University of Minnesota researcher develops an orderly test for spotting brain disorders
People with brain disorders like schizophrenia, Alzheimer's, or multiple sclerosis may not be able to tell a doctor what's bothering them. But now their brain cells can, thanks to some ingenious detective work by University of Minnesota researcher Apostolos Georgopoulos. People with brain disorders like schizophrenia, Alzheimer's, or multiple sclerosis may not be able to tell a doctor what's bothering them. But now their brain cells can, thanks to some ingenious detective work by University of Minnesota researcher Apostolos Georgopoulos.
Using a technique called magnetoencephalography (MEG), Georgopoulos and his research team were able to find patterns of magnetic activity in the brain's cerebral cortex that reliably signaled the presence of those three disorders, plus chronic alcoholism, Sjogren's syndrome, facial pain and normal brain function. The work was published in August in the Journal of Neural Engineering.
The technique is the first to measure how the brain functions in real time. It may lead to a noninvasive test of brain function that could spot trouble in the early stages or monitor progress as patients undergo treatment. Georgopoulos has found that the brain patterns of people with chronic alcoholism tend to revert toward normal as they abstain from alcohol.
"I did not expect to find this," says Georgopoulos, a Regents Professor of neuroscience and neurology. "It's like a silent movie of the brain." Georgopoulos is also director of the Brain Sciences Center at the Minneapolis Veterans Affairs Medical Center, where he holds the American Legion Brain Sciences Chair.
A salty tale
MEG works by picking up magnetic fields generated by ions - mostly sodium, a constituent of table salt - as they cross membranes of neurons. The membranes are in the fingerlike projections of neurons called dendrites, which function as receivers for messages from other cells. It takes the coherent motion of at least 10,000 ions to produce a signal strong enough to detect.
The advantage of MEG is its ability to detect brain activity on a scale of milliseconds. In contrast, MRI scans are like snapshots with about a three-second exposure - much too long to detect the rapid "crosstalk" of brain cells in a meaningful manner. And EEG signals are delayed and distorted by passing through soft tissues and the skull, resulting in imprecise or unreliable readings, Georgopoulos says.
In their MEG studies, the researchers placed an apparatus resembling a helmet on the heads of the subjects, who were asked to follow a point of light with their eyes for forty-five to sixty seconds. Inside the helmet were 248 spike-like sensors, each of which detected the magnetic fields generated in a population consisting of tens of thousands of cortical cells. Together, the sensors scanned the magnetic activity over the whole cortex.
The researchers then used sophisticated statistics to zero in on a few interactions between cell populations that varied according to different brain conditions. From the different patterns of interactions, they were able to identify with 100 percent accuracy which of the 142 subjects had been diagnosed with each of the six brain disorders or had normal brain function.
"[This work] came out of my strong belief that the real function of the brain is in the interaction of its elements - that is, in the crosstalk," says Georgopoulos. "Exchange of information is the essence of brain function, which is defined as all interactions among all populations of cells. The dynamic function of the brain has been my obsession for years. For me, the biggest challenge is to find how the brain works on the millisecond level with all the 'buzzing' going on."
The emphasis on populations of cells is no accident. For many years, neuroscientists have recorded the activities of single neurons. But our brains are more like a vast array of neural choruses, each consisting of many neurons that sing together and respond to other choruses.
Georgopoulos and his colleagues are now beginning long-ter