PRNP and Alzheimer disease: However, memory impairment induced by injection of Aβ oligomers is not reduced in PrPc knockout mice [77], ablation or overexpression of PrPc has no effect on the impairment of hippocampal synaptic plasticity in a transgenic model of AD [78], and synaptic depression, reduction in spine density, or blockade of LTP is induced by Aβ in organotypic hippocampal slice neurons from both wild type and PrPc knockout mice [79].