The hippocampus is not a singular structure, as once believed, but comprises molecularly and functionally distinct subregions, according to a paper that is a cover story of the October 2011 issue of Nature Reviews Neuroscience. Scott A. Small, MD, and his colleagues review current neuroimaging studies and propose a framework of hippocampal dysfunction in which common brain disorders differentially target distinct subregions of the hippocampal circuit and are associated with either hippocampal hypermetabolism or hypometabolism. Dr. Small is Professor of Neurology in the Sergiesvsky Center and in the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain. The framework the researchers propose is expected to help guide future studies involving many common brain disorders, including Alzheimer’s disease, normal cognitive aging, schizophrenia, and depression.