A VR-based experimental system for studying mirror visual feedback effects on cross-education.

Cross-education, a phenomenon where training one limb improves performance in the untrained limb, can be enhanced through mirror visual feedback (MVF), underpinning its potential for rehabilitating hemiparetic patients. While MVF-mediated enhancement is documented for simple motor tasks, its effectiveness in complex, fine finger movements remains underexplored. To address this gap, we developed a novel experimental setup to investigate MVF effects on cross-education for a unique typing task involving fine finger movements. The setup comprises three tightly synchronized systems: A novel typing device to implement the typing task, an IMU-based system for accurate real-time hand movement tracking, and a virtual reality (VR) system that provides normal or mirrored real-time replication of hand movements by virtual hands. Additionally, several methodologies and algorithms critical to the experimental task were developed: (1) Constructing participant-specific virtual hand models to accurately replicate thumb-to-phalanx touches. (2) An intuitive approach to manipulating quaternions for coordinate transformation and mirror animation. (3) Millisecond-level synchronization of movement and typing data. (4) Preventing false key press/release detections by filtering noise specific to the typing device. (5) Correcting reference frame misalignment between IMU sensors and their respective hand segments. Some of these methodologies contribute valuable tools to the hand biomechanics and VR research communities. Technical validation of the setup demonstrated robust real-time performance, millisecond-level data synchronization, and precise hand animation, confirming the system’s readiness for investigating MVF-based cross-education.