New research conducted primarily in the laboratory of Sarkis Mazmanian, Luis B. and Nelly Soux Professor of Microbiology, HRMI Investigator and affiliated faculty member of the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech, shows that germs living inside our bodies could be affecting our ability to socialize and make friends…at least for mice. The new study, which appeared in the journal Nature on June 30, has identified a specific circuit of neurons that is directly influenced by the gut microbiome and is subsequently responsible for antisocial behaviors in mice that lack a gut microbiome. Transplants of fecal matter from mice with healthy gut microbiomes into these germ-free mice were sufficient to change the activity of these neurons and thus improve their social behavior. The researchers also identified a specific bacterial species that can increase sociability. Identifying the interactions between gut microbes, neurons, and whole-organism health effects (like behavioral changes) may be an important line of inquiry into ways to, someday, help improve social deficits, such as those concurrent with depression and autism.