Optimization of Stimulus Color for SSVEP-Based Brain-Computer Interfaces in Mixed Reality

Visual Brain-Computer Interfaces (BCIs) often use LCDs or LEDs to present flickering stimuli, which limits its application scenarios. Mixed reality head-mounted displays (MRHMDs) have the potential of improving the practical applications for BCIs. However, it's unclear whether the visual stimulus color designed for traditional BCIs still works in mixed reality. Therefore, this study developed a 10-command SSVEP-BCI system in mixed reality using Hololens2, and explored the system's performance with two stimulus colors (white and red) against four monochrome backgrounds (green, blue, white, and black). Eight subjects participated in the experiment. Cross-correlation task-related component analysis (xTRCA) was used to recognize the target command. Results showed that both stimulus and background colors affect BCI performance. Specifically, the white stimulus color significantly outperformed the red one on the blue and black backgrounds, while the red stimulus outperformed thewhite one on the green and white backgrounds. The color contrast ratio (CCR) between the background and stimulus colors correlated positively with SSVEP recognition accuracy. In mixed reality, SSVEP-based BCIs must optimize visual stimulus color, and the CCR is an important criterion for optimization.

Automated summary

This study developed a 10-command SSVEP-BCI system in mixed reality using Hololens2 and investigated the impact of two stimulus colors (white and red) on four monochrome backgrounds (green, blue, white, and black). The results showed that both stimulus and background colors significantly affected BCI performance, and color contrast ratio was an important criterion for optimization.