By Erin Jester
The vagus nerve is having a moment.
In the last few years, social media influencers and alternative medicine practitioners have touted stimulation of the vagus nerve as a cure for everything from inflammatory bowel disease to autism spectrum disorder.
While it’s no silver bullet, researchers in the University of Florida’s College of Public Health and Health Professions say, the treatment does have the potential to alleviate a variety of chronic conditions.
“The vagus nerve touches pretty much every body system,” said Tracy Centanni, Ph.D., an associate professor in the Department of Speech, Language and Hearing Sciences and director of the Genetics of Auditory and visual Perception and Plasticity Lab. “I would never say that an approach is magical or a panacea, but I do see promise in vagus nerve stimulation for its ability to help with a lot of different things.”
The vagus nerve is the longest of the cranial nerves, or nerves that originate in the brain and communicate with the rest of the body through electrical signals. Surgical implantation of devices that send mild electrical pulses to the brain through the vagus nerve was first approved by the U.S. Food and Drug Administration in 1997 to treat drug-resistant epilepsy, and later for treatment-resistant depression and post-stroke rehabilitation.
Transcutaneous vagus nerve stimulation, or tVNS, is a method of delivering electrical pulses noninvasively, by applying the stimulation device to the vagus nerve through the skin.
In her lab, Centanni employs auricular tVNS, in which a device attached to the outside of the ear delivers electrical pulses to the vagus nerve through the skin, to study its impact on reading and language acquisition.
Her first study on tVNS focused on letter-sound learning.
When children are first learning to read, they understand what a letter sounds like before they make the link between the sound and the letter.
The study trained young adults in the Hebrew alphabet, mapping the characters to English language sounds, then measured how quickly they could name the new letters and how accurately they could read words using an alphabet that was new to them. Results showed participants had increased success with the task when tVNS was applied during the session.
The second study showed participants performed better on a reading comprehension test if they received tVNS while reading the passage.
In the third study researchers taught participants 30 nouns in Palauan, a rare language none of them had ever heard spoken. After the teaching session, participants received a list of the words and were instructed to translate them into English without any hints.
Once again, the study found that participants who received tVNS during the exercise performed better.
Early research into vagus nerve stimulation’s effect on neuroplasticity — the brain’s ability to learn, change and adapt — began in the early 2000s. Centanni said she’s excited to see the potential impacts of tVNS on other conditions that affect speech, hearing and language acquisition, such as aphasia, dyslexia and hearing loss.
In May, she was awarded a grant through the Aging in Place Funding Initiative for a pilot study to evaluate tVNS for improving speech in noise perception in adults with age-related hearing loss.
Eric Porges, Ph.D., an associate professor in the Department of Clinical and Health Psychology, has been working in the field of vagus nerve stimulation for about a decade. He started out exploring the potential for VNS as a treatment for post-traumatic stress disorder and traumatic brain injury.
Since then, he’s delved into studying the effect of non-invasive VNS on other conditions that cause cognitive decline, including HIV.
People with HIV historically have shown higher rates of cognitive impairment or decline in aging, Porges said. There is a theory that inflammation could be the cause, and another that VNS could be the cure. Preclinical data in animal models with surgically implanted VNS devices has shown promise for combating inflammatory diseases such as rheumatoid arthritis.
Using a hybrid trial design, Porges and co-investigator Natalie Chichetto, Ph.D., an assistant professor in the Department of Epidemiology and Shirish S. Barve, Ph.D., of the University of Louisville, are running a study evaluating the impact of auricular tVNS, paired with a probiotic, on neurocognitive decline in people with HIV who are high-risk drinkers.
Porges was involved in another recent study investigating the effects of tVNS on brain connectivity in patients with mild cognitive impairment, along with John Williamson, Ph.D., an associate professor of psychiatry in the College of Medicine; Ronald Cohen, Ph.D., a professor emeritus in the Department of Clinical and Health Psychology; and faculty members in the McKnight Brain Institute and the Malcom Randall Veterans Affairs Medical Center. Results, published in 2023, suggested tVNS could be a potentially effective intervention.
“We are very excited about the use of tVNS to modulate systemic and, we hope, neuroinflammation,” Porges said. “The hope is that by modulating inflammatory pathways using this approach we can positively impact brain health and cognitive outcomes in aging as well as chronic disease.”
While the clinical applications of tVNS are significant, Centanni said there is potential danger in promoting vagus nerve stimulation as a miracle cure before scientists fully understand how it works.
“A lot of times clinically, the attitude is often ‘If it works, why do we care how it works,’” she said. “We do a real disservice to the field and the patients if we skip some of the mechanistic research.”
Several at-home tVNS devices are already on the market. While some brands promise only to reduce stress and improve sleep, others make more ambitious claims that the devices can help manage chronic pain, improve cognition, ease the symptoms of inflammatory bowel disease or offer a drug-free alternative to depression treatment.
But before rushing out to spend a couple hundred dollars on a tVNS device of their own, consumers should know that without the precise calibration researchers can provide in a clinical setting, results are not guaranteed.
Still, there’s little risk to people who want to try it out at home.
“The good news is that you’re not going do any harm,” Centanni said. “The worst thing that happens is it doesn’t work.”