Nevertheless, some researchers suspect that what goes on in synesthetics' brains could help illuminate how all human brains work. In effect, they think that figuring out where the wires get crossed in synesthesia could help draw the brain's whole wiring diagram. If they're right, they have a long way to go. Though the condition has been recognized as a medical mystery for better than 300 years, until recently research had established little more than that the condition was real and was most often to be found in left-handed women. This accord holds only for the three vowels, and nobody knows what it means.
Nobody really knows either what another accord among some synesthetics means.
Tests made with newly available, high-tech equipment indicate that the blood flow in their brains is peculiar indeed. Generally, the greater the blood flow in some section of the brain, the greater the neuronal activity in that section. While one subject reported a synesthetic experience, overall blood flow in his brain increased, but it decreased markedly in the left hemisphere of his brain.