Brain-Imaging Tools
Zero in on Schizophrenia
(December 3, 2003) -- Using sophisticated imaging technology that peers
deeper into the brain than ever before, scientists reported Tuesday in Chicago
that they are beginning to see where
schizophrenia begins and
possibly what's causing it.
The report highlights the speed of discoveries coming from the new field of
brain imaging that scientists say is helping them understand mental disorders
such as schizophrenia, dyslexia and
antisocial behavior.
"We use a new technique that allows you to peel off the first layer of the
brain and look inside," said Manzar Ashtari, associate professor of
radiology and psychiatry at Albert Einstein College of Medicine in New York
City. "You take all that structure away and see how things are
connected."
Showing images of adolescents newly diagnosed with schizophrenia, Ashtari on
Tuesday presented the first evidence linking the disorder in youngsters to
defective myelination, the white matter that insulates brain cells and allows
them to communicate. She presented her findings at the annual meeting of the
Radiological Society of North America in McCormick Place.
Ashtari and Dr. Sanjiv Kumara, assistant professor of psychiatry, use a
souped-up MRI imaging device known as diffusion tensor imaging to look at the
brain's white matter, which had previously eluded studies in living
patients.
They found that a switching box in the brain called Heschl's gyrus was
defective because of insufficient myelination. Normally the switch box
transfers incoming sounds to the brain's command center, the frontal cortex,
for interpretation.
Some of the most common symptoms of schizophrenia --
hearing voices and other auditory
hallucinations -- may result from a defective switch box that doesn't send
messages to the command center, the scientists said. The disorder affects
between 1 and 2 percent of Americans.
"There's a pathway that's connecting the gyrus to the frontal cortex that
puts all this information together," Kumara said. "If there's some
problem with that pathway and there's not efficient transfer of communication
of information, then you can sort of see how somebody might get confused and
not understand if this is a voice inside of my head or is this a voice outside
of my head."
The study involved 20 adolescents with schizophrenia. Diagnosis is made if they
meet two or more of five criteria--hallucinations, delusions, thought disorder,
bizarre behavior and negative symptoms, such as lack of motivation or loss of
enjoyment in activities. Their brain scans were compared to those of 17 normal
adolescents.
DTI is one of about five imaging techniques that are enabling scientists to
study the way the brain functions under various circumstances, how it is
physically constructed, and its chemical makeup at the time thoughts are being
constructed.
"We're gaining an enormous new body of knowledge on brain factors which
predispose to all sorts of clinical disorders," said neuroscientist Adrian
Raine of the University of Southern California. "We have new vistas today
which were almost undreamt of before.
"In my field we're really beginning for the first time to literally look
inside the brains of murderers and violent offenders in ways that we never
could have done before."
In Raine's MRI study of psychopaths, he found that they have a significant
abnormality in the structure and function of their corpus callosum--the cable
of fibers that allows the left and right sides of the brain to communicate and
process emotions, attention and arousal--which may put them on the path of
violence.
"They're emotionless, cold, blunted and are socially disconnected,"
he said. "We found that the faulty wiring in the corpus callosum of
psychopaths is involved in shaping these classic deficits."
Ashtari said that her findings were similar to those found in adults except
that adults have more areas of the brain that appear to lack adequate
myelination. That may mean schizophrenia starts off in one area and then
spreads to other areas as a person gets older, she said.
The next step is to study younger children who may be at risk for schizophrenia
to look for early gyrus changes that might be used as a diagnostic tool before
full-blown symptoms develop, Ashtari said. Her work is supported by the
National Institute of Mental Health and the National Alliance for Research on
Schizophrenia and Depression.
If further studies confirm that a lack of myelination is involved in
schizophrenia, then it may be possible to develop drugs that stimulate white
matter growth, Ashtari said.
It may also be possible that certain nutritional deficiencies may contribute to
the myelination defect and that special diets might be able to prevent it, she
said.
In another brain-imaging report presented at the RSNA meeting, neuroradiologist
Dr. Jonathan H. Burdette of Wake Forest University found a characteristic
abnormality in the brains of people with dyslexia, which affects an estimated 1
in 10 Americans.
Functional MRI studies showed that an area of the brain called the
temporoparietal region fails to light up properly when dyslexics are given
tests to match letters with their corresponding sound. The job of the
temporoparietal region is to match words and sounds.
Further research may lead to screening techniques to detect children before
they develop language problems, Burdette said.
Source: Chicago Tribune
Related Stories
top ~ articles table of contents
home
~ overview ~ comprehensive
info
meds ~
news stories ~
articles ~
bulletin board
|
