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2003

Head Shots
Newsweek, June 9, 2003

It started as an odd feeling of deja vu. Over a few weeks the sensation grew more and more intense, until finally John (not his real name) had trouble concentrating on teaching his grade-school class. Then he started having seizures. His doctors traced the trouble to a tumor in his brain's left frontal lobe. The best option, they thought, was to remove the tumor surgically, and then, just to make sure there were no stray cancer cells, cut away some of the surrounding tissue. But how much tissue could they safely remove? No two brains are organized identically-losing one slice of the brain might have no effect on one patient but paralyze the next. Probing John's brain with electrodes might have offered some crude clues, but it would have entailed removing the top of his skull.

The dilemma came to the attention of Joy Hirsch, director of a new brain-imaging laboratory at Columbia University. She had John put his head in an MRI scanner and run through a series of exercises. He looked at pictures and thought of names. He looked at words and thought of synonyms. He wiggled his fingers. As each task demanded work from his brain, the scanner registered a slight increase in the flow of blood to the active tissue. Hirsch's software crunched the data and produced exquisitely detailed, rainbow-colored pictures of John's brain in midthought. They show to within a cubic millimeter-the size of a peppercorn-where these active regions are in relation to the tumor. "This is a nice case, as clear as it can be," she says, and marks a rainbow blob with a Post-It note. "They can operate without risk."

The technique of functional neuroimaging has revealed a great deal in recent years about the human brain in general, but little about what patients like John really care about: their own gray matter. Hirsch and her colleagues are pushing to capture the brain's activity the instant a thought occurs, and in enough detail to be able to see the tiniest of structures. Their work is only now beginning to save surgical patients from paralysis and blindness, but there's more to come. In the next decade, brain scans may become common-used to diagnose mental illnesses, identify potential criminals and determine if a crime suspect is lying.

Hirsch's work builds on recent advances in magnetic resonance imaging. In MRI, a powerful magnetic field makes some of the atoms in the brain line up like little compass needles; when you wobble the magnetic field slightly, the atoms wobble, too, giving off signals that reveal the brain's anatomy. In 1992, when a Bell Labs scientist discovered how to pick up the firing of neurons, the technology was still too slow and crude to pinpoint the parts of the brain that became active for any given kind of thought. Hirsch invented statistical tools that let her pick out the busy neurons and ignore the brain's ordinary background noise, so that she could get a more accurate scan of an individual brain's activity. Then she incorporated these techniques into software that interprets the MRI data.

Working with neurosurgeons at Memorial Sloan-Kettering Cancer Center, she began to map the brains of surgical patients who had been told their tumors were inoperable. At Columbia, Hirsch has assembled an even more powerful array of equipment that is helping her push MRI technology further. She has a roomful of supercomputers that she's using to uncover heretofore hidden links between different regions of the brain. She's also working to combine MRI scans, which are good at telling you where brain activity is taking place, with data taken from electrodes placed on the patient's scalp, which can discern brain events as brief as a thousandth of a second.

One of Hirsch's immediate goals is to help surgeons with more-complex brain operations. A bigger ambition is, as she puts it, to uncover "those qualities that actually make us human." Each action or thought-from speaking to feeling in love or adding numbers-brings into play a distinct constellation of brain regions. These networks are pretty much the same from one person to another, but observing them requires looking at individual patients. By scanning people while they speak, Hirsch has mapped the brain network that generates language. When she scanned people speaking a second language, she found that they use an identical network-except for a crucial node that shifts a few millimeters away. "Somehow the network is switching back and forth between those areas when calling upon those language skills," she says.

Understanding these networks promises to put psychiatiy on a new footing. Depression, for example, may come from a defect somewhere in the network that attaches emotional values to specific experiences. If scientists can zero in on the damaged nodes, they may be able to help find more effective medications. "We don't have a well-thought-out rhyme or reason for why we use a drag for particular conditions," says Hirsch. "Doctors and patients have to go through a long trial-and-error process before they find a drug that works for them." Scanning people's brains may make the process less random.

If neuroimaging grows simultaneously more powerful and less expensive, it stands to become a bigger part of our lives. Neuroscientists are now pinpointing brain regions that are most active in those who score highly on intelligence tests. Will we judge the prospects of our children someday with a brain scan instead of the SAT? Should we scan the brains of fetuses in the womb? Will people lose their jobs because their neural networks aren't up to snuff? Will criminals be identified before they commit a crime? This is not cyberpunk fantasy. Hirsch's group has already figured out how to tell the difference between a lying brain and one telling the truth. In certain regions of the lying brain, neurons fire more than in the brain of a truth teller. The pattern is so obvious that even an untrained eye can tell the difference.

Hirsch knows she's moving into dangerous waters here. If neuroscientists can identify the networks that influence the behavior of criminals, what about the rest of us? "It is an omen of the future," Hirsch says. "We are going to think of our qualities as humans-our social being, our inner selves-more in terms of our physiology." It will then be up to each of us, not the scientists, to figure out what those pretty pictures mean for our souls.

Copyright © 2003 Carl Zimmer. Reproduction or distribution is prohibited without permission from the author.

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