Robotic assessment of wrist and arm proprioception in healthy and stroke populations

Proprioception is defined as the ability to know the position of the body in time and space exploiting the information arising from the periphery. It has long been recognized that impaired proprioception may severely affect the control of voluntary movements. However, the impact of these impairments on motor functions has been difficult to elucidate for two reasons: the qualitative nature of available clinical tests and the lack of instrumentation to accurately manipulate human limbs to measure proprioceptive performance. The recent advent of robotic interfaces designed for rehabilitation provides potential tools to quantitatively evaluate proprioceptive function. Up to this point, robotic devices have focused on testing single degree-offreedom (DoF) joints such as the elbow, or were only capable of displacing or moving a joint in a single plane. The devices used to test multi-joint proprioception have a high level of complexity that require trained specialists to be implemented in clinics and can be cost prohibitive. Motivated by the lack of quantitative data on wrist proprioception and the lack of simple and cost-effective robotic protocols for assessment of arm proprioception, this thesis proposes quantitative tests which employ a 3 DoF wrist device and a low-cost planar robot. These robotic devices have first been used to evaluate the sensitivity and reliability of different robotic proprioceptive assessments in healthy individuals. The methodologies include a psychometric task in which participants are asked to discriminate two different positions while feedback is limited to proprioception, the joint position matching (JPM) task, in which participants actively match a predefined target and a revised version of the JPM task designed to overcome the limitations associated to motor impairments often present as a result of brain damage. These studies demonstrate that the quantitative metrics are sensitive and reliable over repeated testing and suitable for proprioceptive evaluation of intact joints. The effect of handedness, available feedback and external forces on proprioceptive measures has been analyzed, as well as the role assignment in the processing of sensory feedback during bimanual tasks and bimanual proprioception. No evidence of proprioceptive dominance was found, while there was a decline in performance when matching a target configuration which is visually and kinesthetically presented. Accuracy and precision in target matching do not change significantly as a function of an external load, while proprioceptive acuity was superior and more consistent during unimanual tasks compared to the bimanual case. Finally, the clinical applicability and validity of the robotic assessment of proprioception was evaluated. The methodology was employed to quantitatively assess deficits in acute, sub-acute and chronic patients. The test was found to be inherently simple such that all participants, regardless of motor impairment level, could complete it in less than 10 minutes. Further, the method provides quantitative metrics able to detect changes in proprioceptive status in clinical settings.