Robot-assisted line bisection test in virtual reality

Abstract

There is growing evidence in the literature suggesting that sensori-motor deficits have a detrimental impact on cognitive abilities, such as the perception and representation of space. Most of the tasks classically used to assess spatial perception abilities after brain damage seem however not adequate to reveal potentially more discrete impairments in patients that are predominantly suffering from sensori-motor symptoms. To this aim we adapted the classic line bisection task in a virtual reality environment for the use with patients with upper-limb sensory-motor deficits. Here, we report the results from two pre-clinical experiments with healthy volunteers. Lines were projected horizontally on a semi-reflective mirror. Participants were asked to bisect the lines at their estimated midpoint by means of a robotic handle. Manipulated factors were the static hand, the position of the static hand (inside or outside of workspace), the visibility of the hands and the location of the lines. Results showed that participants neglected the most lateral part of the lines when they were projected distantly from the starting point. Bisection biases were in general more important when participants could see their hands. Additionally, participants took more time to initiate movements when they had to cover a short distance to reach the lines. We conclude that our robotic adaptation of the line bisection task was able to highlight subtle perceptual asymmetries in healthy individuals and that its use to reveal discrete cognitive deficits in patients with sensory-motor impairments seems therefore promising.

Robot-assisted line bisection in patients with Complex Regional Pain Syndrome

“…participants with CRPS affecting the right hand. In fact, the distance effect we observed in the contralateral workspace was already observed in healthy volunteers [26] and has been hypothesized to be related to different scaling of the movement as a consequence of the different curvatures of the movement between lines at short vs. longer distance [34].…”

“…In brief, lines were presented by means of a horizontal mirror placed in front of patients suffering from upper-limb CRPS, and they were instructed to move a visual cursor towards the estimated midpoint of each line by holding and moving the handle of the robotic device with their unaffected hand. In comparison to standard paper-and-pencil tasks, this device allowed us to precisely control the presentation of the visual stimuli and finely analyze participants’ pointing movements [26]. We hypothesized that, according to the learned nonuse hypothesis, movements of the unaffected limb should not be hindered during visuo-motor coordination task, and therefore, patients with CRPS should not perform the task differently than control participants.…”