Brain pathways. Coloured 3-dimensional magnetic resonance imaging (MRI) scan of the white matter pathways of the brain, side view. White matter is composed of myelin-coated nerve cell fibres that carry information between nerve cells in the cerebrum of the brain (top half of image) and the brain stem (bottom centre). This image was created by an MRI scanner sensitised to the movement of water around the brain. Blue represents neural pathways from the top to the bottom of the brain, green represents pathways from the front (left) to the back (right), and red shows pathways between the right and left hemispheres of the brain.