Comprehensive Summary
The study investigated how a non-invasive neurostimulation tool, transcutaneous auricular vagus nerve stimulation (taVNS), affects autonomic function during visually-induced motion sickness. Participants were given taVNS and sham, in separate instances, while motion sickness was visually-induced, simultaneous with electrocardiogram (ECG) acquisition. ECG morphology and variability were quantified using symmetric projection attractor reconstruction (SPAR). It was found that taVNS-induced reductions in peak theta density correlated with SSQ nausea scores when compared to sham, while taVNS-induced reductions in maximal density was linked with motion sickness susceptibility. Additionally, machine learning models trained on ECG-derived attractor features were able to differentiate between taVNS or sham administration with an area under the receiver operating characteristic curve of 0.81. These findings indicate that there is much potential for taVNS therapy response detection, as well as adaptive taVNS, using machine learning models. The main limitations of the study were that only a small amount of attractor measures were utilized, interpretations may be skewed due to a female-dominant participant pool, and that optimal taVNS dosages were not identified.
Outcomes and Implications
Motion sickness is caused by sensory conflict between the visual and vestibular systems; essentially, when your eyes, inner ear, and body are not in agreement with the movements perceived. It causes people to feel nauseous and includes symptoms like vomiting, dizziness, and cold sweats, degrading cognitive function and task performance. With cervical vagus nerve stimulation (CNS) having known therapeutic benefits, non-invasive taVNS was employed with the aim to manage motion sickness. The study highlighted how ECG-derived attractor features can be utilized for machine learning models, which can be useful for taVNS therapy. The next steps would involve identifying the optimal taVNS protocol using SPAR and employing deep learning for attractor image classification, which may be able to detect taVNS therapy responses.