Alzheimer's, Dementia & Mental Health
Alzheimer’s-like Changes Affect Brains of Senior
Citizens Long Before Symptoms Appear
Indicates Alzheimer’s damage to the brain begins to
occur long before there are clinical symptoms
By Jim
Dryden
 |
|
Yvette I. Sheline,
MD |
April 28, 2010 - Older adults with evidence of
amyloid in the brain but no clinical symptoms of Alzheimer’s disease
have structures in the brain that don’t communicate readily with each
other, according to researchers at Washington University School of
Medicine in St. Louis.
The findings, published in Biological Psychiatry,
may be yet another indicator that Alzheimer’s damage to the brain begins
to occur long before there are clinical symptoms of the disease.
Using brain-mapping techniques, first author Yvette
I. Sheline, MD, and colleagues found that key brain structures don’t
connect as efficiently in brains where positron emission tomography
(PET) scans revealed the abnormal presence of the amyloid protein.
Those PET scans involve a substance called
Pittsburgh compound B (PIB) that binds with amyloid, causing it to
“light up” in a brain scan. Amyloid is the substance that makes up the
senile plaques characterizing Alzheimer’s disease.
“Using PET scans, we’ve been able to identify a
large number of older people who are clinically normal but PIB-positive
for amyloid,” says Sheline, a professor of psychiatry and director of
Washington University’s Center for Depression, Stress and Neuroimaging.
“We then used a different type of brain scan called
functional magnetic resonance imaging, fMRI, to look at the brains at
rest, and we found decreased connections between important brain
structures in people who were PIB-positive compared to those who were
PIB-negative.”
 |
| Brain
images from functional MRI scans show significant differences in
brain connectivity between normal people in blue on the left
side of the illustration and those on the right side in red, who
are cognitively normal but positive for the presence of high
levels of amyloid in the brain during PIB scans. |
The investigators conducted fMRI scans on 35 older
adults previously diagnosed with mild to very mild dementia from
Alzheimer’s disease. They also scanned 68 others who had no clinical
symptoms of the disorder.
However, 20 of those cognitively normal people
previously had been identified as PIB-positive for amyloid in the brain.
In the first phase of the study, researchers looked
at how various brain structures communicate in people with and without
Alzheimer’s disease. Then they examined those same brain regions in PIB-positive
and PIB-negative older adults with no clinical symptoms of Alzheimer’s
disease.
The brains of those who were PIB-positive behaved
like the brains of those with Alzheimer’s, according to Sheline.
“When we looked at key brain structures like the
hippocampus, which is very important in learning and memory, we found
decreased connections to the hippocampus in PIB-positive people compared
to those who were PIB-negative,” she says.
“Our findings suggest brain regions that normally
talk to each other are not communicating as much as they should long
before there’s any clinical evidence of memory loss or other signs of
dementia.”
It’s too early to say for sure whether those who
are PIB-positive will go on to develop dementia, memory loss and other
symptoms of Alzheimer’s disease, Sheline says. But she believes this
study provides further evidence that the PIB scans can identify people
with early Alzheimer’s-like damage who later may develop clinical
symptoms.
“What we need now is more effective treatments for
Alzheimer’s,” she says. “We’re moving forward quickly to identify those
who might be at risk at earlier stages in the disease process, but if we
determine that PIB-positive people do, indeed, have a preclinical form
of the disease, we still need new treatments that stop it from
progressing.”
Information Source:
Washington University School of Medicine's 2,100
employed and volunteer faculty physicians also are the medical staff of
Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine
is one of the leading medical research, teaching and patient care
institutions in the nation, currently ranked fourth in the nation by
U.S. News & World Report. Through its affiliations with Barnes-Jewish
and St. Louis Children's hospitals, the School of Medicine is linked to
BJC HealthCare.
Source: Sheline YI, Raichle ME, Snyder AZ, Morris
JC, Head D, Wang S, Minton MA. Amyloid plaques disrupt testing state
default mode network connectivity in cognitively normal elderly,
Biological Psychiatry, vol. 67(6), pp. 584-587. March 15, 2010.
