A Virtual Reality-based methodology for the Study of Human Body Representations

Background: Performing a voluntaryod movement implies a series of procedural steps whose interaction represents challenging topic for neuroscience researchers. For the execution of a successful movement, being aware of body parts placement in the 3D environment – i.e., of one’s body schema – is also essential1. Nonetheless, humans learn to recognize themselves and their body in the mirror2. This creates a discrepancy, as the imagination of a movement occurs from the first-person point-of-view (PoV), whereas its verification in real life occurs with an inverted pattern. As the disruption of body schemas may hinder rehabilitation effectiveness for patients, investigating body schema integrity represents a key point to define a tailored intervention. Virtual Reality (VR) could be a good tool to modify oneself and environment perception. Methodology: We designed a protocol exploiting immersive VR to study body functional representations in healthy (n=30) and neurological (n=20) populations. Participants are immersed in a room with a table in front of them; their aim is to reach, grab, and transport nine cubes in the hole in front of them. This occurs 5 times in 3 conditions: while seeing the cubes and avatar from a first-person PoV (A condition), only in the mirror (M) and only in an inverted mirror (I). We used HTC Vive Pro VR system in its wireless mode; hands and fingers motions are tracked via Vive Trackers and Manus Prime II gloves, respectively. During the whole experiment EEG data are recorded using a 64-channel head cap. Preliminary results: Up to now, we have enrolled 7 healthy adults above 50 y.o, and analyzed kinematic variablnes during the motion phase from the starting position (the hole in the table) to each of the 9 cubes. Gross results showed that people tended to move slower when the perception was distorted (vpeak A: 0.18±0.03, M: 0.11±0.03, I: 0.10±0.02 m/s) and follow longer trajectories (A: 0.37±0.09; M: 0.40±0.14; I: 0.45±0.3 m). We also noticed that direction changes were more frequent during the I condition (no. peaks A: 1.12±0.39; M: 1.90±1.18; I: 2.84±2.94). Interestingly, the had velocity profile was more skewed (symmetry A: 1.39±0.33; M: 1.58±0.56; I: 1.47±0.51), possibly indicating different strategies to face different perception conditions. Conclusion: VR revealed an effective means to perform this study. In the next future, we will complete the participants enrolment and continue with data analysis. New kinematic variables (e.g., a measure of target overshooting), along with EEG signals and neuropsychological tests will be analyzed to better unveil the mechanism underlying reaching strategies in the 3 different conditions. Moreover, the effects of learning will be evaluated.