ARC and early-onset autosomal dominant Alzheimer disease: Intriguingly, defects in these forms of plasticity are observed in neurological disease models, which are associated with elevated levels of Arc, (e.g., Fragile X syndrome, Angelman syndrome, and Alzheimer’s disease) (Auerbach and Bear, 2010, Greer et al., 2010, Megill et al., 2015, Pastuzyn and Shepherd, 2017, Wu et al., 2011).