Germinal regions of the adult human brain. The subventricular zone (SVZ) is the largest germinal region in the adult mammalian brain. The subgranular zone (SGZ) is located within the dentate gyrus of the hippocampus. The CA1, CA2, and CA3 represent Cornu Annulis fields of hippocampus proper and, along with dentate gyrus, constitute the hippocampal formation, the primary memory center in the brain.