APP and Alzheimer disease: Consistent with these in vitro studies, injection of Aβ oligomers into the hippocampus of p75NTR–/– mice resulted in decreased degeneration of basal forebrain neurons relative to wildtype mice24 and crossing of p75NTR–/– mice with two different APP mutant AD mouse models resulted in decreased neurite degeneration without a decrease in Aβ levels25,26.