Read an Ian Fleming novel, and your brain may be preparing to pull the trigger every time James Bond has a villain in his sights. New research suggests that reading about actions activates the brain regions that plan those actions.
In the new study, researchers used functional magnetic resonance imaging (fMRI) to examine brain activity in 12 volunteers as they silently read phrases on a monitor inside the scanner. Each phrase described movements involving one of three body parts: the mouth (as in "biting the peach"), the hand ("grasping the pen"), or the foot ("pressing the car brake"). All of the phrases activated movement-related regions in the left frontal cortex, says lead author Lisa Aziz-Zadeh, a cognitive neuroscientist at the University of Southern California in Los Angeles. And just as different subregions of these motor areas plan mouth, hand, and foot movements, phrases mentioning different body parts preferentially activated different subregions--presumably the ones responsible for moving the body part in question, Aziz-Zadeh says.
The researchers saw a similar pattern of brain activation when subjects viewed video clips of a person performing some of the actions described by the phrases. This type of "mirror" activity has been described previously (ScienceNOW 23 February, 2005), and many researchers view it as a neural mechanism for interpreting the actions of other people by recreating them in one's own brain. The new findings suggest that mirror activity not only reflects directly observed actions, but also extends to inherently more abstract verbal descriptions of actions, Aziz-Zadeh says.
But there may be a limit to how much abstraction the brain's mirror mechanisms can handle: the researchers found that metaphorical phrases like "kick the bucket" did not activate motor planning regions. Even so, says Aziz-Zadeh, the findings suggest that the brain processes language--in part--by cueing up its own representations of the actions conveyed by the words. "Language is often thought of as a higher cognitive function, but it's actually rooted in these motor representations," says Aziz-Zadeh, whose team reports its findings today in Current Biology.
"This strengthens the idea of the mirror system having something to do with language," agrees Christian Keysers, a neuroscientist at the University of Groningen in the Netherlands. However, Keysers thinks the study would have been more compelling if the researchers had asked the subjects to perform the movements themselves to confirm that the brain regions that plan a given action are in fact the same as those that respond to the action when it's observed in a video clip or described in words. "That would be really convincing," he says.