At 13 months, TgF344-AD rats demonstrate deficits in hippocampal neuronal differentiation, migration, and survival,101 and display significant tau pathology, neuronal damage, and cognitive impairment between 16 and 26 months.10,66,102 Given that reduced synaptic density and neuronal loss are associated with MRI-detectable volume changes,51,103 these reports of altered neurogenesis and neuronal damage may reflect some of the processes underlying the volumetric changes we report. This evidence concerns the gene MAPT and Alzheimer disease.