As suggested above, there is strong evidence to support the role of BDNF in synaptic plasticity and cognitive function (77, 78), and as such, alteration in its function and/or expression has been implicated in the pathophysiology of aged-related neurodegenerative diseases including AD and PD (79–81), and conversely, restoring BDNF expression and/or function may be therapeutic. The gene discussed is BDNF; the disease is Parkinson disease.