Structural Plasticity Induced by Adult Neurogenesis

Memory formation, storage, and retrieval are computationally demanding tasks. To handle this problem, the mammalian brain has developed a form of metaplasticity, whereby new neurons are continuously generated and integrated into preexisting networks to support ongoing information processing throughout life. In particular, neurogenesis in adulthood affects the synaptic landscape of the dentate gyrus (DG) of the hippocampus and the olfactory bulb (OB), where new neurons establish connections with existing cells and contribute to the proper functioning of the circuits. Here we review the current evidence on the structural plasticity of adult-generated neurons and how this relates to the plasticity of the preexisting networks that they modulate, focusing largely on rodent hippocampal neurogenesis, with comparisons drawn to OB neurogenesis. Neurogenesis-induced rewiring occurs in a manner that permits the functional integration of new neurons while maintaining a balance of activity by recruiting inhibitory interneuron networks in the case of the DG, or by directly modulating sensory input and principal neuron output in the case of the OB. As our understanding of these continuously rewiring networks evolves, we expect that computational models will grow in tandem to provide increasingly accurate predictions, and will lead us to ask more informed questions about the nature of these complex information processing systems.