Hippocampus (image) University of Maryland Caption The hippocampus (pictured left), a seahorse-shaped structure located in the brain's temporal lobe, is affected early in the neuropathologic process of Alzheimer's disease, and greater than normal shrinkage occurs as the disease progresses. Healthy asymptomatic older adults who carry the APOE- e4 allele also show greater rates of hippocampal atrophy, which can be attenuated by being physically active. Credit Laszlo Seress/Wikimedia Commons Usage Restrictions Wikimedia Commons Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.