Scans Detail Brain's
Inner Workings
(Dec. 3, 2003) - Advances in
brain imaging technology
are unlocking the secrets of the complex messaging and so-called hard wiring
systems of the brain. In doing so, they are permitting a novel understanding of
two well-known but poorly understood conditions: dyslexia and
schizophrenia.
Dyslexia is estimated to affect about 8 percent of American schoolchildren
and can cause lifelong difficulty with understanding the written word.
Schizophrenia is a mental illness characterized by a variety of symptoms,
including hallucinations, delusions, thought disorder, bizarre behavior and
lack of motivation.
The new imaging studies, which are allowing real-time glimpses of brain
activity associated with these conditions, are typical of the "tremendous
advances in brain imaging that we've seen in the last three years," Dr.
David M. Yousem, director of neuroradiology and professor of radiology at Johns
Hopkins University in Baltimore, told United Press International.
A display of these new brain images, featured at the annual meeting of the
Radiological Society of North America, illustrated Yousem's claim. Stark
black-and-white, cross-section views of the brain are replaced by images that
light up in neon yellows and oranges to illustrate brain function more clearly.
For example, when neuroradiologist Jonathan Burdette, of Wake Forest
University in Winston-Salem, N.C., ran dyslexic and non-dyslexic volunteers
through his functional magnetic resonance imaging scanner, the brains of normal
readers glowed hot orange in regions that control hearing, sight and touch as
the volunteers were put through a series of simple, consonant-and-vowel
recognition exercises.
In addition, in the normal readers, a fourth brain area, called the
parieto-temporal region -- a "well-known component of the language
circuit, also lights up," Burdette said. This region serves as a sorting
station for sensory input, separating the needed information from extraneous
noise, he said.
By contrast, when Burdette ran 34 dyslexic reader volunteers through the
same series of tests with the imaging unit, the crucial sorting region remained
dark. This suggests the dark area could serve as a target for new dyslexia
treatments.
For example, intense, brain-training approaches that seek to wake up this
dark area might improve reading ability in dyslexics. Or, such programs might
speed up information processing in these individuals. Burdette's test also
indicated dyslexic readers process audio and visual stimuli about "75
milliseconds slower than non-dyslexic readers," he said.
Yousem said Burdette's imaging studies offer intriguing opportunities to
develop new approaches for dyslexic patients. But while the studies could pay
off soon for dyslexic readers, the imaging technique also offers new
information that suggests schizophrenia is associated with changes in the hard
wiring of the brain and these changes can be seen even in very young patients.
This study used a brain scan called diffusion tensor imaging, which is able
to detect white matter in the brain. White matter can be likened to electrical
wiring that connects a home's electricity source to wall outlets, always
delivering the correct voltage. White matter connects brain cells so the
correct message is delivered. In patients with schizophrenia, however, changes
disrupt this wiring system in much the same way that a poorly wired outlet can
cause a short in a home power supply.
When Manzar Ashtari used DTI to study the brains of 12 adolescents --
including nine boys -- diagnosed with schizophrenia and nine normal volunteers,
she found clear evidence of this type of faulty wiring in brain regions that
affect emotions, hearing, language, and integration of information -- all areas
affected by schizophrenia.
Ashtari, an associate professor of radiology and psychiatry at North
Shore-Long Island Jewish Health System and Albert Einstein College of Medicine
in New York City, said her work with DTI confirms for the first time white
matter changes associated with schizophrenia have "their origins early in
life."
Asked about a possible clinical role for DTI, she said it is too early in
the research process to say whether it can be used as a diagnostic tool,
"although we hope that is the case. Early onset schizophrenia is
especially disheartening because so many of these teens aren't diagnosed until
they are adults. Because these patients develop the disease at an early age
when they have not yet built their lives, they tend to have a worse prognosis
than those who have adult-onset schizophrenia."
Yousem cautioned it is unlikely the recent advances in brain imaging will
yield immediate clinical applications. "I think that is the work of the
next 10 years," he said.
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