Can a small electrical stimulus improve our memory, attention and other cognitive functions? And does such a stimulus activate fundamental brain systems involved in arousal and learning? Cognitive neuroscientist Sander Nieuwenhuis has been awarded an NWO grant of €800,000 to investigate these questions.
Transcutaneous vagus nerve stimulation (tVNS) is a non-invasive technique in which the vagus nerve is gently stimulated electrically through the skin, either at the ear or the neck. In recent years, interest in this method has grown rapidly among scientists, healthcare professionals and commercial companies. Some manufacturers are even marketing tVNS devices directly to consumers, claiming benefits such as reduced stress and improved concentration and memory.
'There is tremendous enthusiasm about the potential of vagus nerve stimulation, but many of the promises currently being made are not yet supported by robust scientific evidence,' says Sander Nieuwenhuis, Professor of Cognitive Neuroscience of Decision Making. 'With this project, we aim to be among the first to investigate thoroughly whether tVNS genuinely improves cognitive functions and how this technique affects the brain.'
'Many of the promises currently being made about stimulating the vagus nerve are not yet supported by robust scientific evidence'
Testing claims of cognitive enhancement
In the four-year project Neurocognitive effects of non-invasive vagus nerve stimulation, Nieuwenhuis and his colleagues will investigate whether tVNS can improve cognitive functions such as perception, working memory and cognitive control. They will study both younger and older adults, examining not only the immediate effects of stimulation but also whether repeated use over several weeks can lead to lasting improvements.
A unique aspect of the project is that it compares two forms of stimulation: auricular tVNS, in which stimulation is delivered via the ear, and cervical tVNS, in which stimulation is applied via the neck. Although most previous research has focused on stimulation through the ear, recent findings suggest that stimulation through the neck may have stronger effects on cognitive functioning.
The results will determine whether the widely made claims about cognitive enhancement are actually justified and will provide scientifically grounded information for consumers, healthcare professionals and policymakers.
The brain's arousal systems
In addition to its potential practical applications, tVNS may also provide neuroscientists with a powerful new tool for studying the brain. Through this project, Nieuwenhuis and his colleagues will also investigate whether brief pulses of vagus nerve stimulation activate the brain's neuromodulatory alertness systems: networks located deep within the brain that play a central role in attention, learning, memory, decision-making and adapting to changing circumstances.
These systems are among the most important, but also the most difficult, brain networks to study in humans. To investigate them, the research team will combine tVNS with advanced research methods, including pupillometry, electroencephalography (EEG) and ultra-high-field 7-Tesla functional MRI.
'If we can demonstrate that tVNS reliably activates these alertness systems, researchers will have a new, non-invasive method for studying some of the brain's most fundamental mechanisms,' says Nieuwenhuis.
Open and transparent science
The project will involve a PhD candidate, a postdoctoral researcher and a research assistant. All studies will be preregistered, and the data and analysis code will be made publicly available, fully in line with Leiden University's commitment to transparent and reproducible science.
By combining rigorous research methodology with advanced neuroimaging, the researchers aim to answer an increasingly important question: can non-invasive vagus nerve stimulation genuinely improve brain function, or are some of the claims running ahead of the scientific evidence?
Thanks to this grant, the research team expects to provide the most comprehensive answer to this question to date within the next few years.
