"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."

"Evelyn, Sam’s twin sister Beatrice and I don’t eat this way. But Sam has epilepsy, and the food he eats is controlling most of his seizures (he used to have as many as 130 a day). The diet, which drastically reduces the amount of carbohydrates he takes in, tricks his body into a starvation state in which it burns fat, and not carbs, for fuel. Remarkably, and for reasons that are still unclear, this process — called ketosis — has an antiepileptic effect. He has been eating this way for almost two years."