Ageing brain `clogs network`

Scientists have mapped human brain`s neural networks and linked them to specific cognitive functions.

Last Updated: Feb 09, 2011, 13:09 PM IST

Washington: An Indian-origin-led team of scientists has found that connectivity is very important for the human brain`s processing speed -- and old age damages it,
raising hopes for a cure for cognitive declines.

Perminder Sachdev of University of New South Wales and and colleagues have found that the brain operates as a highly interconnected small-world network -- and not as a collection of discrete regions as previously believed -- with important
implications for why many have cognitive declines in old age.

In their research, the scientists have mapped human brain`s neural networks and linked them to specific cognitive functions such as information processing and language, the `Journal of Neuroscience` reported.

They are now examining what factors may influence the efficiency of these networks in the hope that they can be manipulated to reduce age-related decline.
"While particular brain regions are important for specific functions, the capacity of information flow within and between regions is also crucial. We all know what happens when road or phone networks get clogged or interrupted.

"It`s much the same in the brain. With age, the brain network deteriorates and this leads to slowing of the speed of information processing, which has the potential to impact on other cognitive functions," said Prof Sachdev.

The advent of new MRI technology and increased computational power had allowed the development of the neural maps, resulting in a paradigm shift in the way scientists view the brain, say the scientists.

"In the past when people looked at the brain theyfocused on the grey matter in specific regions because they thought that was where the activity was. White matter was the poor cousin. But white matter is what connects one brain
region to another and without the connections grey matter is
useless," Prof Sachdev said.

In their research, the scientists performed magnetic resonance imaging scans on 342 healthy individuals aged 72 to 92, using a new imaging technique called diffusion tensor imaging (DTI).

Using a mathematical technique called graph theory, they plotted and measured the properties of the neural connectivity they observed.

"We found that the efficiency of the whole brain network of cortical fibre connections had an influence on processing speed, visuospatial function -- the ability to navigate in space ? and executive function.

"In particular greater processing speed was significantly correlated with better connectivity of nearly all the cortical regions of the brain," said team member Dr
Wei Wen.

Prof Sachdev said the findings help explain how cognitive functions are organised in the brain, and the more highly distributed nature of some functions over others.

"We are now examining the factors that affect age-related changes in brain network efficiency – whether they are genetic or environmental -- with the hope that we can influence them to reduce age-related decline.

"We know the brain is not immutable; that if we work on the plasticity in these networks we may be able to improve the efficiency of the connections and therefore cognitive functions," Prof Sachdev said.

PTI