The Utilization of Visual Feedback Information during Rapid Pointing Movements

The accuracy of a long aiming movement was studied as a function of whether it was performed toward or away from the midline of the subject's body in the presence or absence of visual feedback. 30 right-handed, male university students (19-26 yr.) served as subjects. With movement distance and duration controlled, the mean percentage of error was 6.34% less for movements made toward the body's midline than for those performed away from the midline. The mean percentage of error was also 48% less in the presence of visual feedback than in its absence. However, contrary to our expectation, movements executed toward the body's midline were not appreciably less disrupted in the absence of visual feedback than movements performed away from the midline.

The downstream movements of wild Atlantic salmon, Salmo salar L., from their established feeding territories in the River Itchen, Hampshire, UK, were logged continuously over an 11‐month period using a passive integrated transponder (PIT) antenna system. The time of these movements was then related to a number of monitored and calculated environmental parameters. Initial downstream movement of smolts in April was correlated with the onset of darkness, at which time salmon moved from their established feeding territories alone. No relationship was found between the number of smolts migrating and river flow or maximum daily water temperature. The timing of downstream movement of parr between October and March was random with regard to sunset and time of maximum daily water temperature, suggesting the environmental cue that initiates movement may be different outside the spring smolt period.

A self paced linear positioning task was used to study the effects of visual and proprioceptive feedback on learning and performance. Subjects were trained with knowledge of results (KR) and tested without it. The analysis of the absolute error scores of the no-KR trials is discussed in this paper. Visual feedback was the more effective source of sensory feedback, but proprioceptive feedback was also effective. An observation that the response did not become independent of sensory feedback as a result of learning, was interpreted as supporting Adams closed loop theory of motor learning in preference to the motor program hypothesis. Other data showed that the presence of visual feedback during learning could inhibit the later effectiveness of proprioceptive feedback.

Conventionally, hitting movements in response to different advanced kinematic information have been investigated from the perspective of chronometric analysis, such as measuring the timing of movements. This is the first study to investigate the effect of manipulating advanced kinematic information on the hitting movement pattern organization based on both kinematics and kinetic analyses in addition to the conventional chronometric analysis. Specifically, the hitting movement of experienced batters in response to visual stimuli consisting of different pitching movement speeds with the same ball trajectory information was measured by an optical motion capture camera system and a foot force sensor inside the shoes. The occurrence timings of specific events (e.g., movement initiation), some kinematic parameters (e.g., maximum rotate angle of the shoulder and hip), and the balance of the ground reaction force between the ball of the big and small toes of both feet were compared between experimental conditions. This was done to test the hypothesis that the hitting movement is coupled with the visual information given to batters based on an expert anticipatory model. The results indicated that for a faster pitching speed, the batter tended to react with a significantly smaller preparatory movement (e.g., smaller weight shift and shoulder rotate angle during backswing) and put significantly larger weight on the rear foot during the swing execution phase. The situation was exactly reverse in the case of a slower pitching movement. These results suggest for the first time that manipulating advanced kinematic information not only affects the timing of the movement, but also the whole-body kinematics and lower body kinetics. The results also indicate that the hitting movement pattern of experienced batters is highly dependent on the advanced kinematic information.

Human computer interface (HCI) is often regarded as the intersection of computer science, behavioral sciences, design and several other fields of study. In order to improve the usability of HCI, investigation of the interaction between human and computers is an important issue. In present study, we use a pointing movement experimental device with visual feedback control function which developed in our companion research to investigate the human movement characteristics. Fitts' law is a successful model of human movement that predicts the time required to rapidly move to a target. According to Fitts' law, the relationship between the movement time (MT) and the index of difficulty (ID) can be demonstrated as a linear function. Here, we designed a series of rectangle boxes as using in Fitts' study as pointing stimuli. Ten subjects were asked to do pointing movement with different visual feedback conditions. The findings of present study suggest that the pointing performance was not only depending on the size of targets but also the quantity of visual feedback information. Therefore, both visual feedback and target size need to considered for HCI design.

Vestibular information is available to the brain during navigation, as are the other self-generated (idiothetic) and external (allothetic) sensorimotor cues that contribute to central estimates of position and motion. Rodent studies provide strong evidence that vestibular information contributes to navigation but human studies have been less conclusive. Furthermore, sex-based differences have been described in human navigation studies performed with the head stationary, a situation where dynamic vestibular (and other idiothetic) information is absent, but sex differences in the utilization of vestibular information have not been described. Here, we studied men and women with severe bilateral vestibular damage as they navigated through a visually barren virtual reality environment and compared their performance to normal men and women. Two navigation protocols were employed, which either activated dynamic idiothetic cues ('dynamic task', navigate by turning, walking in place) or eliminated them ('static task', navigate with key presses, head stationary). For both protocols, we employed a standard 'triangle completion task' in which subjects moved to two visual targets in series and then were required to return to their perceived starting position without localizing visual information. The angular and linear 'accuracy' (derived from response error) and 'precision' (derived from response variability) were calculated. Comparing performance 'within tasks', navigation on the dynamic paradigm was worse in male vestibular-deficient patients than in normal men but vestibular-deficient and normal women were equivalent; on the static paradigm, vestibular-deficient men (but not women) performed better than normal subjects. Comparing performance 'between tasks', normal men performed better on the dynamic than the static paradigm while vestibular-deficient men and both normal and vestibular-deficient women were equivalent on both tasks. Statistical analysis demonstrated that for the angular precision metric, sex had a significant effect on the interaction between vestibular status and the test paradigm. These results provide evidence that humans use vestibular information when they navigate in a virtual visual environment and that men and women may utilize vestibular (and visual) information differently. On our navigation paradigm, men used vestibular information to improve navigation performance, and in the presence of severe vestibular damage, they utilized visual information more effectively. In contrast, we did not find evidence that women used vestibular information while navigating on our virtual task, nor did we find evidence that they improved their utilization of visual information in the presence of severe vestibular damage.

How efficient are central mechanisms for the learning and retention of coincident timing actions?

Purpose: This study investigates the effect of ankle joint strategy exercise and visual feedback training on proprioception and balance ability in stroke patients. Materials and Methods: 26 stroke patients were divided evenly at random into a visual feedback group(VFG) (n=13) and a visual disuse group(VDG) (n=13). For the ankle strategy exercise, the intervention session lasted 30 minutes and each session ran 3 times a week, for 6 weeks. Depending on the absence and presence of visual feedback, a pre- and post-intervention measurement was gathered for the proprioception test and balance ability. The proprioception test measured the angle of the knee joint with the subject blindfolded. The Berg Balance Scale (BBS) was used to measure balance ability. Results: For the proprioception test, there was no statistically significant difference. For the BBS measuring balance ability, there was a significant increase post-intervention (p<.05). Conclusion: During ankle strategy exercise, it is slightly more effective to apply visual feedback training in order to improve proprioception and balance ability. In is necessary for future studies to expand upon the topic of visual feedback.

Performers adopt strategies to use visual information if they know that it will be available whereas uncertainty about its availability leads performers to prepare for the worst-case scenario. Since the impact of prior knowledge has generally been examined as performance-based changes across a series of trials, this study investigates the impact of prior knowledge on learning. Participants practiced target-directed aiming movements either with cues about the random availability of vision, no cues regarding vision or in blocks of stable visual information availability. Participants who received prior knowledge were more efficient in preparing their acquisition movements when vision was available. In retention and transfer, all participants were able to take advantage of the visual information available in order to optimize performance outcome. Thus, adult performers appear able to change their strategic behavior quickly to accommodate new sensory and prior knowledge conditions.

The effects of target location and uncertainty of target position on reaching movements while standing were investigated. Ten healthy, right-handed adults stood facing a 17'' touchscreen. They were instructed to press with their right index fingertip a push bottom and touch the center of the target displayed on the screen after it was lighted on, moving quickly their arm. The target was shown either ipsi- or contralateral to the right arm and either in a certain or uncertain position. Reaction time (RT), movement time (MT), and radial error (RE) were assessed. Results revealed shorter RT (≈ 35 ms) and smaller RE (≈ 0.19 cm) for certain than for uncertain condition and slightly longer RT (≈ 8 ms) and MT (≈ 18 ms) for reaches towards the contralateral target. In conclusion, the findings of this study showing the effect of uncertainty of target location as well as target position are also applied to arm reaching in standing position.

Six adult stutterers and six normal speakers were instructed to make the smallest possible movements of the jaw, lower lip, tongue and right index finger, both with and without continuous visual feedback. In the non-visual (kinaesthetic) condition, the stutterers showed significantly larger minimal displacements (MDs) than did the non-stutterers for oral but not for finger movements. However, movements made in the presence of visual feedback were consistently smaller for all subjects than those made without, and no differences in MD were found between the stutterers and the non-stutterers when visual feedback was provided. The results suggested the presence of a sensorimotor deficit among at least some adult stutterers that is confined to oral movements. Given the importance of somatic sensory feedback during speech production, these observed orosensory deficiencies among stutterers may provide important insights into causal factors which contribute to the breakdowns in stutterers' speech.

This paper addresses a fundamental question of how motor commands specify target torque levels. Human subjects produced fast and accurate changes in torque with the isometric elbow joint. Visual stimuli were used to indicate target torque levels as well as to cue subjects to initiate their responses. During rapid changes in torque from one steady-state level to another, target torque was achieved through a sequence of approximations. During the first 200-250 msec of responses produced in the presence of visual feedback, 3 distinct control mechanisms were recruited to guide torque to the target level. The timing and accuracy of each control mechanism were evaluated. The first control mechanism was triggered by the visual stimulus and produced the initial rise in torque. Target torque predictability was found to strongly influence the accuracy of this control mechanism. The second control mechanism produced a corrective adjustment in torque within roughly the first 100 msec of responses. This mechanism incorporated target torque information provided by the stimulus into the response. The third control mechanism began 200-250 msec after response onset and produced corrective adjustments based on visual feedback of torque errors. The stability of the visual feedback mechanism was evaluated because of a long loop delay. Two strategies were used to control stability: low gain and information transfer between the visual feedback mechanism and the preceding (second) control mechanism.

Background: The purpose of this study was to determine the reaction time (RT) and movement time (MT) in Down syndrome children under two different visual feedback conditions. Methods: An observational cross-sectional study was conducted in which 30 mild to moderate Down syndrome children were allocated randomly into two groups. The full visual feedback group comprised 15 participants with an average age of 12(± 1.4) years, and the no visual feedback group comprised 15 participants with an average age of 12(± 1.7) years. All the participants repeated the same activity 20 times with the order of conditions randomized across individuals. Results: RT and MT were analyzed while participants performed the movement sequence. After 20 trials, both groups showed significant differences in their MT but no significant differences in RT. Intergroup analysis also showed that there was no statistically significant difference in either RT or MT. Conclusion: Down syndrome children exhibited longer movement and RTs than normal children regardless of vision condition. Knowledge of their performance at regular intervals and encouragement helped to improve their MT. Down syndrome children were less affected by the elimination of visual feedback and showed no significant variation in RTs.

The role of perceptual-motor processes in the coordination and control of movement is a long standing issue. Nevertheless, there is no coherence on theoretical perspectives with their being frameworks that emphasize perceptual, motor and perceptual-motor processes in coordination and control. The purpose of this study was to examine the interactive effects of visual information and factors of neuromuscular organization (force level, force direction, and homologous muscle pairs) on coordination patterns in bimanual isometric force production. In Experiment 1, the participants were required to abduct two index fingers isometrically and produce simultaneous forces such that their sum matched the constant force target specified at two force levels (10 and 40% of maximum voluntary contraction (MVC)). Visual information of the force outputs was either present or absent between conditions. The results showed that the coordination patterns interact with visual feedback in that the two finger forces exhibit negative correlation with vision and positive correlation without vision, with stronger correlation in each case found at higher force levels. In Experiment 2, the force direction and muscles involved in the task were different between the hands. In comparison with Experiment 1, the negative correlation was stronger with vision at 40% MVC (but equal at 10% MVC), and positive correlation was weaker without vision at 10% MVC (but equal at 40% MVC). The findings provide further evidence that the coordination patterns in bimanual isometric force production are specified by the interaction of task-relevant visual information and force level and, to a lesser degree by force direction and the muscles involved in the task. The capacity to exploit information mediates coordination and control, and the effective utilization of information is dependent on the specific action.

Successful navigation through an environment requires precise monitoring of direction and distance traveled ("path integration" or "dead reckoning"). Previous studies in blindfolded human subjects showed that velocity information arising from vestibular and somatosensory signals can be used to reproduce passive linear displacements. In these studies, visual information was excluded as sensory cue. Yet, in our everyday life, visual information is very important and usually dominates vestibular and somatosensory cues. In the present study, we investigated whether visual signals can be used to discriminate and reproduce simulated linear displacements. In a first set of experiments, subjects viewed two sequences of linear motion and were asked in a 2AFC task to judge whether the travel distance in the second sequence was larger or shorter than in the first. Displacements in either movement sequence could be forward (f) or backward (b). Subjects were very accurate in discriminating travel distances. Average error was less than 3% and did not depend on displacements being into the same (ff, bb) or opposite direction (fb, bf). In a second set of experiments, subjects had to reproduce a previously seen forward motion (passive condition), either in light or in darkness, i.e., with or without visual feedback. Passive displacements had different velocity profiles (constant, sinusoidal, complex) and speeds and were performed across a textured ground plane, a 2-D plane of dots or through a 3-D cloud of dots. With visual feedback, subjects reproduced distances accurately. Accuracy did not depend on the kind of velocity profile in the passive condition. Subjects tended to reproduce distance by replicating the velocity profile of the passive displacement. Finally, in the condition without visual feedback, subjects reproduced the shape of the velocity profile, but used much higher speeds, resulting in a substantial overshoot of travel distance. Our results show that visual, vestibular, and somatosensory signals are used for path integration, following a common strategy: the use of the velocity profile during self-motion.