The Effect of Microbiota on Behaviour

There is currently enormous interest in the impact of the intestinal microbiota on the development and function of the brain via activity of the microbiota-gut-brain axis. It has long been recognised that symbiotic microorganisms influence host behaviour, but in recent years evidence has accumulated that this can, in fact, be beneficial to the host. Indeed, substantial research has now demonstrated an influence of the intestinal microbiota on a wide range of mammalian behaviours. Here, we review what is currently known about the influence of intestinal microbiota on learning and memory, olfaction, social behaviours, and circadian processes. While work in animal models is compelling, further work is required to elucidate mechanisms whereby bacterial influence is occurring, as well as to determine the extent to which gut microbiota can influence similar phenotypes in humans.