151 research outputs found
Size-Change Detection Thresholds of a Hand-Held Bar at Rest and during Movement
No full textWe measured the minimum transient change of length of a bimanually hand-held bar that could be detected. A bimanual haptic interface was used to haptically render the bar in a static condition and two dynamic conditions involving discrete movements. The detection thresholds were much lower in the static ( 10 mm). This finding suggests that our proprioceptive acuity markedly decreases during movement
Predicted sensory feedback derived from motor commands does not improve haptic sensitivity
No full textAdaptive regulation of assistance ‘as needed’ in robot-assisted motor skill learning and neuro-rehabilitation
No full textWe propose a general adaptive procedure to select the appropriate degree of assistance based on a Bayesian mechanism used to estimate psychophysical thresholds. This technique does not need an accurate model of learning and recovery processes. This procedure is validated in the context of a motor skill learning problem (control of a virtual object), in which the controller is used to gradually increase task difficulty as learning proceeds. These automatic adjustments of task difficulty or the degree of assistance can be used to promote not only motor skill learning but also neuromotor recovery
Testing proprioception in intrinsic and extrinsic coordinate systems: Is there a difference?
No full textAn intact position sense is considered important for neuromotor recovery, but the available methods and protocols for its assessment are still limited. In the clinical practice it is generally tested trough a bimanual position matching test, that consists of replicating with one arm the angular positions of the other arm in space (intrinsic coordinates matching). However, the same test could be carried out by matching the hand location in space (extrinsic coordinates matching). Is there any difference between the procedures that may be relevant to the evaluation of position sense deficits? In this study we compared the performance of eight right handed subjects and two stroke survivors with left hemiparesis performing the test in the two conditions. A robotic manipulandum passively moved the left arm of the participants in twenty-four positions in the workspace. Subjects had to match the left arm position with their right arm either in intrinsic or extrinsic coordinates. The results show that all the subjects (impaired and controls) performed better when using the extrinsic paradigm
A strategy of assistance in robot-therapy for promoting the emergence of voluntary control in stroke patients
No full textRobot therapy for severely impaired stroke survivors: Toward a concurrent regulation of task difficulty and degree of assistance
No full textMany exercise protocols for robot therapy are designed to adjust their degree of difficulty in order to maintain a constant challenge level. A simple way to do this is to design exercises that consist of a variable number of sub-movements in different directions - task difficulty is determined by the number of sub-movements. But, how does recovery proceed in these tasks, and how to regulate the magnitude of the assistance provided by the robot in this case? Here we focus on a simple task in which subjects had to complete a square figure. At every trial, an adaptive regulator selects the appropriate degree of robot assistance needed to complete the entire figure. We tested this protocol with four severely impaired stroke survivors during a multisession study. Robotic training succeeded - the controller gradually reduced the degree of assistance while performance remained constant, suggesting that in fact recovery took place. We used a dynamic model of the recovery process to further analyze the effects of the assistive force and the temporal evolution of the subjects' voluntary control. The model provided an excellent fitting of the subjects' performance and revealed that magnitude and modalities of recovery are very different in the different sub-movements. These results suggest that in order to maximize the recovery the modulation of assistance should occur at the level of each sub-movement
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