"At Stanford University, the Thaiss Lab revealed that changes to the composition of microorganisms that live in the gut during aging can affect memory in mice. The study found increased abundance of the bacteria Parabacteroides goldsteinii in older mice with cognitive decline, and that this bacteria could affect the memory of younger mice. The digestive tract connects to the brain via the vagus nerve, which then influences brain regions like the hippocampus, which is responsible for memory. P. goldsteinii abundance is associated with higher production of a metabolite that triggers inflammation, inhibiting activity of the vagus nerve, and thus the hippocampus. This association is being investigated in humans, in which cognitive decline could be treated by targeting the gut." - Iphia Zhang, OCW