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PubMed2005

Visual kinesthesia and locomotion in Parkinson's disease.

We investigated predominance of visual control in Parkinson's disease (PD) gait regulation and whether visual kinesthesia has systematic effects on gait parameters. Effects of artificial optic flow were studied on walking velocity (WV), stride length (SL), and stride frequency (SF) during treadmill walking in PD patients and young and elderly adults. The independent variable was relative optic flow (rOF), ranging from -1 times (forward flow, i.e., in walking direction) to 3 times WV (backward flow, natural direction). All walkers were influenced similarly by rOF, inducing systematic changes of WV. Backward flow caused a decrease and forward flow an increase of WV. Without effect of rOF, PD patients on average walked at 0.89 meters per second compared to 1.31 meters per second in the age-matched healthy group. The rOF-induced mean changes of WV in all PD patients amounted to 0.45 meters per second (50.4%), with 45.1% due to changes in SL and 5.3% to SF. In the age-matched, rOF-induced WV changes reached 0.18 meters per second (13.8%), with 10.8% due to SL and 3.2% to SF. Thus, compared to the results of the age-matched group, effects of rOF in PD patients were stronger, which increased WV to a normal level by normalization of SL. Contrary to the healthy subjects, no attenuation of optic flow effects over time was observed in the PD patients. Predominance of visual control in PD gait is suggested due to deficits in proprioception compensated by visual kinesthesia, causing exaggerated reaction to visual feedback. The results extend beyond earlier findings, generally stating improvement of PD gait by presence of visual feedback but show systematic effects on gait parameters due to reweighting of visual kinesthesia.

Adaptation, Psychological↗
PubMed1980

A simplified mercury switch head-control biofeedback device.

A simplified mercury switch head-control device is reported. It is easily duplicated and amenable to quantitation. Advantages include simplicity and easy use at home, in school, or during therapy. Directionality of the feedback signal and visual feedback do not seem necessary to produce benefit. The results in six patients and two controls are consistent with other studies. This is the second study using mercury switches for feedback.

Adolescent↗
PubMed1995

The influence of external information on judgements of pain.

Two studies were performed to assess the relationship between estimates of subjective pain and a graduated ischemic pain stimulus. In the first, 20 subjects received a 7-minute pressure stimulus with a blood-pressure cuff and then rated their pain on a 0-5 scale. At three separate sessions, subjects saw either no feedback or a visual feedback slide that ostensibly depicted cuff pressure. The numbers were either accurate, too high, or too low. Subjective estimates of pain rose with increasing cuff pressure, but pain ratings were higher during high-feedback conditions, and lower during low-feedback conditions than during either the no- or true-feedback conditions, which did not differ. Study 2, which evaluated subjective estimates of actual cuff pressure as well as pain, replicated these results. Both studies suggest that false information may alter a subject's report of pain and of the stimulus causing it.

Adolescent↗
PubMed1976

A comparison of direct blood pressure feedback and electromyographic feedback on the blood pressure of normotensives.

Groups of 20 normotensive subjects were assigned to one of three conditions to help them lower their blood pressure: (1) intermittent visual feedback of blood pressure; (2) continuous analogue auditory feedback of frontal EMG; (3) an instructed, no-feedback condition. Both groups receiving feedback showed greater within-session lowering of systolic blood pressure than the no-feedback control group. Although the group receiving intermittent visual feedback of blood pressure lowered blood pressure more than the EMG feedback group at the first session, in three subsequent sessions, the two feedback groups did not differ.

Adolescent↗
PubMed2005

Interaction of neuromuscular, spatial and visual constraints on hand-foot coordination dynamics.

In the present study, we investigated the contributions of motor and perceptual processes to directional constraints as observed during hand-foot coordination. Participants performed cyclical flexion-extension movements of the right hand and foot under two coordination modes: in-phase (isodirectional) and antiphase (non-isodirectional). Those tasks were performed either with full vision or no vision of the limbs. Depending on the position of the forearm (prone or supine), the coordination patterns were performed with similar and dissimilar neuro-muscular coupling with respect to their phylogenetic origin as antigravity muscles. Results showed that the antiphase pattern was more difficult to maintain than the in-phase pattern and that neuro-muscular coupling significantly influenced the coordination dynamics. Moreover, the effect of vision differed as a function of both neuro-muscular coupling and coordination mode. Under dissimilar neuro-muscular coupling, the presence of visual feedback stabilized the in-phase pattern and destabilized the antiphase pattern. In contrast, visual feedback did not influence pattern stability during conditions of similar neuro-muscular coupling. These results shed light on the complex interactions between motor and perceptual (visual) constraints during the production of hand-foot coordination patterns.

Adult↗
PubMed2004

Memory for actions: enactment and source memory.

Enacting simple action phrases enhances item memory but may not enhance other aspects of memory. The present experiment examines the effects of enactment on source memory. During the study phase, participants performed some actions (subject-performed tasks, SPTs) and observed the experimenter perform other actions (experimenter-performed tasks, EPTs). One group performed the SPTs with eyes closed, one group with eyes open (the standard condition), and one group performed SPTs facing a mirror (EPT presentation was constant across groups). As expected, item memory was better for SPTs than for EPTs. More importantly, source memory for SPTs was affected by the amount of visual feedback. As predicted by the source-monitoring framework, source memory for SPTs decreased as the amount of visual feedback increased from none (eyes closed) to moderate (standard condition) to maximal (mirror condition). In addition, SPT encoding failed to increase source memory and in one condition actually decreased source memory, relative to EPT encoding. Thus, enactment dissociated item and source memory, enhancing the former but not the latter.

Affect↗
PubMed1992

Visual-vestibular interaction during head-free pursuit of pseudorandom target motion in man.

Recordings of head and eye movement were made during pursuit of mixed-frequency, pseudorandom target motion to study the mechanism of vestibulo-ocular reflex (VOR) suppression during head-free pursuit. When high velocity stimuli were used, slow-phase gaze velocity gains decreased significantly with increases in both absolute target velocity and the velocity ratio between the frequency components. These changes occurred independently of changes in the head displacement gain, which remained relatively constant at the lower frequency and were directly attributable to impaired suppression of the VOR. Similar effects were seen when visual feedback was degraded by tachistoscopic illumination of the target. The results indicate that visual feedback, rather than an efference copy of the head velocity signal, is essential for suppression of slow-phase vestibular eye movement during head-free pursuit. When head-free and head-fixed pursuit were compared, striking similarities were seen for both slow phase gaze velocity gain and phase, indicating that gaze control during smooth pursuit is largely independent of the degree of associated head movement. This suggests that the VOR is not switched off during head-free pursuit. An estimate of the underlying VOR gain was obtained by recording the vestibular response produced by active head movements in darkness. The rather higher estimates of VOR gain obtained using an imaginary earth-fixed target paradigm were found to predict head-free gains more closely than the gains obtained during imaginary pursuit of a moving target, suggesting that such measures may be more representative of the underlying VOR gain.

Eye Movements↗
PubMed1963

Maturation of performance with space-displaced vision.

This study tests two specific hypotheses of neurogeometric theory: that acritical period in maturation of space-displaced visual feedback in behavioroccurs in childhood, and that a differential organization of inverted, reversed, and inverted-reversed visual feedback in motion will be found at the time when children are first capable of giving compensatory response to the spatial disorientatiop of vision. In keeping with theoretical expectations theresults showed that when the different inverted and reversed feedback conditions could be performed, the response to the inverted feedback condition wasthe poorest, while that to the reversed condition was the most effective.

Feedback↗
PubMed2002

How the lack of visuomotor feedback affects even the early stages of goal-directed pointing movements.

Pointing movements made with a hidden cursor from the center of gaze to a stationary, visible target overshot the actual target location. The systematic error decreased when the final cursor location from the previous trial was shown, which likely led to the creation of an internal sensorimotor model of movement. However, the putative model had a short memory, and could not substitute for on-line visuomotor feedback on subsequent trials. Contrary to common belief, the effect of a lack of visuomotor feedback was seen even in the early acceleration stage of the movement trajectory. Unchecked in the absence of visual monitoring, the acceleration stage of the movement lasted longer, as was evidenced by the significantly larger value of the peak cursor speed. Moreover, the speed peaked much later in the course of the movement. Speed declined more rapidly thereafter. Consequently, the delayed deceleration stage lasted far less than the acceleration stage. In the absence of visual feedback, the shift rightward in time of the peak speed position (PSP) in relation to total movement duration and other changes in the trajectory imply that visual feedback must play a significant role in determining when acceleration ceases (d V/d t=0), and argue against the traditional notion that visuomotor feedback is unavailable until the later stages of movement. Moreover, our data suggest that non-visual modalities, e.g., proprioception, may be too slow to make up for the absence of vision.

Feedback↗
PubMed2003

Watching a cursor distorts haptically guided reproduction of mouse movement.

Participants moved a mouse along a force-feedback-defined linear path, either without vision or while watching a cursor set to 1 of 3 levels of visual:haptic gain (all >1:1). They attempted to haptically reproduce the movement without visual feedback. Errors increased with gain, reaching 70% overestimation at the highest gain. Forewarning participants about gain variability did not eliminate this effect. The gain level was potentially cued during the movement by the mismatch between visual feedback and kinesthetic feedback. Moreover, because participants did not achieve cursor-speed constancy across gain levels, visual speed was another cue to gain. Collectively, these cues failed to prevent visual distortion of movement reproduction.

Attention↗
PubMed2006

Is there "feedback" during visual imagery? Evidence from a specificity of practice paradigm.

The specificity of practice hypothesis predicts the development of a sensorimotor representation specific to the afferent feedback available during skill acquisition (Proteau, 1992; Proteau, Marteniuk, Girouard, & Dugas, 1987). In the present investigation, we used the specificity of practice hypothesis to test whether skill acquisition through visual imagery would lead to the development of a sensory-specific movement representation similar to one resulting from actual practice. To accomplish this objective, participants practiced walking a 12-m linear path in one of three practice conditions, full-vision (FV), no-vision (NV), or visual imagery (VI), for either 10 or 100 trials. Knowledge of spatial and/or temporal results (KR) was provided to participants following each trial during this phase. Following acquisition, participants completed 10 NV trials without KR. An analysis of root-mean-squared-error (RMSE) indicated NV participants were more accurate than both FV and VI participants in the transfer condition. We believe the equivalence in transfer RMSE between FV and VI suggests that there are similarities between the movement representations attained by FV and VI practice.

Adolescent↗
PubMed1995

Are arm trajectories planned in kinematic or dynamic coordinates? An adaptation study.

There are several invariant features of point-to-point human arm movements: trajectories tend to be straight, smooth, and have bell-shaped velocity profiles. One approach to accounting for these data is via optimization theory; a movement is specified implicitly as the optimum of a cost function, e.g., integrated jerk or torque change. Optimization models of trajectory planning, as well as models not phrased in the optimization framework, generally fall into two main groups-those specified in kinematic coordinates and those specified in dynamic coordinates. To distinguish between these two possibilities we have studied the effects of artificial visual feedback on planar two-joint arm movements. During self-paced point-to-point arm movements the visual feedback of hand position was altered so as to increase the perceived curvature of the movement. The perturbation was zero at both ends of the movement and reached a maximum at the midpoint of the movement. Cost functions specified by hand coordinate kinematics predict adaptation to increased curvature so as to reduce the visual curvature, while dynamically specified cost functions predict no adaptation in the underlying trajectory planner, provided the final goal of the movement can still be achieved. We also studied the effects of reducing the perceived curvature in transverse movements, which are normally slightly curved. Adaptation should be seen in this condition only if the desired trajectory is both specified in kinematic coordinates and actually curved. Increasing the perceived curvature of normally straight sagittal movements led to significant (P < 0.001) corrective adaptation in the curvature of the actual hand movement; the hand movement became curved, thereby reducing the visually perceived curvature. Increasing the curvature of the normally curved transverse movements produced a significant (P < 0.01) corrective adaptation; the hand movement became straighter, thereby again reducing the visually perceived curvature. When the curvature of naturally curved transverse movements was reduced, there was no significant adaptation (P > 0.05). The results of the curvature-increasing study suggest that trajectories are planned in visually based kinematic coordinates. The results of the curvature-reducing study suggest that the desired trajectory is straight in visual space. These results are incompatible with purely dynamic-based models such as the minimum torque change model. We suggest that spatial perception--as mediated by vision--plays a fundamental role in trajectory planning.

Adaptation, Physiological↗
PubMed1980

Left-hemisphere motor dominance in righthanders.

Left-hemisphere dominance for motor programming was tested in two experiments by measuring acquisition and cross-hand transfer of a complex key-pressing skill in righthanded adults. In the first experiment, visual feedback was excluded to insure unilaterality of motor control. Consistent with left-hemisphere motor dominance, males showed faster acquisition with righthand training than with lefthand training and greater transfer from left to right then vice versa; but females exhibited neither asymmetry. To investigate the possibility that females relied on verbal strategies to remember which keys to press and that this prevented them from showing the predicted asymmetries, the need for such strategies was reduced in a second experiment by allowing visual feedback. Although the provision of visual input may have mitigated against motor asymmetries by directly engaging both hemispheres in the task, results showed more rapid improvement in skills with the right hand than with the left for both sexes, extending evidence for left-hemisphere motor dominance to a population including females as well as males.

Dominance, Cerebral↗
PubMed2006

Effect of reducing frequency of augmented feedback on manual dexterity training and its retention.

OBJECTIVE: The study addressed the impact of the frequency of tutorial-enriched augmented visual feedback, provided by a virtual simulation system (DentSim), on the skill acquisition for a cavity preparation task in novice dental students. METHODS: Thirty-six subjects were assigned to two training groups and a control group. The task consisted of a geometrical cross preparation on the lower left first molar. All subjects performed a pre-test to assess their basic skill level. The training groups received simulation feedback, enriched with tutorial information, across acquisition. One group trained under continuous augmented feedback, while a second group trained under an intermittent (66% of the time) feedback. At both 1-day and 4-month interval, subjects performed a retention test to explore learning specific effects. Two transfer tests were added to assess the extrapolation of the learned skills to an adjacent molar. All tests were performed in the absence of feedback. A control group performed all the tests, without preceding training. All preparations were graded by the simulation system. RESULTS: The training groups performed similarly across acquisition and improved with practice (ANOVA, P<0.001). After 1 day and 4 months of no practice, the training groups outperformed the control group on a retention test (ANOVA, P<0.001) and transfer test (ANOVA, P<0.001). CONCLUSIONS: Performance and learning of a cavity preparation task on a simulation unit was independent of the frequency of tutorial-enriched augmented visual feedback within the range tested. Training sessions on a simulation unit could be alternated with training sessions in the traditional phantom head laboratory.

Adolescent↗
PubMed2006

Internalizing agency of self-action: perception of one's own hand movements depends on an adaptable prediction about the sensory action outcome.

Extensive work on learning in reaching and pointing tasks has demonstrated high degrees of plasticity in our ability to optimize goal-directed motor behavior. However, studies focusing on the perceptual awareness of our own actions during motor adaptation are still rare. Here we present the first simultaneous investigation of sensorimotor adaptation on both levels, i.e., action and action perception. We hypothesized that self-action perception relies on internal predictions about the sensory action outcome that are updated in a way similar to that of motor control. Twenty human subjects performed out-and-back pointing movements that were fed back visually. Feedback was initially presented in spatiotemporal correspondence with respect to the actual finger position, but later rotated by a constant angle. When distorted feedback was applied repetitively, subjects' perceived pointing direction shifted in the direction of the trajectory rotation. A comparable perceptual reinterpretation was observed in control trials without visual feedback, indicating that subjects learned to predict the new visual outcome of their actions based on nonvisual, internal information. The perception of the world, however, remained unchanged. The changes in perception of one's own movements were accompanied by adaptive changes in motor performance of the same amount, i.e., a secondary motor compensation opposite to the direction of the imposed visual rotation. Our results show that the perception of one's own actions depends on adaptable internal predictions about the sensory action outcome, allowing us to attribute new sensory consequences of our actions to our own agency. Furthermore, they indicate that the updated sensory prediction can be used to optimize motor control.

Adult↗
PubMed2005

Effect of sensory substitution on suture-manipulation forces for robotic surgical systems.

OBJECTIVES: Direct haptic (force or tactile) feedback is not yet available in commercial robotic surgical systems. Previous work by our group and others suggests that haptic feedback might significantly enhance the execution of surgical tasks requiring fine suture manipulation, specifically those encountered in cardiothoracic surgery. We studied the effects of substituting direct haptic feedback with visual and auditory cues to provide the operating surgeon with a representation of the forces he or she is applying with robotic telemanipulators. METHODS: Using the robotic da Vinci surgical system (Intuitive Surgical, Inc, Sunnyvale, Calif), we compared applied forces during a standardized surgical knot-tying task under 4 different sensory-substitution scenarios: no feedback, auditory feedback, visual feedback, and combined auditory-visual feedback. RESULTS: The forces applied with these sensory-substitution modes more closely approximate suture tensions achieved under ideal haptic conditions (ie, hand ties) than forces applied without such sensory feedback. The consistency of applied forces during robot-assisted suture tying aided by visual feedback or combined auditory-visual feedback sensory substitution is superior to that achieved with hand ties. Robot-assisted ties aided with auditory feedback revealed levels of consistency that were generally equivalent or superior to those attained with hand ties. Visual feedback and auditory feedback improve the consistency of robotically applied forces. CONCLUSIONS: Sensory substitution, in the form of visual feedback, auditory feedback, or both, confers quantifiable advantages in applied force accuracy and consistency during the performance of a simple surgical task.

Anastomosis, Surgical↗
PubMed1991

Basal ganglia motor control. I. Nonexclusive relation of pallidal discharge to five movement modes.

1. To evaluate the various hypotheses that the basal ganglia preferentially control one mode of movement to the exclusion of others, we recorded the discharge of single neurons in the globus pallidus (GP) in rhesus monkeys during their performance of five trained wrist-movement tasks. The tasks were designed to dissociate several modes and parameters of movement to see whether pallidal neurons would discharge in relation to one and not the others. All tasks were performed by flexing and extending the wrist with opposing or assisting torque loads (0.2 Nm). The five tasks included 1) VisStep, a visually cued step tracking task; 2) VisRamp, a visually guided hold-ramp-hold tracking task; 3) VisSine, a visually guided rapid sinusoidal tracking task; 4) SelfRamp, a self-paced hold-ramp-hold task with delayed alternation, trained velocity, and no visual feedback of wrist position; and 5) SelfSine, a self-paced rapid sinusoidal movement without visual feedback of wrist position. Wrist position and velocity were monitored during all recordings; and wrist, arm, shoulder, and back electromyographs (EMGs) were monitored periodically. Unit discharge was recorded extracellularly from both segments of the GP. The results were similar in the present analysis and are considered together. As a control, units were also recorded in the dentate nucleus of the lateral cerebellum, and the EMGs of many muscles were recorded in limbs, neck and trunk. 2. For 100 GP neurons [41 in the internal segment (GPi) and 59 in the external segment (GPe)], the activity of which changed with task performance, the discharge patterns varied greatly across tasks. The discharge of 96/97 neurons (99%) changed during VisStep, 66/91 neurons (73%) changed during VisRamp, 41/81 neurons (51%) changed during VisSine, 7/34 neurons (21%) changed during SelfRamp, and 25/80 neurons (31%) changed during SelfSine. Of 74 neurons that were fully tested in four or more tasks, 16 (21%) were related only to one task; only 17 cells (23%) were related to all tasks; and, for the remaining 41 (55%) neurons, the relation of the discharge of a given neuron to one task did not predict its relation to other tasks. These task-dependent differences in the discharge of pallidal neurons were not correlated with differences in wrist position, velocity, load, or muscle activity (see also the following paper--Mink and Thach, 1991a). 3. From these data, we conclude that no one task engaged all pallidal neurons to the exclusion of other tasks.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗