"The study of synesthesia has helped shift the way scientists think about the brain. In the past, they have focused on matching different areas with specific functions; now, the entire organ is viewed as a tapestry of interwoven connections.

"The whole system is a giant network," Eagleman says. "It's no longer sufficient to think about single areas in isolation."

Like synesthesia, many neurological disorders — such as schizophrenia, autism,Alzheimer's disease, depression and epilepsy — have been linked to abnormal communication between brain regions. The hope is that as neuroscientists learn about how the connections in the synesthetic brain differ from those in normal brains, they will also gain insight into how these differences develop — and how they sometimes manifest as harmful disorders."