COLUMBUS, Ohio – Using a prebiotic to influence bacterial activity in the gut after a traumatic brain injury may help reduce impulsive behavior, one of the common symptoms to follow a moderate blow to the head, a new study in rats suggests.
Following up on previous work showing a connection between negative changes to gut bacteria after a traumatic brain injury (TBI) and poor decision making, researchers at The Ohio State University are now exploring whether the gut problems may actually cause some long-term symptoms.
They found that adding the prebiotic galacto-oligosaccharide (GOS) to rat diets before and after a TBI lowered their impulsivity in a decision-making gambling test in which they are rewarded with sweets.
"We found in this study that their impulse control has improved," said senior author Cole Vonder Haar , assistant professor of neuroscience in the Ohio State College of Medicine .
"In our task, we basically ask them to make a decision, but they have to wait for the cue light to come on. And that's hard to do if you're a hungry rat, right? So it sets up a measure of impulsivity, and that's where we saw one of the most robust effects."
The poster was presented Nov. 17 at Neuroscience 2025 , the annual meeting of the Society for Neuroscience.
Almost 3 million TBI-related emergency department visits are reported in the United States each year, and over 11 million Americans over 40 who lost consciousness with a TBI are living with a disability, according to the Brain Injury Association of America .
"There's no FDA-approved treatment for TBI. People are stuck with their symptoms and do whatever they can to manage those symptoms, whether it's rehabilitation or pharmacological help for specific symptoms like depression," Vonder Haar said.
His lab is studying several interventions to see if a gut-based treatment could provide some relief. "We're trying to improve the quality of life for people who are suffering and struggling with brain injury-related problems," he said.
The work focuses on symptoms that follow a moderate TBI – an injury in rats (occurring under anesthesia) intended to mimic what might happen to a person in a car accident or a fall from a ladder.
Within the past decade, researchers in the field have determined that gut dysbiosis – a negative change to the collection of bacteria in the digestive tract – occurs in patients after they suffer a moderate brain injury.
"The core question we're trying to understand now is whether this is a causal force," Vonder Haar said. "We've previously published data showing that there's a very strong predictive correlation: If you measure the gut microbiome acutely after the brain injury, it can predict very long-term deficits in decision making. So it seems something is going on, but this earlier work was all correlative."
In the new study, rats were fed a control diet or a diet supplemented with 2% GOS beginning six weeks before the injury and continuing for another 60 days after injury. The animals were then tested for anxiety-like and depressive-like behavior, learning and memory, and impulsivity and decision making.
During the rodent gambling task, which assesses decision making and impulsivity, rats are offered four choices resulting in rewards of varying amounts of sugar pellets, and they learn over time what each option provides.
"And one of the key things we see is that brain injuries really suppress the ability to do this well," Vonder Haar said. "Our rat models really show this long-term chronic impairment, which patients also struggle with."
Rats on the GOS diet had better outcomes in impulsivity after TBI than injured rats that ate a non-supplemented diet.
"It's a modest effect. They're still more impulsive than control animals without injury, but it's reduced compared to their counterparts," Vonder Haar said. "Most of the studies we've done to try to treat impulsivity haven't worked out. This is one of the few times where it looks like a treatment has some beneficial effects."
Vonder Haar also chaired a Nov. 16 Neuroscience 2025 minisymposium on the gut microbiome in traumatic brain injury and is the lead author of a new Journal of Neuroscience article reviewing the evidence establishing the gut as a modulator of TBI and potential underlying mechanisms.
"We know what the behavioral outcome from TBI looks like, but the mechanism, why and how this is happening, is the other big question," he said.
The prebiotic study was supported by the U.S. Department of Defense.
Co-authors of the study include Alexandra Dorinsky, Katie Koontz, Berkin Bilgin, Lizza O'Connell, Jenna McCloskey, Michael Bailey and Kris Martens, all of Ohio State, and Miranda Hilt of Nationwide Children's Hospital.
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