Investigating Flicker-Free Steady-State Motion Stimuli for VEP-Based BCIs

A modern emerging trend in electroencephalography (EEG) - based brain-computer interface (BCI) systems is the implementation of moving objects as visual stimuli to elicit steady- state visual evoked potential (SSVEP) responses. Motion based stimulation has been proven to be less annoying, while at the same time it elicits a comparably strong response as the commonly used SSVEP. In this paper, we present a BCI system that utilizes an oscillation-like (pendulum) behavior for generating steady- state motion visual evoked potentials (SSMVEP), and evaluate its practical use in a four target BCI spelling application. The SSMVEP was investigated with three different frequency sets (Low 3.00 - 4.29 Hz, Mid 6.00 - 8.57 Hz, and High 9.23 - 12.00 Hz) and compared to the standard SSVEP stimulation. In the online experiment seven participants reached average accuracies of 99.0%, 100%, and 98.65% and average information transfer rates of 25.4, 32.5, and 31.05 bits/min for the Low, Mid and High frequency sets, respectively, with the SSMVEP paradigm. The results showed that the presented SSMVEP approach is suitable for BCI application without the typical discomfort for the user. Interestingly, the Low frequency set evoked a relatively strong harmonic response in this study, with performance comparable to the higher frequency sets.