ABSTRACT
The diversity (bacteria, viruses and fungi) and distribution of the microbes that inhabit our digestive system, i.e. the microbiome, are described. The anatomical mechanism by which the brain and gut communicate (the gut–brain axis) including the enteric nervous system and the vagus nerve, is highlighted. The normal healthy effects these have on mental health are discussed. The involvement of the immune system communication with the brain is highlighted. Abnormal gut microbiota conditions, such as dysbiosis, are described. Probiotics, prebiotics, psychobiotics and pharmacomicrobiomics are discussed. The latest information regarding the question of brain gender, indicating that there is little difference other than size between male and female brains, is presented.
