Child's brain. Magnetic resonance imaging (MRI) scan of an coronal section through the healthy brain of a three and a half year old child at the level of the ears. Seen here is the cerebrum, the largest part of the brain. It is divided into two hemispheres and is responsible for conscious thought, emotion and voluntary movement. The dark areas at the centre of the brain are the ventricles (cavities), which are filled with cerebrospinal fluid that cushions the brain. At lower centre is the cerebellum, which controls voluntary muscular movement and maintains posture and balance. The spine is seen at bottom centre.