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Nearly everybody has heard of MRI (magnetic resonance imaging) as a way of scanning the inside of the body, yet few laymen know about functional MRI (fMRI) a heavily used neuroscience research and clinical tool. But until now, no researcher has been able to correlate actual electrical activity in brain cells with fMRI signals. Now neuroscientists at the Weizmann Institute in Rehovot and the University of California at Los Angeles (UCLA) have done just that. Their findings appear in the August edition of Science.
At UCLA, the research team recorded responses of single brain cells in the auditory cortex of two pre-surgical patients wired with intracranial electrodes as they watched a nine-minute clip of the 1967 movie, The Good, the Bad and the Ugly. They then used the data to accurately predict the configuration of fMRI signals measured in 11 healthy subjects as they watched the same clip while lying in an MRI scanner on the other side of the globe near Tel Aviv.
"Although functional magnetic resonance imaging is widely accepted as an important research tool, the relationship between fMRI signals in the brain and the underlying neuronal activity has been unclear until now," said study co-investigator and corresponding author Dr. Itzhak Fried, professor-in-residence of neurosurgery, psychiatry and biobehavioral sciences at UCLA's David Geffen School of Medicine and the Semel Institute for Neuroscience and Human Behavior.
The study was conducted in collaboration with Rafael Malach at the Weizmann Institute; the lead author was Roy Mukamel, with Hagar Gelbard and Amos Arieli of Weizmann's department of neurobiology and Uri Hasson of the Center for Neural Science at New York University.
"Our findings help validate the use of fMRI in a wide array of leading-edge neuroscience research. However, additional research will be needed to see whether this striking correlation between fMRI signals and single neuronal activity exists in brain regions other than the auditory cortex," Fried cautioned.
Most neurobiological research involves animals, tissue removed from human cadavers, or one of a range of imaging techniques. The magnetic properties of blood allow fMRI to show changes in neural activity as a measure of blood flow in the brain. The technique is popular because it is safer and less invasive than some other imaging options, such as positron emission tomography (PET).
In contrast to imaging techniques, Fried and his UCLA team measured electrical activity directly from the brains of consenting epilepsy patients at UCLA Medical Center who had been wired with intracranial electrodes to identify the seizure origin for potential surgical treatment. The study is the latest of several landmark observations made by the UCLA team, which is probing the underpinnings of the human mind at the single-neuron level. Two years ago, they identified single cells in the human hippocampus specific to places during human navigation. Earlier this year, they found that single cells can translate varied visual images of the same item into a single instantly and consistently recognizable concept.
CLALIT TRACKS AGEING BRAINS
Clalit Health Services, the country's largest health fund, has reached an agreement with NeuroTrax Corporation to use its Mindstreams computer technology for early detection and tracking of cognitive dysfunction such as that caused by Alzheimer's disease. Eighty percent of Israel's pensioners are among Clalit's 3.8 million members.
Last fall, Clalit started using the patented software in its outpatient clinics. It is comprised of a computerized battery of tests user friendly enough for a 90-year-old who has never used a mouse. After being downloaded from the company site, the tests take only about 30 minutes to complete and generate an instant report for the diagnostician. The software can make it possible to distinguish people who have only benign forgetfulness from those who are actually demented. Although the main application is early detection of mental decline and the tracking of cognitive function in different stages of dementia, later applications may include mental health and learning disorders.
Clalit medical services director Dr. Nicky Lieberman explained: "One of our most difficult challenges is providing uniform care throughout our healthcare system, especially for the ageing adult population. We rely on NeuroTrax to provide objective and standardized cognitive measurement on which to base state-of-the-art care throughout our geriatric care system. I am impressed with the practical nature of the Mindstreams products, and with the high scientific standards of NeuroTrax."
NeuroTrax Corporation was established five years ago in New York, with its development facilities in Modi'in. Its goal is to improve the practice of medicine by offering practical low-cost products and services for neurological and psychiatric disease management.
"Accurate and standardized office-based measurement of cognitive function has become critical for neurological and psychiatric disease management. NeuroTrax offers user-friendly, technologically advanced solutions for large organizations such as Clalit, which depend on reliable approaches to outcomes measurement," said NeuroTrax CEO Dr. Ely Simon, the neurologist who created Mindstreams.