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Results for “visual feedback”

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PubMed2000

Role of the cerebellar flocculus region in cancellation of the VOR during passive whole body rotation.

A series of studies were carried out to investigate the role of the cerebellar flocculus and ventral paraflocculus in the ability to voluntarily cancel the vestibuloocular reflex (VOR). Squirrel monkeys were trained to pursue moving visual targets and to fixate a head stationary or earth stationary target during passive whole body rotation (WBR). The firing behavior of 187 horizontal eye movement-related Purkinje (Pk) cells in the flocculus region was recorded during smooth pursuit eye movements and during WBR. Half of the Pk cells encountered were eye velocity Pk cells whose firing rates were related to eye movements during smooth pursuit and WBR. Their sensitivity to eye velocity during WBR was reduced when a visual target was not present, and their response to unpredictable steps in WBR was delayed by 80-100 ms, which suggests that eye movement sensitivity depended on visual feedback. They were insensitive to WBR when the VOR was canceled. The other half of the Purkinje cells encountered were sensitive to eye velocity during pursuit and to head velocity during VOR cancellation. They resembled the gaze velocity Pk cells previously described in rhesus monkeys. The head velocity signal tended to be less than half as large as the eye velocity-related signal and was observable at a short ( approximately 40 ms) latency when the head was unpredictably accelerated during ongoing VOR cancellation. Gaze and eye velocity type Pk cells were found to be intermixed throughout the ventral paraflocculus and flocculus. Most gaze velocity Pk cells (76%) were sensitive to ipsilateral eye and head velocity, but nearly half (48%) of the eye velocity Pk cells were sensitive to contralateral eye velocity. Thus the output of flocculus region is modified in two ways during cancellation of the VOR. Signals related to both ipsilateral and contralateral eye velocity are removed, and in approximately half of the cells a relatively weak head velocity signal is added. Unilateral injections of muscimol into the flocculus region had little effect on the gain of the VOR evoked either in the presence or absence of visual targets. However, ocular pursuit velocity and the ability to suppress the VOR by fixating a head stationary target were reduced by approximately 50%. These observations suggest that the flocculus region is an essential part of the neural substrate for both visual feedback-dependent and nonvisual mechanisms for canceling the VOR during passive head movements.

Action Potentials↗

PubMed2004

Initiation of rapid reach-and-grasp balance reactions: is a pre-formed visuospatial map used in controlling the initial arm trajectory?

In order to recover balance by grasping an object for support, the CNS must rapidly move the hand toward a specific target (handhold) in the environment. The early latency (80-140 ms) of these grasping reactions would seem to preclude a role for online visual feedback in the control of the initial limb movement; however, some studies have shown that vision can influence initiation of lower-limb postural reactions at similar latency. This study explored the role of vision in controlling the initial trajectory of grasping reactions triggered by sudden unpredictable medio-lateral platform translation. Healthy young adults were instructed to recover balance by grasping a marked section of a handrail, located to their right. To reinforce a dependence on arm reactions, movement of the feet was prevented by barriers. Liquid-crystal goggles were used to occlude vision during response initiation (200 ms interval starting at perturbation onset, PO). Results showed that the initial grasping trajectory (first 100 ms) and associated muscle activation were heavily modulated to take into account the direction and speed of the perturbation-induced body motion in relation to the handrail. This modulation was unaffected by occlusion of vision at PO, indicating that information about the rail location obtained prior to PO was incorporated into the control. These findings are consistent with the view that the CNS tunes the initial arm trajectory by combining an egocentric spatial map, formed prior to PO, with online feedback about the body motion from non-visual inputs (somatosensory and/or vestibular). This prevents potential delays associated with visual processing and ensures very rapid onset of arm movement that is directed appropriately even though the position of the body is perturbed unpredictably with respect to the target.

Adult↗

PubMed1987

The psychological impact of diagnostic ultrasound.

The psychological impact of ultrasound scanning in pregnancy was examined in low- and high-risk pregnancies. Women in each category were assigned consecutively to a condition of either low or high feedback. In the latter condition, the women received extensive verbal and visual feedback, whereas in the former, subjects were denied visual access to the monitor. Psychological changes were measured using the State Anxiety Inventory and the Subjective Stress Scale. When a male partner attended, he was included in the assessment. The emotional impact of ultrasound was influenced by the level of feedback provided, with those in the high-feedback condition indicating significantly less anxiety and more positive emotional experiences during the scan, compared with those who received less feedback.

Adult↗

PubMed2006

Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: a prospective interventional study.

AIMS: To compare quality of CPR during out-of-hospital cardiac arrest with and without automated feedback. MATERIALS AND METHODS: Consecutive adult, out-of-hospital cardiac arrests of all causes were studied. One hundred and seventy-six episodes (March 2002-October 2003) without feedback were compared to 108 episodes (October 2003-September 2004) where automatic feedback on CPR was given. Automated verbal and visual feedback was based on measured quality with a prototype defibrillator. Quality of CPR was the main outcome measure and survival was reported as specified in the protocol. RESULTS: Average compression depth increased from (mean +/- S.D.) 34 +/- 9 to 38 +/- 6 mm (mean difference (95% CI) 4 (2, 6), P < 0.001), and median percentage of compressions with adequate depth (38-51 mm) increased from 24% to 53% (P < 0.001, Mann-Whitney U-test) with feedback. Mean compression rate decreased from 121 +/- 18 to 109 +/- 12 min(-1) (difference -12 (-16, -9), P = 0.001). There were no changes in the mean number of ventilations per minute; 11 +/- 5 min(-1) versus 11 +/- 4 min(-1) (difference 0 (-1, 1), P = 0.8) or the fraction of time without chest compressions; 0.48 +/- 0.18 versus 0.45 +/- 0.17 (difference -0.03 (-0.08, 0.01), P = 0.08). With intention to treat analysis 7/241 control patients were discharged alive (2.9%) versus 5/117 with feedback (4.3%) (OR 1.5 (95% CI; 0.8, 3), P = 0.2). In a logistic regression analysis of all cases, witnessed arrest (OR 4.2 (95% CI; 1.6, 11), P = 0.004) and average compression depth (per mm increase) (OR 1.05 (95% CI; 1.01, 1.09), P = 0.02) were associated with rate of hospital admission. CONCLUSIONS: Automatic feedback improved CPR quality in this prospective non-randomised study of out-of-hospital cardiac arrest. Increased compression depth was associated with increased short-term survival. TRIAL REGISTRATION: ClinicalTrials.gov (NCT00138996), http://www.clinicaltrials.gov/.

Aged↗

PubMed1996

[Age dependence of the interaction between proprioception and vision--a posturographic study].

BACKGROUND: The influence of fixation on the vestibulo-ocular reflex and the synergistic stabilising effect of vision on the body equilibrium are well known. In this study interactions between the visual and the proprioceptive systems in patients of different ages are analysed. We tried to find out whether body equilibrium reactions, recorded by posturography, are influenced qualitatively and quantitatively by visual inputs. METHODS AND PATIENTS: 349 neurotologic patients aged between 3 and 80 years were included in this study. We applied different optical patterns by means of a videoscreen to the patients standing on a posturographic platform. The patients were asked to follow the pattern with their centre of the gravity, which was also shown on the video screen. The patterns consisted of a line that had to be followed in the anterior-posterior and in the lateral plane and of a circle which had to be followed clockwise and counterclockwise. RESULTS: We recognised definite age-related changes in all tests used. The precision to follow a visual target with the body equilibrium increased with increasing age to the age of forty. With the beginning fifth decade this postural ability decreases slowly and decreases particularly markedly in patients of over 70 years of age. CONCLUSIONS: Posturography in combination with visual feedback is a valuable technique for testing visual-proprioceptive interactions. It can be employed over a large age bracket.

Adolescent↗

PubMedDate not supplied

Posterior cingulate cortex: sensory and oculomotor properties of single neurons in behaving cat.

The posterior cingulate cortex of the cat is strongly linked to cortical areas with sensory and oculomotor functions. We have now recorded from feline posterior cingulate neurons in order to determine whether they are active in conjunction with sensory events and eye movements. The results described here are based on monitoring the electrical activity of 195 single neurons in the posterior cingulate cortex of three cats equipped with surgically implanted scleral search coils and trained to fixate visual targets. Posterior cingulate neurons carry tonic orbital position signals and are phasically active in conjunction with saccadic eye movements. Activity related to eye movements and gaze is attenuated but not abolished by the elimination of visual feedback. Posterior cingulate neurons also are responsive to visual, auditory, and somatosensory stimulation. Systematic testing with visual stimuli revealed that responses are sharply reduced due to refractoriness at rates of stimulation greater than a few per second. These results conform to the theory that posterior cingulate cortex is involved in processes underlying visuospatial cognition.

Acoustic Stimulation↗

PubMed2005

Adaptation to separate kinematic and dynamic transformations in children and adults.

The question addressed in the present study is whether children and adults are able to combine and decompose separate kinematic (visual-feedback-shift) and dynamic (velocity-dependent force) transformations in goal-directed arm movements. A total of 64 participants (32 adults and 32 children) performed horizontal forearm movements using a single-joint arm manipulandum. When participants first learned kinematic and dynamic transformations separately, target error decreased in a subsequent combined transformation task. This effect was based on previous learning of the kinematic transformation. When they first learned the combined transformation, target error was smaller in the following kinematic-but not in the dynamic-transformation. No difference was found in adaptation performance between children and adults. The results suggest that there are two separate models for the kinematic and dynamic transformation and that a possible differentiation of kinematic and dynamic features of the motor task might already be present at age 11.

Adaptation, Physiological↗

PubMed1995

[A case of pure alexia whose writing ability with eyes closed was superior to that with eyes open].

We compared the writing ability between eyes open (looking at one's writing) and eyes closed (without looking) in a case of pure alexia. The patient is a 84-year-old right handed man who developed pure alexia following an infarction in the distribution of the left posterior cerebral artery. He showed right homonymous hemianopsia, slight memory disorder and slight anomia. He could not read any kinds of letters and words at all though he could categorize letters: Kana (phonograms), Kanji (morphograms) and Arabic numbers, and he could distinguish the real letters from false ones. He could achieve almost 60-70% of Kana and Kanji dictation, though it was not perfect. He was often confused and could not continue writing correct letters once interrupted. He wrote poorly when looking at what he was writing. So we compared the ability of dictation with his eyes closed, and that with his eyes open. We found the former way never caused confusion and got better results, which was statistically significant (Fisher's exact test (p < 0.05)). It seemed that his visual feedback of his own writing rather caused trouble in his writing. Thus we concluded that input (reading) process and output (writing) process work simultaneously and bi-directionally. Slight impairment of writing in pure alexia patients might be caused by the effect of impairment of input (reading) process, which is simultaneously connected with the output (writing) process.

Aged↗

PubMed1998

Computer assistance in arthroscopic anterior cruciate ligament reconstruction.

Accurate placement of the graft is considered one of the most important factors in anterior cruciate ligament surgery. However, reconstruction with contemporary guiding systems still can result in unacceptable graft placement variability. To improve the reproducibility of graft placement, intraoperative visual feedback was added to the arthroscopic technique. First, fluoroscopic visualization was added to evaluate guidewire placement before tunnel drilling. Second, computer graphic overlays were added to the fluoroscopic view. Three groups of patients were treated: 29 patients with arthroscopy, 53 patients with fluoroscopy added, and 50 patients with computer overlays added. Graft placement variability was reduced significantly with fluoroscopic visualization. Computer overlays resulted in additional significant reductions in graft placement variability. Simple visual enhancements seem to be useful in improving the accuracy of arthroscopic anterior cruciate ligament reconstruction.

Anterior Cruciate Ligament↗

PubMed2006

Event-related fMRI of category learning: differences in classification and feedback networks.

Eighteen healthy young adults underwent event-related (ER) functional magnetic resonance imaging (fMRI) of the brain while performing a visual category learning task. The specific category learning task required subjects to extract the rules that guide classification of quasi-random patterns of dots into categories. Following each classification choice, visual feedback was presented. The average hemodynamic response was calculated across the eighteen subjects to identify the separate networks associated with both classification and feedback. Random-effects analyses identified the different networks implicated during the classification and feedback phases of each trial. The regions included prefrontal cortex, frontal eye fields, supplementary motor and eye fields, thalamus, caudate, superior and inferior parietal lobules, and areas within visual cortex. The differences between classification and feedback were identified as (i) overall higher volumes and signal intensities during classification as compared to feedback, (ii) involvement of the thalamus and superior parietal regions during the classification phase of each trial, and (iii) differential involvement of the caudate head during feedback. The effects of learning were then evaluated for both classification and feedback. Early in learning, subjects showed increased activation in the hippocampal regions during classification and activation in the heads of the caudate nuclei during the corresponding feedback phases. The findings suggest that early stages of prototype-distortion learning are characterized by networks previously associated with strategies of explicit memory and hypothesis testing. However as learning progresses the networks change. This finding suggests that the cognitive strategies also change during prototype-distortion learning.

Brain↗

PubMed1985

Differences between visually triggered human forearm movements with visual and auditory relevant feedback.

The effects of visual and auditory relevant feedback on human forearm movements elicited by random position signal sequences were examined. Forearm movements were performed with four feedback conditions. We observed the reaction time, the holding time, and the adjustment error sequences when the arm moved briskly and accurately to the target position. As the results, the reaction times for auditory relevant feedback were shorter than those for the others (visual or no feedback). The holding times for auditory relevant feedback were longer than those for the others. And the subjects had about one adjustment error to terminate on the target zone.

Acoustic Stimulation↗

PubMed2003

System identification applied to a visuomotor task: near-optimal human performance in a noisy changing task.

Sensory-motor integration has frequently been studied using a single-step change in a control variable such as prismatic lens angle and has revealed human visuomotor adaptation to often be partial and inefficient. We propose that the changes occurring in everyday life are better represented as the accumulation of many smaller perturbations contaminated by measurement noise. We have therefore tested human performance to random walk variations in the visual feedback of hand movements during a pointing task. Subjects made discrete targeted pointing movements to a visual target and received terminal feedback via a cursor the position of which was offset from the actual movement endpoint by a random walk element and a random observation element. By applying ideal observer analysis, which for this task compares human performance against that of a Kalman filter, we show that the subjects' performance was highly efficient with Fisher efficiencies reaching 73%. We then used system identification techniques to characterize the control strategy used. A "modified" delta-rule algorithm best modeled the human data, which suggests that they estimated the random walk perturbation of feedback in this task using an exponential weighting of recent errors. The time constant of the exponential weighting of the best-fitting model varied with the rate of random walk drift. Because human efficiency levels were high and did not vary greatly across three levels of observation noise, these results suggest that the algorithm the subjects used exponentially weighted recent errors with a weighting that varied with the level of drift in the task to maintain efficient performance.

Adult↗

PubMed2005

Differential influence of vision and proprioception on control of movement distance.

The purpose of this study was to investigate the contribution of proprioceptive and visual information about initial limb position in controlling the distance of rapid, single-joint reaching movements. Using a virtual reality environment, we systematically changed the relationship between actual and visually displayed hand position as subjects' positioned a cursor within a start circle. No visual feedback was given during the movement. Subjects reached two visual targets (115 and 125 degrees elbow angle) from four start locations (90, 95, 100, and 105 degrees elbow angle) under four mismatch conditions (0, 5, 10, or 15 degrees). A 2 x 4 x 4 ANOVA enabled us to ask whether the subjects controlled the movement distance in accord with the virtual, or the actual hand location. Our results indicate that the movement distance was mainly controlled according to the virtual start location. Whereas distance modification was most extensive for the closer target, analysis of acceleration profiles revealed that, regardless of target position, visual information about start location determined the initial peak in tangential hand acceleration. Peak acceleration scaled with peak velocity and movement distance, a phenomenon termed "pulse-height" control. In contrast, proprioceptive information about actual hand location determined the duration of acceleration, which also scaled with peak velocity and movement distance, a phenomenon termed "pulse-width" control. Because pulse-height and pulse-width mechanisms reflect movement planning and sensory-based corrective processes, respectively, our current findings indicate that vision is used primarily for planning movement distance, while proprioception is used primarily for online corrections during rapid, unseen movements toward visual targets.

Adult↗

PubMed1999

Prism adaptation to dynamic events.

In the present study, we explored adaptation to prism-displaced dynamic and static events under conditions of minimal information. Many of our interactions with the world are dynamic and involve reaching for or intercepting moving objects. The consequences (or feedback) of those interactions entail the presence or absence of physical contact with the moving objects. In this study, humans learned, with only heptic feedback, to intercept optically displaced falling balls. To eliminate visual feedback, the falling balls disappeared behind an occluder (which systematically varied in size across groups) prior to either striking or missing a subject's hand. As occluder size decreased, adaptation increased. With minimum occluder sizes, the greatest adaptation occurred around the training position, and adaptation decreased as distance between training and testing positions increased. The results can best be described in terms of a generalization gradient centered around the training position. This generalization gradient was not present when subjects were trained with ecologically similar static arrays. Implications for models of adaptation are discussed.

Adult↗

PubMed2006

Activation of insular cortex and subcortical regions related to feedback stimuli in a time estimation task: an fMRI study.

We used functional magnetic resonance imaging to investigate brain activity related to motivational function of informative feedback stimuli in a time estimation task. In that task, subjects pressed a button as a response 3 s after a cue stimulus; a visual feedback stimulus was presented 2 s after the response. In a true feedback condition, subjects received true information (informative feedback) about their time-estimation performance. In the false feedback condition, the same visual signs were used, but they were presented randomly. Therefore, they were not related to actual performance. In the 20 subjects examined, higher hemodynamic responses were identified in the insular cortex, the thalamus, and the striatum by comparing the true feedback condition to the false feedback condition. The time estimation performance and subjective score on motivation were also markedly higher in the true feedback condition. The anterior insular cortex and striatal regions are known to be involved in motivational and reward processing. Therefore, the hemodynamic responses observed in this study suggest that the motivational function of the feedback information is a crucial factor for behavioral learning; it is considered that the informative feedback might serve as an implicit reward for humans.

Brain↗

PubMed2001

Visual influences on the development and recovery of the vestibuloocular reflex in the chicken.

Whenever the head turns, the vestibuloocular reflex (VOR) produces compensatory eye movements to help stabilize the image of the visual world on the retina. Uncompensated slip of the visual world across the retina results in a gradual change in VOR gain to minimize the image motion. VOR gain changes naturally during normal development and during recovery from neuronal damage. We ask here whether visual slip is necessary for the development of the chicken VOR (as in other species) and whether it is required for the recovery of the VOR after hair cell loss and regeneration. In the first experiment, chickens were reared under stroboscopic illumination, which eliminated visual slip. The horizontal and vertical VORs (h- and vVORs) were measured at different ages and compared with those of chickens reared in normal light. Strobe-rearing prevented the normal development of both h- and vVORs. After 8 wk of strobe-rearing, 3 days of exposure to normal light caused the VORs to recover partially but not to normal values. In the second experiment, 1-wk-old chicks were treated with streptomycin, which destroys most vestibular hair cells and reduces hVOR gain to zero. In birds, vestibular hair cells regenerate so that after 8 wk in normal illumination they appear normal and hVOR gain returns to values that are normal for birds of that age. The treated birds in this study recovered in either normal or stroboscopic illumination. Their hVOR and vVOR and vestibulocollic reflexes (VCR) were measured and compared with those of untreated, age-matched controls at 8 wk posthatch, when hair cell regeneration is known to be complete. As in previous studies, the gain of the VOR decreased immediately to zero after streptomycin treatment. After 8 wk of recovery under normal light, the hVOR was normal, but vVOR gain was less than normal. After 8 wk of recovery under stroboscopic illumination, hVOR gain was less than normal at all frequencies. VCR recovery was not affected by the strobe environment. When streptomycin-treated, strobe-recovered birds were then placed in normal light for 2 days, hVOR gain returned to normal. Taken together, the results of these experiments suggest that continuous visual feedback can adjust VOR gain. In the absence of appropriate visual stimuli, however, there is a default VOR gain and phase to which birds recover or revert, regardless of age. Thus an 8-wk-old chicken raised in a strobe environment from hatch would have the same gain as a streptomycin-treated chicken that recovers in a strobe environment.

Aging↗

PubMedDate not supplied

Extrinsic feedback for motor learning after stroke: what is the evidence?

PURPOSE: There is little guidance on using extrinsic feedback to enhance motor learning after stroke. This narrative review synthesises research findings and identifies questions remaining to be answered. METHOD: A summary is given relating to the use of extrinsic feedback in healthy subjects. Then, research concerning content of feedback, feedback scheduling, and attentional focus is discussed in relation to patients with stroke. RESULTS: Though research is scarce, preliminary key findings were as follows: Patients' balance performance can improve from receiving visual feedback about weight distribution during practice; auditory feedback of force production may improve performance of sit-to-stand; providing feedback on less than 100% of trials, and giving summary or average feedback may enhance learning; instructions or feedback inducing an external focus may be more effective than those with an internal focus. Further research is needed concerning the relative benefits of verbal, visual, video and kinematic feedback; reduced feedback frequencies and summary feedback schedules; feedback delays, error estimation, and self-controlled feedback; and attentional focus of feedback. CONCLUSIONS: Although there are some indications that feedback might enhance motor learning after stroke, there are many areas as yet not examined and there is clearly a need for considerable research in this area.

Evidence-Based Medicine↗

PubMed1989

On the role of feedback in maintaining constant grip force in patients with cerebellar disease.

The effect of visual feedback on maintaining low finger forces was investigated in patients with chronic cerebellar disease. Precise information about deviation from target force was compared with discrete feedback signaling only 3 states of performance and a condition of withdrawal of feedback. Forces were produced under isometric conditions and against a spring load (anisometric condition). Large performance differences were observed dependent on feedback condition. Maintenance of anisometric force was found to be nearly normal in patients with severe deficits in controlling isometric force.

Biofeedback, Psychology↗