London, Oct 25 (IANS): Young adults with genetically-increased Alzheimer's risk have altered activation patterns in a brain region that is crucial for spatial navigation, a study has found.

Alzheimer's patients suffer from severe memory loss and disorientation. One of the areas affected by the disease at an early stage is the entorhinal cortex that is crucial for navigation.

A team led by Nikolai Axmacher from Germany's Ruhr-University Bochum, together with colleagues from the universities of Bonn, Nijmegen and Ulm found an altered grid cell system in the entorhinal cortex of young students with Alzheimer's risk genes.

"The risk carriers showed a less stable grid pattern in the entorhinal cortex many decades before they might develop Alzheimer's dementia," said Lukas Kunz, who conducted the experiment at the German Centre for Neurodegenerative Diseases in Bonn.

Moreover, risk carriers moved less frequently in the centre of the virtual landscape, which indicated an altered navigation strategy, Kunz added.

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.

At present, there is no curative treatment for Alzheimer's dementia. A potential reason is that drugs are only administered after large parts of the brain have been destroyed. Therefore, the study aimed at identifying Alzheimer's dementia early on and yield a better understanding of early disease stages.

"Our studies may contribute to a better understanding of early changes of Alzheimer's dementia," Axmacher said.

"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."

The study finds were published in the October 23 issue of the journal Science.