Coloured nuclear magnetic resonance (NMR) scan showing a normal brain in a sagittal section. The brain is formed by three main structures: the cerebrum, the cerebellum and the brainstem. The cerebrum, which occupies most of the frame at upper centre, is the largest part of the brain and the site of most conscious and intelligent activities. The brainstem (centre) is a stalk of nerve tissue that forms the lowest part of the brain and links it with the spinal cord within the spinal column. The cerebellum (centre right) is a rounded structure found behind the brainstem. It is a region of the brain primarily concerned with the maintenance of posture and balance.