Right-and-left field stimulation with two frequencies for a SSVEP-based brain-computer interface

Only a small number of targets can be presented when using limited frequencies in brain-computer interfaces(BCI) based on SSVEP(steady-state visual evoked potentials).A method was developed for simultaneous right-and-left field stimulation with two frequencies to acquire more targets when using a screen display as the stimulator in SSVEP-BCIs.Canonical correlation analysis(CCA) was applied to extract the frequency components of the right-and-left visual fields.Offline analyses of 5 subjects show that the final accuracy for four of the subjects was more than 85%.Thus,the method with two frequencies can recognize more than twice as many targets as conventional SSVEP-BCIs.