Brain-Computer-Interfaces (BCIs) provide a novel way of communication by interpreting different types of brain states. This principle of reading minds makes BCIs a challenging but at the same time fascinating topic among the different disciplines of electrophysiology and biomedical-signal-processing. Every BCI is dependent on a specific mental strategy. The mental strategy, or paradigm, can be seen as the BCI’s core translation algorithm, which defines specific brain activation induced by the intention of the BCI user. This activation has to be recognized in the BCI’s input data and must be transformed into classifiable features. Consequently, an Electroencephalography (EEG) based BCI requires an electrophysiological effect, which indicates special intentions of the subject.
Flicker stimuli of variable frequency (5-90 Hz) elicit steady-state visual-evoked potentials (SSVEP) in the EEG signals of occipital area with the same frequency as the stimulus. A SSVEP-BCI enables the user to select among several commands, where each command is associated with a distinct flickering frequency in the operating protocol. These frequencies have to be exposed and evaluated by a SSVEP based BCI’s processing pipeline. Therefore, SSVEP based BCIs require an external visual stimulation. Looking at rectangles, flashing with different frequencies, enables the user to navigate (up, down, left, right) through an alphabet displayed on the LCD-screen. This way the subject can spell complex phrases without the need of physical interaction. In particular, this kind of BCI control is interesting for locked in syndrome patients or patients who lost their motor function due to stroke or other diseases.
We recently started the development of a non-invasive BCI approach using steady-state-visual-evoked-potentials (SSVEP) as a mental strategy. During the development of the BCI at the BMTI (TU Ilmenau), a visual reactive BCI was integrated as a plug-in into the MNE-Scan software. The two videos below show a demo of the proposed BCI and the EEG dry caps developed at the BMTI.