Improving SSVEP-BCI System Interaction Efficiency: Design Recommendations for Shape of Visual Stimuli and Number of Auxiliary Stimuli

Currently, brain-computer interfaces (BCIs) have become an important part of advanced human-computer interactions. Its essence is to infer people's ideas or purposes through brain signals to realize human-computer communication. BCI systems based on steady-state visual-evoked potentials (SSVEP) are widely used in the field of BCI because of their high information transfer rate (ITR), low training requirements, and simple system structure. To explore a reasonable design method of visual stimulation in an SSVEP-BCI interactive interface, this study completed two experiments based on the shape and presentation of visual stimulation. Experiment 1 explored the optimal shapes of different visual stimuli. The results indicated that there were significant differences in task completion times for different stimulus shapes. Combined with ergonomics experiment and subjective evaluation results, the circular was the optimal stimulus shape. Experiment 2 used different numbers of auxiliary stimuli under the condition of circular stimulus. The results showed significant differences in task completion time for various auxiliary stimuli, and the number of auxiliary stimuli negatively correlated with task completion time. Through subjective evaluation, it was found that all the median scores of the usability index increased when there were more auxiliary stimuli. The recommended number of auxiliary stimuli was eight. This research provides significant evidence for the design of visual stimulation for SSVEP-BCI systems. The experimental conclusions are of great value for improving the interaction efficiency of SSVEP-BCI systems, enhancing user experience, and expanding application fields. They will also provide new directions and ideas for the interface design of BCI systems, visual stimulation design, and application of advanced interaction technology.