A Comparative Analysis of 2D and 3D Tasks for Virtual Reality Therapies Based on Robotic-Assisted Neurorehabilitation for Post-stroke Patients

Abstract

Post-stroke neurorehabilitation based on virtual therapies are performed completing repetitive exercises shown in visual electronic devices, whose content represents imaginary or daily life tasks. Currently, there are two ways of visualization of these task. 3D virtual environments are used to get a three dimensional space that represents the real world with a high level of detail, whose realism is determinated by the resolucion and fidelity of the objects of the task. Furthermore, 2D virtual environments are used to represent the tasks with a low degree of realism using techniques of bidimensional graphics. However, the type of visualization can influence the quality of perception of the task, affecting the patient's sensorimotor performance. The purpose of this paper was to evaluate if there were differences in patterns of kinematic movements when post-stroke patients performed a reach task viewing a virtual therapeutic game with two different type of visualization of virtual environment: 2D and 3D. Nine post-stroke patients have participated in the study receiving a virtual therapy assisted by PUPArm rehabilitation robot. Horizontal movements of the upper limb were performed to complete the aim of the tasks, which consist in reaching peripheral or perspective targets depending on the virtual environment shown. Various parameter types such as the maximum speed, reaction time, path length, or initial movement are analyzed from the data acquired objectively by the robotic device to evaluate the influence of the task visualization. At the end of the study, a usability survey was provided to each patient to analysis his/her satisfaction level. For all patients, the movement trajectories were enhanced when they completed the therapy. This fact suggests that patient's motor recovery was increased. Despite of the similarity in majority of the kinematic parameters, differences in reaction time and path length were higher using the 3D task. Regarding the success rates were very similar. In conclusion, the using of 2D environments in virtual therapy may be a more appropriate and comfortable way to perform tasks for upper limb rehabilitation of post-stroke patients, in terms of accuracy in order to effectuate optimal kinematic trajectories.

Keywords: post-stroke; rehabilitation robotics; sensorimotor function; upper extremity; virtual reality.

Figures

Figure 1

Neurorehabilitation system based in PUPArm robot.

Figure 2

Targets and visual feedback of the 2D task.

Figure 3

Targets and visual feedback of the 3D task.

Figure 4

Structural correlation between 2D Roulette and 3D Roulette (zenithal view).

Figure 5

Workflow to complete one trial.

Figure 6

Statistical analysis of the data acquired by the robotic device, represented in box plots.

Figure 7

Movement trajectories to reach the targets by one patient. Sensorimotor function assessment for two tasks. In the left are shown trajectories performed in 2D task during the first and the last session. In the right side are shown the trajectories performed in 3D task.

Figure 8

Average of the survey patient responses.

Figure 9

Score contribution from each aspect of the survey.

Figure 10

Dispersion diagram with the most significant variables that affect the initial deviation of the trajectories.

Figure 11

Dispersion diagram between Path Length and Time parameters.

Figure 12

Dispersion diagrams with the significative correlation of speed maximum.