SYN1 and Cognitive impairment: To investigate the direct impact of synapsin I C83 fragment on the synaptic dysfunction and cognitive impairment, AAVs encoding EGFP, EGFP‐synapsin I, and EGFP‐synapsin I C83 were injected into the bilateral CA1 hippocampal region of 2‐month‐old wild‐type mice.