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