Scientists in the U.S. believe that mental stimulation along with drug therapy may help people with diseases such as Alzheimer's and dementia regain some of their lost memories.
The scientists at the Howard Hughes Medical Institute and the Massachusetts Institute of Technology studied mice with an artificially induced Alzheimer's-like illness.
The team altered the gene p25 in the mice, causing their brains to shrink which led to severe learning and memory impairment and a loss of synapses, the connections between nerve cells.
The mice experienced two methods in an attempt to reverse their memory loss; they were placed in "enriched environment" with an exercise treadmill, colourful toys of different shapes and textures that were changed daily, and the company of other mice; they were also given a type of drug that encourages growth of brain nerve cells; another group of mice lived in a standard, bare cage.
Neuroscientist Li-Huei Tsai says the study provides the first evidence that even if the brain has suffered very severe neurodegeneration and severe learning impairment and memory loss are evident, there remains the possibility of improving learning ability and recovering some lost long-term memories.
Tsai says if lost long-term memories could be retrieved, the suggestion is that the memories had not been actually erased from the brain but probably remained in storage but could not be accessed or retrieved due to the brain damage.
The researchers had earlier put the mice through a "fear-conditioning" test by placing them in a chamber and delivering a mild electric shock to their feet in order to establish an 'enduring' memory.
The stimulated mice remembered the shock test far better than the mice kept in standard cages and they were also better at learning new things.
The researchers then injected the mice with a class of drugs called histone deacetylase, or HDAC, inhibitors and found that memory and learning improvements were comparable to those caused by the environmental stimulation.
Tsai says the research shows that even after major brain damage had occurred it was still possible to improve learning and memory.