An independent brain-computer interface based on covert shifts of non-spatial visual attention

Modulation of steady-state visual evoked potential (SSVEP) by directing gaze to targets flickering at different frequencies has been utilized in many brain-computer interface (BCI) studies. However, this paradigm may not work with patients suffering from complete locked-in syndrome or other severe motor disabilities that do not allow conscious control of gaze direction. In this paper, we present a novel, independent BCI paradigm based on covert shift of non-spatial visual selective attention. Subjects viewed a display consisting of two spatially overlapping sets of randomly positioned dots. The two dot sets differed in color, motion and flickering frequency. Two types of motion, rotation and linear motion, were investigated. Both, the SSVEP amplitude and phase response were modulated by selectively attending to one of the two dot sets. Offline analysis revealed a predicted online classification accuracy of 69.3+/-10.2% for the rotating dots, and 80.7+/-10.4% for the linearly moving dots.