TLR4 and Cognitive impairment: A recent study showed that an oral gavage of LPS or EVs isolated from Paenalcaligenes hominis caused cognitive impairment in aged mice whereas an oral gavage of both led to severer cognitive impairment These effects are associated with hippocampal inflammation by inducing TLR4- and IL-1R-mediated NF-κB activation in innate immune cells such as microglial cells and successively suppress NF-κB-mediated BDNF expression in the hippocampus.