Sufferers of Alzheimer's disease may not have "lost" their memories, but could simply have difficulty accessing them, researchers said as they unveiled a possible treatment that could one day offer a cure to the ravages of dementia. Nobel Prize-winner Susumu Tonegawa said studies on mice showed that by stimulating specific areas of the brain with blue light, scientists could make the creatures recall thoughts that were otherwise unavailable to them.
The results published Wednesday offer some of the first evidence that Alzheimer's disease does not destroy specific memories, but rather makes them inaccessible. Tonegawa's team used mice that had been genetically modified to exhibit symptoms similar to those of humans suffering from Alzheimer's disease -- a degenerative brain condition that affects millions of adults around the world. The animals were put in a box which had a low level electrical current passing through the floor -- giving an unpleasant, but not dangerous, shock to their feet.
An unaffected mouse that is returned to the same box 24 hours later freezes in fear, anticipating the same nasty sensation. Mice with Alzheimer's do not, suggesting they have no recollection of the experience. But when researchers stimulated targeted areas of the animal's brains -- the "engram cells" associated with memory -- using a blue light, they appeared to recall the shock. The same result was noted even when placing the creatures in a different box during stimulation, suggesting the memory had been retained and was being reactivated.
By examining the physical structure of the mice's brains, researchers noted that those affected with Alzheimer's-like conditions had fewer "spines" -- conduits through which synaptic connections are formed. The research, carried out by the RIKEN-MIT Center for Neural Circuit Genetics, is among the first to prove that recall -- rather than memory -- is the problem,
Tonegawa said the research on mice offered hope for a future treatment for Alzheimer's disease, a condition that accounts for between 60-to-70 percent of the 47.5 million people around the world suffering from dementia, figures that are expected to increase as developed countries such as Japan grow older. But he cautioned more work was yet to be done.
