People with schizophrenia look a little different than that of healthy normal people, but the differences are usually small. Sometimes the fluid-filled cavities at the center of the brain, called ventricles, are larger in people with schizophrenia; overall gray matter volume is lower; and some areas of the brain have less or more metabolic activity, less electrical output. Microscopic studies of brain tissue after death have revealed notable alterations in the characteristics of brain cells in people with schizophrenia.  It appears that many of these changes were prenatal because they are not accompanied by glial cells, which are always present when a brain injury occurs after birth.