This is just a short article about how learning new things and exercise can help neurons. The story centers around oligodendrocytes which wrap axons in mylin insulation to protect them and speed electrical signal conduction. Like many things in the body this system is a type of feedback loop because being more active and maxing the axons fire stimulates the oligodendrocytes to wrap more mylin around the axon.

http://www.sciencenews.org/view/generic/id/333026/description/How_exercise
_benefits_nerve_cells