Brain. Coloured magnetic resonance imaging (MRI) scan of a sagittal section through a healthy human brain. The highly folded area (orange) is the cerebrum, which is responsible for conscious thought, emotion and voluntary movement. The orange arch beneath it is the corpus callosum, which facilitates communication between the hemispheres. Down centre is the brainstem (pink and yellow), which controls automatic functions, sleep and arousal and relays messages from the brain to the spinal cord. At bottom left is the cerebellum (red), which controls muscle coordination and balance.