APA Dictionary of Psychology

a strip of gray matter that is part of the hippocampal formation, connecting the entorhinal cortex with the CA3 region of the hippocampus proper. It comprises the granular layer, which is densely packed with the bodies (somas) of elongated neurons called granule cells; the molecular layer, which contains the dendrites of the granule cells and is divided into outer, middle, and inner sublayers; and the polymorphic layer (or hilus), which contains the axons of the granule cells (see mossy fiber). At the border between the granular and polymorphic layers is the subgranular zone, one of only two currently known areas in the adult brain in which new neurons are formed (the other is the subventricular zone in the lateral ventricles). This multistage creation process, called neurogenesis, is modulated by many factors (e.g., age, environmental stimuli, hormones, neurotransmitters, neurotrophins, stress) and essential to several activities, notably information processing and learning, memory formation, spatial representation, and affect regulation. Structural and functional abnormalities of the dentate gyrus are associated with an increasing number of pathologies, including Alzheimer’s disease, autism spectrum disorder, epilepsy, depression and other mood disorders, schizophrenia, and substance use and dependence. Consequently, novel therapeutic approaches focused on enhancing the rate of neurogenesis and the successful survival of newborn neurons are being explored.