The Allen Brain Atlas, unveiled Tuesday by multibillionaire Paul Allen, is a 3-D map that displays where each of 21,000-plus genes is activated in the mouse brain.

The computerized project cost an estimated $41 million to complete. It consists of 85 million photographs, 250,000 slides, and a gigabyte of data for each gene.

Allen, who cofounded Microsoft, reportedly provided $100 million in funding to launch the research.

The atlas is available on the Internet at www.brainatlas.org.