Boosting Spatial Properties of Single-Flicker SSVEP via Laplacian Electrodes

Spatially-encoded steady-state visual evoked potentials (SSVEP) acquired by electroencephalography (EEG) are extensively utilized in brain-computer interface and neuroscience research. However, EEG suffers from low spatial resolution due to volume conduction effects. To tackle this problem, this study developed a bipolar concentric ring electrode (CRE) for collecting high-resolution Laplacian EEG (LEEG), which was validated through a tank simulation experiment and a human experiment. The tank simulation experiment confirmed its high spatial resolution, and the results showed that LEEG acquired by CRE achieved 2.35 times greater spatial attenuation than EEG. Meanwhile, the human experiment designed a single-flicker SSVEP paradigm with stimuli positioned at different visual field orientations. The results revealed that LEEG had lower inter-channel similarity than EEG, with average coefficients of 0.63 for EEG and 0.46 for LEEG (p<0.01). Topographical analysis further demonstrated that CRE sharpened the spatial features of spatially-encoded SSVEPs, and indicated a clear visual hemifield dominance phenomenon. This study effectively enhances the spatial properties of SSVEP and holds promise for advancing high-resolution LEEG.