A Brain-Switch based on change in SSVEP Magnitude

A brain-switch is a two-command Brain-Computer Interface (BCI) that can be used to detect control and no-control intentions of a BCI operator. This paper presents a brain-switch that works on the principle of detecting change in the Steady-State Visually Evoked Potential (SSVEP) magnitude. The SSVEP magnitude was modulated using eyeaccommodation or focusing mechanism. This switch works on the principle that when a person keeps his/her focus stable on an SSVEP stimulus or at a fixation target (kept between the stimulus and the subject), the change/variation in the SSVEP magnitude is lesser as compared to the change that is observed when the subject shifts the focus between the stimulus and the fixation target. Detecting this change, the switch was said to be operated (in control state) when a subject shifted his focus away from the stimulus or towards the stimulus. This switch could achieve an offline accuracy of 97.8 %, True Positive Rate (TPR) of 93.3 % and False Positive Rate (FPR) of 0 % for a subject.