It turns out that when scientists wan't to study aging on lab animals and artificially "age them." they feed them D-Galactose.
D-Galactose is milk sugar found in milk but not to worry because You won't find it in fermented milk products like cheese or yogurt.
According to sciencedirect.com "The administration of D-galactose into animals can induce aspects of brain aging similar in many ways to human brain aging, including memory deficit, neuronal degeneration and apoptosis, (apoptosis means "cell death") raised oxidative stress, decreased ATPproduction, increased mitochondrial DNA mutation, impaired mitochondrial structure and control of abnormal gene expression in the brain (Banji et al., 2014; Kumar et al., 2009; Lei et al., 2008; Prakash and Kumar, 2013; Ullah et al., 2015)"."