"The brain undergoes structural changes in response to experience, known as structural plasticity. Loss of plasticity most likely underlies brain changes associated with aging and neurodegeneration. Neurotrophins (NTs) are the main proteins linking structure and function in the human brain. Lack of NTs underlies neurodegeneration and NTs are the favored factors to promote nervous system repair. How NTs implement these functions, and how alterations in NT function lead to neurodegeneration, is not yet solved. The fruit fly Drosophila is a powerful model to study gene function. Investigation of NT functions in flies was only recently made possible by the discovery of the Drosophila NT family by the Hidalgo team. Here, I will investigate if Drosophila NTs (DNTs) underlie structural plasticity in the fly brain and if their loss leads to neurodegeneration. I aim to: 1) Define the circuits involving DNTs in the fly brain. 2) Identify the cellular events underlying brain developmental plasticity in response to DNTs. 3) Test if DNTs are involved in experience dependent plasticity in the adult. 4) Test if interfering with DNT functions in structural plasticity promotes neurodegeneration. The resulting findings will increase our understanding of brain evolution, function, formation and degeneration."