Coloured diffusion tensor imaging (DTI) magnetic resonance imaging (MRI) scan showing the white matter fibres that make up the cingulum bundle of the brain. The front of the brain is at left. The cingulum bundle connects the frontal, parietal, and temporal lobes, and the subcortical structures (lower centre). Abnormalities in particular locations within the cingulum bundle are associated with specific psychiatric disorders, including depression and bipolar disorder. Diffusion tensor imaging measures the direction of water diffusion, which in the brain reveals the orientation of nerve fibres. Red fibres have a left to right orientation, green a front to back orientation and blue an up and down orientation.