Scientists funded by Microsoft Corp. co-founder Paul Allen unveiled a $55 million computerized atlas of the human brain Tuesday, offering the first interactive research guide to the anatomy and genes that animate the mind.

A project of the Seattle-based Allen Institute for Brain Science, the online atlas offers researchers a powerful new tool to understand where and how genes are at work in the brain. That could help them find new clues to conditions rooted in the brain, such as Alzheimer's disease, autism and mental-health disorders like depression.

"Until now, a definitive map of the human brain at this level of detail simply hasn't existed," said Allan Jones, the nonprofit institute's chief executive. "For the first time, we have generated a comprehensive map of the brain that includes the underlying biochemistry."

The institute is making the atlas freely available at www.brain-map.org as a resource for scientists studying brain diseases, along with a set of computational tools to help them analyze the data for clues to conditions such as Alzheimer's disease, autism and mental-health disorders like depression.

Advances in the ability to probe the human brain have driven a renaissance in neuroscience in recent decades. The new online atlas is considered significant because it combines several reliable imaging techniques into one three-dimensional interactive archive that accurately maps overall anatomy, nerve structure, cell features and a comprehensive read-out of gene activity.