The brain in your head and the one in your gut are always exchanging info. But how do they do it? Neuroscientist Diego Bohórquez is trying to find out the answers.
If you were asked where the human body’s nervous system is located, you’d probably answer “the brain” or “the spinal cord.” But besides the central nervous system, which consists of those two organs, our bodies also contain the enteric nervous system, a two-layer lining with more than 100 million nerve cells that spans our guts from the esophagus to the rectum. The enteric nervous system has been called “the second brain,” and it’s in constant contact with the one in our skull. That’s why just thinking about food can lead your stomach to start secreting enzymes, or why giving a speech can lead to your feeling queasy.
Until recently, scientists thought the two systems communicated solely via hormones produced by enteroendocrine cells scattered throughout the gut’s lining. After sensing food or bacteria, the cells release molecular messengers that prompt the nervous system to modulate behavior. But it turns out the process may be much more direct. Intriguingly, Duke University gut-brain neuroscientist Diego Bohórquez, a TED Fellow, has found that some enteroendocrine cells also make physical contact with the enteric nervous system, forming synapses with nerves. This revelation opens the door to rethinking how we might affect these signals — and might someday change how we treat conditions as varied as obesity, anorexia, irritable bowel syndrome, autism and PTSD.
What fueled Bohórquez’s interest in the gut-brain connection? Chickens. After he moved to the US from Ecuador, his first position was as a visiting research scholar at North Carolina State University, where he worked in a nutrition laboratory that focused on chickens. “In poultry production, the biggest challenge is to feed the hatchling chicks as soon as possible so the bird can achieve its maximum growth potential,” Bohórquez says. “My PhD advisor came up with the idea to feed the chicks in the egg before they hatch. This in-ovo feeding consisted of delivering enzymes into the amniotic fluid of the embryo right before it hatched.” Bohórquez was surprised at how this practice changed what the chicks did after they hatched. “The unfed chickens came out of the egg and slept for five or six hours. But the ones fed in ovo went straight to eat,” he says. “They were also more alert, spent time looking around, and pecked each other. I became intrigued about how ingested nutrients alter behavior.”
A friend’s gastric bypass surgery also fueled his curiosity. “A friend was struggling with obesity and, as a last resort, decided to have gastric bypass surgery. It worked. She lost a lot of weight, and it resolved her diabetes,” he recalls. “But most strikingly, her perception of taste changed. She used to be repulsed by the sight of runny egg yolks, but after the surgery, she craved them.” Such a change in taste has been well documented in some patients who’ve undergone bariatric surgery, but scientists aren’t sure how or why it happens, says Bohórquez. “It’s a new subject, but rewiring the gut appears to physically change how we perceive the taste of food in the brain.”