Besides the gut flora being capable of some neurological effects it has demonstrated to be psychoactive. Professor Robert Sapolsky[1] has an amazing course on Behavorial Evolution. The toxoplasmic gondii comes from the rat -> cat -> gut -> brain, it is profound that side effects in the brain are chemically constructed from the stomach. Considering that most animals do not even have a brain,but usually have a stomach, it is evident that the gut is underestimated in the evolutionary tree.