APP and early-onset autosomal dominant Alzheimer disease: This is consistent with indentation studies in the cortex of APP/PS1 mutant mice (Menal et al., 2018), MRE studies in mice (Munder et al., 2018), and with MRE experiments in humans with Alzheimer’s disease (Murphy et al., 2011; Arani et al., 2015; Hiscox et al., 2020) that report softening of cortical brain regions.