BDNF and Parkinson disease: Increased BDNF enhanced endogenous neurogenesis in the SVZ and SGZ of the adult brain (Zhao et al., 2008), while GDNF promoted survival of grafted midbrain-derived NSCs in a PD rat model (Lei et al., 2011) and CDNF and CNTF enhanced memory function, neurogenesis and synaptic plasticity in the SGZ (Chohan et al., 2011).