Abstract
Invasive and transcutaneous vagus nerve stimulation [(t)-VNS] have been used to treat epilepsy, depression and migraine and has also shown effects on metabolism and body weight. To what extent this treatment shapes neural networks and how such network changes might be related to treatment effects is currently unclear. Using a pre-post mixed study design, we applied either a tVNS or sham stimulation (5 h/week) in 34 overweight male participants in the context of a study designed to assess effects of tVNS on body weight and metabolic and cognitive parameters resting state (rs) fMRI was measured about 12 h after the last stimulation period. Support vector machine (SVM) classification was applied to fractional amplitude low-frequency fluctuations (fALFF) on established rs-networks. All classification results were controlled for random effects and overfitting. Finally, we calculated multiple regressions between the classification results and reported food craving. We found a classification accuracy (CA) of 79 % in a subset of four brainstem regions suggesting that tVNS leads to lasting changes in brain networks. Five of eight salience network regions yielded 76,5 % CA. Our study shows tVNS’ post-stimulation effects on fALFF in the salience rs-network. More detailed investigations of this effect and their relationship with food intake seem reasonable for future studies.
Highlights
The vagus nerve is a key structure connecting the brain with the internal organs
The additional inclusion of the l-RN, the l-NTS and the VTA yielded a classification accuracy (CA) of 76.5 %. Both subsets showed a good detection rate as indicated by the sensitivity (> 0.8) and specificity (> 0.7) values (Table 3.a). While both permutation tests were significant for the smaller subset (Table 4.a), the larger subset only showed a significant result in the traditional control and a trend effect in the FSC
The present study used an objective machine learning classification approach to assess whether five weeks of intermittent tVNS led to a modulation of rs-fMRI activity
Summary
The vagus nerve is a key structure connecting the brain with the internal organs It plays an important role in the control of food intake (de Lartigue, 2016). Germany 5 Centre of Brain, Behavior and Metabolism (CBBM), Universität of Lübeck, Building 66 Ratzeburger Allee 160, 23562 Lübeck, Germany pathways – cortical regions (Henry, 2002). Because of this anatomical arrangement, the vagus nerve has been considered as a target for neuromodulatory therapy of conditions like epilepsy, depression and migraine starting in the ninth decade of the last century (Penry & Dean, 1990; Rutecki, 1990; Sadler et al, 2002). Invasive VNS has been shown to lead to loss of weight (Banni et al, 2012; Bugajski et al, 2007; Burneo et al, 2002; Gil et al, 2011; Pardo et al, 2007; Vijgen et al, 2013), in particular in patients with elevated BMI, raising the possibility to use VNS as an adjunct treatment of obesity (Göbel et al, 2017, Val-Laillet et al, 2015)
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