The findings were presented on Thursday at the 7th International Geneva/Springfield Symposium on Advances in Alzheimer Therapy in Switzerland.

New York-based biotechnology company Axonyx Inc., which is developing the drug, Gilatide, plans to start human trials with it as a treatment for Alzheimer's disease later this year.

A growing number of companies are probing the mechanisms of memory formation, hoping to find drugs that can help offset memory loss in patients with diseases ranging from Alzheimer's to depression, schizophrenia, stroke, Parkinson's and AIDS. There are 500 million people in the world's major markets with diseases whose symptoms include memory loss, a market representing billions of dollars, according to industry estimates. There are millions more whose memory is impaired simply because of advancing age.

One of the leaders in developing memory-enhancing drugs is Memory Pharmaceuticals, a privately held U.S. company founded by Eric Kandel, a Columbia University researcher who won the Nobel Prize in 2000. Kandel began his experiments into memory with the Aplysia sea slug.

Memory Pharmaceuticals has discovered several compounds that show promise in counteracting memory loss in animals and is hoping to start testing at least one in humans within a year. Memory's aim is not to root out the cause of diseases such as Alzheimer's, the most common form of dementia, but to treat the symptom of memory loss.

"What we have are broader range drugs that would work in different diseases," said Tony Scullion, the company's chief executive.

Tully's tests showed that fruit flies genetically engineered to produce more of a molecule known as CREB were able to remember a smell connected with an electric shock much longer than those genetically engineered to produce less CREB.