In accordance with this, in APP/PS1 double transgenic mice overexpressing hAPP and PS1, a genetic candidate for familial AD, social isolation compounded AD-related memory impairments, increased MnSOD levels (indicative of an adaptive response to oxidative stress), and increased the ratio of Aβ42 to Aβ40 as compared to non-isolated mice (Huang et al., 2011). This evidence concerns the gene PSEN1 and Alzheimer disease.