I've been lying on my back inside a coffin-sized tube for what seems like hours. My head is wedged tight to avoid movement and I have plugs in my ears to cut down on the loud clicks and odd clanks, bings, and bongs inside the tube.

EXPERIMENTAL MAN David Ewing Duncan explores advances in personalized medicine and what they can tell us about ourselves.

My eyes are locked onto a series of images on a screen above my head that display different bets I can choose that involve winning or losing the $100 in cash I was given before climbing into the tube.

I'm undergoing a functional magnetic resonance imaging scan at the Center for Neural Science at New York University to see what happens inside my head when I gamble. The scan, by continually monitoring the flow of oxygen-rich blood, can show which regions of my brain activate and connect to one another based on my expectations, decisions, victories, and defeats.

Understanding this circuitry is part of a decade-old field called neuroeconomics, which is searching for nothing less than a physical basis for why people make the choices they do in business and other activities, and how we might better predict behaviors.

In the tube, I'm given a choice between two pie charts, each one offering a chance to make or lose money. One pie might offer a 50/50 chance of making or losing $5; the other pie would offer a 75 percent chance of losing $5, and a 25 percent chance of winning the same amount.

Obviously, I pick pie No. 1, clicking a button on a small box in my hand. Then the computer decides whether I win or lose, with the odds of each decision dependent on the pie I chose. The test is timed—if I hesitate and don't click a choice in one second, I lose $10.

While I'm gambling, a giant magnet surrounding the tube is zapping my brain with harmless radio waves that can detect subtle changes in the density of tissue inside my head, and measure spikes in blood flow to regions that have been activated either consciously or subconsciously.

In this case, the region is the striatum, which receives inputs from the dopamine neurons in the midbrain. When you get rewards, the brain carries extra oxygen into the stratium, and these increases can be detected by the fMRI.

"We believe that this activity reflects not just the actual outcomes, but also depends on what your expectations were," says Robb Rutledge, a graduate student running this experiment. "We hypothesize that this signal is then used to update your expectations, to learn the value of actions so you make better choices in the future."

I'm also being tested in three days of scans for how risk-adverse I am, and how I make decisions on consumer goods, such as choosing between a DVD of Pirates of the Caribbean versus a CD of the hip-hop artist Axon.

Results are pending, though I suspect my brain was more interested in buying Pirates, with all due respect to Axon.

Rutledge and his colleagues work in the laboratory of neuroscientist Paul Glimcher, author of Decisions, Uncertainty, and the Brain: The Science of Neuroeconomics.

Glimcher is a strong proponent of the idea that brain science can elucidate certain human behaviors that economics theory cannot entirely explain. For example, Glimcher asks: "Why do so many traders buy stocks when prices are high and sell when they're low?"

Good question, I responded, remembering a certain technology stock I bought in the late 1980s.

One explanation is that economic theory has no way of testing or truly understanding how different people assess value, says Glimcher, or how to assign probabilities to outcomes based on these values.

Glimcher says this is critical in understanding how we make choices and execute decisions. "Bill Gates will value a dollar differently than I will," he says. "What is happening in his brain versus mine when he's deciding what to do with that dollar?"
 
Also, how do personal values and decisionmaking pathways in brain circuitry affect risk-taking, and how are repeated experiences with relative values learned by our gray matter?

"Many of us in neuroeconomics believe that we are on the verge of a major new theory using what happens in the brain to explain economic behavior," says Glimcher.

His enthusiasm has not entirely caught on with economists. N.Y.U. and Tel Aviv University economist Ariel Rubinstein has criticized the field as overselling itself because it relies on experiments run on small numbers of subjects—usually students—and uses a machine that does not accurately capture the speed of decisions made in the brain. The brain usually acts at the speed of electrical and chemical signals, while it takes several seconds for blood to reach an area of the brain that has been activated.

Glimcher concedes that the field is still establishing itself. "These are early days," he says, although he contends that the results are already proving insightful.

Back in the tube, I was winning, with my earnings up to $120 at one point—a 20 percent increase. Then came a disastrous final few rounds of betting where my luck shifted and my portfolio tumbled in a matter of minutes to a mere $25.

The scans showed that my brain was not happy about these losses. A more precise assessment will come in a few weeks when my results and scans have been analyzed.

In real life I would have stopped at about $50 and held onto my money, since the original $100 was not mine, and I was still ahead unless I hit zero (which would cause the game to stop).

But in the tube, I was forced to continue, a form of subtle torture that is not unlike what happens when a stock crashes and there is nothing to be done—except to keep it in the hope it will go back up, or sell at a loss.

My midbrain is probably lighting up now even thinking about this hypothetical decision, though I'm not sure if knowing my neural patterns will make the choice any easier.

It might, however, help economists one day understand why I dumped that tech company stock back in the 1980s—which, by the way, turned out to be a good decision since the company later tanked.

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Note: These tests were conducted as research for a book I'm writing, tentatively titled Experimental Man: One Man's Intimate Journey Inside Himself, Cell by Cell. For the book I'm taking high-tech exams of my genes, brain, and body to investigate what can be found out about a person's health, behavior, and future.