White matter fibres. Frontal coloured 3D diffusion tensor imaging (DTI) scan of a healthy brain showing the bundles of white matter nerve fibres. The fibres transmit nerve signals between brain regions and between the brain and the spinal cord. The cingulum (green) connects the components of the limbic system, which are involved in emotions such as aggression, fear and pleasure and the formation of memories. The corona radiata (blue) connects to the spinal cord and is involved in finely coordinated movements. The commissural fibres (red) connect the hemispheres of the brain. DTI scans show the diffusion of water along white matter fibres, allowing their orientations and the connections between brain regions to be mapped.