MEG Scanners


MEG Scanners

Postby dignan » Thu Jan 04, 2007 9:51 pm

Not MS-specific, but the technology sounds impressive.

MEG Scanners Are Mega Powerful

January 4, 2007 - Wired - Magneto-encephalography, or MEG, scanners are proving to be one of the most powerful tools in the hands of scientists using the machines to observe important details about epilepsy, brain tumors, emotions, pain perception and more.

While the technology has existed for decades, improved computing power and hardware have recently increased interest in the scanners. There are an estimated 100 MEG scanners around the world -- at a potential cost of $2 million each -- and their numbers are growing.

"The MEG is just exploding," said Robert Knowlton, director of the University of Alabama at Birmingham's Magnetic Source Imaging Laboratory. "It's been around a long time, but it's only now gotten into enough researcher's hands with the technology (being) mature enough."

While other types of brain scans detail the geography of the brain or detect blood flow, the MEG scanners track the magnetic signals that neurons throw off as they communicate. "You can look at how the networks of the brain are talking to each other in real time," said Greg Simpson, director of the Dynamic Neuroimaging Laboratory at the University of California at San Francisco.

The machines are designed to "measure the magnetic field pattern around the entire head and deduce from those patterns where the current flows are occurring within the brain," said Eugene Hirschkoff, vice president of engineering at 4-D Neuroimaging, a MEG scanner manufacturer.

This allows scientists to study magnetic changes in the brain and figure out which areas are busy doing things each millisecond. By contrast, functional magnetic resonance imaging, or fMRI, technology measures the movement of blood within the brain. The scans reveal which brain areas are active and need oxygen from the blood, Simpson said.

But it takes a while for oxygen-filled blood to move in the brain. "If a brain area was active for a 10th of a second, the blood-flow response to that area would take a second or two to start," said Simpson.

That may not sound like a long time, but this is the lickety-split world of the brain. "If I had you read a sentence during an fMRI scan, we'd see the visual cortex light up, the language cortex light up, and other things that would light up," Knowlton said. "But they'd all be lit up, and you wouldn't know which one was first (to become active), which one was most important."

"With the MEG, the sequence becomes more clear," Knowlton said.

One thing they can't do is analyze the physical parts of the brain, so MEGs become even more powerful when combined with other technologies.

When combined with fMRI scans, in particular, "you get the best of everything," Knowlton said.

In a recent experiment, scientists tried to figure out what you might call the Grey's Anatomy effect. When characters on the show get lonely, they act out -- drinking too much at the local bar, baking up a storm in the kitchen, having sex with a guy who ends up with a permanent erection.

Self-medication? Maybe. But a team of scientists prefers to describe the tendency toward bad behavior as cognitive disruption brought on by social exclusion -- a process they think they can see with the help of the MEG.

W. Keith Campbell, a psychology professor at the University of Georgia, and his colleagues recruited 30 female students who underwent what they thought were ordinary personality tests while being monitored by an MEG scanner.

Half the women were told that their test results suggested they would have trouble maintaining relationships and "end up alone in later life." The other women, a control group, got only neutral feedback to their answers, with no indications their lives were destined to go to pot.

Afterwards, all the subjects worked on a long series of math problems. Those who were told they'd grow old alone scored worse than the other women, and "showed less activation in parts of the brain associated with self-control," Campbell said, which is common among people who feel isolated.

"It's almost like it's difficult to think," he said.

A flurry of other MEG studies have come out in the last few months. One German study found that the brain processes pain signals faster than sensations of touch; another measured how quickly subjects recognized people they know.

Scientists are also using MEG scanners to study whether brain waves can be harnessed to control devices outside the body. And researchers are still searching for the holy grail -- an understanding of how parts of the brain communicate with each other, Simpson said. The answer could help autistic people and others whose mental wires are crossed.

For now, though, "MEG allows us to really study in much more detail how brain networks operate," Simpson said. "That makes it extremely powerful and important." ... wn_index_1
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