A comprehensive atlas of the adult human brain that reveals the activity of genes across the entire organ has been created by scientists. The map was created from genetic analyses of about 900 specific parts of two “clinically unremarkable” brains donated by a 24-year-old and 39-year-old man, and half a brain from a third man.

Detailed analysis of the cortex revealed patterns in gene activity that corresponded to regions with specific roles in the brain, such as movement and sensory functions. The atlas revealed no major divide in gene activity on the left and right sides of the brain, suggesting that expertise generally handled by one hemisphere, such as language, comes from more subtle differences than the study could spot.

Scientists have constructed similar genetic atlases for rodents in the past, but the shortage of donated human brains, their size and the destructive nature of the tests meant a human equivalent was more of a challenge.

The atlas, which overlays the genetic results on to a 3D image of the brain, is freely available for researchers to use online.

Future studies will be to connect the genetic brain atlas with other genetic studies or brain scans of abnormal or diseased brains. That could highlight genes that play a role in brain conditions and point the way to drug treatments.