New data shows that an old model of the brain's motor cortex is incomplete
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The simple act of reaching for a cup of coffee takes a lot of brainpower. The brain has to control dozens of muscles, process information from the eyes and the fingertips, and make sure you get that jolt of caffeine. And as NPR's Jon Hamilton reports, scientists now think they know how all of this happens so smoothly.
JON HAMILTON, BYLINE: Researchers at Washington University in St. Louis have spent years using MRI scans to create detailed maps of the wiring in people's brains. Dr. Nico Dosenbach says one day they noticed something odd in the primary motor cortex, an area that controls muscles.
NICO DOSENBACH: It just didn't make sense if the textbook was right.
HAMILTON: Textbooks show an unbroken ribbon of cortex, with segments devoted to specific muscle groups, like the tongue or a toe. But the scientists were seeing areas between these segments that were not in textbooks, and these areas were not controlling muscles. Dosenbach's colleague, Evan Gordon, says, at first, they thought it might be a mistake.
EVAN GORDON: Is this just something weird about the data we have collected, or is this present in other people? So we went and gathered together data from a bunch of different sources.
HAMILTON: Dosenbach says the data confirmed their own observations.
DOSENBACH: This heretical thought that maybe this is right and the book is wrong started to take hold.
HAMILTON: But if these mysterious bits of brain weren't controlling muscles, what were they doing? Gordon says to find out, the team did some experiments on their favorite subject - Nico Dosenbach.
GORDON: We put Nico in the scanner a long time and had him do a whole bunch of different stuff until we figured it out.
HAMILTON: Complicated stuff, like rotating his left hand in one direction while rotating his right foot the other way. This meant Dosenbach's brain had to plan his movements before carrying them out, and Gordon says that revealed something surprising.
GORDON: We found that these regions in motor cortex were more active during this planning phase. And that's what really pointed us in the right direction.
HAMILTON: Ultimately, Dosenbach says this led to a new map of the motor cortex.
DOSENBACH: There's two interleaved systems. So it's a checkerboard pattern. It's specific body parts. So it would be like your fingers and your hand, and then below it will be a region that is essentially whole-body integrative action.
HAMILTON: In other words, these areas integrate information from all over the body and brain in order to carry out a movement. Dosenbach says the finding, which appears in the journal Nature, contradicts a central belief about motor cortex.
DOSENBACH: The region that controls your finger is not going to be connected to a region that has something to do with like, what am I going to do today? And that's exactly the kind of connectivity we found.
HAMILTON: To be sure, they reviewed several huge databases of MRI brain scans. And once again, Gordon says, they found evidence of two interleaved systems, one for specific muscles and one for the whole body and brain.
GORDON: It always was there, but we had not perceived it, and it was because of the things we learned in the first neuroscience class that we ever took.
HAMILTON: Early on, the team shared their finding with Peter Strick, the scientific director of the University of Pittsburgh Brain Institute.
PETER STRICK: Sometimes you have this aha experience. And they showed me some of their data, and it instantly clicked.
HAMILTON: Strick says other groups have noted flaws in the textbook version of the motor cortex, but the Washington University team is offering a totally new explanation.
STRICK: I see this as a really fundamental change in how we're going to view the motor cortex.
HAMILTON: Strick says the finding helps explain how the brain solves a difficult problem created by actions like getting out of a chair.
STRICK: Even simple movements require nuanced control of all organ systems. You control heart rate. You have to control blood pressure. You have to control the so-called fight and flight responses.
HAMILTON: And Strick says the interleaved system probably helps explain the mysterious connection between what's going on in our bodies and what's going on in brain areas involved in thoughts and emotions.
STRICK: How you move can have an impact on how you feel. And how you feel is going to have an impact on how you move. There's potential for interplay. You know, my mother would tell me, stand up straight, you'll feel better. Well, maybe that's true.
HAMILTON: All because of a system not found in any medical textbook, yet.
Jon Hamilton, NPR News.
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