Postmortem brain tissue analysis of PD patients revealed hippocampal atrophy, reduced NSCs in the DG region, as well as an increased number of reactive microglia and elevated levels of pro-inflammatory factors, such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, and IL-6 in the midbrain and cerebrospinal fluid [47]. The gene discussed is TNF; the disease is hippocampal atrophy.