Old brains communicate differently

Ageing makes the networks in our brain less specific. Linda Geerligs, PhD student at the University of Groningen, has used fMRI scanning to prove that the connections in our brain change as we grow older.

When compared with their younger counterparts, connectivity in the brain networks of older people decreases, while connectivity between brain networks increases. Geerligs also found evidence to suggest that the decrease in connectivity in the brain networks corresponds with slower reaction times and declining memory among the elderly. The research findings will be published online in the Human Brain Mapping journal on Thursday 23 August.

Our brain is made up of various areas that work together by communicating intensively with each other. The areas that connect in this way form networks with a specific task. Geerligs: ‘The somatomotor network, for example, plays an important part in the sense of taste and in planning and executing movements. However, the default mode network is mainly active when thinking about yourself, your past or your plans for the future. This particular network becomes less active while actually carrying out a task.’ Like the brain areas, the brain networks also communicate with each other, but on a much smaller scale.

Unique decline?

According to Geerligs, optimal performance depends on smooth connections in each separate brain network and efficient transmission of information between the various networks. It has already been proved that in the elderly, connectivity in the default mode network decreases, corresponding with a decline in reaction times and memory. To find out whether this process only occurs in that specific brain network, or if connectivity also changes in other networks, Geerligs examined the connections in and between brain networks in young people and the elderly.

fMRI experiment

Using an fMRI scanner, Geerligs compared the brain activity of twelve young people (18-30 years old) with that of thirty older people (60-75 years old). She ran a number of psychological tests to make sure that the older participants were still in good mental health. During the experiment itself, the participants watched a computer monitor from inside the fMRI scanner. The monitor showed a series of single numbers and letters. Participants were instructed to press a button whenever an ‘X’ appeared. Geerligs: ‘The participants were asked to perform this simple task so that we knew that they were all focusing their attention constantly on the same thing.’

During the experiment, Geerligs measured the brain activity of every participant in 16,000 minuscule three-dimensional brain areas. She compared the brain activity in all these areas to find out which areas displayed the same patterns and were therefore connecting with each other. She then divided the brain areas into four networks, before comparing young with old.

Less specific networks

She discovered that the connections within our brain change as we grow older. Compared with young people, it would seem that there is less internal communication in two brain networks of the elderly (the default mode network and the somatomotor network), while communication between all the four brain networks that had been identified actually increases. In Geerligs’ opinion, this means that the networks in the older brains are less specific. Geerligs: ‘The division between the networks is less distinct than in young people.’ The researcher also found evidence suggesting that the decrease in connectivity between the two brain networks corresponds with slower reaction times and a decline in memory in older people.

Compensation theory

At the moment, it is not clear why brain networks become less specific during the ageing process. It is possibly a form of compensation on the part of the brain. Geerligs: ‘Brain cells die during the ageing process and so the brain networks cannot perform their specific tasks as efficiently. The compensation theory says that this causes increased connectivity between brain areas as the brain networks try to support each other in carrying out their tasks.’

Fundamental research

‘The insights provided by this kind of fundamental research are very interesting,’ says Geerligs. ‘If we can discover exactly what changes in the brain during the ageing process and what the effects of these changes are, this will give us new leads for finding new treatments for elderly people with concentration and memory problems.’

Curriculum Vitae

Linda Geerligs (Sneek, 1986) studied psychology at the University of Groningen. In 2009, she graduated in two subjects, obtaining a Master’s degree in brain and behaviour and a Research Master’s in cognitive neuroscience. She immediately embarked on a PhD research project with Dr M.M. Lorist and Prof. N.M. Maurits, and expects to complete her PhD in September 2013. The article from this press release is part of her thesis.

Note for the press

More information: Linda Geerligs

Reference: Reduced specificity of functional connectivity in the aging brain during task performance; Linda Geerligs, Natasha M. Maurits, Remco J. Renken, Monicque M. Lorist1,2; 1 Department of Experimental Psychology, University of Groningen, The Netherlands, 2 BCN-Neuroimaging Center, University Medical Center Groningen, 3 Department of Neurology, University Medical Center Groningen, The Netherlands; Human Brain Mapping, DOI 10.1002/hbm.22175.