A novel command generation method for SSVEP-based BCI by introducing SSVEP blocking response

Abstract

Increasing the number of commands in a steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) by increasing the number of visual stimuli has been widely studied. This paper proposes a novel BCI paradigm based on SSVEP and SSVEP blocking responses (defined as the disappearance or attenuation of the ongoing SSVEP) to increase the number of BCI commands with limited visual stimuli, in which the duration of SSVEP blocking response can be voluntarily controlled by users. Besides, this paper also proposes a frequency-specific threshold method and a unified threshold method to identify SSVEP blocking response. The paradigm includes a frequency recognition phase and an SSVEP blocking response identification phase. Filter bank canonical correlation analysis is used to detect the stimulation frequency, and the proposed threshold method is used to identify the SSVEP blocking response and calculate the blocking duration. The experimental results show that the two proposed threshold methods can effectively identify the SSVEP blocking response with different blocking duration and alternative stimulation frequencies. When there are Nf stimulation frequencies, the number of commands can be increased to Nf×Nt using the proposed paradigm, where Nt blocking durations correspond to each stimulus. This study demonstrates that the proposed paradigm based on SSVEP and SSVEP blocking responses is effective in increasing the number of BCI commands and has great potential for practical applications.