fMRI maps electrical activity in brain as precisely as more invasive methods, study finds

A commonly used brain scanning technique can map electrical activity under the skull as precisely as more invasive methods that rely on probes or electrodes, according to a research team led by John Gore, director of the Vanderbilt University Institute of Imaging Science and professor of biomedical engineering.

The study supports the potential usefulness of the technique, a version of functional magnetic resonance imaging (fMRI), for diagnosing and monitoring treatment of brain injuries, tumors and conditions ranging from epilepsy to psychiatric disorders, the researchers said.

The study in animals, published this month in the Proceedings of the National Academy of Sciences, “validates the use of high-field, high-resolution fMRI as a mapping tool to tell where things are happening,” said Gore, who is senior author of the paper.

The scanning technique detects blood oxygenation level-dependent (BOLD) signal changes related to oxygen levels in the blood. These changes had been thought to be indirect measures of neuronal activity in the brain.

From left are Pai-Feng Yang, Feng Wang, Ruiqi Wu, Zhaoyue Shi, Limin Chen, and John Gore at the Vanderbilt University Institute for Imaging Science (Photo by Joe Howell)

However, the Vanderbilt study found that fMRI “actually does reflect directly electrical activity — not only where it is but how strong it is,” said Gore, also the Hertha Ramsey Cress University Professor of Radiology and Radiological Sciences.

“It clarifies one of the uncertainties in the fMRI field,” he said.

The researchers used high-field fMRI, in the range of 188,000 times the strength of the earth’s magnetic field.

They found that the technique can accurately map functional connectivity — synchronous fluctuations in the electrical frequencies of two parts of the brain that suggest they are working together — both when the brain is at a resting state and when it is actively engaged.

“BOLD at high field provides a reliable tool for the investigation of cortical micro-organization,” said first author Zhaoyue Shi, a graduate student in biomedical engineering.

Co-author Li Min Chen, Vanderbilt physician and associate professor of Radiology and Radiological Sciences, said fMRI use may help improve the precision of neurosurgery and monitoring of recovery from spinal cord injuries and brain injuries such as stroke.

“This gives you a very powerful tool,” she said.

Other co-authors were researchers Ruiqi Wu, Pai-Feng Yang, Feng Wang, Tung-Lin Wu and Arabinda Mishra. The research was supported by National Institutes of Health grants NS078680 and NS069909.

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