LOS ANGELES - Scientists have created a three-dimensional virtual brain that not only maps the organ's anatomy in unprecedented detail but also allows researchers to see how the invisible connections between cells produce the complex behaviors that make us human.

The BigBrain atlas, produced after a five-year effort, was hailed by neuroscientists as a technological tour de force that promises to speed discoveries in an increasingly important field. The work was reported in Friday's edition of the journal Science.

"It absolutely will help us build bridges between the brain's structure and its function," said Dr. John Mazziotta, a UCLA neuroscientist not involved in the effort. "The more we understand the components of the machinery, the better position we're in to understand how it works. It's pretty hard to understand how a complex electronic device works if you don't have a good wiring diagram."

BigBrain reveals the brain's structures with a resolution 50 times better than the brain maps produced by MRI scanners. More important, it will make it possible for researchers, physicians and drug developers to examine the brain in a way that neither MRIs nor tissue samples on microscope slides can provide.

Samples under a microscope can provide a high level of detail, but they don't help researchers figure out where the samples belong in the brain or see all the cells around them.

And MRI scans offer a global view of the brain and its large structures, but aren't detailed enough to show how one type of brain cell may connect others elsewhere in the brain.

The virtual model - based on thousands of slices of an actual organ - will help researchers understand how the brain's smallest building blocks work together to produce an array of intricate, mystifying and often amazing behaviors.

The BigBrain atlas promises to allow more accurate location of brain tissues implicated in diseases such as epilepsy, Alzheimer's and Parkinson's.

With better guides to the cells they are looking for, surgeons can implant stimulating devices more precisely, create smaller lesions to short-circuit electrical storms in the brain, and remove tumors with less collateral damage.

It is also a key step in unifying the far-flung communities of brain scientists around a single anatomical standard - a "reference" brain by which all variations, normal and pathological, can be described, labeled and understood.

"People are pretty excited about it," said Mazziotta, who was attending a meeting of the Organization for Human Brain Mapping in Seattle, where BigBrain was presented to scientists. In a research field awash in brain images, "what was needed was a gold standard that would have microscopic resolution. This is it."

The brain at the heart of the project belonged to a 65-year-old woman in Europe who had no neurological disease and willed her remains for research.