The Aged Brain

Now that the boomers are entering their sixties, the problem of age-related cognitive decline is going to become a serious mental health issue. The aged brain often suffers from a bevy of symptoms, from memory loss to problems with concentration. The question, of course, is what causes these symptoms?

Over at Mind Matters, we recently featured an interesting post on some recent research that tried to answer these pertinent questions. The short answer is that, over time, the different parts of the brain becomes less interconnected.

Jessica Andrews-Hanna and her colleagues at Harvard University, the University of Michigan and Washington University School of Medicine have explored the possibility that cognitive decline during aging results in part from a loss of coordination and communication among large-scale brain systems. They used magnetic resonance imaging to examine the brain activity of young (ages 18 to 34) and old (ages 60 to 93) subjects when they were either resting or engaged in certain tasks, such as classifying words into different categories. The researchers then analyzed the fMRI data to compare fluctuations in activity between brain regions in response to the experimental task, thus providing a measure of coordination between different systems in the cerebral cortex. The authors compared the strengths of these correlations with measures of cognitive performance based on several tests of intellectual fluency and memory.

The most important finding was a "dramatic reduction" in the functional correlation, or interaction, between two well-defined large-scale brain networks in the aged brain. The first network is associated with a resting "default" state of the brain, whereas the other network is responsible for the control of goal-directed behavior and "executive" brain functions, such as concentration on a particular task.

I'm particularly interested in the data on the default state, which is what your brain is doing when it's not doing anything. (The default state is often measured in an fMRI machine when people are told to not do anything.) Nobody is quite sure what less cortical interactions during the default state might mean for the brain - fewer daydreams? slower response times? - but it's an interesting take on what's sure to become an important societal issue.


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I like the idea of the default state, too. I mean, is that even a valid thing? I have never experienced such difficulty as when willing myself not to think. Thoughts pop up out of nowhere and take hold before I've even noticed I'm having them. It seems like the sort of thing--object of study--that you could try to pin down for your entire career and (a) never get it; (b) never know you never got it.

It is very interesting. There was some research done in 1993 by Deary and Carrol I believe, that showed that higher alpha rhythms (which are apparent when the brain is in a relaxed, wakeful state, ie default state) correlate reasonably well with intelligence. The whole intelligence debate is too much to get into, but it does make you wonder what you can tell from a static, relaxed brain state. And then consider the implications of being able to regulate this state, as in many meditative practices.

By Michael Woods (not verified) on 01 May 2008 #permalink