A color-coded SSVEP-based brain-computer interface

OBJECTIVE: Steady-state visual evoked potential (SSVEP) based brain-computer interfaces (BCIs) predominantly employ frequency, phase, or spatial coding. This study proposes a color-dimension SSVEP encoding scheme and evaluates its feasibility and elicited response characteristics. APPROACH: Seven isoluminant colors were paired to form 21 combinations, and four stimulation paradigms (sliding checkerboard, reversing checkerboard, flickering checkerboard, and solid-color flicker) were used to investigate the modulatory effects of color on SSVEP. Offline simulations and an online four-target SSVEP-BCI were conducted for validation purposes. MAIN RESULTS: Under identical frequencies and initial phases, different color combinations produced separable SSVEP patterns in amplitude, topography, and phase, enabling reliable classification. At 10 Hz, the online four-target system with solid-color flicker achieved an average information transfer rate (ITR) of 80 ± 0 bits per minute (bits/min). SIGNIFICANCE: The proposed approach introduces an additional encoding dimension for SSVEP-BCI, expanding stimulus design options and supporting broader applications.