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Research Highlights
Brain-imaging tool may offer quick
mental-health diagnostics
October 20, 2007
Researchers at the Minneapolis VA have found that a brainimaging
technology called magnetoencephalograpy, or
MEG, may be a fast, accurate, non-invasive way to diagnose
mental-health and neurological disorders such as Alzheimer’s
disease, schizophrenia and multiple sclerosis.
"The test takes only three minutes, and it’s totally non-invasive,"
said Apostolos P. Georgopoulos, MD, PhD, director of
the Brain Sciences Center at the Minneapolis VA and professor
of neuroscience, neurology and psychiatry at the University of
Minnesota.
His team recently published a study
involving 142 volunteers—one group of
healthy controls, and six groups representing
six different brain conditions: Alzheimer’s,
schizophrenia, alcoholism, Sjogren’s
syndrome, multiple sclerosis, and facial
pain. The researchers showed that each condition
corresponds to a particular pattern of
neural activity in the brain, as recorded by
MEG. The results appeared in the Aug. 27
issue of the Journal of Neural Engineering.
The MEG machine itself resembles a
giant, space-age salon hair dryer. It has
hundreds of sensors that pick up miniscule
magnetic signals that result when brain
cells “talk” to each other through electrical
impulses.
The setup at the Minneapolis VA costs
about $2 million, almost a quarter of
which funded the construction of a special
shielded room, made of a nickel-iron alloy
and aluminum, to reduce magnetic interference
from the outside. "If you’re in a place
like downtown New York City, with subways
running underground, you need a lot
of shielding," said Georgopoulos. "We’re
extremely quiet here in Minneapolis, and
we were able to get away with the first tier
of shielding, which costs about $400,000."
MEG is relatively rare technology
The scientist points out that there are
fewer than 100 MEG instruments in the
world, and only about a dozen that are as
high-density as the one in his lab. Density is
a function of the number and positioning of
the super-conducting sensors in the unit; the
higher the density, the more sensitive and
accurate the instrument.
Electroencephalography, or EEG—an
older, more commonplace technology—also
eavesdrops on the brain’s electrical activity.
But the signals get distorted as they pass
through the skull and the soft tissue surrounding
the brain.
Other types of brain scans, such as functional
MRI and PET, measure metabolic
factors such as blood flow or oxygen use in
the brain. Other scans, like CT and conventional
MRI, offer static images of structure.
None of these shows how neurons communicate
with each other, which in some brain
diseases is the only evidence of abnormality.
Some of these techniques, however,
can be used in conjunction with MEG to
provide a fuller picture of brain function.
Perhaps the key difference between other
brain-imaging technologies and MEG, says
Georgopoulos, has to do with speed. MEG
records brain activity essentially in real
time—down to a thousandth of a second.
That’s how fast brain cells talk with each
other. Other types of scans involve lags of
three seconds or longer. In trying to understand
brain function, says the researcher,
that difference is critical.
“From the time you see the red light to
the time you step on the brakes, everything
happens in a fraction of second. The whole
brain—the cerebellum, the visual cortex, the
motor cortex—is involved in an extremely
fast loop of processing. So if you’re waiting
three seconds to get an integrated picture of
what’s happening in the brain, there’s a lot of
potentially valuable information you’ve lost.”
Georgopoulos’ lab is now collecting
MEG data from patients with other conditions,
such as PTSD, Parkinson’s disease
and depression. "We need about 100 per
group to really develop the template and
start using this as a diagnostic test," he says.
Tracking Alzheimer’s disease
The VA researcher foresees a great demand
for MEG as a screening and diagnostic
tool—especially in cases that involve subtle
progressions of a disease over time. He offers
the example of tracking the brain-cell-firing
patterns of older patients with signs of
memory loss. "Some people with mild cognitive
impairment will develop frank Alzheimer’s,
and others will not. The outcome of our
MEG analysis is a continuum. We differentiate
between normal and a particular diagnosis
if there’s a probability of more than 50
percent. Say you have an older person who
tends to forget, and you get a reading of .2
Alzheimer’s and .8 normal. After six months
or a year, that reading could change, and
you would have a good objective measure
of whether the person is progressing toward
Alzheimer’s or remaining stable."
In his research with chronic alcoholics,
he was able to detect subtle improvements
in their neural patterns as they went successive
days without drinking. “By day seven,
they were much closer to normal,” he said.
The work recently published in the
Journal of Neural Engineering was funded
mainly by the University of Minnesota, VA
and the American Legion.
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