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Session: Poster session 2 (Odd numbers)
Session starts: Friday 27 January, 10:00
Presentation starts: 10:00

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Alex van den Berg (Delft University of Technology, MLN Lab)
Bart de Vries (Delft University of Technology, MLN Lab)
Zoë Breedveld (Delft University of Technology, MLN Lab)
Annelouk van Mierlo (Delft University of Technology, MLN Lab)
Marnix Tijhuis (Delft University of Technology, MLN Lab)
Laura Marchal-Crespo (Delft University of Technology, MLN Lab)

Abstract:
Virtual Reality (VR) has been gaining popularity in neurorehabilitation for its potential benefits of increasing patients’ motivation and engagement [1]. An important yet relatively unexplored aspect of VR interfaces is how the patient is represented in the virtual world, e.g., with an avatar. A higher level of embodiment over avatars has been shown to enhance motor performance during upper limb training [2], [3] and has the potential to be employed to enhance neurorehabilitation [4]. However, the relationship between avatar embodiment and gait performance remains unexplored. In this work, we present the results of an experiment conducted with 12 healthy young participants to evaluate the effect of different virtual representations of the participants’ lower limbs on foot placement accuracy while stepping over a trail of 16 virtual targets. We compared three levels of virtual representation: i) a full-body avatar, ii) only feet, and iii) no representation. Full-body tracking was computed using standard VR trackers to synchronize the avatar with the user’s motions. Foot placement accuracy was measured as the distance between the foot’s center of mass and the center of the selected virtual target. Additionally, the level of embodiment of each virtual representation was evaluated through a questionnaire. We found that foot placement accuracy increased with some form of virtual representation, either full-body or foot, compared to having no virtual representation. However, the foot and full-body representations did not show significant differences in accuracy. Importantly, we found a negative correlation between the level of embodiment of the foot representation and the distance of placed foot to the target(r_Pearson=-.65,p=.02). However, no such correlation was found for the full-body representation. Our results indicate the importance of embodying a virtual representation of the foot when performing a task that requires accurate foot placement. However, showing a full-body avatar does not seem to enhance accuracy further. Furthermore, our results suggest that motor performance in this stepping task might be modulated by the level of embodiment of the virtual feet. This work motivates future research on the effect of the embodiment of virtual representations on motor control to be exploited for VR gait rehabilitation.