We reversed the downregulation of miR-338-5p in the brain of APP/PS1 mice aged 8-month-old and 10-month-old through intrahippocampal injection of lentiviral vector overexpressing miR-338-5p to test whether miR-338-5p affects cognitive deficits in APP/PS1 mice [23]. The gene discussed is APP; the disease is Cognitive impairment.