A University of Iowa College of Medicine research team has pinpointed specific areas of the brain where damaged cells may be responsible for the dramatic loss in memory characteristic of Alzheimer's disease, a major cause of senility in the elderly.

Alzheimer's afflicts more than 2 million Americans with a progressive and thus far irreversible destruction of brain tissue, costing the nation an estimated $25 billion annually and presenting a growing problem as the population ages.

Dr. Antonio R. Damasio, a professor of neurology and co-author of the study to be published today in Science magazine, said the findings overturn some previous theories about the disease and move scientists closer to "understanding what's wrong. The most fundamental problem of these patients is their memory loss."

He cautioned that the study offers no leads about "immediate treatment" and does not show what causes brain cells to go awry. But it helps provide a better way to track the origin of one of the most dreaded diseases of aging, he said.

"By knowing which type of cell is damaged, we can concentrate on the possibility of how the injury occurred," Damasio said. "It narrows the search for the possible causes of the disease."

Since German physician Alois Alzheimer discovered the disease in 1906, scientists have known that victims' brains contain twisted nerve fibers, called neurofibrillary tangles, and degenerating nerve terminals. Later studies suggested that the severity of the disease was proportionate to the number of such defects.

The new study refines that concept, suggesting that the tangles are not randomly and widely distributed but located in "remarkably specific" areas of the brain, particularly in the memory processing center called the hippocampus.

The study found that nerve-cell destruction appeared to be concentrated in areas that control incoming and outgoing messages, essentially cutting the hippocampus off from the rest of the brain.

"This is remarkably different from previous accounts which placed these lesions anywhere within this structure," Damasio said. "The tangles are not every which way. It's as if a tornado had gone through a city and hit a line of buildings, leaving everything else intact around it."