Determining Optimal Frequency for Brain-Computer Interface (BCI)-Based Color Vision Assessment

Color vision deficiencies (CVDs) affect over 20% of the population (Delpero et al., 2005). Thus, it is essential to test for CVDs in occupational and academic settings, especially for people with other disabilities. The goal of the present study was to identify the optimal stimulation frequency for BCI-based color vision assessment that enables the assessment of both luminance and hue differences between the light sources. To identify this optimal frequency, settings of the stimulator were chosen from the following criteria: equal luminance but a different hue; equal hue but a different luminance; equal in hue and luminance (i.e., were metamers); elicited an SSVEP of maximum size. Stimulation frequencies ranging from 2-38 Hz were tested. To verify the relationship between SSVEP amplitudes and hue/luminance, this set of test source settings included settings of similar luminances but different hues in addition to settings of different luminances but similar hues. Results suggest that SSVEP size is influenced by hue differences at low frequencies, and SSVEP size at high frequencies is influenced by luminance differences. Additionally, 16 Hz was identified as the optimal frequency for metamer detection. These findings should be used to increase the speed of BCI systems and improve their use in people with color vision deficits