Through what mechanisms does the gut microbiota influence mood and cognition?
Evidence from both animal studies and research in healthy individuals and clinical populations, identifies neural, immune, and metabolic mechanisms in microbiota-brain communication. This work recognizes the importance of neural connections between the body and brain through peripheral nerves, such as the vagus nerve. Vagal afferents respond to intestinal and gut-microbe signals and the vagus nerve is important in the bottom-up communication between microbiota and the brain.Microbiota-immune-brain signaling is also important. Gut bacteria are critical to the development and function of the immune system and increasingly researchers in psychiatry and behavioral neuroscience are recognizing the importance of immune signaling in emotional behavior and cognition.Both the innate and the adaptive immune system are integral in microbiota to brain communication, and in addition, the development and function of the brain’s resident immune cell, the microglia is influenced by microbiota. Microbes are also importance to metabolism—microbiota are responsible for our ability to digest plant polysaccharides. Moreover, microbiota-produced metabolites influence gut homeostasis but also are important to microbiota-host signaling that extends beyond the gut.