By Stephen Easton

Researchers at the University of New South Wales have looked at the cognitive decline that occurs with ageing from a new perspective – the network that carries information through the brain – and the results could have far-reaching implications.

The research team, led by Scientia Professor Perminder Sachdev from the UNSW School of Psychiatry, has mapped the network of fibres or ‘white matter’ for the first time, allowing them to examine the strength of connections between different cortical regions, or ‘grey matter’, which are responsible for specific functions.  In the past, most research has focused on the more complicated grey matter without looking at how information flows between separate regions.

A new type of magnetic resonance imaging (MRI) called diffusion tensor imaging (DTI) combined with powerful computers allowed the team to create the map and see the whole network in great detail.

“Using a mathematical theory you can see how strongly the different regions are connected to each other,” Professor Sachdev said.  “You can basically look at the efficiency of the network and with ageing, we can see a reduction in the efficiency of these networks.”

“What we wanted to see is how this relates to cognitive function, and we found that the best relationship was with processing speed, which makes sense because we’re talking about strength of information connections.”

Other areas strongly affected by the efficiency of neural networks were executive functions that manage other brain processes and the ability to navigate in space, known as visuospatial function.

Sachdev said the findings could help to some extent with dementia research, by offering another way of looking at the condition, but had already helped explain what happens in the brain when physical reaction time slows down in older people. 

“It’s not that they can’t do the task, it just takes longer, and we have shown that this is related to structural changes in the brain, in terms of its neural networks.”

“The next step is looking at what determines the efficiency of these networks.  We want to see if they are flexible or plastic, and whether maybe we can intervene.”

“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.”

The results of the study, which was based on a sample of 342 healthy people aged between 72 and 92, have been published in the January edition of the Journal of Neuroscience.

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