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Figure 1. Granule cell neurogenesis and mossy fiber sprouting. A: Neurogenesis occurs in the dentate gyrus of the hippocampus. The cells proliferate in the subgranular zone and then migrate a short distance to the granule cell layer where they differentiate into mature granule cells; B: the axons of granule cells (mossy fibers) normally project to the cells in the CA3 region of the dentate gyrus; C: during seizures, several factors contribute to aberrant migration of granule cells that leads to their ectopic placement in the hilus. Ectopic granule cells (red cells) form functioning neural connections to the pyramidal neurons in the CA3 region and contribute to hyperexcitability and epileptogenesis through aberrant ‘sprouting’ along the mossy fiber pathway. Image created with BioRender.com