Einstein Science Reporting for Kids
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15-Oct-2009

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From thought to speech in 600 milliseconds



Brain scan showing electrodes that surgeons use to find and remove the source of seizures (to cure epilepsy), while sparing the source of mental functions like language. In this study, recordings when patients spoke words revealed that one small part of the brain computes the meanings, structure, and sounds of words, separately and in a quick sequence.
[Illustration courtesy of Ned T. Sahin, PhD / Brain Image Reconstruction courtesy of Sean McInerney]

If a biologist wants to know how something in the human body works, one of the best ways to do this is to study the same process in other animals. But, what about language? We're the only animals who talk!

Not having animal "models" to study is a key reason that we still have so much to learn about what's happening in our brains when humans use language. In fact, it was way back in 1865, that a French doctor named Pierre Paul Broca discovered a region of the brain -- now known as Broca's area -- that is important for the production of language. But scientists haven't made very much progress since then in understanding this brain region.



Brain scan showing electrodes that surgeons use to find and remove the source of seizures (to cure epilepsy), while sparing the source of mental functions like language. In this study, recordings when patients spoke words revealed that one small part of the brain computes the meanings, structure, and sounds of words, separately and in a quick sequence.
[Illustration courtesy of Ned T. Sahin, PhD / Brain Image Reconstruction courtesy of Sean McInerney]

Ned Sahin of the University of California, San Diego and Harvard University and his colleagues had an unusual opportunity study the Broca's area in action. Sometimes, patients with epilepsy undergo surgery in which electrodes are implanted in parts of their brains, in order to treat their seizures. This is one of the few times that humans ever get electrodes implanted in their brains. The scientists got permission from some of these patients to also record from these electrodes, before the surgery, while the patients were doing some language exercises.

The patients were asked to complete an exercise that involved thinking of a single word, changing it from one tense to another (if it was a verb) or from single to plural (if was a noun), and then saying the word silently to themselves. These three tasks correspond to the three basic components of language. The researchers then saw spikes in the electrical activity within the patients' Broca's areas as the patients completed each of the three steps in this exercise. The spikes occurred within an extremely short period of time less than 600 milliseconds which is the amount of time it generally takes us to turn a thought into spoken words.

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This research appears in the 16 October issue of the journal Science.