• Cognition and microbes; emerging a new era in Neuroscience
  • Soroush Fazel,1,* Fatemeh Yousef Saber,2
    1. Department of Cognitive Neuroscience, Faculty of Education and Psychology, University of Tabriz, Tabriz, Iran
    2. Department of Cell and Molecular Biology and Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan, Iran


  • Introduction: Each human body has a unique microbial signature consisting of approximately ten trillion microbes (mainly bacteria; Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, etc.) that strongly affect all aspects of their physiology, pathology, and even cognition. Several studies have indicated the evolutionary role of microbial composition and complexity in human brain development, behavior regulation, and cognitive functions such as sociability. However, neural pathways and neurotransmitters could strongly affect the microbiota dynamics as well.
  • Methods: This article is a brief review on how the human microbiome could affect various cognitive processes as well as cause/controlling different diseases and behaviors. Google Scholar and Pubmed databases were used to gather this information using these keywords: microbiota, cognitive neuroscience, cognitive disorders, and gut-brain axis.
  • Results: It has been documented that there are numerous bidirectional associations between the brain and human microbiome, especially gut microbiota which could be divided into 4 main categories: i) The vague nerve and central lymphatic vessels, ii) the hypothalamic-pituitary-adrenal axis (HPA), iii) the immune system and its cytokines, iv) essential metabolisms like Tryptophan–Kynurenine and short-chain fatty acids. These communications could result in both regulating behaviors and causing diseases which could be discussed as follows: Aside from the effect of bacterial genes and metabolites on different levels of brain structure and function, they also participate in a wide range of cognitive processes such as memory and learning. Recent studies have reported other behavior-related impacts of microbiota like social behavior, intimate relationship, sexual behavior, mate selection, and maternal care. On the other hand, simultaneous gut microbiota colonization and cognitive development occur right after childbirth. Conducting different experimental methods namely germ-free studies, antibiotic administration, assessing probiotic effects and microbial transplant confirmed the crucial role of bacteria in causing major cognitive deficits. Addiction to alcohol, opiates, and psychostimulants, eating disorders, depression, anxiety, and stress, autism, and schizophrenia are just a few approved examples.
  • Conclusion: Microbiome-brain association has attracted significant attention in the past decade. The implication of this system could be a turning point in characterization and more importantly in the treatment of severe psychiatric disorders by altering microbial population using probiotics, prebiotics, or other natural compounds.
  • Keywords: Microbiota, Cognitive neuroscience, Cognitive disorders, Gut-brain axis