Economics theory can help trace information flow between brain regions

October 10th, 2008 - 11:52 am ICT by ANI  

Washington, October 10 (ANI): Researchers at Washington University School of Medicine in St. Louis and Florida Atlantic University say that they have adapted a technique originally developed for economic study to determine the flow of information from one part of the brain to another.
Writing about the use of the technique called Granger causality in The Journal of Neuroscience, the researchers said that it could provide important insights into brain organization and function, advancing efforts to help patients recover from brain injuries and mental disorders.
For years, scientists have used scanners to identify the brain regions involved in particular mental tasks, but have failed to get the required data fast enough to trace the flow of information from one area of the brain to another.
“It’’s been like getting a picture of the members of an orchestra but not knowing the sequence in which each instrument was playing,” says senior author Dr. Maurizio Corbetta, the Norman J. Stupp Professor of Neurology.
“Now, for the first time, we can look at the questions of who’’s talking to whom in the brain, and what directions the activations of brain areas are flowing in,” the researcher added.
Granger causality was developed by Sir Clive Granger, a co-recipient of the 2003 Nobel Memorial Prize in Economic Sciences, who is now an emeritus economics professor at the University of California, San Diego.
It involves comparisons of streams of data known as time series, such as fluctuations in the stock market index and changes in employment levels.
Dr. Steven L. Bressler, professor of psychology at Florida Atlantic University, said that the technique might also help reveal if one brain area was passing data to or influencing another brain area.
For their study, the researchers gave volunteers a cue that a visual stimulus would be appearing soon in a portion of a computer display screen, and asked them to report when the stimulus appeared and what they saw.
They had already shown in a previous study that such a task could activate two brain areasthe frontoparietal cortex, which is involved in the direction of the attention, and the visual cortex, which became more active in the area where volunteers were cued to expect the stimulus to appear.
The researchers believed the frontoparietal cortex was influencing the visual cortex, but the brain scanning approach they were using, functional magnetic resonance imaging (fMRI), was much too slow to catch that influence in action.
However, using Granger causality enabled them to show conclusively that as volunteers waited for the stimulus to appear, the frontoparietal cortex was influencing the visual cortex, not the reverse.
“Once the visual stimulus appears, we expect that the direction of influence between the frontoparietal cortex and the visual cortex will be less asymmetric, but this remains to be proven,” says co-author Gordon L. Shulman, Ph.D., research professor of neurology at Washington University.
Corbetta wants to apply Granger causality to a number of important questions about relationships in the brain, including attention’’s interactions with vision and memory.
He will also use it to learn more about the extent to which the brain can adapt to injury by examining whether lesions in one area affect the flow of information processing in another area. (ANI)

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