Early-stage neural processing reveals distinctive responses to saliency-differentiated colors in various types of color vision
Individuals with minority color vision phenotypes have been reported to exhibit enhanced color discrimination and color recognition, which deviate from predictions based on their receptoral sensitivities. However, the specific mechanisms underlying this enhanced sensitivity remain unclear. In this study, we examined the commonality and diversity of neural activity between typical and anomalous trichromats in response to differences in color saliency. Electroencephalography was recorded during an oddball task, in which participants discriminated each of two target stimuli, blue-green and red, from a green standard stimulus. The chromaticity of the stimulus was identical across participants, whereas the relationship of saliency between the target stimuli was expected to be reversed between color vision types. The spatiotemporal dynamics of event-related potentials (ERPs) were analyzed using cluster-based permutation tests. Typical trichromats demonstrated faster behavioral and neural responses to the more salient red target stimulus, with pronounced neural activity spreading from the occipital to the parietal regions in the comparison between the target stimuli. Anomalous trichromats also exhibited similar temporal patterns toward the more salient target stimulus when each target stimulus was compared with the green standard stimulus, indicating comparable processing toward saliency across color vision types. Although a similarity was observed, neither behavioral nor neural responses in anomalous trichromats reflected saliency contrast differences. In addition, a comparative analysis of ERPs between color vision types did not reveal any distinct differences in either target stimulus. Given the large variations in color sensitivity in individuals with anomalous trichromacy, further investigation is required to understand the detailed neural processing in individuals with various color vision types.