Neuroscience is tackling a problem that obsessed Hamlet: What is the difference in our minds between talk and action?

Less than you would expect, an international research group reports in the Sept. 19 issue of Current Biology.

The brain's premotor cortex shows the same activity pattern when subjects observe an action as when they hear words describing the same action, the study's authors said.

"If you hear the word 'grasp,' it's actually the premotor cortex that's active, not just a separate, abstract semantic area in the brain," said lead investigator Lisa Aziz-Zadeh, assistant professor of occupational sciences with a joint appointment in the Brain and Creativity Institute of the USC College of Letters, Arts and Sciences.

The premotor cortex has long been identified as a center of activity for actions. The notion that it could also process verbal descriptions of those actions has met some resistance.

"Neuroscience is coming around to this idea, but there hasn't been much data supporting it," Aziz-Zadeh said.

To change that, Aziz-Zadeh recruited 12 volunteers and used functional magnetic resonance imaging (fMRI) to compare the same areas of the premotor cortex in the same subject as the person observed an action and heard language describing the action.

The premotor area involved during observation of a specific action, such as kicking, also lit up when the subject heard the corresponding word. This was the first study to make such a direct comparison, Aziz-Zadeh said.

Other studies found activity in the same areas during execution of an action, Aziz-Zadeh added, offering indirect evidence for the existence of "mirror neuron" systems that activate both when a person performs a task and when the person watches someone else perform the task.

"The study does demonstrate the intimate linkage between the way we talk about actions and the neural machinery that supports those ac
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Contact: Carl Marziali
marziali@usc.edu
213-740-4751
University of Southern California
18-Sep-2006