For this study, the researchers studied transgenic mice that progressively lose cognitive function at the same time as they develop amyloid plaques in their brains, similar to those seen in human Alzheimer's patients.
On the other hand, the animals don't develop other hallmarks of the human disease, such as loss of neurons and the development of neurofibrillary tangles, the researchers noted.
Mice -- both transgenic and normal type littermates -- were exposed to electromagnetic waves at cell phone levels of 918 megaHertz with a specific energy absorption rate of 0.25 Watts per kilogram. The exposure lasted for an hour twice a day.
Transgenic and normal type mice that weren't exposed to the radiation acted as controls. Cognitive function was measured using a so-called radial arm water maze, a standard method of testing memory in mice.
The researchers used the maze to generate a test that they said was functionally equivalent to tests used in humans that can distinguish between Alzheimer's, mild cognitive impairment, and normal cognition.
They conducted two main experiments, one in adolescent mice and one in older animals.
In the first, radiation exposure began at two months, before the transgenic animals had begun to lose cognitive function, and maze tests 2.5 months showed no difference in function between the groups of animals.
Subsequent tests -- at four months and seven months -- showed the un-exposed transgenic mice losing cognitive function, while the normal animals and the exposed transgenic mice did not.
Interestingly, in this experiment, the exposed normal mice also did significantly better than all other groups on a so-called "Y-maze alternation test," which measures basic memory function, the researchers reported.
In the second experiment, the researchers waited to start radiation exposure until the age of five months, when the transgenic animals had started to show signs of cognitive decline.
Testing two and five months later showed no evidence of benefit or harm, the researchers said, but after eight months of exposure to radiation, the transgenic mice had recovered some cognitive function and were significantly better than transgenic controls.
In the transgenic animals, radiation exposure was also associated with changes in the deposition of amyloid in the brain, including an increase in the more soluble form of the protein, the researchers said.