Optimization of SSVEP-BCI Virtual Reality Stereo Stimulation Parameters Based on Knowledge Graph

Abstract

The steady-state visually evoked potential (SSVEP) is an important type of BCI that has various potential applications, including in virtual environments using virtual reality (VR). However, compared to VR research, the majority of visual stimuli used in the SSVEP-BCI are plane stimulation targets (PSTs), with only a few studies using stereo stimulation targets (SSTs). To explore the parameter optimization of the SSVEP-BCI virtual SSTs, this paper presents a parameter knowledge graph. First, an online VR stereoscopic stimulation SSVEP-BCI system is built, and a parameter dictionary for VR stereoscopic stimulation parameters (shape, color, and frequency) is established. The online experimental results of 10 subjects under different parameter combinations were collected, and a knowledge graph was constructed to optimize the SST parameters. The best classification performances of the shape, color, and frequency parameters were sphere (91.85%), blue (94.26%), and 13Hz (95.93%). With various combinations of virtual reality stereo stimulation parameters, the performance of the SSVEP-BCI varies. Using the knowledge graph of the stimulus parameters can help intuitively and effectively select appropriate SST parameters. The knowledge graph of the stereo target stimulation parameters presented in this work is expected to offer a way to convert the application of the SSVEP-BCI and VR.

Optimal Stimulus Properties for Steady-State Visually Evoked Potential Brain–Computer Interfaces: A Scoping Review

“…Green and colors with smaller wavelength such as red performed the best in terms of their SSVEP response, SNR and accuracy [14,27,29,31,50,57]. However, in other papers, red or green performed worse than the other colors [38,45]. Duart et al reported that the best-performing color is frequency-dependent, with no significant difference between the colors found for the frequencies above the medium-frequency band [31].…”

“…In several articles, the medium-band frequencies (with maxima at 13 Hz, 14 Hz, 15 Hz and 16 Hz) resulted in a higher SSVEP response, SNR and accuracy than the lower-band frequencies with the exception of 10 Hz, which is also a local maximum [14,25,27,31,36,37,45]. In contrast, some work also found higher responses at lower frequencies (e.g., 8.33 Hz) [40] or no significant difference [23].…”

“…Blue, violet and colors with a longer wavelength are assumed to perform the worst in terms of SSVEP response, SNR and accuracy [29,38,50,57]. However, in other articles, blue or violet performed better than the other colors [38,45]. Green and colors with smaller wavelength such as red performed the best in terms of their SSVEP response, SNR and accuracy [14,27,29,31,50,57].…”

“…Duart et al reported that the best-performing color is frequency-dependent, with no significant difference between the colors found for the frequencies above the medium-frequency band [31]. Regarding user comfort, green, violet and blue are reported to be most comfortable, whereas red is reported to provide the worst comfort [14,27,38,45].…”

A comparative study of stereo-dependent SSVEP targets and their impact on VR-BCI performance

“…However, the use of dry electrodes and the characteristics of AR perspective led to interference by various factors, resulting in overall low performance. Zhu et al ( 2023 ) examined the effects of shape, color, and frequency parameters on 3D SSVEP in a VR setting, but without specifically focusing on comparing the characteristics or performance differences between 3D stimulation and flat stimuli.…”