The color of scents: chromatic stimuli modulate odor responses in the human brain

Color has a profound effect on the perception of odors. For example, strawberry flavored drinks smell more pleasant when colored red than green and descriptions of the “nose” of a wine are dramatically influenced by its color. Using functional magnetic resonance imaging (fMRI) we demonstrate a neurophysiological correlate of these crossmodal visual influences on olfactory perception. Subjects were scanned while exposed either to odors or colors in isolation, or to color-odor combinations that were rated on the basis of how well they were perceived to match. Activity in caudal regions of the orbitofrontal cortex and in the insular cortex increased progressively with the perceived congruency of the odor-color pairs. These findings demonstrate the neuronal correlates of olfactory response modulation by color cues in brain areas previously identified as encoding the hedonic value of smells.