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Inside Two Brains at Once

THINKING ABOUT ROLESCourtesy P. Read MontagueThe brain images show activity for two subjects engaged in a social exchange. The difference in activity may be a result of their different roles in the context of the task.Today's imaging technology can practically gauge brain activity in real time. But scans of a single brain don't offer much information about real life, according to P. Read Montague. "There's a reason that you don't have a cocktail party one person at a time," says Montague, profes

By | March 1, 2004

<p>THINKING ABOUT ROLES</p>

Courtesy P. Read Montague

The brain images show activity for two subjects engaged in a social exchange. The difference in activity may be a result of their different roles in the context of the task.

Today's imaging technology can practically gauge brain activity in real time. But scans of a single brain don't offer much information about real life, according to P. Read Montague. "There's a reason that you don't have a cocktail party one person at a time," says Montague, professor of neuroscience at the Baylor College of Medicine. One partygoer – standing alone, nursing a drink, and chitchatting to no one – hardly replicates people gabbing and gossiping in groups. "The most important things in human life come down to relationships with other people," says Michael Huerta, associate director of neuroscience and basic behavioral science at the National Institute of Mental Health.

To view those relationships, Montague recently upped the ante using a technique he calls hyperscanning to scan the brains of two individuals while they played a game together.1 He selected functional magnetic resonance imaging (fMRI) because it is noninvasive and gives a good view of activity throughout the brain. "I'm kind of simpleminded," Montague says. "If I want to use imaging to study social interaction and I can't put two people in the bore of one magnet, I have to put the scanners together." Luckily, Baylor owns two.

These scanners predict brain activity by measuring the so-called blood oxygenation level-dependent (BOLD) contrast, changes in blood's magnetic characteristics related to differences in levels of oxygenated and deoxygenated hemoglobin. The trouble, Montague says, is that BOLD is sluggish. It takes two seconds to scan an entire brain. To see what goes on in each brain at the same time, the scans must be perfectly synchronized. "Once you have that," Montague says, "you can hunt for cross correlations between the brains, or regions that get activated together between the subjects."

THE BRAIN'S TRUST

Montague's subjects watch each other on video monitors as they are being scanned. In one set of experiments, they play a trust game. In essence, subjects keep or invest money in a common pot, where the money can grow or be taken by the opponent. All the while, Montague scans their brains. In recent results, Montague may have found the first social interaction map. The data, which have yet to be published, show specific areas activated while playing such a game.

Maps of brain activation patterns make sense for perceptual tasks, such as audition and vision, because highly specialized brain regions provide those capabilities. It is harder to interpret similar maps generated for a process as complex as social interaction. Huerta says that neuroscientists generally think of high-level functions as being distributed or spread over a considerable area. "Any social map would be very high level," he says, "and it's always possible that the map is of something else, something that you are not controlling for." He adds, however, "The other possibility is that Montague is absolutely right."

Other research does reveal high-level function localized to specific areas. For instance, a recent study by Jeffrey Schall's group at Vanderbilt University examined the activity of single neurons in the anterior cingulate cortex.2 In the experiment, a monkey was rewarded if it looked at the right place for the right amount of time. This revealed a group of neurons that responded to whether the monkey got the reward. Schall says this suggests that part of the anterior cingulate cortex "is sensitive to the consequences of actions."

Paul Matthews, director of the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, says there's potential in Montague's work. "This might provide a way of looking more precisely at context-dependent brain reactions." Broader applications may exist. "This is linked to theory of mind," Matthews adds, an understanding of why one person empathizes with another or even knows that another exists. This capability helps humans socialize, but deficits make up prominent features of many diseases, including autism, depression, and schizophrenia. Huerta says, "Knowing what's going on in a normal brain compared to one affected by one of these disorders would be tremendously exciting and important."

Moreover, if two brains are better than one, more brains could be better still. So, Samuel McClure – Montague's former graduate student and now a postdoctoral fellow at Princeton University – plans to simultaneously image the brains of four subjects as they make related economic decisions. Overall, Huerta says, "this work is just getting started. Maybe Montague will interest other scientists, especially social psychologists, to bring their expertise and acumen to this technology."

Mike May mikemay@mindspring.com is a freelance writer in Madison, Ind.

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