PTK2 and Alzheimer disease: To examine the effect of depletion of FAK on learning and memory in the 3xTg-AD mice, a lentivirus containing shRNA sequence specific for the Ptk2 gene (FAK-KD) or a control virus was introduced into the hippocampi of 8-month-old 3xTg-AD mice by stereotaxic injection (Figure 1A–D).