SYP and Alzheimer disease: In the current study, we compared the olfactory stimulation effects of “olfactory three-needle” and eugenol on the spatial learning and memory; the protein expression of β-amyloid (Aβ), phosphorylated p38 MAPK (P-p38 MAPK), phosphorylated tau protein (P-tau), and synaptophysin (SYP); and the activation status of microglia (MG) in the hippocampi of SAMP8 mice, to explore the mechanism of “olfactory three-needle” in improving AD cognitive and memory abilities.