The researchers performed the study in genetically engineered mice. A protein was activated in these mice to trigger a neurodegenerative change in the brain, similar to that seen in people with Alzheimer's.
The mice had previously been taught to avoid an electric shock when negotiating a maze to find food.
Some of the mice were then placed in an environment which provided more mental stimulation. The researchers found that these mice were more able to remember the shock test, than mice which had remained in the basic cages.
The scientists then investigated a class of drugs called histone deacetylse, or HDAC, inhibitors which are known to encourage growth of brain nerve cells. These drugs caused improvements in memory and learning which were similar to the improvements seen with mental stimulation.
The researchers conclude that memories are not lost in individuals with degenerative brain disease, rather these memories cannot be accessed as a result of the disease.
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