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What Are You Thinking?

Breaking the Brain's Code


Scientists at Carnegie Mellon have taken an important step toward understanding how the human brain codes the meanings of words.

Their work could have applications in the study of autism, paranoid schizophrenia and Pick's disease. Ultimately, it could lead to the use of brain scans to identify thoughts.

The team, led by computer scientist Tom M. Mitchell and cognitive neuroscientist Marcel Just, has created the first computational model that can predict brain activation patterns associated with the names of things you can see, hear, feel, taste or smell.

Researchers previously have shown that they can use functional magnetic resonance imaging (fMRI) to detect which areas of the brain are activated when a person thinks about a specific word.

The Carnegie Mellon team has taken that a step further — by predicting these activation patterns for concrete nouns for which fMRI data does not yet exist. The findings are published in the May 30, 2008, issue of the journal Science.

"We believe we have identified a number of the basic building blocks that the brain uses to represent meaning," said Mitchell, who heads the School of Computer Science's Machine Learning Department. "Coupled with computational methods that capture the meaning of a word by how it is used in text files, these building blocks can be assembled to predict neural activation patterns for any concrete noun."

Just, a professor of psychology who directs Carnegie Mellon's Center for Cognitive Brain Imaging, said the computational model provides insight into the nature of human thought.

"We are fundamentally perceivers and actors," he said. "So the brain represents the meaning of a concrete noun in areas of the brain associated with how people sense it or manipulate it."

He explained, "The meaning of an apple, for instance, is represented in brain areas responsible for tasting, for smelling, for chewing. An apple is what you do with it. Our work is a small but important step in breaking the brain's code."

In addition to representations in these sensory-motor areas of the brain, the Carnegie Mellon researchers found significant activation in other areas, including frontal areas associated with planning functions and long-term memory. When someone thinks of an apple, for instance, this might trigger memories of the last time the person ate an apple, or initiate thoughts about how to obtain an apple.

"This suggests a theory of meaning based on brain function," Just added.

Plans for future work include studying the activation patterns for adjective-noun combinations, prepositional phrases and simple sentences. The team also plans to study how the brain represents abstract nouns and concepts.

The research was funded by grants from the W.M. Keck Foundation and the National Science Foundation.

Related Links: Read More  |  Machine Learning Dept  |  Center for Cognitive Brain Imaging

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