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ASU engineer demystifies brain functions with electricity

December 21, 2017

Much of what we know today about how the human brain operates was learned from when it failed to operate correctly.

Over time, as patients arrived at hospitals with injuries or tumors, physicians and researchers learned about which parts of the brain controlled different activity from the patients' symptoms. For example, if a patient injured their frontal lobe, they may also have experienced correlated speech or mobility problems.

“Understanding how the normal brain operates is a holy grail for researchers,” said Rosalind Sadleir, an Arizona State University assistant professor in the School of Biological and Health Systems Engineering.

In a paper  published Dec. 14 in the journal IEEE Transactions on Medical Imaging, Sadleir presents the first images of the electrical conductivity distribution generated inside the  human brain. The technique used in the study, magnetic resonance electrical impedance tomography, allows researchers to probe the electrical properties of a living brain.

“The tools we used in the study have given us new ways of approaching and understanding tissue conductivity,” Sadleir said. “We’re able to actually measure things inside the brain that previously weren’t able to be measured. Knowing brain conductivity helps us understand how electricity distributes through the brain.

Sadleir’s study was funded by an award from the National Institutes of Health’s Brain Research through Advancing Innovative Neurotechnologies (BRAIN) initiative.

“Being able to make structure-function associations and building a better understanding of the brain will allow us to learn more about everything: Alzheimer’s, Parkinson’s, everything,” she said.

Participants in the study had electrodes placed on their scalps for transcranial alternating current stimulation. The electrodes applied energy through the brain at about 10Hz, which is the mid-range of typical brain frequencies. At that frequency, researchers were able to learn more about the conditions encountered by electrical activity generated by the brain. 

The new technique Sadleir’s team developed differs from existing magnetic resonance techniques that map water relaxation times and other conductivity-mapping techniques, such as electrical impedance tomography, that cannot image absolute conductivity or obtain signals from deep within the brain.

Sadleir’s technique encodes information about how current flows through the brain in MR phase images, part of complex MR images, that are normally hidden.

Sadleir’s group's findings may help to improve the study of brain activity using electroencephalograms (EEG). EEG tests involve placing electrodes on a person’s scalp in order to detect electrical activity in the brain. The results of EEG tests are instantaneous and provide data useful for diagnosing brain disorders, such as epilepsy. EEG data can also be used to guess where activity occurs inside the brain, but these estimates depend upon knowing head conductivities well. Having actual measurements of brain conductivities should allow these techniques to locate brain activity more precisely.

Sadleir worked with Munish Chauhan, a postdoctoral researcher in ASU’s Neuro-electricity Laboratory, ASU doctoral candidate Aprinda Indahlastari, and researchers from the University of Florida and Johns Hopkins University on the research. 

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