It's not unlikely that Rushdie and Ramachandran may have met of even know each other, given that they are both of Indian descent, but I found it odd or perhaps its Rusdhie's sense of black humor, that the character who displays synesthesia is crippled by it and in no way is an artist, poet or writer, but instead a warrior.
As far as synesthesia goes, I've talked to some fellow artists, actually quite a number of them and a good many exhibit some of the characteristics and are grateful for them, while a few do feel the genetic trait as a curse.
As Ramachandran explains, the brain in the fetus is a mass of connected cells. As it grows the embryo eliminates portions of the brain, cells structures, as it carves out our personality, qualities, limits and awareness. In some people the organism forgets to disconnect various senses from each other leading to an automatic way of perceiving reality which is combined in the individual. Some people with such a c9onnection don't even realize other people don';t have it, others feel different and outcast, yet even others capitalize on it in their creative work through perception, metaphor, expression that is unique and often found strange or intoxicating and intriguing.