Neurogenesis (birth of new neurons) occurs in many vertebrates, including humans. Most of the new neurons die before reaching destination. Those which survive migrate to various brain regions, replace older ones and connect to existing circuits. Evidence suggests that this replacement is related to acquisition of new information. Therefore, neuronal replacement is seen as a form of brain plasticity that enables organisms to adjust to environmental changes. However, direct evidence of a causal link between replacement and learning remains elusive.
I will review a few of our studies which tried to uncover conditions that influence new neuronal recruitment and survival, and how these phenomena relate to the life of birds. The hypothesis is that an increase in new neuron recruitment is associated with expected or actual increase in memory load, particularly in brain regions that process and perhaps store this new information. Moreover, since new neuronal recruitment is part of a turnover process, we assume that the same conditions that favor the survival of some neurons induce the death of others.
I will offer a frame and rational for comparing neuronal replacement in the adult avian brain, and try to uncover the pressures, rules, and mechanisms that govern its constant rejuvenation. I will discuss a variety of behaviors and environmental conditions (especially birds' migration, and if time permits - parent-offspring recognition) and their effect on new neuronal recruitment in relevant regions in the avian brain. I will describe various approaches and techniques which we used in those studies (behavioral, anatomical, cellular and hormonal), and will emphasize the significance of studying behavior and brain function under natural or naturalistic conditions.
