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Clues to the brain's knowledge systems.

The peculiar inability of a 70-year-old woman to name animals has led scientists to propose that the brain harbors separate knowledge systems, one visual and the other verbal or language-based, for different categories of living and inanimate things, such as animals and household objects. Moreover, testing of the woman suggests that verbal knowledge about the physical attributes of members of a category exists apart from verbal knowledge about their other properties, according to neurologist John Hart Jr. and psychologist Barry Gordon, both of Johns Hopkins University in Baltimore.

The woman, referred to as K.R. by the researchers, suffered brain damage in both temporal lobes as well as patches of damage elsewhere.

K.R. showed no ability to name animals portrayed in pictures. Nor could she name animals based on recordings of easily recognizable sounds they make. Yet pictures and sounds associated with other living or inanimate things posed no problems for her.

K.R. also lacked the ability to identify physical attributes of animals, such as color or number of legs. For instance, when asked about the color of elephants, she claimed they are orange. However, she retained functional knowledge about animals, such as the realization that elephants are not kept as pets.

Further tests indicated that K.R. specifically lacked verbal knowledge about the physical attributes of animals. Her naming of animals did not improve with the aid of physical attributes as clues, such as a picture of an udder following a picture of a cow. But clues involving nonverbal perceptions of an animal, such as the sound "moo," significantly boosted K.R.'s naming accuracy.

She also correctly matched pictures of animal bodies to the appropriate heads and knew when an animal's picture portrayed the wrong color. But when asked, she still could not say which color belonged on, say, a lion pictured as gray,

A verbal system in K.R.'s brain must have mediated her intact knowledge of the functional properties of animals, while a separate visual system allowed her to recognize the physical attributes of animals in pictures, Hart and Gordon contend in the Sept. 3 NATURE.

The verbal system contains "subdomains" of knowledge, they add, since K.R. could not identify visual physical attributes of an animal from its name, but could recall other information about the same animal from its name.

Areas throughout the brain probably coordinate these knowledge systems, the researchers conclude. --B. Bower
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Title Annotation:differences in verbal and visual systems
Author:Bower, Bruce
Publication:Science News
Article Type:Brief Article
Date:Sep 5, 1992
Words:403
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