did not completely inhibit reaching and retrieving, although reaching and retrieving were reduced in this situation for infants 5 1/2 months and older. It was hypothesized that infants of this age expected to see their hands within their visual fields. When this expectation was not met, the infant's ongoing behavior was disrupted.

Age Factors↗
PubMedDate not supplied

Changes in postural balance in frail elderly women during a 4-week visual feedback training: a randomized controlled trial.

BACKGROUND: Balance training programs have not shown consistent results among older adults, and it remains unclear how different training methods can be adapted to frail elderly people. OBJECTIVE: The purpose of this study was to investigate the effects of a 4-week visual feedback-based balance training on the postural control of frail elderly women living in residential care homes. METHODS: Elderly women of two residential care facilities were randomized to an exercise group (EG, n = 20) and to a control group (CG, n = 7). The EG participated in training sessions three times/week for 4 weeks. The exercises were carried out with a computerized force platform with visual feedback screen. The dimensions of balance function studied were standing body sway, dynamic weight shifting, and Berg Balance Scale performance. RESULTS: The EG showed significant improvement in balance functions. The performance time in dynamic balance tests improved on average by 35.9% compared with a 0.6% increase in the CG (p = 0.025-0.193). The performance distance in these tests decreased on average by 28.2% in the EG as compared with a 9.8% decrease seen in the CG. The Berg Balance Scale performance improved by 6.9% compared with a 0.7% increase in the CG (p = 0.003). The standing balance tests in the more demanding standing positions showed improvements in the EG, whereas similar changes in the CG were not found. CONCLUSIONS: Our findings suggest that balance training based on visual feedback improves the balance control in frail elderly women living in residential care, also enhancing the performance of functional balancing tasks relevant to daily living. The subjects were motivated to participate in the training, as indicated by the high compliance (97.5%) with the program.

Aged↗
PubMed2026

Webcam-Based Real-Time Visual Feedback During Baduanjin Practice in Older Adults: 6-Week Pilot Randomized Study.

BACKGROUND: Baduanjin qigong is a traditional mind-body exercise used to support balance and physical health in older adults. Age-related changes in proprioception may make accurate self-directed performance difficult without external guidance. OBJECTIVE: The aim of this study is to explore whether webcam-based real-time visual feedback delivered during supervised laboratory sessions was associated with differences in webcam-derived 2D pose discrepancy and movement consistency during Baduanjin practice in older adults. METHODS: A total of 31 older adults were enrolled, and 28 participants with complete analyzable records were included in this complete-case dataset (feedback group, n=14; nonfeedback group, n=14). All sessions were conducted face-to-face in a supervised motion-analysis laboratory. Weekly 2D pose-discrepancy values were analyzed using a linear mixed-effects model with fixed effects for group, categorical week, and the group-by-week interaction and a participant-specific random intercept. Joint- and movement-specific participant-level 6-week means were analyzed exploratorily using Welch independent-samples t tests. Holm correction was applied across 24 exploratory contrasts (6 week-specific, 8 joint-specific, and 10 movement-specific comparisons), and Hedges g and 95% CIs were reported. Participant-specific weekly slopes and within-participant variability were additionally examined to directly assess longitudinal error drift. RESULTS: The linear mixed-effects model showed no significant group-by-week interaction (Wald &#x3c7;25=1.09; P=.96) and no significant overall week effect (Wald &#x3c7;25=6.40; P=.27). Averaged across 6 weeks, the feedback group had an estimated mean 2D pose discrepancy 1.20&#xb0; lower than the nonfeedback group (95% CI -2.38&#xb0; to -0.02&#xb0;; P=.046), although this marginal pilot finding was sensitive to an analytic approach. No week-specific contrast remained significant after Holm adjustment. Nominal right elbow, right shoulder, and right knee differences did not survive global Holm correction. Form 3 showed a lower mean discrepancy in the feedback group (mean difference -3.70&#xb0;, 95% CI -5.86&#xb0; to -1.54&#xb0;; Hedges g=-1.30; unadjusted P=.002; Holm-adjusted P=.04). Direct analyses of participant-specific slopes and within-participant SDs did not support a significant between-group difference in longitudinal error drift. CONCLUSIONS: In this small exploratory pilot study conducted under supervised laboratory conditions, the 6-week trajectories did not differ significantly between groups. A marginally lower average 2D pose discrepancy was observed in the feedback group across the 6 weeks, but no individual week- or joint-specific comparison remained significant after multiplicity adjustment. Form 3 was the only exploratory contrast that remained significant after global Holm correction. Direct longitudinal analyses did not demonstrate prevention of error drift. Larger studies using validated reference measurements, prespecified outcomes, and adequately powered longitudinal designs are required.

Humans↗
PubMed2004

Optimising the visual feedback technique for improving upright stance maintenance by delaying its display: behavioural effects on healthy adults.

The visual feedback technique (VFB) is recognized by several studies as a valuable tool for re-establishing the balance functions. However, one former study has highlighted the fact that the increased control induced by this technique infer both favourable (the amplitudes of the horizontal motions of the centre of gravity (CoG(h)) are diminished) and unfavourable features (the vertical difference between the CoG(h) motions and centre of pressure (CoP) trajectories are enhanced). One means to decrease these CoP-CoG(v) motions is to delay their display on the screen of the monitor. To assess these behavioural effects, 16 healthy adults were evaluated with various delays from 0 to 1200 ms. CoP displacements, measured through a force platform, were decomposed into two elementary motions: CoG(h) and the difference CoP-CoG(v). A fractional Brownian motion modelling of these motions allowed to determine from which distance and for how long the corrective process takes over and to what extent the motion is controlled. Compared to the VFB real time condition, increasing the delay induces some effects mainly on the CoP-CoG(v) motions which are largely diminished, the most striking effect appearing for delays exceeding 600 ms. Despite the lower forces these reduced amplitudes infer to control body sways, the amplitudes of the CoG(h) motions tend to increase slightly. Considered as a whole, whilst retaining the beneficial aspects of VFB without delay and significantly suppressing the unfavourable features, the data suggests that the method of delaying the screen display optimises the VFB technique.

Adult↗
PubMed1983

Comparison of auditory and visual feedback for EMG training.

27 undergraduate students participated in an experiment on EMG biofeedback. Three groups were employed (visual feedback, audio biofeedback, and control) to determine which group learned to reduce frontalis muscle tension more quickly. All subjects were trained during a 30-min. period for five days. The time consisted of a 10-min. baseline and a 20-min. biofeedback session. Over a 5-day period relaxation in the forehead due to biofeedback improved significantly. More training time yielded an increased relaxation in this area, and most learning occurred during the first two days. The significant interaction of training and time illustrated that the two biofeedback groups produced a more pronounced relaxation in the forehead muscle than did the control group. No significant difference was found between the two biofeedback groups.

Adolescent↗
PubMed1992

Oculo-manual coordination control: ocular and manual tracking of visual targets with delayed visual feedback of the hand motion.

The aim of this study was to examine coordination control in eye and hand tracking of visual targets. We studied eye tracking of a self-moved target, and simultaneous eye and hand tracking of an external visual target moving horizontally on a screen. Predictive features of eye-hand coordination control were studied by introducing a delay (0 to 450 ms) between the Subject's (S's) hand motion and the motion of the hand-driven target on the screen. In self-moved target tracking with artificial delay, the eyes started to move in response to arm movement while the visual target was still motionless, that is before any retinal slip had been produced. The signal likely to trigger smooth pursuit in that condition must be derived from non-visual information. Candidates are efference copy and afferent signals from arm motion. When tracking an external target with the eyes and the hand, in a condition where a delay was introduced in the visual feedback loop of the hand, the Ss anticipated with the arm the movement of the target in order to compensate the delay. After a short tracking period, Ss were able to track with a low lag, or eventually to create a lead between the hand and the target. This was observed if the delay was less than 250-300 ms. For larger delays, the hand lagged the target by 250-300 ms. Ss did not completely compensate the delay and did not, on the average, correct for sudden changes in movement of the target (at the direction reversal of the trajectory). Conversely, in the whole range of studied delays (0-450 ms), the eyes were always in phase with the visual target (except during the first part of the first cycle of the movement, as seen previously). These findings are discussed in relation to a scheme in which both predictive (dynamic nature of the motion) and coordination (eye and hand movement system interactive signals) controls are included.

Adult↗
PubMed2003

Odor localization requires visual feedback during free flight in Drosophila melanogaster.

Adult fruit flies follow attractive odors associated with food and oviposition sites through widely varied visual landscapes. To examine the interaction between olfactory and visual cues during search behavior, we recorded three-dimensional flight trajectories as individuals explored controlled sensory landscapes. When presented with the source of an attractive odor invisibly embedded in the floor of a 1 m arena, flies spend most of their time hovering back and forth over the source when flying within a randomly textured visual background but fail to localize the source when searching within a uniform white surround. To test whether flies are associating unique features of the visual background with the strength of odor cues, we flew them within arenas containing evenly spaced vertical stripes. Flies readily localized the odor when flying within visual landscapes lacking azimuthal landmarks provided that vertical edges were present. Flies failed to localize odor when flying within a background pattern consisting of horizontal stripes. These results suggest that, whereas flies do not require spatially unique visual patterns to localize an odor source, they do require visual feedback generated by vertical edges. Quantitative shifts in several components of flight behavior accompanied successful odor localization. Flies decrease flight altitude, turn more often and approach visually textured walls of the arena near an odor source. A simple model based on the statistics of flight behavior supports the hypothesis that a subtle influence on these behaviors is sufficient to lead a fly to its food.

Animals↗
PubMed1975

The use of visual feedback in establishing normal vocal intensity in two mildly retarded adults.

A voice-activated relay was used to provide visual feedback of vocal amplitude for two subjects who habitually used very soft voices. The relay system caused a light to go on when vocal intensity was 65 dB SPL or greater. Both subjects demonstrated significant increases in their use of normal vocal intensity. One subject was able to transfer this progress to spontaneous conversational settings. Though some difficulties in generalization and automatization were evident, this system is recommended for use with persons exhibiting functional intensity deficiences.

Adult↗
PubMed2005

Balance training with visual feedback in children with hemiplegic cerebral palsy: effect on stance and gait.

The aim of the present study was to examine the effects of balance training with visual feedback on stance and gait in school-age children with hemiplegic cerebral palsy. Ten participants between 5 and 11 years of age were assigned to either the training or the control group according to an aged-stratified randomization. The training corresponded to three sessions per week during six weeks. Stance and gait parameters- based on force plate data, were assessed three times in both groups: (a) at the beginning of the study (before training); (b) after six weeks; (c) after ten weeks. Spatial and temporal parameters were calculated. The results for stance showed that the training improved the performances on the tasks that were trained. More interesting, the results for gait showed that the walking pattern became more symmetrical after the training.

Cerebral Palsy↗