March 12, 2007 4:16 AM PDT

This is your brain on TED

MONTEREY, Calif.--If you sense numbers as colors, or see images when hearing a tone, you might be a poet and not know it.

Atypical and subjective responses to colors, sounds, numbers and the like are caused by a neurological condition called synesthesia, a mutation in an area of the brain that can result in a cross-wiring of hearing, vision and touch senses. According to neurologist Vilayanur Ramachandran, synesthesia is eight times more common among creative people such as artists, musicians, writers and poets. (It affects a small portion of the population.)

"One theory (is that) they're just crazy," Ramachandran joked, while speaking here Saturday at the Technology, Entertainment and Design conference (TED), an exclusive confab that draws scientists, tech moguls, politicians and celebrities.

"What's really going on (is that) concepts in different parts of the brain are cross-wired in some people, resulting in a greater sense of metaphorical thinking."

Ramachandran, a fellow of the Neurosciences Institute in La Jolla, Calif., and of the Institute for the Advanced Studies of Behavioral Sciences at Stanford University, was one of the bright spots in Saturday's lineup of speakers on the final day of the four-day TED conference. He touched on various areas of study that he's been investigating to gain a better understanding of the brain--or as he called it, the "3-pound mass of jelly."

He said that scientists advance their understanding of gray matter by examining patients with damage to a small region of the brain. By looking at the selective loss of brain function in a damaged area while other functions are intact, neuroscientists can create a map of functional structure throughout the brain.

Citing one example of such work, Ramachandran talked about a rare condition called cognitive graphical delusion. A male patient suffering from the condition can't recognize his own mother and believes she's an impostor. The condition occurs following a coma caused by a blow to the head.

The Freudian view of this illness, Ramachandran said, would be that the coma had caused the man to get in touch with sexual urges toward his mother from early childhood--urges that are inhibited as the child's cerebral cortex matures. A blow to the head would allow the urges to emerge, and the brain responds incredulously, denying that such attraction is possible.

"That argument never made sense to me," Ramachandran said.

Ramachandran disproved the Freudian view by studying such patients' emotional responses to their mothers, and by studying the portion of the brain that governs emotion, the amygdala. He said that most normal people have an emotional response--perhaps warmth, perhaps terror--when they see their mother (or a picture of their mother). One way to measure that response is by detecting how a patient's hands sweat, an indicator of emotion. If the response is flat, the emotional cord in the brain is cut, Ramachandran said.

"When this chap looks at an object, the visual image goes to the brain and is filtered through the emotional centers. If it's my mother, and I don't experience warmth or terror, how can I account for this inexplicable lack of emotion? It can't be my mother."

He added: "No response (in the patient) shows that that wire going from visual center to the emotion center is cut, the emotions are gone."

Going back to synesthesia, Ramachandran gave the TED audience a visual test to see how many in the audience, which included New Yorker artist Maira Kalman and musicians such as Thomas Dolby, had a touch of the condition. He asked audience members to match each of two names, Kiki and Booba, with either of two different shapes, one bulbous, the other sharply angled.

He said that by matching a name with an image the "brain is engaging in a primitive form of abstraction."

"I suspect you're all synesthesic, and in denial about it."

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