A novel calibration method for SSVEP based brain-computer interfaces

A brain-computer interface (BCI) provides the possibility to translate brain neural activity patterns into control commands without user's movement. In recent years, there has been increasing interest in using steady-state visual evoked potential (SSVEP) in BCI systems. The SSVEP based BCI system requires several simultaneously flickering light sources of distinct frequencies, enabling the user to interact by focusing on one of the stimuli. However, the amplitude of the SSVEP is not the same for different stimulation frequencies or for different subjects. In order to find optimal stimulation frequencies, stimuli are usually processed sequentially; this can take several minutes. This paper introduces a novel multitarget calibration method for SSVEP-based BCIs, which allows significant shortening of the calibration procedure. This approach was successfully evaluated in 5 neurologically intact subjects, shorting the calibration time by four. No major influence on the quality of calibration could be observed.