Child's head and brain. Magnetic resonance imaging (MRI) scan of a midsagittal section of the healthy brain of a 2-year-old child. Neural circuits, or connections between neurons that communicate information throughout the brain, continue to form after the foetal period and throughout early childhood. Development of neuronal axon insulation also takes place during infancy (until the age of 4) - this includes glial cell multiplication, and formation of the myelin sheath surrounding neurons. At upper centre is one of the hemispheres of the cerebrum, which is responsible for conscious thought, emotion and voluntary movement. At the centre of the cerebrum is the corpus callosum, which connects the right and left cerebral hemispheres and enables communication between them. At lower right is the cerebellum, which controls voluntary muscular movement and maintains posture and balance.