Alzheimer's risk impairs 'satnav' function of brain

Young adults with genetically increased risk of Alzheimer's have altered activation patterns in a brain region that is crucial for spatial navigation, scientists have found.
A team headed by Professor Nikolai Axmacher from the Ruhr-Universitat Bochum, Germany, analysed the grid cell system in the entorhinal cortex of young students with and without Alzheimer's risk genes.
Grid cells in the entorhinal cortex fire in a spatial grid pattern.
In 2010, Christian Doeller, presently at Radboud University in Nijmegen, demonstrated that the grid cell system in humans can be recorded indirectly using functional magnetic resonance imaging when the test subjects navigate in a virtual environment.

Axmacher, together with his graduate student Lukas Kunz, Doeller and other colleagues applied that method.
The risk carriers showed a less stable grid pattern in the entorhinal cortex - many decades before they might develop Alzheimer's dementia, according to Lukas Kunz, who conducted the experiment at the German Center for Neurodegenerative Diseases in Bonn.

Moreover, risk carriers moved less frequently in the centre of the virtual landscape, which indicates an altered navigation strategy.
In the risk group, the brain activity in the memory system was generally increased. That might be short-term compensation of the reduced grid pattern, but it may also contribute to the development of Alzheimer's dementia in the long term, according to the researchers.

"Our studies may contribute to a better understanding of early changes of Alzheimer's dementia," said Axmacher.
"Now, it has to be verified if such changes also occur in older people at an early stage of Alzheimer's dementia and if they can be affected by the application of drugs," said Axmacher.
The study was published in the journal Science.