Similarly, colonization of healthy C57BL/6 mice with microbiota derived from 5xFAD mice induces colonic inflammation, abnormal microglial activation in the hippocampus, reduced hippocampal neurogenesis, and decreased brain-derived neurotrophic factor (BDNF) expression, ultimately resulting in memory impairments (Kim et al., 2021). This evidence concerns the gene BDNF and memory impairment.