Social behavior is most commonly associated with electrical and chemical signaling in the brain. But, did you know that your gut may also communicate with your brain? There is emerging evidence that the gut microbiome, a population of about 100 trillion microorganisms that resides in the gastrointestinal tract, may communicate with the central nervous system to mediate cognitive function and behavior. In both rodent models and humans, gut dysbiosis (an imbalance in gut microbial communities) is associated with a suite of immune and psychological disorders, including anxiety and depression. Therefore, exploring the mechanisms by which the gut microbiome affects social behavior not only aids in the development of treatments for these psychopathologies, but it also enhances our understanding of how this complex system contributes to fitness.
Research in Dr. Greg Demas’s lab in the Department of Biology at IU focuses on investigating how disrupting the gut microbiome influences different social behaviors. Kristyn Sylvia, a fifth year Ph.D. student in the lab, has spent much of her graduate career exploring the physiological and hormonal underpinnings of gut-microbiome interactions. Kristyn’s research is unique among the majority of gut microbiome studies as her work utilizes a non-traditional animal model, Siberian hamsters, to examine the behavioral consequences of gut dysbiosis. Unlike germ-free mice, which are the model system of choice for most microbiome research, non-model species allow research to examine the natural functions of gut microbiota in mammals.
Kristyn’s recent project on sex differences in gut microbiota and behavior following dybiosis was published in the journal Brain, Behavior, and Immunity. In this study, Kristyn used a broad-spectrum antibiotic to manipulate the gut microbiome of adult male and female hamsters. She then examined the potential consequences of gut dysbiosis on two sets of social behaviors that are particularly relevant to organismal fitness: reproduction and aggression.
Kristyn found that microbiome disruption exclusively affects aggressive behaviors in both males and females. Interestingly, she observed sex differences in the behavioral response to gut dysbiosis, where females required fewer antibiotic treatments than males to show reduced levels of aggression. Furthermore, while males exhibited a recovery in aggressive behavior after antibiotic treatment, females still exhibited significantly lower levels of aggression following a recovery period. Kristyn’s results demonstrate that modest antibiotic treatment can have marked consequences on social behavior and indicate that gut dysbiosis has sex-specific effects on aggression.
Future studies in the Demas lab will build on Kristyn’s findings and pinpoint the specific mechanisms by which the gut microbiome interacts with the brain to influence aggression. In addition, Dr. Demas, along with Dr. Jeff Alberts and Dr. Cara Wellman in IU’s Department of Psychological and Brain Sciences, recently received funding from the National Science Foundation to explore the influence of the maternal microbiome on the development of offspring social behaviors. This collaborative research will provide insight into how the microbiome influences parent-offspring interactions and the development of social behavior.