Tuesday, March 03, 2015

Is your hippocampus shrinking?

Do you use a satellite navigation system in your car? You may be withering
away your 'caveman' ability to familiarize yourself with new surroundings by memorizing snapshots of them.

...At the beginning of a journey, a region of the brain called the entorhinal cortex mentally constructs an as-the-crow-flies line to the destination. Once we are under way, however, a different area of the brain computes the precise distance along the path to get there. This region is the posterior hippocampus, which is also known for its role in forming memory.

Disturbingly, the study, published in the journal Current Biology, found that neither of these brain regions was active when the volunteers used satnavs. In fact, the volunteers' brains were much less active in general.

Previous studies have shown how London taxi drivers who have done 'the knowledge' show an increase in the size of their hippocampus as a consequence of rote-learning the city's streetscape. Dr Spiers, a member of the Memory Disorders Research Society, says his results may explain why London taxi drivers' brains grow: 'They indicate that it is the daily demand on processing paths in their posterior hippocampus that leads to the impressive expansion in their grey matter.'

Dr Spiers told Good Health how this part of the brain, so vital to memory, may also shrink with disuse - such as relying on satnavs. 'My research with taxi drivers found indications which suggest there is some shrinkage of their hippocampus after they retire,' he explained.

The hippocampus and entorhinal cortex are among the first regions to be damaged in age-related cognitive impairment and dementia associated with Alzheimer's disease. The concern must be that losing our ancient way-finding skills may make us more prone to such conditions.

That was the controversial suggestion from research published in 2010 by McGill University in Canada.

Researchers had scanned the brains of older adults who used GPS and compared the results with those who read maps. The map-readers showed higher activity and a greater volume of grey matter in the hippocampus than those relying on GPS. The map-readers also did better on a test used in the diagnosis of mild cognitive impairment, which often precedes Alzheimer's.

The lead investigator, neuroscientist Veronique Bohbot, told the Society for Neuroscience that the results suggest that using spatial memory regularly may improve the function of the hippocampus and help to ward off cognitive impairment as we age.

She feared that relying on computer navigation aids may lead to earlier onset of Alzheimer's or dementia. 'Society is geared in many ways toward shrinking the hippocampus,' she argued. 'In the next 20 years, I think we're going to see dementia occurring earlier and earlier.'

But this isn't just about satnavs. Over-reliance on computer aids of all kinds may rob our brains of the stimulation they need to stay healthy. Research suggests that people who don't regularly challenge themselves intellectually through work or learning are more likely to suffer from dementia in later life.

This has been demonstrated by scientists at Sydney University's Brain & Mind Research Institute. Their study of more than 1,000 people aged over 70 found those who had challenging roles in their working lives, such as being managers and supervisors, showed far less shrinkage in their hippocampus regions.

In fact, over a three-year period, those who had been senior managers in mid-life had their hippocampuses shrink at a rate that was five times slower than those who had worked in less demanding roles.

Until recently, it was thought that our brains grew and developed until we reached adulthood, then stayed unchanged for the rest of our lives.

Research shows quite the opposite - that everything we do in life actually causes our brains to reconfigure themselves in myriad ways.

Read more here.

No comments: