Evaluation of different spelling layouts for SSVEP based BCIs

Brain-computer interface (BCI) systems enable humans to communicate with their environment by directly using brain signals. This way, body movement is not explicitly required for communication making this technology especially useful for people with limited mobility. In this study, the system performance and well-being of 38 subjects are investigated using two different layouts of graphical user interfaces (GUI) presented on a computer screen. A steady state visual evoked potential (SSVEP) based BCI speller is used. Furthermore, three different predefined stimulus frequency sets are tested. Results show that the system works best for 55 % of the test subjects using visual stimuli in the range of 8.57 Hz-15 Hz. The majority of subjects (71 %), prefers the graphical user interface layout called Layout 2. Main advantage of this layout is that each desired letter or symbol can be selected with only two commands in contrast to Layout 1, where usually more than two commands are needed to select a desired object.