Visualisation of white matter pathways in a healthy human adult brain using diffusion imaging tractography. The front of the brain is facing the left side of the image and the back of the brain is on the right. Diffusion weighted imaging is a specialised type of magnetic resonance imaging (MRI) scan which measures water diffusion in many directions in order to reconstruct the orientation of bundles of nerve fibres. Tractography is used to indirectly model these bundles of nerve fibres (tracts), which support communication between different brain regions. Tracts connecting different regions of the brain are colour-coded as follows: fibres travelling up and down (superior-inferior) are blue, front to back (anterior-posterior) are green, and left to right are red. This colour representation helps distinguish between different tracts which pass close to each other.