Optimization of Transcutaneous Vagus Nerve Stimulation Using Functional MRI.

Area of Science:

• Neuroscience
• Medical Imaging
• Neuromodulation

Background:

• Vagus nerve stimulation (VNS) is an established therapy for various disorders.
• Transcutaneous vagus nerve stimulation (tVNS) offers a non-invasive alternative.
• Optimal tVNS parameters and locations require further investigation.

Purpose of the Study:

• To determine the most effective ear location for transcutaneous vagus nerve stimulation (tVNS) using fMRI.
• To compare the neural activation patterns resulting from tVNS at different auricular sites.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to assess brain activity in 37 healthy subjects.
• Four ear stimulation locations were tested: inner tragus, ear canal, cymba conchae, and earlobe (sham).
• Stimulation involved 6-minute runs with specific pulse parameters (25 Hz, 500 μs).

Main Results:

• tVNS at the ear canal showed the weakest activation of the nucleus of the solitary tract (NTS) and locus coeruleus (LC).
• Inner tragus and cymba conchae stimulation activated the NTS and LC compared to sham.
• Cymba conchae stimulation resulted in significantly stronger NTS and LC activation than sham stimulation.

Conclusions:

• tVNS applied to the cymba conchae effectively activates the vagal pathway.
• The cymba conchae appears to be the optimal location for auricular tVNS therapies.
• This finding supports the use of cymba conchae tVNS for therapeutic applications.