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PubMed2005

The influence of visual feedback on closed-set word test performance over time.

Closed-set word tests can be implemented with or without trial-by-trial visual feedback. Feedback is considered to increase subject motivation yet its influence on performance is unknown. The aim of this study was to compare performance on the Four Alternative Auditory Feature (FAAF) test with and without visual feedback over a 24-week period following fitting of a hearing aid. A total of 32 elderly subjects were recruited as new users and fitted monaurally with the same model of linear, programmable hearing aid that provided in excess of 20 dB insertion gain at 2-4 kHz. Half of the subjects were provided with visual feedback. In these subjects, mean performance increased by 5% across the study period. The improvement in performance over time was statistically significant on analysis of variance (p < 0.05). Mean performance did not increase in the remaining subjects who were not provided with feedback. If closed-set word tests are to be used with visual feedback to measure changes over time, the potentially confounding effects of practice must be controlled carefully. Alternatively, omitting feedback leads to simpler experimental designs.

Aged↗

PubMed1981

Influence of the visual feedback for some parameters of the body oscillations on their stability.

In accordance with the hypothesis that in addition to the generalized information from the visual feedback about the body oscillations, the information from the different parameters of the oscillations may also play a stabilizing role for the vertical posture of the body and its balance, studies were carried out on the influence of the parameters of body position, velocity of the body oscillations and accelerations on body stability. The results have shown that the visual feedback about the position of the body and about the velocity of the oscillations leads to stabilization of its balance. Visual feedback about the accelerations of the body oscillations also has a stabilizing action on the vertical posture and equilibrium. Its influence did not prove greater than the visual feedback about the velocity of body oscillations. Repeated recordings of the body oscillations under the experimental conditions manifested a slight initial training effect, expressed in a decrease of the total way of the body oscillations.

Biofeedback, Psychology↗

PubMed2004

Measures of accuracy for active shoulder movements at 3 different speeds with kinesthetic and visual feedback.

STUDY DESIGN: Repeated-measures experiment. OBJECTIVE: To compare measures of end point accuracy (EPA) for 2 feedback conditions: (1) visual and kinesthetic feedback and (2) kinesthetic feedback alone, during shoulder movements, at 3 different speeds. BACKGROUND: Shoulder joint kinesthesia is typically reported with EPA measures, such as constant error. Reporting multiple measures of EPA, such as variable error and absolute error, could provide a more detailed description of performance. METHODS AND MEASURES: Subjects were seated with the shoulder abducted 90 degrees in the scapular plane and externally rotated 75 degrees, with the forearm placed in a custom shoulder wheel. Subjects internally rotated the shoulder 27 degrees to a target position at 48 degrees of shoulder external rotation for both conditions. Motion analysis was used to determine peak angular velocity and 3 EPA measures for shoulder movements. Each EPA measure was compared between the 2 feedback conditions and among the 3 speeds with a separate 2-way analysis of variance. RESULTS: Movements performed with kinesthetic feedback alone, measured by constant error (P<.01), variable error (P<.01), and absolute error (P<.01), were less accurate than movements performed with visual and kinesthetic feedback. Faster movements were less accurate when measured by constant error (P = .01) and absolute error (P<.01) than slower movements. Subjects tended to overshoot the target in the absence of visual feedback; however, movement speed played minimal role in the overshooting. CONCLUSIONS: Multiple measures of EPA, such as constant, variable, and absolute error during simple restricted shoulder movements may provide additional information regarding the evaluation of a motor performance or identify different central nervous system control mechanisms for joint kinesthesia.

Adult↗

PubMed1981

Processing visual feedback information for movement control.

The time needed to process visual feedback information for the control of aimed movements was investigated. Experiment 1 demonstrated that withdrawing visual feedback information from the initial portions of aiming responses had little effect on movement outcome. This finding suggested that visual processing times may be faster than previous estimates. The vision manipulation paradigm employed in Experiment 1 was combined with high-speed cinematography. Examination of movement patterns indicated that the average time between the presentation of visual error information and the initiation of a movement correction was 135 msec. The findings from these two experiments support the contention that the time needed to process visual error information and to use this information for movement control is shorter than previous estimates of 190 to 300 msec.

Discrimination Learning↗

PubMed1983

Rapid visual feedback processing in single-aiming movements.

A major line of behavioral support for motor-program theory derives from evidence indicating that feedback does not influence the execution and control of limited duration movements. Since feedback cannot be utilized, the motor-program is assumed to act as the controlling agent. in a classic study, Keele and Posner observed that visual feedback had no effect on the accuracy of 190-msec single-aiming movements. Therefore visual feedback processing time is greater than 190 msec, and, more importantly, limited duration movements are governed by motor programs. In the present paper, we observed that visual feedback can affect the spatial accuracy of movement with durations much less than 190 msec. We hypothesize that visual feedback can aid motor control via processes not associated with intermittent error corrections.

Journal Article↗

PubMed1994

Partial visual feedback and spatial end-point accuracy of discrete aiming movements.

Five experiments are reported in which the effect of partial visual feedback on the accuracy of discrete target aiming was investigated. Visual feedback was manipulated through a spectacle-mounted liquid-crystal tachistoscope. The length of the visual feedback interval was varied as a percentage of the instructed movement time. In Experiment 1, the length of the vision interval was manipulated symmetrically at the beginning- and end-phase of the movement, whereas in the remaining experiments, the vision time was varied with respect to the end-phase only. The variations at the end were examined for different distances (Experiment 2), different movement speeds at the same distance (Experiment 3), and in small interstep intervals (Experiment 4). A vision time of more than 150 ms at the end-phase of the movement enhanced aiming performance in all experiments. Longer vision times monotonously improved aiming accuracy; the fifth experiment showed that a vision time of about 275 ms was sufficient for near-perfect aiming. Furthermore, the significance of vision during the first phase of a movement was demonstrated again. The results of the five experiments pointed to shorter visuomotor processing times. To explain the beneficial effects of short vision times for aiming accuracy, we propose a model of visuomotor processing that is based on the stochastic optimized submovement model of Meyer, Abrams, Kornblum, Wright, and Smith (1988).

Journal Article↗

PubMed2001

Increased response to visual feedback of drug-induced dyskinetic movements in advanced Parkinson's disease.

To investigate the response to visual feedback of involuntary movements which have a frequency composition similar to cerebellar tremor but are not caused by cerebellar damage, we have tested six advanced Parkinson's disease (PD) patients with drug-induced dyskinetic movements using visually guided wrist tracking tasks. Tracking performance was assessed under three visual conditions: (1) both guiding target and movement cursor were displayed continuously; (2) the target display was turned off for the second half of each trial; or (3) the cursor display, but not the target, was turned off for the second half of each trial. The response to visual feedback of drug-induced dyskinetic movements at 1-5 Hz in these advanced PD patients were significantly increased than in normal controls. This suggests that increased response to visual feedback might be a common feature of low frequency involuntary movements and not directly caused by cerebellar damages.

Aged↗

PubMed2005

Visual feedback schedules influence visuomotor resistance to the Müller-Lyer figures.

We examined whether blocked or random visual feedback schedules influence visuomotor resistance to the Müller-Lyer (ML) illusion. Participants completed closed-loop (CL) and open-loop (OL) grasping movements to an object embedded within fins-in and fins-out ML configurations. In the blocked feedback schedule, CL and OL trials were completed in separate blocks of trials, whereas visual conditions were randomly interleaved in the random feedback schedule. The results of the blocked feedback schedule showed that OL, but not CL, trials were influenced in a direction consistent with the perceptual effects of the ML illusion. For the random feedback schedule, however, both CL and OL trials were influenced by the illusion. We have interpreted these results to reflect the fact that participants evoked distinct control strategies based on the predicted availability of visual feedback. Specifically, the refractory nature of CL trials in the blocked feedback schedule suggests that advance knowledge that visual feedback would be available during a response encouraged an online control strategy wherein metrical visual information supported grasping. When visual feedback was unavailable (i.e., blocked OL trials), or could not be predicted in advance of a response (i.e., random CL and OL trials), it is proposed that movements were structured offline via perception-based visual information that was "tricked" by the cognitive properties of the ML illusion.

Feedback↗

PubMed2006

The occluded onset pursuit paradigm: prolonging anticipatory smooth pursuit in the absence of visual feedback.

Humans can produce anticipatory smooth pursuit (ASP) for a few hundred ms prior to the appearance of a moving target. Once visual feedback is available, however, it is difficult to distinguish ASP from the visually-driven response with which it merges. Here we have developed a paradigm that extends the anticipatory period to show unequivocally how ASP can evolve over periods of up to 600 ms before being influenced by visual feedback. ASP was evoked by repeated presentation of constant velocity (ramp) stimuli preceded by auditory cues. The target was occluded during the initial part of the ramp, so that when it became visible it had already moved to an eccentric position. The occlusion period (T occ) varied from 0 to 500 ms in 100 ms increments; for each period ramps were presented in blocks of 8 with velocity held constant at 8, 16, 24 or 32 degrees/s. Eye displacement trajectories showed that subjects attempted to match the unseen target trajectory with a mixture of saccades and smooth pursuit. The smooth component was initiated progressively earlier in relation to target appearance as T occ increased, leading to progressively higher ASP gains by the time the target became visible. This prolongation of ASP throughout the occlusion period reveals the underlying internal drive that produces it, a drive that under normal circumstances quickly becomes masked by visual feedback.

Cues↗

PubMed1990

Effects of delayed visual feedback on motor control performance.

The effects of delay of visual feedback on two kinds of sensorimotor tasks were investigated. On the reciprocal tapping task, accuracy of performance decreased for 200, 500, and 767 msec. delay. The number of errors for the 1000-msec. delay is smaller than those for the other three conditions of delay. On the hand-writing task of both Kanji letters and English words, performance showed a large decrement with increasing delay. The most frequent kinds of error were the type of insertion of line elements or letter duplication. It was interesting that the size of written letters increased with lengthening delays of visual feedback.

Attention↗

PubMed2003

Internal vs external generation of movements: differential neural pathways involved in bimanual coordination performed in the presence or absence of augmented visual feedback.

It is commonly agreed that a functional dissociation with respect to the internal vs external control of movements exists for several brain regions. This has, however, only been tested in relation to the timing and preparation of motor responses, but not to ongoing movement control. Using functional magnetic resonance imaging (fMRI), the present study addressed the neuroanatomical substrate of the internal-external control hypothesis by comparing regional brain activation for cyclical bimanual movements performed in the presence or absence of augmented visual feedback. Subjects performed a bimanual movement pattern, either with the help of on-line visual feedback of the movements (externally guided coordination) or with the eyes closed on the basis of an internal representation of the movement pattern (internally generated coordination). Visual control and baseline rest conditions were also added. Results showed a clear functional dissociation within the network involved in movement coordination. The hMT/V5+, the superior parietal cortex, the premotor cortex, the thalamus, and cerebellar lobule VI showed higher activation levels when movements were guided by visual feedback. Conversely, the basal ganglia, the supplementary motor area, cingulate motor cortex, the inferior parietal, frontal operculum, and cerebellar lobule IV-V/dentate nucleus showed higher involvement when movements were internally generated. Consequently, the present findings suggest the existence of distinct cortico-cortical and subcortico-cortical neural pathways for externally (augmented feedback) and internally guided cyclical bimanual movements. This provides a neurophysiological account for the beneficial effect of providing augmented visual feedback to optimize movements in normal and motor disordered patients.

Adult↗

PubMed2006

Effects of visual feedback on manipulation performance and patient ratings.

OBJECTIVE: This study examined the explicit targeted outcome (a criterion standard) and visual feedback on the immediate change in and the short-term retention of performance by novice operators for a high-velocity, low-amplitude procedure under realistic conditions. METHODS: This study used a single-blind randomized experimental design. Forty healthy male (n = 26) and female (n = 14) chiropractic student volunteers with no formal training in spinal manipulative therapy participated. Biomechanical parameters of an L4 mammillary push spinal manipulation procedure performed by novice operators were quantified. Participants were randomly assigned to 2 groups and paired. One group received visual feedback from load-time histories of their performance compared with a criterion standard before a repeat performance. Participants then performed a 10-minute distractive exercise consisting of National Board of Chiropractic Examiners review questions. The second group received no feedback. An independent rating of performance was conducted for each participant by his/her partner. Results were analyzed separately for biomechanical parameters for partner ratings using the Student t test with levels of significance (P < .01) adjusted for repeated testing. RESULTS: Expressed in percent change for each individual, visual feedback was associated with change in the biomechanical performance of group 2, a minimum of 14% and a maximum of 32%. Statistical analysis rating of the performance favored the feedback group on 4 of the parameters (fast, P < .0008; force, P < .0056; precision, P < .0034; and composite, P < .0016). CONCLUSION: Quantitative feedback, based on a tangible conceptualization of the target performance, resulted in immediate and significant improvement in all measured parameters. Newly developed skills were retained at least over short intervals even after distractive tasks. Learning what to do with feedback on one's own performance may be more important than the classic teaching of how to do it.

Adult↗

PubMed2006

Corrective movements in response to displacements in visual feedback are more effective during periods of 13-35 Hz oscillatory synchrony in the human corticospinal system.

Oscillatory synchronization in the beta (approximately 20 Hz) band is a common feature of human motor control, manifest at cortical and muscular levels during tonic contraction. Here we test the hypothesis that the influence of visual feedback on performance in a positional hold task is increased during bursts of beta-band synchrony in the corticospinal motor system. Healthy subjects were instructed to extend their forefinger while receiving high-gain visual feedback of finger position on a PC screen. Small step displacements of the feedback signal were triggered either by bursts of beta oscillations in scalp electroencephalogram or randomly with respect to cortical beta activity, and the resulting positional corrections expressed as a percentage of the step displacement. Corrective responses to beta and randomly triggered step changes in visual feedback were 41.7+/-4.9 and 31.5+/-6.8%, respectively (P<0.05). A marked increase in the coherence in the beta band was also found between muscle activity and cortical activity during the beta-triggered condition. The results suggest that phasic elevations of beta activity in the corticospinal motor system are associated with an increase in the gain of the motor response to visual feedback during a tonic hold task. Beta activity may index a motor state in which processing relevant to the control of positional hold tasks is promoted, with behavioural consequences.

Adult↗

PubMed1979

The use of visual feedback to control vocal intensity and nasalization.

A device which provides visual feedback of vocal intensity, nasalization, or a ratio of nasalization to vocal intensity, is described. The device was used in several experiments in which control of vocal intensity was a necessary component. Normal and hypernasal speakers were able to control their vocal intensities successfully when using the visual display. The display also was used in an experiment designed to determine how well normal speakers can manipulate their nasalization without visual feedback and whether they improve when feedback is provided. Subjects manipulated their nasalization first without feedback, then with feedback, then, again, without feedback. The subjects' performance improved when feedback was provided and determined when feedback was removed. It appears that this device is useful for many applications in a variety of settings.

Adult↗

PubMed2005

Visual feedback attenuates force fluctuations induced by a stressor.

PURPOSE: The fluctuations in force during a steady contraction can be influenced by age, vision, and level of physiological arousal. The aim of this study was to determine the effects of a stressor on the force fluctuations and information transmission exhibited by young, middle-aged, and older adults when a pinch-grip task was performed with and without visual feedback. METHODS: Thirty-six men and women (19-86 yr) participated in a protocol that comprised anticipatory (30 min), stressor (15 min), and recovery periods (25 min). The stressor was a series of noxious electrical stimuli applied to the dorsal surface of the left hand. Subjects sustained a pinch-grip force with the right hand at 2% of the maximal voluntary contraction force. The normalized fluctuations in pinch-grip force (coefficient of variation), information transmission (log2 signal:noise), and the spectra for the force were quantified across the 70-min protocol. RESULTS: Removal of visual feedback exacerbated the force fluctuations (3.83+/- 3.15 vs 2.82+/- 1.64%) and reduced the information transmission (5.01+/- 0.86 vs 5.34+/- 0.71 bits) only during the stressor period. The effect was similar for all age groups. Older adults exhibited greater force fluctuations and lower information transmission compared with young and middle-aged adults, especially during the stressor period. The impairments in fine motor performance during the stressor were associated with an enhancement of the power at 1-2 Hz in the force spectrum (R=0.41-0.52). CONCLUSION: Removal of visual feedback increased the force fluctuations and decreased information transmission during a stressor period, which suggests that integration of visual feedback can attenuate the stressor-induced enhancement of synaptic input received by the motor neuron pool.

Adaptation, Physiological↗

PubMed2004

Effects of visual feedback rhythmic weight-shift training on hemiplegic stroke patients.

OBJECTIVE: To assess the balance function of hemiplegic stroke patients and to investigate whether visual feedback rhythmic weight-shift training following acute stroke can decrease falls among patients with hemiplegic stroke. DESIGN: A prospective study, using a Balance Master. SETTING: Hospital-based rehabilitation units. SUBJECTS: Fifty-two hemiplegic stroke patients (28 in the training group and 24 in the control group). INTERVENTIONS: Conventional stroke rehabilitation programme plus visual feedback rhythmic weight-shift training. Training effect was evaluated by assessing the static and dynamic balance performance as well as comparing the occurrence of falls in the training and control groups at six-month follow-up. MAIN MEASURES: Occurrence of falls; static balance in different sensory conditions; and dynamic balance performance, including on-axis velocity and directional control during rhythmic weight-shift. RESULTS: Significant improvement in dynamic balance performance was found in hemiplegic patients in the training group. The improvement was sustained for six months. With regarding to static balance function, no significant improvement was found. At six-month follow-up, 5 of 28 patients (17.8%) in the training group had fallen, compared with 10 of 24 patients (41.7%) in the control group. The occurrence of falls decreased, although not statistically significantly (p=0.059). CONCLUSIONS: Visual feedback rhythmic weight-shift training may improve dynamic balance function for hemiplegic stroke patients. The effects of training may be sustained for six months. The occurrence of falls decreased in the training group, but not statistically significantly.

Accidental Falls↗

PubMed1989

Effects of a verbal and visual feedback system on running technique, perceived exertion and running economy in female novice runners.

The purpose of this study was to determine the effects of a verbal and visual feedback system on running technique, ratings of perceived exertion (RPE), and running economy. Twenty-two female novice runners were randomly assigned to experimental (n = 11) and control (n = 11) groups. The experimental subjects received verbal and visual feedback concerning their running technique prior to and during each training run. Training involved 15 20-min treadmill running sessions over a 5-week period. The control group adhered to the same training routine but did not receive feedback concerning their running technique. High-speed (100 Hz) photography was used to collect biomechanical data. A submaximal oxygen consumption test and Borg's RPE scale were used to collect data concerning running economy and perceived exertion, respectively. Statistical analysis using ANCOVA revealed that the proposed feedback system had a significant (P less than 0.01) effect on the experimental group's running technique by affecting the following desired changes relative to the control group: greater relative stride lengths, shorter support time, greater ankle dorsiflexion during support and greater knee flexion during support and non-support. There were no significant differences between the groups in submaximal VO2 or RPE. The results of this study suggest that verbal and visual feedback are effective means of eliciting modifications in running style in female novice runners. The link between modifications in running style and improvements in running economy and perceived exertion remains unclear.

Adolescent↗

PubMed1996

Delayed visual feedback while learning to track a moving target.

Two studies investigated the effects of delayed visual feedback on manual tracking. In Experiment 1, individuals practiced with visual feedback provided either immediately (0 delay) or with a 333-ms delay. During acquisition, the 0 delay group performed with less error than the 333-ms delay group. A retention test with 0 delay feedback was performed with the least error by the 0 delay group. A transfer test using a different 0 delay tracking pattern, was performed with the least error by the 333-ms delay group. In Experiment 2, individuals practiced at six different delays. Error increased as training feedback delay increased. For retention there were no differences between the delay groups during the 0 delay retention. At a 417-ms retention, test error decreased as training feedback delay increased. Results indicate that error during acquisition does not necessarily impair learning and that feedback delays can be beneficial for learning.

Analysis of Variance↗