The Allen Institute for Brain Science is launching a four-year, $55-million effort to build a 3D map documenting activity levels of some 20,000 different genes across the human brain.

The scientists will divide the human brain into 500 to 2000 anatomical regions and study gene activity in each by using gene chips to record which messenger RNA is present in different regions of the brain.

For instance, some neuroscientists suspect that autism may be linked to abnormalities in the amygdala, involved in processing emotional information. This can be tested by comparing patterns of gene activity in autistic people with those in the atlas.

The Allen institute created a similar atlas of the mouse brain, unveiled in December 2006.