Tractography

What you are looking at

A tractogram is a reconstruction of the brain's wiring, built from diffusion MRI: the scanner measures which way water molecules are free to move in each voxel, and since water travels more easily along a nerve fibre than across it, those measurements trace out the paths that bundles of axons follow. Each thread here is a streamline, an estimate of one such path through the white matter.

The colours are not tissue types or measurements — they say which way a fibre is running at that point, the standard convention in the field:

Drag to turn the brain; use the zoom slider, or scroll over the view. It rotates on its own until you touch it. This is a population average rather than any one person's brain, so it shows the pathways people generally share.