392161 Projekt "Agency in Stroke Survivors" (PjS) (SoSe 2017)

Summary
Motion capture, body modeling, and eye-tracking in a functional virtual environment for research on the cognitive neuroscience of stroke rehabilitation, with core features and additional opportunities for skill development in programming and VR design.

Project Background & Aims
Stroke is a leading cause of disability. A stroke results from a blood clot blocking oxygen from reaching the brain, resulting in cell death. Stroke survivors often suffer from chronic disability, including sensorimotor and cognitive impairments. These functional deficits result in a decreased sense of agency (control; volition; authorship) in everyday life due to inability to execute normal movements and other actions. The sense of agency has been shown to modulate or affect the sense of body ownership (the feeling of one's body or body parts being one's own). A neuro-computational interpretation of disability in stroke would view the stroke-affected brain area(s) as being unable to reliably update sensory information about the affected limb, manifesting as disrupted proprioceptive accuracy and movement.This forms a cycle of progressively learned disuse and impaired sensorimotor information processing. Novel rehabilitation techniques and interventions are in dire need, and a cognitive neuroscience characterization of sensorimotor agency in stroke is poised to significantly aid rehabilitation. So far, the aforementioned neuro-computational view—termed “predictive processing”—remains to be validated in stroke pathology. My PhD work aims to characterize agency deficits in stroke survivors using multisensory experimental paradigms, cognitive modeling and analysis of kinematics, and a predictive processing perspective. The proposed project will utilise virtual reality to manipulate multisensory information in order to elucidate the impairments in agency and body ownership in stroke survivors. This project would form a touchstone for potential further development of this type of application and aid in the rehabilitation of movement disorders.

Project Description
The project involves crafting a virtual environment in which stroke survivors and healthy age-matched controls would be tested in trials, each consisting of several scenes, with the participant's virtual avatar in the 1st-person. Participants are first exposed to exposed to a virtual version of the famed Rubber Hand Illusion (RHI), followed by a reach-to-grasp task (with eye-tracking) that employs experimenter-chosen manipulations in visual feedback of actual movement (e.g., veridical/ no change, kinematic noise, & enhanced/amplified movement toward target), after which they make explicit judgments about their performance and the sense of agency/control over their movements. Participants are then re-exposed to the RHI and asked to make a precisely timed explicit judgment via footswitch of tactile stimulation. Finally, participants are asked to perform a reach-to-grasp task with eye-tracking. The project has core features as well as additional opportunities for further skill development in programming and design.

The core/required features of the project are

• A stable, simple, and relatively high-quality virtual environment that promotes an aesthetically pleasant and non-distracting user experience
• 3D modeling of arms
• Motion capture of arm and finger movements reaching towards a target; recorded and continuous real-time saving of kinematic data at a strong (as much as possible) sampling rate
• Eye-tracking during all reach-to-grasp movements
• Code editable by experimenter
• Options configurable and pre-selected by experimenter via user-friendly menu-style interface that can toggle various parameters:
• Ability to skip certain scenes; visuo-tactile stimulation frequency and speed; arm skin color; arm mirroring (actual movement of one arm is mirrored onto the contralateral virtual arm); display of either one or both arms; visual movement feedback parameters (veridical, noise, & enhancement); number and length of trials of each kind; automated vs. veridical representation of finger movements; position and angle of virtual arm(s); footswitch integration for answering prompt; ability to black out visual feedback of arm movements in the final reach-to-grasp

Potential additional features of the setup could include:
1. Achieving a high degree of realism in arm modeling; utilizing scans of actual arms and representing them in the virtual environment
2. Comparison of motion tracking systems for the application
3. Comparison and configuration of eye tracking systems for the application
4. …

The project should be made for the HTC Vive and preferably be coded in Unity.

Requirements for participation, required level

Previous participation in the lecture Virtual Reality is required.

Bibliography