• 4/18
zebra finch
Source: iStock.com/GlobalP.image_jungle

It may seem outlandish, but what if studying the bacteria living in a bird’s gut could help researchers understand more about how humans learn to talk or even human brain diseases?

Billions of microorganisms, such as bacteria, yeasts, fungi and viruses, live inside the human digestive tract dubbed the gut microbiota. In recent years, studies have linked this microbiome with heart health, brain function, the immune system, mood and sleep. Some even call gut bacteria the “second brain,” which actually refers to the communication between the digestive system and central nervous system (the brain and spine) through biochemical messages. Yet, few studies have examined this relationship in species other than mammals, like rats and humans. However, researchers at FAU set out to change that.

In a recent study published in the Royal Society’s journal Biology Letters, Morgan Slevin, lead and corresponding author and an FAU doctoral student in integrative biology and neuroscience, studied the gut microbiota in relation to cognitive performance in 38 zebra finches, a common, small, striped bird originally from Central Australia. “Ultimately, we were interested in how the gut microbiome affects the brain and decision making,” Slevin said.

Ultimately, we were interested in how the gut microbiome affects the brain and decision making.

— Morgan Slevin, an FAU doctoral student in integrative biology and neuroscience

The zebra finch is a songbird, and just like humans, songbirds are among only a few animal groups in the world considered vocal learners, which means they must hear the sounds of adults of their species to develop normal adult vocalizations. This makes them a good model for understanding human learning, he said.

“If we can find parallels with the avian gut, like we see in rodents, then we might be able to use songbirds as yet another way to understand human cognitive performance, whether that relates to vocal development or other aspects of human cognitive performance,” said Rindy C. Anderson, Ph.D., senior author, assistant professor of biological sciences in FAU’s Charles E. Schmidt College of Science.

To study the link between cognition and gut bacteria, Slevin first needed to know what the microbiome of each bird looked like. He took a swab from the birds’ cloaca, an all-purpose vent used for excretion, urination, mating and laying eggs. Then, his colleagues at Cornell University genetically analyzed the samples, so Slevin could determine what different species were present (called alpha diversity), but also the composition of the entire microbial community in each sample (beta diversity). Next, he tested the birds’ cognition by assessing how quickly they could learn a completely novel feeding technique. "Animal cognition is incredibly complex, so trying to find the right way to analyze behavioral tests of cognition is really a challenge,”

zebra finch
A male zebra finch, learning to flip lids in search of food rewards, is midway through solving the final stage of the novel foraging task.

Anderson said. “But, I think we’re on the vanguard. There are only a few labs in the country that are studying avian gut microbiomes and how that might be linked to behavior, including cognition.”

Results of the study showed that male and female finches had different microbiomes, and that some groups of females or males with a certain type of microorganism community structure, the beta diversity, did worse on cognitive performance tests, while others with a different type of diversity structure did better. Slevin and Anderson also found that birds that did worse on the cognitive tests tended to have a greater abundance and prevalence of two genera of bacteria, Helicobacter and Gallibacterium. This raises the question, do certain species influence cognitive performance?

Many experts advocate for probiotics to help the gut, even if the science is still a bit murky. “It can’t hurt,’ jokes Slevin, who said he plans to continue this work in wild birds and with experiments.