The large-scale structural organization of the adult brain is relatively stable and unchanging. However, in some animal species, including humans, new neurons are born and integrated into the hippocampal network throughout lifetime. The hippocampus is involved in functions such as memory formation, contextual pattern separation, and spatial navigation, among others. However, it is currently not clear how the integration of newborn neurons in the hippocampus affects its function.
Most neurons in the hippocampus are born early in development and have functional properties that are distinct from adult-born cells. These initially distinct properties of adult-born cells gradually converge to those of developmentally-born neurons in an age-dependent manner. It is suspected that this functional distinction and gradual maturation is responsible for the integration of adult-born cells into the existing brain networks.
To assay the dynamics of adult neurogenesis, we developed a model in which adult-born neurons form plastic connections and interact with other neurons in the hippocampal network. Large-scale numerical simulations revealed that age-dependent functional properties are indeed critical for the integration of adult-born neurons into the preexisting network. Furthermore, an analysis of the network dynamics suggests that, if large numbers of adult-born neurons are rapidly added, pathological states may emerge. Data also suggest that adult-born and developmentally-born neurons may be involved in a competition-based appropriation of synapses.