Coloured 3D magnetic resonance imaging (MRI) scan of a sagittal section through a healthy human brain. The front of the brain is at left. 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 (pink).