Researchers have discovered that transcutaneous Vagus Nerve Stimulation (tVNS) administered to the auricular (at the left ear) branch of the vagus nerve can enhance language learning in adults.
The findings were reported this month by a team of scientists from the University of Pittsburgh and University of California, USA; and published in the Nature Partner Journal, Science of Learning.
Llanos, F., McHaney, J.R., Schuerman, W.L. et al. Non-invasive peripheral nerve stimulation selectively enhances speech category learning in adults. npj Sci. Learn. 5, 12 (2020). https://doi.org/10.1038/s41539-020-0070-0
Their experiments were conducted on native English speakers who were exposed to Chinese Mandarin tonal categories while undergoing stimulation. A control group was exposed to the same language sounds without receiving the stimulation. The findings were supported by analysing brain signals using electroencephalography (EEG), which showed that the improved learning was facilitated by enhancing perception processing and memory consolidation.
Experimental subjects who received the stimulation were able to learn new language sounds twice as quickly, in some cases, as those who received no stimulation.
Adult language learners find it notoriously difficult to recognise non-native speech sounds and Mandarin is one of the hardest languages to learn for native English speakers because of its use of subtitle tones to change the meaning of words.
Stimulation was delivered using a custom made earbud-like device. The researchers speculated that a similar approach might have further applications in other kinds of learning.
“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,” said lead author Fernando Llanos, PhD, a postdoctoral researcher in Pitt’s Sound Brain Lab.
tVNS has received considerable scientific attention in the last few years, but most of the previous studies have focused on the nerve’s central role in regulating bodily functions such as the functioning of major organs, maintaining nervous system balance (homeostasis) and the body’s inflammatory response. However the majority of the signalling along the auricular branch of the vagus nerve is actually afferent, meaning it is towards the brain. Some evidence has previously indicated that mood and cognition is positively affected by auricular vagus nerve stimulation in a much broader sense, but this is the first study that demonstrates such a direct link between stimulation at this location and an enhancement of a specific neurological function.
The exact mechanism of how these benefits are incurred from tVNS are still not fully understood and more work is needed to explore this. It is possible that the effects are very specific and it will take the development of better stimulation protocols to improve and broaden the beneficial effects.