NEW YORK — Brain scans offer a tantalizing glimpse into the mind’s mysteries, promising an almost X-ray-like vision into how we feel pain, interpret faces and wiggle fingers.
Studies of brain images have suggested that Republicans and Democrats have visibly different thinking, that overweight adults have stronger responses to pictures of food and that it’s possible to predict a sober person’s likelihood of relapse.
But such buzzy findings are coming under growing scrutiny as scientists grapple with the fact that some brain scan research doesn’t seem to hold up.
Such studies have been criticized for relying on too few subjects and for incorrectly analyzing or interpreting data. Researchers have also realized a person’s brain scan results can differ from day to day — even under identical conditions — casting a doubt on how to document consistent patterns.
Earlier this year, Duke University researcher Annchen Knodt’s lab published the latest paper challenging the reliability of common brain scan projects, based on about 60 studies of the past decade, including her own.
“We found this poor result across the board,” Knodt said. “We’re basically discrediting much of the work we’ve done.”
Watching brains ‘light up’
The research being re-examined relies on a technique called functional magnetic resonance imaging, or fMRI.
Using large magnets, the scans detect where oxygenated blood rushes to when someone does an activity — such as memorizing a list of words or touching fingertips together — allowing scientists to indirectly measure brain activity.
Other previous imaging techniques tracked brain activity through electrodes placed on the skull or radioactive tracers injected into the bloodstream. In comparison, fMRI seemed like a fast, high-resolution and noninvasive alternative.
A flurry of papers and press coverage followed the technique’s invention, pointing to parts of the brain that “light up” when we fall in love, feel pain, gamble or make difficult decisions. But as years passed, troubling evidence began to surface that challenged some of those findings.
“It’s a very powerful thing to show a picture of the brain. It lends itself to abuse, in some ways,” said Damian Stanley, a brain scientist at Adelphi University. “People eat them up, things get overblown. Somewhere in there, we lost the nuance.”
Alternatives
With doubts growing, many labs have become more cautious about what imaging techniques to use in efforts to unravel the average brain’s 110,000 miles of nerve fibers.
Yale University researcher Joy Hirsch, for example, wants to understand “the social brain” — what happens when people talk, touch or make eye contact. She’s opted out of fMRI, since it can only be used on a single person who must remain perfectly still for imagining inside a large scanner.
Instead, Hirsch uses an alternative technology that bounces laser lights off of a fiber optic cable-laced skullcap into the brain to detect blood flow. The technique, functional near infrared spectroscopy, allows her subjects to move freely during scanning and permits her to study live social interactions between several people.
