What Color is an Orange?
Brain stores knowledge, hue of things separately
THURSDAY, May 24, 2001 (HealthDayNews) -- Knowing that an orange is a fruit and that an orange is orange are retrieved from different parts of your brain, new research shows.
A study of a woman whose brain was damaged by stroke shows that knowledge about an object and information about its color are segregated in the brain, not all crammed together in the same place. The study provides researchers with important new clues as to how knowledge is organized in the brain.
"What we've been trying to figure out is how the brain is organized, how it carries out the remarkable tasks of language and of reasoning out the world," says Alfonso Caramazza, a professor of psychology in Harvard University's Cognitive Neuropsychology Laboratory in Cambridge, Mass. "And what our study shows is that multiple levels of information are processed in different parts of the brain and processed in different ways."
Caramazza and his colleagues say the stroke left the woman without the ability to link colors to objects.
"The picture of her stroke was quite complex, as it is in most cases of brain damage," Caramazza says. "She had extremely severe difficulties in actually naming objects, but what was remarkable about the patient is that she was essentially spared the knowledge of the object she could not name."
"If you asked her to name a chair, she'd have trouble naming it," Caramazza says. "But she knew it was a chair. And what was especially remarkable is that she could provide you, in exquisite detail, information about a banana, for instance: that you eat it, where it grows, its shape. And if you gave her a color chart, she could identify all the colors without any problem and she could name all the colors."
"But she could not tell you that a banana was typically yellow, and she had difficulty saying that a fire truck was typically red," he says.
The study shows that the knowledge of an object like a banana or a fire truck and the properties of that object are stored independently in the brain, Caramazza says. "Knowledge of what red is is independent of the knowledge that a fire truck is red," Caramazza says. "What this study leaves unanswered is how the brain creates a unified representation of a yellow banana or a red fire truck. What we now know is that the brain pulls from different areas the information necessary to create a whole picture of an object."
The findings were published in June's issue of Nature Neuroscience.
"These are extremely exciting findings that are consistent with clues from our earlier imaging studies," says Alex Martin, chief of the National Institute of Mental Health's Section on Cognitive Neuropyschology in Bethesda, Md. "This really demonstrates the separation between perception and knowing, but also demonstrates the separation between knowing about one type of feature of an object, like color versus another feature, like form."
Martin says understanding how the brain is organized answers a "basic question about human cognition, to the extent that people think it's important to understand how memory is organized and how the brain works."
"Our hope is that understanding brain organization will provide us with some clues as to how to help people with brain damage, like those who are having trouble remembering names, for example," Martin says.
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