A method of treating neurodegenerative conditions is provided. Neural stem cells may be implanted at and/or remote from a region of neuron degeneration. The methods can include isolating neural stem cells from regions where specific types of neurons corresponding to the neurons to be replaced are generated. The methods can include isolating neural stem cells secreting growth factors affecting the growth and/or regeneration of specific types of neuron. In this invention, we disclose a method of treating such disorders, including several neurodegenerative disorders arising from the lack of cells that produce particular neurotransmitters in neural circuitry by transplanting exogenously cultured and expanded neural progenitors which, upon transplantation into a neural tissue, differentiate into neurons capable of integrating and producing neurotransmitters in sufficient quantities and in a sufficient manner to overcome the symptoms associated with the neurodegeneration.