Mechanisms of nervous system structural and functional maintenance during aging

How do neurons and circuits change at the molecular, structural, and functional levels as an organism ages? 

Neurons undergo a number of profound changes as animals age.  These responses are often cell-type or region specific.  What are the molecular alterations that lead to neuronal morphological and functional changes with age?  We are exploring this problem and identifying molecules that help to maintain structural and functional integrity of neurons during aging.