A primer on the problem with fMRI

"There are so many bad brain imaging studies, it's hard to believe," says Nikos K. Logothetis, director of the Max Planck Institute for Biological Cybernetics in Germany. "Too many of these experiments are being done by people who, unfortunately, don't really understand what the technology can and cannot do."

Logothetis and others believe that much of the misuse stems from the visual nature of the data. One study, by researchers at Colorado State University, showed that simply giving neuroscience students images from an fMRI machine, even if the images were redundant or irrelevant, made the students significantly more likely to find the data credible. According to Paul Bloom, a psychologist at Yale, this is because fMRI "has all the trappings of work with great lab-cred: big, expensive, and potentially dangerous machines, hospitals and medical centers, and a lot of people in white coats."

The data looks rigorous - it has the veneer of cutting-edge science - and people assume it's valid, even when the reasoning is shoddy.

"You can't just put people in a scanner and ask them whatever question you want," Logothetis says. "Many of these [fMRI] papers are such oversimplifications of what's happening in the brain as to be worthless."

A typical fMRI experiment goes like this: a subject is slipped into a tight space that's about the size of a coffin. The person is told to lie perfectly still, as even the slightest movement will muddy the results. At first, the subject does nothing. Then, he or she performs the experimental task, which might involve looking at a picture or making a decision.

While this is happening, noisy magnets whir overhead, as the machine detects the slightly different magnetic properties of blood with and without oxygen. The underlying assumption is that more active neurons require more oxygenated blood. Follow the oxygen, and you can construct precise maps of the brain at work.

Last year, the New York Times published an op-ed that used fMRI to investigate the brains of swing voters as they stared at photos and videos of presidential candidates. For instance, the scientists found that pictures of Mitt Romney led to activity in the amygdala, while pictures of Hillary Clinton activated the anterior cingulate. (Interestingly, the only two candidates who inspired "little activity in areas of the brain associated with thought or feeling" were Barack Obama and John McCain.)

Within days, 17 prominent cognitive neuroscientists signed a letter criticizing the study. "We are distressed," the scientists wrote, "by the publication of research . . . that uses flawed reasoning to draw unfounded conclusions about topics as important as the presidential election." The critics pointed out that a specific brain area, such as the amygdala, can be involved in the production of a wide variety of emotions, from fear to pleasure. This makes it extremely difficult, if not impossible, to decipher the hidden feelings of people based on brain scans alone.

This 2008 article from Jonah Lehrer, one of my favorite science journalists, gives a nice commentary on the problems associated with fMRI. For you non-science geeks, this is a technique used to ostensibly take pictures of your brain while you do stuff, like make decisions or view images. It sounds cool, right? Well, that may also be the problem.