Past studies have found that gut activity can have significant impacts on the brain , and vice versa. Now, new research in mice explains how some of that communication might occur: through very small numbers of live bacteria traveling from the gut to the brain via the vagus nerve. Researchers from Emory University in the US used a variety of mouse models designed to trigger 'leaky gut' conditions that might allow bacteria to seep into wider circulation – including mice put on high-fat diets