ARC and Alzheimer disease: The potential role of Arg3.1/Arc in AD is indicated by two key findings: (i) single-nucleotide polymorphisms in the 3′ UTR of Arg3.1/Arc are associated with an increased susceptibility to AD [274]; (ii) Arg3.1/Arc protein levels in the medial frontal cortex are elevated in patients with AD vs. age-matched healthy persons [177].