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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Feet That Know What Hands Are Doing
13 July 2007 (All day)
Monkeys imitate what they see, but so do humans, only more discreetly. Whether any muscles actually flex, our brains fire up the same pathways needed to perform any action we observe another person perform. But new work on disabled volunteers indicates that the brain instead activates alternate circuits when faced with an action its body cannot physically copy. The research suggests that the brain's motor system may be wired to work toward a goal rather than just duplicating a movement.
Every time you watch someone press a computer key or pick up a cup, regions of your brain unconsciously respond, mapping what you see onto the motor pathways you would use to carry out that same motion. Researchers believe that this so-called mirror neuron system, which consists of a subclass of motor neurons, is critical to learning new behaviors, and perhaps for developing skills like recognizing facial expressions. But neuroscientists have long wondered how the brain reacts if the body lacks the ability to replicate the action.
In a study reported 12 July in Current Biology, a team from the Netherlands, Italy, and France showed videos of hands performing simple actions, like grasping a cup, to 16 "normal" people and two aplasic people born without hands or arms. While the volunteers watched the video, the researchers spied on their brain activity using MRI.
The team found that when observing the hand motions, all the normally developed people activated motor pathways that would have allowed them to hold a cup. The aplasic people activated motor pathways too, but not the same ones, says neuroscientist and senior author Christian Keysers of the University of Groningen in the Netherlands. Their brains lit up in regions needed for moving the feet. The results underscore that the mirror neuron system isn't mindlessly imitating, but working toward a goal, he says. The two people without hands or arms recognized they could lift a cup with their feet--and their brain lit up accordingly.
According to Marco Iacoboni, a neuroscientist at the University of California, Los Angeles, the study nicely demonstrates that "the role of mirror neurons is to let us mirror people, not just actions." However, he points to a great deal of variability in the level and location of brain activity in both groups. Without a larger study, he says, it's impossible to determine whether these phantom movements are universal.