Failings in the brain’s ‘GPS’ navigation system are what cause dementia patients to become confused and go missing, suggests new research.
Two new studies, which potentially pave the way for future treatments, show how changes in two interlinked networks within the brain may play a “key role” in the development of dementia symptoms.
Researchers say the studies, led by scientists at the University of Exeter Medical School, move doctors a step closer to understanding the onset of dementia which currently effects 850,000 people in Britain.
Both studies, published in the Journal of Neuroscience, shed light on how two parts of the brain’s ‘GPS’ navigation system malfunction, and point to likely underpinning causes for loss of orientation that is commonly experienced by people living with the condition.
In the first study, researchers studied a part of the brain called the entorhinal cortex.
Located near the base of the brain, this region is associated with functions including memory formation and navigation, and contains so-called “grid cells”. These nerve cells fire electrical discharges in a grid-like pattern – like the grid on an Ordnance Survey map.
The researchers said, lust like the different scales used on different maps, the grid firing patterns in the entorhinal cortex also have different scales, with cells at the top of the cortex having a more tightly packed grid pattern than those at the bottom.
Scientists believe that the top-to-bottom gradient of different grid scales plays a pivotal role in our sense of spatial location.
The researchers compared the activity in the entorhinal cortex of healthy mice and mice with dementia. They found that top-to-bottom gradients in electrical activity in the entorhinal cortex are not present in mice with dementia.
Their findings suggest that the fine navigational detail, such as you would find on a large-scale map, is not correctly represented in patients with dementia.
Dr Jon Brown, who led the studies, said: “This is an exciting discovery because it is the first time grid cell activity has been linked to the onset of disease.
“We now need further research to better establish how these findings translate to dementia in humans.”
In the second study, researchers examined “place cells” located in the hippocampus, a brain structure known to be critical in processing learning and memory, both affected by dementia. Place cells help us to identify where we are within a certain space.
The team found that the hippocampus of mice with dementia was associated with specific disturbances in synaptic, cellular, and network-level function, meaning that spatial information was wrongly encoded and spatial memory was impaired.
Dr Brown saidd: “Dementia is one of the greatest health challenges of our time, and we still have so much to learn about its causes, as well as about how our brains work.
“This research makes progress in both areas, and is another small step along the road to earlier diagnoses and finding new treatments and therapies.”
Dr Laura Phipps, of Alzheimer’s Research UK which part-funded the studies, added: “It is vital that researchers explore the complexities of the brain, to understand more about the causes of the condition and how we can tackle it.
“Dementia is not just a synonym for forgetfulness – these findings in mice highlight the impact that diseases such as Alzheimer’s can have on spatial orientation.
“It will now be important to build on this research, to understand whether this chain of events can be targeted in the hunt for new treatments.”
by Stephen Beech
