In rats, at least, the vagus nerve is a link. Supplementing a rat's diet with Lactobacilus Rhamnosus reduces their anxiety level. Cut the vagus nerve, the eff

In rats, at least, the vagus nerve is a link. Supplementing a rat's diet with Lactobacilus Rhamnosus reduces their anxiety level. Cut the vagus nerve, the effect disappears. http://www.pnas.org/content/108/38/16050 http://www.pnas.org/content/108/38/16050 This doesn't mean that other bacteria may affect the brain through the immune system, though.