[Editors] MIT: Memory, cognition suffer when brain connections decay

[Teresa Herbert]

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MIT neuroscientists ID source of cognitive decline in aging brains
--Memory suffers when brain-communication network decays
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For Immediate Release
TUESDAY, JAN. 6, 2009

Contact: Teresa Herbert, MIT News Office
E: therbert at mit.edu, T: 617-258-5403


CAMBRIDGE, Mass. -- As people age, memory and the ability to carry out  
tasks often decline. Scientists looking for ways to lessen that  
decline often have focused on the “gray matter” — the cortical regions  
where high-level functions such as memory are located.

But there are signs that the search may need to be expanded: A new  
study by MIT neuroscientists has found that memory and cognitive  
impairments were more associated with loss of brain “white matter,”  
which forms connections within and between brain regions.

“Historically a lot of people have put their eggs in the gray matter  
basket. This study suggests that what might really be important are  
the connections and the integrity of the connections,” said David  
Ziegler, a graduate student in the Department of Brain and Cognitive  
Sciences and lead author of a paper on the work that appeared in the  
online edition of Neurobiology of Aging in December.

Enhancing white matter in older people through drug intervention or  
changes in diet or cardiovascular fitness could offer a new approach  
to countering some of the cognitive declines that are typical of  
advanced age, said Ziegler, who works in the laboratory of Suzanne  
Corkin, professor of behavioral neuroscience.

The study is the first to examine changes in both white and gray  
matter and correlate those changes with declines in memory and  
cognition, said Ziegler.

White matter consists of bundles of neuronal axons that form  
connections between neurons, allowing brain regions to communicate  
with each other. Gray matter, or cortex, is where the bodies of  
neurons are located.

The researchers used a new MRI brain scanning technique, known as  
diffusion tensor imaging, to study the white and gray matter of two  
groups of healthy adults — one group aged 18 to 30, and the other aged  
60 to 85.

They also measured subjects’ performances in three categories — memory  
for specific events; memory for vocabulary; and ability to plan and  
carry out everyday tasks.

In the older subjects, the researchers found a correlation between  
decline in cognitive performance and deterioration in the white matter  
of the frontal brain regions, where planning and executive functions  
are located. Similarly, deterioration of white matter in the parietal  
and temporal lobes, which are involved in memory, was associated with  
memory impairment.

“Thus, age-related impairments in specific cognitive capacities may  
arise from degenerative processes that affect the underlying  
connections of their respective neural networks,” the researchers  
wrote in their paper.

Other authors of the paper are former MIT postdoctoral associates  
Olivier Piguet, who is now at the Prince of Wales Medical Research  
Institute, Sydney, Australia; David Salat, now at the Athinoula A.  
Martinos Center for Biomedical Imaging; and former MIT laboratory  
technicians Keyma Price and Emily Connally.

The research was funded by the National Institute on Aging.

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Written by Anne Trafton, MIT News Office
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