Mayer thinks the bacteria in our digestive systems may help mold brain structure as we're growing up, and possibly influence our moods, behavior and feelings when we're adults. "It opens up a completely new way of looking at brain function and health and disease," he says.
So Mayer is working on just that, doing MRI scans to look at the brains of thousands of volunteers and then comparing brain structure to the types of bacteria in their guts. He thinks he already has the first clues of a connection, from an analysis of about 60 volunteers.
Mayer found that the connections between brain regions differed depending on which species of bacteria dominated a person's gut. That suggests that the specific mix of microbes in our guts might help determine what kinds of brains we have — how our brain circuits develop and how they're wired. [...]