Brain. Model of a section through a healthy human head showing the brain. The largest part of the brain is the forebrain (pink) which mainly comprises the folded cerebrum where conscious brain activity takes place. The rod-like brainstem (white, at the base of the brain) relays signals to and from the brain through the spinal cord (white, lower centre). At the back of the brain (to the right of the brainstem) is the cerebellum which is responsible for posture, balance and the coordination of movement. The rest of the forebrain is white including the large curved corpus callosum (above the brainstem), a band of tissue that connects the brain's two hemispheres.