THURSDAY, March 18, 2004 (HealthDayNews) -- At the same time your brain is deciding if a sentence or phrase makes grammatical sense, it's also assessing the truth of the statement.
That's the conclusion of a study appearing in the March 18 issue of Science online.
To see how your brain deals with untrue statements and sentences that just don't make sense, researchers from the Netherlands used two different brain-scanning technologies to determine which areas of the brain were activated for each circumstance.
"Semantic interpretation and sentence verification are done in parallel," says the study's lead author, Peter Hagoort, a professor of cognitive neuroscience at the University of Nijmegen and the director of the F.C. Donders Centre for Cognitive Neuroimaging in Nijmegen, The Netherlands.
And, says Hagoort, all of this activity takes place in the left inferior prefrontal cortex.
Hagoort says this study should settle the debate among scientists, some of whom believe that the meaning of a sentence had to be deciphered before a person could assess whether a statement is true.
For this study, Hagoort and his colleagues used functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) scans to study the brains of 30 Dutch-speaking volunteers as they read aloud different sentences.
One sentence -- "Dutch trains are yellow" -- was true. One -- "Dutch trains are white" -- was false. And one simply didn't make semantic sense -- "Dutch trains are sour."
Hagoort explains that knowing whether Dutch trains are white or yellow has to do with your world knowledge. But trying to decipher the sentence about Dutch trains being sour calls on word meaning knowledge.
In another example, Hagoort says the sentence, "George Bush is the President of Mexico," would call on your world knowledge, while the statement, "The rock is President of Mexico," would call on your word knowledge to decipher.
In this study, the researchers found that both the EEG and the fMRI data were very similar.
That means, the researchers conclude, "It does not take longer to discover that a sentence is untrue than to detect that it is semantically anomalous. While reading a sentence, the brain retrieves and integrates word meanings and world knowledge at the same time."
The researchers also discovered that the brain uses the left prefrontal cortex to complete either task.
Hagoort says this knowledge could be useful in several ways, such as diagnosing people with left frontal brain damage, or in adding to the understanding of certain disorders, such as autism, where people have a hard time invoking world knowledge.
The authors add that the brain also keeps track of what makes a statement hard to understand.
Language researcher Maryellen MacDonald, from the University of Wisconsin, says this study confirms a lot of what is already known.
"This is entirely consistent with how we know people understand language," says MacDonald. "Even though we can distinguish different shades of language, it need not mean that difference is realized in different regions of the brain."
While she says she doesn't see any immediate practical implications from this work, she adds, "Every step that helps us understand the brain mechanisms and the location of language comprehension brings us that much closer to helping people with brain injuries and language deficits."
More information
To learn more about how the brain processes language, visit the Linguistic Society of America. For more information on how the brain works, go to the National Institute of Neurological Disorders and Stroke.
