Analysis of Pleasure and Displeasure in Harmony Between Colored Light and Fragrance by the Left and Right OFC Response Differences

Daily actions are influenced by sensory information. Several studies have investigated the multisensory integration of multiple sensory modalities, known as crossmodal perception. Recently, visual-olfactory crossmodal perception has been studied using objective physiological measures rather than subjective evaluations. This study focused on sensing in the orbitofrontal cortex (OFC), which responds to visual and olfactory stimuli, and may serve as a physiological indicator of perception. Using near-infrared spectroscopy (NIRS), we analyzed the emotions evoked by combinations of colored light and fragrance with a particular focus on the lateralization of brain function. We selected pleasant and unpleasant fragrances from some essential oils, paired with colored lights that were perceived as either harmonious or disharmonious with the fragrances. NIRS measurements were conducted under the four following conditions: fragrance-only, colored light-only, harmonious crossmodal, and disharmonious crossmodal presentations. The results showed that the left OFC was activated during the crossmodal presentation of a harmonious color with a pleasant fragrance, thereby evoking pleasant emotions. In contrast, during the crossmodal presentation of a disharmonious color with an unpleasant fragrance, the right OFC was activated, suggesting increased displeasure. Additionally, the lateralization of brain function between the left and right OFC may be influenced by 'pleasure-displeasure ' and 'crossmodal perception-multimodal perception'.