My thesis project focuses on studying fibroblast growth factor 21 (FGF21) role in mice learning and memory. We found FGF21 is expressed in the central nervous system and central FGF21 deletion impairs spatial learning and memory. Retrosplenial cortex FGF21 overexpression improves spatial learning and memory. Hippocampus is a potential target for FGF21 signaling for spatial memory.