ABSTRACT
In the rst view, it is unbelievable to imagine that there can be an association between the intestinal microbiota and the central nervous system (CNS). However, a growing body of data indicates a bidirectional interaction between CNS and the phyla of bacteria living in the gut. Importantly, the microbiota population is considerably changeable by numerous interventions, for example, antibiotic treatment or probiotic supplements. Before paying attention to the role of probiotics in the brain function, an explanation of natural population of bacteria living in the lower intestine is necessary.
