For scientist Dr. Anne Adams (and composer Maurice Ravel), a rare disease called frontotemporal dementia caused a burst of creativity.
The disease apparently altered circuits in their brains, changing the connections between the front and back parts and resulting in a torrent of creativity. "We used to think dementias hit the brain diffusely," Dr. Miller said. "Nothing was anatomically specific. That is wrong. We now realize that when specific, dominant circuits are injured or disintegrate, they may release or disinhibit activity in other areas. In other words, if one part of the brain is compromised, another part can remodel and become stronger."
Some of Adams' work can be seen here...her portrait of pi contains a touch of synesthesia. (thx, cory)