In AD, the lowered expression of NTFs, such as nerve growth factor (NGF) [65], BDNF [66], glial cell line-derived neurotrophic factor (GDNF) [67] and ciliary neurotrophic factor (CNTF), have been observed in affected brain regions, including the temporal cortex and hippocampus [68]. Here, BDNF is linked to Alzheimer disease.