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Cell phones may cause long-term memory loss, a recent study on laboratory rats indicates.

Dr. Henry Lai, a research professor in bioengineering at the in Seattle has linked long-term memory loss and diminished navigating skills in rats with the microwaves emitted by mobile phones.

"This is the first study that shows that radio frequencies can affect long-term memory functions in rats," Lai said. Previous studies have focused mainly on short-term memory.

Lai placed 100 rats in a large tank of water and taught them to swim to a platform in the middle of the tank. He mixed powdered milk into the water so the rats couldn't see the platform. Instead, they had to navigate their way and remember the route. After swimming to the platform six times, the rats were easily able to find their way to it.

Next, half of the rats were exposed to microwaves similar to those emitted by mobile phones. All of the exposed rats forgot the way. The unexposed rats, once again, had no problem swimming to the platform.

"Then we played a trick on them -- we took the platform away," Lai said. "The normal rats went to the location and swam around in that area. They seemed to be scratching their heads, wondering what happened to the platform."

The irradiated rats, on the other hand, swam around randomly, and did not approach the former location of the platform.

"The rats that got exposed somehow could not make a map inside their head," Lai said.

"What Lai is showing is that there is a change in the learning, and there is a change in reference memory," said Louis Slesin, editor and publisher of .

"We have to be careful extrapolating the results to humans," Slesin said. "But the amount of energy going into these animals is really small and not all that different, potentially, from a cell phone."

Previous studies have shown that the chemical that controls this type of navigation in animals is called acetylcholine, according to Lai.

No one knows if the chemical also controls the navigation function in humans, Lai said. There is indirect evidence, however, that the chemical controls a similar function in humans. Alzheimer's patients -- who often show symptoms of forgetting their way to familiar places -- show a decrease in acetylcholine.

"If [radiation] is changing learning and reaction times, maybe we should take the trouble to do more work to get to the bottom of these questions," Slesin said.

In addition, the studies should be done by unbiased organizations, Slesin said.

"Too many interested parties are doing the work and they have too much to lose on the results," he said.

Several studies sponsored by the industry's Wireless Technologies Organization have found a correlation between cell phone emissions and a slightly higher incidence of human brain tumors, cell growth in human blood micronuclei, and DNA breakage in rats.