A fight for survival: the challenges faced by a newborn neuron integrating in the adult hippocampus.

The hippocampus is one of the only two regions in the adult mammalian brain endowed with life-long neurogenesis. Yet this adult neurogenesis is a challenging process as newborn neurons face several times life-and-death decisions while in the process of stably integrating into a pre-existing network. Here we describe the morphological and physiological changes a young neuron experiences during its first few weeks of life of stepwise integration into the circuit. This process is competitive in nature, with only few of the newly generated neurons being awarded with a grant of survival. Although the underlying mechanisms are far from being understood, evidence suggests that this competition for stable integration and survival amongst cohorts of newborn neurons occurs to large degree on a synaptic level and may involve specific patterns of neural activity.