Eliciting dual-frequency SSVEP using a hybrid SSVEP-P300 BCI

• Published in: Journal of neuroscience methods Vol. 258; pp. 104 - 113
• Main Authors: Chang, Min Hye, Lee, Jeong Su, Heo, Jeong, Park, Kwang Suk
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.01.2016
• Subjects: Adult; Algorithms; BCI speller; Brain-Computer Interfaces; Brain–computer interface (BCI); Communication Aids for Disabled; Dual frequency; Electroencephalography - methods; Evoked Potentials, Visual - physiology; Female; Humans; Hybrid BCI; Male; P300; Photic Stimulation; Signal Processing, Computer-Assisted; Steady-state visual-evoked potential (SSVEP); Young Adult; Dual frequency; BCI speller; Hybrid BCI; Steady-state visual-evoked potential (SSVEP); P300; Brain–computer interface (BCI)
• ISSN: 0165-0270; 1872-678X; 1872-678X
• DOI: 10.1016/j.jneumeth.2015.11.001

•We propose a hybrid BCI speller that generates both dual-frequency SSVEP and P300.•The hybrid speller employs harmonic flickering frequencies for different stimuli.•The hybrid speller improves SSVEP recognition and reduces stimulation time.•The hybrid speller outperforms conventional SSVEP and P300 spellers. Steady-state visual-evoked potential (SSVEP)-based brain–computer interfaces (BCIs) generate weak SSVEP with a monitor and cannot use harmonic frequencies, whereas P300-based BCIs need multiple stimulation sequences. These issues can decrease the information transfer rate (ITR). In this paper, we introduce a novel hybrid SSVEP-P300 speller that generates dual-frequency SSVEP, allowing it to overcome the abovementioned limitations and improve the performance. The hybrid speller consists of nine panels flickering at different frequencies. Each panel contains four different characters that appear in a random sequence. The flickering panel and the periodically updating character evoke the dual-frequency SSVEP, while the oddball stimulus of the target character evokes the P300. A canonical correlation analysis (CCA) and a step-wise linear discriminant analysis (SWLDA) classified SSVEP and P300, respectively. Ten subjects participated in offline and online experiments, in which accuracy and ITR were compared with those of conventional SSVEP and P300 spellers. The offline analysis revealed not only the P300 potential but also SSVEP with peaks at sub-harmonic frequencies, demonstrating that the proposed speller elicited dual-frequency SSVEP. This dual-frequency stimulation improved SSVEP recognition, increased the number of targets by employing harmonic frequencies, reduced the stimulation time for P300, and consequently improved ITR as compared to the conventional spellers. The new method reduces the stimulation time and allows harmonic frequencies to be employed for different stimuli. The results indicate that this study provides a promising approach to make the BCI speller more reliable and efficient.