NEWTON may have discovered the laws of gravity while relaxing under an apple tree, but his brain knew about them all along, according to an imaging study. It suggests that our brains have an internal model of gravity that helps us understand how objects move under its influence.
Francesco Lacquaniti at the Santa Lucia Foundation and the University of Rome, and his colleagues came up with this idea after observing how poor astronauts are at predicting the motion of objects in zero gravity. Now, using brain imaging, they have pinned down the brain region involved to the vestibular cortex, which handles information from the balance organs in the inner ear. It lit up when subjects saw objects moving normally under the influence of gravity, but was much less active when the movements were unnatural. So the region must be responding to gravity, not just movement.
The vestibular cortex seems to build up an internal model of gravity to help predict an object鈥檚 motion. This is much more efficient than mentally running through thousands of possible types of motion, when most objects move in quite predictable ways, says Lacquaniti. And links to the balance organs may 鈥渃alibrate鈥� the gravity model.
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