Connections in the brain of a healthy 29 year old female human viewed from underneath (inferior view). The front of the brain is facing the right side of the image and the back of the brain is on the left. Brain cells communicate with each other through these nerve fibres, which have been visualised using diffusion imaging tractography. 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 axons. Tractography is used to indirectly model these bundles of axons (nerve fibres), which transmit information between cortical regions at the brain's surface. For example, bundles of red and green fibres (tracts) travelling between the cerebellum (left of centre) and each side of the back of the brain can be clearly seen (left side of image). The brain measures approximately 18 cm from front to back.
