A Novel Three-Dimensional P300 Speller Based on Stereo Visual Stimuli

Abstract

Goal : P300 spellers are among the most popular types of brain–computer interfaces (BCIs) and are extremely useful assistive devices that enable severely disabled patients to communicate. However, P300 speller performances should be further improved to translate laboratory designs into practical applications. We aimed to design a new speller paradigm that could evoke higher event-related potentials (ERPs) than traditional P300 spellers, thus improving the performance of BCI systems. Methods : We proposed a new P300 speller paradigm based on three-dimensional (3-D) stereo visual stimuli. In this paradigm, flashing buttons are presented in 3-D stereo form. We designed two experiments, one that tested a traditional two-dimensional (2-D) speller and another that tested the proposed 3-D speller. Twelve healthy volunteers participated in our experiments. We compared the ERPs elicited by the 2-D speller and the 3-D speller, and we also compared the classification accuracy, information transfer rate (ITR), and user workload between the two paradigms. Results : The 3-D P300 speller elicited higher amplitudes of P300 waveforms than the traditional 2-D P300 speller. The online experimental results showed that the classification accuracy and the ITR were significantly improved with the 3-D P300 speller. We also found that the user workload of the 3-D P300 speller was significantly lower than that of the 2-D P300 speller. Conclusion : The proposed 3-D P300 speller based on stereo visual stimuli outperformed a traditional 2-D P300 speller. This finding indicates that our 3-D paradigm offers a new method that will improve the performance of P300 BCI systems.