Hope for an Aging Population: STAC

By 2050 in wealthy, developed countries it is estimated that there will be many more older adults (26%) than children under 15 (about 16%). Today adults aged 85 and older have a dementia rate of nearly 50%. Projecting this into the future yields a frightening prospect. It portends a large percentage of underproductive older people. Beyond that, there would be a large percentage of older people living unfulfilling lives.

Looking at both the neurological and behavioral changes that occur in the aging brain can also be discouraging. There are decreases of volume in the caudate nucleus, the lateral prefrontal cortex, both cerebral hemispheres, and the hippocampus. There are also decreases in processing speed and in the ability to focus and screen out extraneous information. Fortunately, not everything declines. The primary visual cortex and the entorhinal cortex suffer minimal or no loss in volume. Similarly our vocabularies and expertise typically do not decline. Although sometimes it might be difficult finding a word, it usually comes to mind eventually.

Fortunately there is evidence that there are compensatory mechanisms to counter or ward off this decline (see the Healthymemory Blog Post “HAROLD”). And it is clear that these mechanisms work. Many people function quite well even in to advanced old age. What is even more remarkable that some people show little or no evidence for cognitive decline in spite of a great deal of pathology discovered during autopsies.

What is needed is a theory to understand the mechanisms that ward off this decline. The Scaffolding Theory of Aging and Cognition (STAC)1 provides such a theory. Some of the basis of this theory comes from brain imaging, fMRI especially. This imaging has revealed differences in the pattern of neural activation between young and older adults. Whereas young adults show focal left prefrontal activity when engaged in certain cognitive tasks, older adults show activity in both the left and right prefrontal areas.

It should be understood that scaffolding is a process that occurs across the lifespan. It is not just the brain’s response to normal aging; it is the brain’s response to challenge. For anyone acquiring a new skill an initial set of neural circuits must be engaged and developed to provide the structure for task performance in the early stages of skill acquisition. With practice, performance becomes less effortful and the neural circuitry becomes more specific to the task.

The basic idea underlying STAC is that this same mechanism can compensate for losses in brain structure and function as we age. So what can be done to activate this mechanism? The answer is to challenge the brain and then address this challenge. As we age it becomes easier to rely upon old habits and ways of thinking and to avoid new challenging activities. But it is these challenging activities that activate the STAC process that can ward off cognitive decline.

One can regard the Healthymemory Blog as a means of providing this cognitive challenge. First of all, it provides information and data about human cognition. This can be new learning that can provide challenge in itself if not insight into the working and malfunctions of human cognition. It also presents mnemonic techniques that not only can improve cognitive performance, but offer cognitive exercise and challenge in trying to implement them. Finally, there is transactive memory, where there is knowledge from fellow humans and from the internet (and more traditional sources of knowledge) to challenge the mind.

1Park, D.C. & Reuter-Lorenz, P. (2009). The Adaptive Brain: Aging and Neurocognitive Scaffolding. Annual Review of Psychology,60, 173-196.

© Douglas Griffith and healthymemory.wordpress.com, 2010. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

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