When Peter Graser underwent an MRI scan at Emory University, doctors weren't looking for disease.

Instead, brain researchers flashed images -- Madonna, broccoli, sushi, a Ford truck, a golden retriever, Bill Clinton, Coca-Cola -- before the 37-year-old Marietta resident's eyes as he lay inside the coffin-like tube of the magnetic resonance imaging machine.

The scientists discovered a biological clue to what drives consumers: Whenever Graser and a dozen other study volunteers saw a picture they particularly liked, their brains showed increased activity in the medial prefrontal cortex -- an area associated with preference, or sense of self.

On this Super Bowl Sunday, when advertising swells to a fever pitch, the researchers' conclusion is especially appropos: What really makes us loyal purchasers is a brand that reflects our self-image, not a product's taste, size, color or convenience.

The study, funded through the Atlanta consulting firm BrightHouse by an undisclosed Fortune 500 client, has stirred up controversy about the emerging -- and some say Orwellian -- field of "neuromarketing." Scientific tools such as MRI scanners, which allow researchers to peer into the brain and better understand depression, addiction, autism and schizophrenia, should not be used by Coca-Cola, McDonald's or Ford to entice people to buy more of their soda, french fries or sport utility vehicles, critics say.

"It's wrong to use medical technology for marketing and not for healing," said Gary Ruskin, executive director of Commercial Alert, a Portland, Ore.-based nonprofit organization that has worked to bar advertising from schools and other public areas. "We have epidemics of obesity, diabetes, alcoholism, gambling and smoking -- all tied to marketing. Any increase in the effectiveness of advertising can be devastating to the public."

Justine Meaux, research director of BrightHouse Neurostrategies Group, a division of BrightHouse, said neuromarketing helps companies understand customers' true desires better than the standard marketing approach, focus groups.

"A lot of what motivates our behavior occurs below the level of conscious awareness," said Meaux, a neuroscientist. "We give [companies] insight into how to develop relationships with consumers."

Meaux winces at the allegation by some that BrightHouse is searching for a "buy button" in the brain.

"The brain is not that simple," she said. "It's not like consumers are going to run out like automatons and buy your product no matter what they think or feel."

Unease about advertising

Neuromarketing is a commercial offshoot of the burgeoning field of medical research known as cognitive neuroscience. Researchers are using souped-up MRI scanners and other brain-imaging machines to uncover biological explanations for mental illness -- and to elucidate why we hate, envy, love or cooperate.

BrightHouse and Emory are among a few neuromarketing pioneers. The Mind of the Market Laboratory at Harvard Business School also has conducted similar studies.

Read Montague, a neuroscientist at Baylor College of Medicine, has applied MRI technology to the "Pepsi Challenge." In his lab, the brains of test subjects who prefer Pepsi lit up in the region where people process feelings of reward, such as taste. But Coca-Cola lovers displayed activity of a higher order -- in the medial prefrontal cortex, the same sector revealed in the Emory experiment.

Pepsi wins many taste tests, but Coke sells better because people are subconsciously influenced by Coke's full-of-life image, Montague said. "Nobody had ever measured the neurocorrelate of it," he said.

He said he is organizing a national neuromarketing conference at Baylor this spring, to allow companies considering the technique to hash out economic and ethical issues.

Many Americans have felt uneasy about the power of advertising since the post-World War II explosion of consumerism. Fears of subliminal messages and corporate manipulation took root following Vance Packard's 1957 book, "The Hidden Persuaders." The anxieties continue to echo through cultural references such as Steven Spielberg's 2002 movie "Minority Report."

Most ethicists have only recently heard of neuromarketing, said Jonathan Moreno, president of the American Society for Bioethics and Humanities and director of the Center for Bioethics at the University of Virginia.

"It kind of distorts the marketplace relationship," Moreno said. "There's supposed to be a level playing field between a buyer and a seller. But [with neuromarketing], there isn't an opportunity for the consumer to create a screen against the information. It violates the notion that it's possible for the buyer to beware."

Coercive technology?

Richard Glen Boire, legal counsel for the Center for Cognitive Liberty and Ethics in Davis, Calif., said marketers have tried to tease out subconscious attractions to products for decades.

Neuromarketing "seems like it's really getting close to coercive use of technology," Boire said. "But so far we don't see it crossing that line. People have enough self-responsibility to say, 'I'm not going to buy it.' "

The leaders of BrightHouse, located in a former soap factory on Atlanta's west side, say neuromarketing empowers consumers. By stressing brand affiliation over product design, the technique encourages companies to develop positive images and act accordingly, instead of hawking endless streams of "new and improved" products, they maintain.

Clinton Kilts, an Emory behavioral scientist who is scientific director of BrightHouse Neurostrategies, said people choose Ben & Jerry's ice cream largely for reasons other than taste. The Vermont company is community conscious, its owners reject the power structure by wearing flannel shirts, and flavor names such as "Cherry Garcia" appeal to baby boomers who identify with such bands as the Grateful Dead, he said.

The more people's brains illuminate a longing for good corporate citizenship, Kilts said, the more companies will respond.

"We want to give consumers the power to influence companies," he said. "I, like everyone else, have become fed up with the saturation of advertising."

Joey Reiman, chief executive of BrightHouse, said he's really after the consumer's heart, not the brain.

"We're trying to understand what makes people resonate," Reiman said. "Do I fly an airline that gets me there faster, or do I fly an airline that actually lifts me up? Do I wear pants that fit or that fit into my life?"

Ruskin, of Commercial Alert, doesn't buy the pitch that neuromarketing will help people. "I think they're spinning faster than a drill bit," he said. "It's plain old market research taken to a new and potentially more damaging level."

BrightHouse won't name the Fortune 500 client that paid about $250,000 for services including the neuromarketing study at Emory, conducted by Kilts and Meaux. But BrightHouse's only current Fortune 500 clients are Coca-Cola, Delta Air Lines, Georgia-Pacific and MetLife.

Emory officials weigh in

BrightHouse isn't conducting any neuromarketing studies at Emory now but plans to do more. Kilts said Emory administrators have asked him to prepare a conflict-of-interest management plan before pursuing more studies using one of Emory's two research-designated MRI machines. The request came after Commercial Alert sent a letter to Emory complaining about the research.

Dr. Robert Rich, executive associate dean of Emory's School of Medicine, defended the BrightHouse study, saying the researchers presented their findings at a scientific meeting and expect to publish them in a peer-reviewed journal.

"It's obvious that if you understand how people make decisions, there would be commercial uses for it," Rich said. "I see nothing nefarious in that."

Graser, the study volunteer, said he isn't worried that his half-hour entombed inside the MRI scanner could arm marketers with dangerous insights into his mind.

"Big government and big companies have been trying to manipulate us since the start of time," he said. "What's different about this?"