Can Vagus Nerve Stimulation Improve How We Learn?
Vagus nerve stimulation via the outer ear may enhance general-purpose learning.
Posted Aug 07, 2020
In the past year or so, vagus nerve stimulation via the outer ear has shown promise as a non-invasive way to rebalance the autonomic nervous system, slow some adverse effects of aging, reduce inflammation, and relieve indigestion. (See "Vagus Nerve Stimulation via the Outer Ear Takes Center Stage")
Now, a new study by a team of researchers from the University of Pittsburgh and the University of California, San Francisco (UCSF), reports that transcutaneous vagus nerve stimulation (tVNS) using a small ear-bud like device shows potential as a general-purpose learning aid. This study (Llanos et al., 2020) was published on August 6 in the journal npj Science of Learning.
"[Our study] is one of the first demonstrations that non-invasive vagus nerve stimulation can enhance a complex cognitive skill like language learning in healthy people," co-senior author Matthew Leonard, who is an assistant professor in the Department of Neurological Surgery at the UCSF Weill Institute for Neurosciences, said in a news release. Leonard's team at UCSF developed this particular tVNS device.
To test the ability of transcutaneous vagus nerve stimulation to enhance cognitive learning, the researchers focused on teaching adult study participants foreign language sounds as a way to gauge whether or not tVNS affected the wearer's ability to learn a higher-level cognitive task. This part of the study was conducted at The University of Pittsburgh's Sound Brain Lab, which specializes in the neurobiology of language learning.
Three dozen English-speaking adults were recruited for this study and trained to identify four distinct changes in pitch (i.e., "tones") that alter the meaning of similar-sounding Mandarin Chinese words. Study participants who wore the tVNS learned these new Mandarin tones twice as quickly as participants in a control group who were given sham vagus nerve stimulation.
Based on these findings, the authors conclude: "[T]he results of the present study demonstrate that non-invasive, sub-perceptual threshold VNS can selectively enhance the learning of complex, behaviorally relevant speech categories in adult humans."
"Showing that non-invasive peripheral nerve stimulation can make language learning easier potentially opens the door to improving cognitive performance across a wide range of domains," first author Fernando Llanos said in the news release. Llanos is a postdoctoral researcher in Pitt's Sound Brain Lab.
How does tVNS improve language learning? The researchers aren't quite sure. In response to their research question: "What are the neurophysiological mechanisms that can explain this enhancement effect?" The authors responded: "We posit that sub-threshold tVNS engages the ascending brainstem network, as indicated by significant vagal evoked potentials that are highly consistent with prior studies examining supra-threshold VNS."
Although much more research is needed, the researchers are hopeful that this type of tVNS peripheral neuromodulation might, someday, be a useful learning aid. "Together with rigorously tested training paradigms, tVNS may allow adults, who lack the neural plasticity characteristic of early childhood, to achieve substantially better outcomes in challenging tasks like learning a new language," the authors stated.
"We're showing robust learning effects in a completely non-invasive and safe way, which potentially makes the technology scalable to a broader array of consumer and medical applications, such as rehabilitation after stroke," co-senior author Bharath Chandrasekaran concluded. "Our next step is to understand the underlying neural mechanism and establish the ideal set of stimulation parameters that could maximize brain plasticity. We view tVNS as a potent tool that could enhance rehabilitation in individuals with brain damage."
Fernando Llanos, Jacie R. McHaney, William L. Schuerman, Han G. Yi, Matthew K. Leonard, Bharath Chandrasekaran. "Non-invasive Peripheral Nerve Stimulation Selectively Enhances Speech Category Learning in Adults." npj Science of Learning (First published: August 06, 2020) DOI: 10.1038/s41539-020-0070-0