**Abstract**

Hippocrates statement that "All disease begins in the gut" continues to be up to date more than 2000 years later. Growing number of scientific reports focus on the important role of intestinal microorganisms for modulation of many systems and human behavior. As a key component of the gut brain, gut microbiota influences the development and maturation of the hypothalamic-pituitary-adrenal axis, affects the development and function of the immune system, regulates the blood-brain barrier, modulates the synthesis and recognition of neurotransmitters, regulates neurogenesis, formation of myelination and supports the development and function of the brain. Disruption of gut-brain axis function is associated with alterations in the stress response and might contribute to neuropsychiatric diseases as depression, autistic spectrum disorders, rapid eye movement sleep behavior disorder, Parkinson disease, Alzheimer disease and other mental conditions. Studies in animal models are crucial for guiding research on brain-gut-microbiome axis in humans, as the impact of microbiota on specific brain regions and aspects of animal behavior will help in the selection of tasks for cognitive assessment. Exploring the interaction of gut microbes and human brain will not only allow us to better understand the pathogenesis of neuropsychiatric disorders, but will also provide us new opportunities for the design of novel immuno- or microbe-based therapies.

**Keywords:** gut microbiota, brain, gut-brain axis, behavior disturbances, modulation, human behavior, animal models
