The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ferdinando A Mussaivaldi - One of the best experts on this subject based on the ideXlab platform.
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adaptation to Visual Feedback delay in a redundant motor task
Journal of Neurophysiology, 2015Co-Authors: Ali Farshchiansadegh, Rajiv Ranganathan, Maura Casadio, Ferdinando A MussaivaldiAbstract:The goal of this study was to examine the reorganization of hand movements during adaptation to delayed Visual Feedback in a novel and redundant environment. In most natural behaviors, the brain mu...
Denise Y P Henriques - One of the best experts on this subject based on the ideXlab platform.
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reach adaptation and proprioceptive recalibration following terminal Visual Feedback of the hand
Frontiers in Human Neuroscience, 2014Co-Authors: Victoria Barkley, Danielle Salomonczyk, Erin K Cressman, Denise Y P HenriquesAbstract:We have shown that when subjects reach with continuous, misaligned Visual Feedback of their hand, their reaches are adapted and proprioceptive sense of hand position is recalibrated to partially match the Visual Feedback (Salomonczyk et al., 2011). It is unclear if similar changes arise after reaching with Visual Feedback that is provided only at the end of the reach (i.e., terminal Feedback), when there are shorter temporal intervals for subjects to experience concurrent Visual and proprioceptive Feedback. Subjects reached to targets with an aligned hand-cursor that provided Visual Feedback at the end of each reach movement across a 99-trial training block, and with a rotated cursor over 3 successive blocks of 99 trials each. After each block, no cursor reaches, to measure aftereffects, and felt hand positions were measured. Felt hand position was determined by having subjects indicate the position of their unseen hand relative to a reference marker. We found that subjects adapted their reaches following training with rotated terminal Visual Feedback, yet slightly less (i.e., reach aftereffects were smaller), than subjects from a previous study who experienced continuous Visual Feedback. Nonetheless, current subjects recalibrated their sense of felt hand position in the direction of the altered Visual Feedback, but this proprioceptive change increased incrementally over the three rotated training blocks. Final proprioceptive recalibration levels were comparable to our previous studies in which subjects performed the same task with continuous Visual Feedback. Thus, compared to reach training with continuous, but altered Visual Feedback, subjects who received terminal altered Visual Feedback of the hand produced significant but smaller reach aftereffects and similar changes in hand proprioception when given extra training. Taken together, results suggest that terminal Feedback of the hand is sufficient to drive motor adaptation, and also proprioceptive recalibration.
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intermanual transfer and proprioceptive recalibration following training with translated Visual Feedback of the hand
Experimental Brain Research, 2014Co-Authors: Ahmed A Mostafa, Danielle Salomonczyk, Erin K Cressman, Denise Y P HenriquesAbstract:Reaching with Visual Feedback that is misaligned with respect to the actual hand’s location leads to changes in reach trajectories (i.e., visuomotor adaptation). Previous studies have also demonstrated that when training to reach with misaligned Visual Feedback of the hand, the opposite hand also partially adapts, providing evidence of intermanual transfer. Moreover, our laboratory has shown that visuomotor adaptation to a misaligned hand cursor, either translated or rotated relative to the hand, also leads to changes in felt hand position (what we call proprioceptive recalibration), such that subjects’ estimate of felt hand position relative to both Visual and non-Visual reference markers (e.g., body midline) shifts in the direction of the visuomotor distortion. In the present study, we first determined the extent that motor adaptation to a translated cursor leads to transfer to the opposite hand, and whether this transfer differs across the dominant and non-dominant hands. Second, we looked to establish whether changes in hand proprioception that occur with the trained hand following adaptation also transfer to the untrained hand. We found intermanual motor transfer to the left untrained (non-dominant) hand after subjects trained their right (dominant) hand to reach with translated Visual Feedback of their hand. Motor transfer from the left trained to the right untrained hand was not observed. Despite finding changes in felt hand position in both trained hands, we did not find similar evidence of proprioceptive recalibration in the right or left untrained hands. Taken together, our results suggest that unlike visuomotor adaptation, proprioceptive recalibration does not transfer between hands and is specific only to the arm exposed to the distortion.
Hermano Igo Krebs - One of the best experts on this subject based on the ideXlab platform.
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effects of implicit Visual Feedback distortion on human gait
Experimental Brain Research, 2012Co-Authors: Seungjae Kim, Hermano Igo KrebsAbstract:Gait rehabilitation after stroke often utilizes treadmill training delivered by either therapists or robotic devices. However, clinical results have shown no benefit from this modality when compared to usual care. On the contrary, results were inferior; perhaps, because in its present form it is not interactive and at least for stroke, central pattern generators at the spinal level do not appear to be the key to promote recovery. To enable gait therapy to be more effective, therapy must be interactive and Visual Feedback appears to be an important option to engage patients’ participation. In this study, we tested healthy subjects to see whether an implicit “Visual Feedback distortion” influences gait spatial pattern. Subjects were not aware of the Visual distortion nor did they realize changes in their gait pattern. The Visual Feedback of step length symmetry was distorted so that subjects perceived their step length as being asymmetric during treadmill training. We found that a gradual distortion of Visual Feedback, without explicit knowledge of the manipulation, systematically modulated gait step length away from symmetry and that the Visual distortion effect was robust even in the presence of cognitive load. This indicates that although the Visual Feedback display used in this study did not create a conscious and vivid sensation of self-motion (the properties of the optical flow), experimental modifications of Visual information of subjects’ movement were found to cause implicit gait modulation. Nevertheless, our results indicate that modulation with Visual distortion may require cognitive resources because during the distraction task, the amount of gait modulation was reduced. Our results suggest that a therapeutic program involving Visual Feedback distortion, in the context of gait rehabilitation, may provide an effective way to help subjects correct gait patterns, thereby improving the outcome of rehabilitation.
J K Jackson - One of the best experts on this subject based on the ideXlab platform.
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adaptation to Visual Feedback delays in manual tracking evidence against the smith predictor model of human Visually guided action
Experimental Brain Research, 2006Co-Authors: R C Miall, J K JacksonAbstract:We report adaptation to delayed Visual Feedback during a manual tracking task, testing the nature of the adapted responses with frequency analysis. Two groups of seven subjects tracked unpredictable targets using a handheld joystick, alternating between pursuit and compensatory display trials. The test group then practised for 1 h per day with a Visual Feedback delay of 300 ms; the control group practice under normal undelayed conditions. Introduction of the Visual Feedback delay significantly disrupted tracking performance, with an increase in errors and a reduction in frequency of corrective movements. Subjects showed clear evidence of adaptation during the 5 day experiment, decreasing tracking error and decreasing the mean power of intermittent corrections. However, there was no evidence of a return towards the initial high frequency intermittent tracking. We suggest that the adaptation observed in this study reflects the modification of predictive feedforward actions, but that these data do not support control based on Smith Prediction.
Yoky Matsuoka - One of the best experts on this subject based on the ideXlab platform.
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Visual Feedback distortion in a robotic environment for hand rehabilitation
2018Co-Authors: Bambi R. Brewer, Roberta Klatzky, Yoky MatsuokaAbstract:Robotic therapy offers a means of enhancing rehabilitation for individuals with chronic stroke or traumatic brain injury. The present research targets members of this population who demonstrate learned nonuse, a tendency to use affected limbs below the level of the individual's true capability. These individuals may not strive for difficult goals in therapy, which ultimately hampers their progress and the outcome of rehabilitation. Our research uses a paradigm called Visual Feedback distortion in which the Visual Feedback corresponding to force or distance is gradually changed by an imperceptible amount to encourage improved performance. Our first set of experiments was designed to assess the limits of imperceptible distortion for Visual Feedback concerning the force exerted or the distance moved by the index finger. A second set of experiments used these limits to gradually distort Visual Feedback in order to manipulate a subject's force or distance response. Based on this work, we designed a paradigm applying Visual Feedback distortion to the rehabilitation of individuals with chronic stroke and traumatic brain injury. Initial tests are reported for two subjects who participated in a six-week rehabilitation protocol. Each patient followed Visual Feedback distortion to levels of performance above that predicted by her performance during an initial assessment. Both patients showed functional improvements after participating in the study. Visual Feedback distortion may provide a way to help a patient move beyond his or her self-assessed “best” performance, improving the outcome of robotic rehabilitation.
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perceptual limits for a robotic rehabilitation environment using Visual Feedback distortion
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2005Co-Authors: Bambi R. Brewer, Roberta Klatzky, M Fagan, Yoky MatsuokaAbstract:Imperceptible Visual distortion, in the form of a disguised progression of performance goals, may be a helpful addition to rehabilitation after stroke and other brain injuries. This paper describes work that has been done to lay the groundwork for testing this hypothesis. We have constructed and validated an experimental environment that provides controllable Visual distortion and allows precise force and position measurements. To estimate the amount of Visual distortion that should be imperceptible, we measured the limits for force and distance/position perception in our rehabilitation environment for young and elderly unimpaired subjects and for a single traumatic brain injury (TBI) patient. We found the Just Noticeable Difference (JND) for produced force to be 19.7% (0.296 N) and the JND for movement distance/finger position to be 13.0% (3.99 mm) for young subjects (ages 18-35). For elderly subjects (ages 61-80), the JND for force was measured to be 31.0% (0.619 N) and the JND for distance/position was 16.1% (5.01 mm). JNDs of 46.0% (0.920 N) and 45.0% (14.8 mm) were found for the motor-impaired individual. In addition, a subject's rating of effort was found to be profoundly influenced by Visual Feedback concerning the force magnitude. Even when this Feedback was distorted, it accounted for 99% of the variance of the effort rating. These results indicate that substantial Visual distortions should be imperceptible to the subject, and that Visual Feedback can be used to influence the subject's perceived experience in our robotic environment. This means that we should be able to use imperceptible Visual distortion to alter a patient's perception of therapeutic exercise in a robotic environment.
