Brief and context-free color-pain interaction: Behavioral and electrophysiological evidence for awareness-dependent effects

Pain experience extends beyond nociceptive processing, being modulated by other senses. It has been demonstrated that prolonged exposure to colorful lights and brief exposure to color manipulation in embodied context modulate pain. The present study revealed that pain can be modulated by color in a third approach, in which color is briefly flashed within a context devoid of embodiment. Our behavioral results demonstrated that viewing brief and context-free red significantly increased both thermal and electrical pain experience, but only when color was consciously perceived. Our electroencephalography (EEG) results further characterized the neural dynamics of color-pain interaction by employing Global Field Power analysis. Color significantly shortened the latencies of the two pain-related components (237-287 ms and 346-446 ms), with red selectively accelerating the earlier one. Bidirectionally, pain significantly enhanced the amplitude of color-related component (120-170 ms). When the amplitudes of the three components evoked by simultaneous color-pain stimulation were compared with their summed unimodal responses, we only observed a subadditive nonlinear effect for the late pain-related component. Overall, the current study bridges previous research by introducing a simplified framework for investigating color-pain interaction, and demonstrates that color exposure can modulate pain perception in an awareness-dependent manner without requiring prolonged exposure and embodied context. It further illustrated that the neural correlates of color-induced pain modulation emerge at a later stage compared to pain-induced color modulation. This temporally asymmetrical interaction between color and pain possibly reflects an innate priority or strategies in sensory processing when encountering harmful dangers.