Limit-Push – Reduction of Motor Variability in a Virtual, Haptic Environment with Visual Distortions
thesisposted on 27.02.2015 by Eyad Hajissa
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
As a problem in physical rehabilitation and performance training, there is interest in studying arm movement variability. This study builds on previous motor control work in which subjects performed a projectile catching task with a robotic arm endpoint to control a cursor in a virtual reality environment. In that study it was seen that the distribution of arm movement positions can be influenced by a bounded region. The bounded region was the only space in which subjects would not experience a distortion while they did the task. That is, leaving a pre-defined bounded region caused them to experience a catastrophe where force feedback pushed them further away from the boundary. The subjects’ conception of the boundary, which they otherwise did not see, was evidenced by the reduction in the distance to the edge of the boundary. In this work we have collected a new treatment group using the same setup except that subjects only receive visual feedback in response to leaving the boundary. The visual feedback is a distortion of the cursor away from the boundary rather than a robotic push. We have seen that visual feedback shows promise in manipulating arm movement distribution in the distance to edge and percent outside metrics. These metrics showed a reduction of the subjects’ distance to edge and a shift of their movement distribution inside the boundary compared to a control group that received no distortion. Further work could seek to manipulate the spread of movement distribution perhaps by creating a more appropriate visual distortion. Constructing and evaluating the use of such virtual environments is important as they have potential to help those with limited arm movement due to stroke or traumatic brain injuries. However, in order for such methods to expand out of the laboratory and be validated clinically, their apparatus must be low cost and portable. In this regard, visual distortions are preferable to force feedback because future experiments can implement them without the use of an expensive robot. In the same effort, we have contracted a new apparatus that provides the same virtual reality environment as the VRROOM system. This system, the LookingGlass, utilizes 3D LCD technology and fewer materials than the old VRROOM system. Future work could implement optical arm movement tracking to conduct motor control experiments such as the one presented here without a robot.