Coloured 3D magnetic resonance imaging (MRI) scan of the human brain with the left half of the cerebrum removed. At centre is the limbic system, whose structures include the caudate nucleus, basal ganglia, thalamus, amygdala, and hippocampus. It is a primitive part of the brain involved in emotions, learning and the formation of memories. Surrounding the limbic system is the lateral ventricle (light purple). The optic nerves (yellow) are at left centre. At lower right is the cerebellum (blue and yellow), which controls voluntary muscular movement and maintains posture and balance. To the left of the cerebellum is the brainstem (yellow), which controls subconscious functions such as breathing and the regulation of heart rate, and also connects the brain to the spinal cord.