The largest part of the brain is the cerebrum. The outer surface of the cerebrum is covered with a series of elevated ridges called gyri, and grooves or shallow depressions called sulci. The deepest sulci are called fissures. The cerebrum is divided into the right and left hemispheres. The corpus callosum connects the two halves at their lower midportion. Each hemisphere is divided into four sections called lobes, which have been named for the bones of the skull that cover them. The lobes are identified as the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe.