UC San Diego

Synesthesia is a perceptual experience in which stimuli presented through one perceptual stream will spontaneously evoke unrelated sensory experiences. While synesthesia can occur in response to drugs, sensory deprivation, or brain damage, research has largely focused on heritable variant comprising roughly 4% of the general population. This condition is by definition involuntary, automatic, and stable over time, and evidence suggests that the condition occurs from increased connectivity between the senses. However, the precise mechanisms that give rise to these sensations remain a matter of active debate. Across five studies using electroencephalography, magnetoencephalography, and behavioral measures, we present evidence that early and quick communication between low-level perceptual centers mediates the initial processing stage in synesthesia. Furthermore, this research also suggests early synesthetic mechanisms partially overlap with those that support multisensory processes in the general population. This work clarifies the mechanisms that underlie this interesting condition, and provides a roadmap to using synesthesia as a tool to better understand perceptual and conceptual processes present in all individuals