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Vagal nerve stimulation (VNS) has proven to be effective in the treatment of epilepsy and severe depression. In human subjects, VNS showed effects on mood and memory. Extinction learning is an effective way to reduce fear responses. Besides its positive effects, extinction learning has some limitations. A return of previously extinguished fear responses can show up after a successful extinction procedure, therefore there is a lot of interest and need to enhance extinction effects. In a rat study of Peña et al. (2013), VNS has been proposed to enhance and accelerate extinction memory through the increase of noradrenergic transmission. Although there are few studies in humans available, preliminary findings (Burger et al., 2015) suggest that tVNS also accelerates extinction in healthy humans. This study investigates whether transcutaneous VNS (tVNS) improves extinction learning and could reduce spontaneous recovery of fear in healthy humans. The experimental paradigm consisted of three separate days in which fear was acquired the first day (24 trials), followed by extinction of fear during the second day (40 trials). On the third day, we tested the retention of extinction (12 trials). Geometrical figures were presented for 30 seconds and served as CSs. During acquisition, the CS+ was reinforced 75% of the times with one or two painful electrical shocks. During extinction, the tVNS condition (N = 20) received verum tVNS concurrently with each CS, whereas both control conditions (N = 20, N = 20) received sham stimulation. All three groups received sham stimulation during acquisition and retention. Continuous US-expectancy ratings, skin conductance and startle blink EMG were measured. Results showed successful acquisition and extinction of fear to the CS+, without significant group differences in the rate of acquisition or extinction. On the first trial of the third day, spontaneous recovery of US-expectancy occurred to the same extent in both groups, but subsequently extinguished again only in the tVNS condition. Spontaneous recovery for the skin conductance response on day 3 occurred only in the sham group. No group differences were found for startle blink EMG on day 3. Our findings partly support the hypothesis that transcutaneous VNS can improve the retention of extinction, but failed to replicate previous findings of an accelerated extinction.

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Good executive functioning is related to beneficial outcomes including life success, mental and physical health. Although beneficial, humans are unable to consequently use executive functions to obtain these goals. Therefore it is in our interest to understand which factors promote executive functioning. Earlier research demonstrated that executive functioning can affect the main energy resource of our brain, glucose. Glucose can enhance executive functioning after depletion. Further research found a range of non-invasive methods that could replenish executive functioning after depletion without affecting blood glucose levels. In light of this we propose another mechanism that might positively shape executive functioning, namely increased vagal tone. We studied this via another macro nutrient, fatty acid, and its immediate effect on executive functioning. To our knowledge this is the first study to propose that executive functioning might be enhanced through vagal activation, and it is also the first to investigate the effect of fatty acids on executive functioning via direct infusion in to the stomach. Fatty acids with a chain length equal to 12 or longer have shown to innervate the afferents of the vagus nerve. The consumption or infusion of these fatty acids causes the release of CCK which innervates the vagus nerve thereby increasing the vagal tone. The hypotheses is that the infusion of the fatty acids with a chain length greater than 11 will cause an increase in vagal tone, indexed as HRV, and thereby improve executive functioning compared to control conditions. To evaluate this, a within-subject design with four conditions was set up. In the two control conditions saline or C10 (capric acid) was administered via the esophageal tube. In the two experimental conditions either C12 (lauric acid) or C16 (palmitic acid) was administered. Participants came fasted to the lab where a baseline HRV measure was obtained. After this the esophageal tube was placed and participants watched a video whilst getting used to the tube. Then infusion took place and 10 min later the tube was removed. After infusion subjects completed three executive functioning tasks. First, a dual-processing task comprised of an immediate recall test and a delayed recognition test. The other tests were the trail making test and a forward digit span task. Throughout the whole process mood and satiety questionnaires were completed four times (two pre- and two post-infusion). Once participant finished the tasks and the last questionnaires a post infusion HRV measurement was obtained. Preliminary results of 13 participants did not show a significant effect of condition on executive functioning. Vagal tone increased significantly in the saline and C16 condition. The effects on mood were similar for all nutrients. Valance became more positive, positive affect and the feeling of control increased and negative affect decreased. These changes might be influenced by the placement and removal of the intragastic tube, and also the increased nausea ratings in the C10 condition call for extra caution with the interpretation of the results.

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Background: Dyspnea is a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity. Inaccurate dyspnea perception may interfere with an adequate and timely intervention. An important perceptual component is the individual sensitivity which is measured through the slope of log (ψ)/ log (ϕ) for which the perceived magnitude (ψ) can be plotted against the actual stimulus intensity (φ; e.g. weight of respiratory resistance). Furthermore, the multidimensional model for dyspnea stipulates that dyspnea sensations consist of sensory and affective dimension. Affective states have been shown to increase symptom reports and affect magnitude estimations on the affective dimension. However, little is known about the direct effect of verbal descriptors on slopes as measure of perceptual sensitivity. Study’ aims: The effect of labels was studied on the perceptual sensitivity. Secondly, the test-retest reliability of the estimation scores was assessed over a one-week period. Design: A controlled laboratory study with a between group design. Participants: 39 healthy subjects (mean age: 18.25 years, range 17-22, 10 male) Method: Dyspnea-sensations were induced through five inspiratory resistive loads (range 2.4 - 20 cmH2O/L/s) and one sham load (0 cmH2O/L/s). Loads were presented for one single inspiration after which a magnitu and sham load were presented 10 times, resulting in a total of 60 trials. The entire procedure was repeated one week later. Results: Overall test-retest correlations were high for all load intensities in the sensory condition and load intensities upward from 5 cmH2O/L/s in the symptom condition. Magnitude estimations in both conditions increased with increasing load intensity. The slopes of the log (ψ) / log (φ) ratio did not differ between conditions. However, estimations for the sham load were significantly lower in the symptom condition as compared to the sensory condition which may account for the slightly increased slope in the symptom condition as compared to the sensory condition. Conclusions: Test-retest reliability of the Borg-scores was confirmed for both conditions for all load intensities upward from 5 cmH2O/L/s. Further, an increased slope was observed in the symptom condition compared to sensory condition. This increased slope effect was mainly due to significant lower estimation ratings at baseline level (0 cmH2O/L/s) in the symptom condition compared to the sensory condition Thus, ‘symptom’ labels (e.g. ‘unpleasant’) slightly seem to cause a heightened sensitivity. Suggestions for future studies for investigating the effect of labels on breathlessness sensitivity are provided.

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Anxiety disorders are among the most common psychiatric disorders in our society. Excessive fear can succesfully be reduced using exposure therapy. In the long term, however, fear reduction is not always retained. Anxiety disorders are sometimes associated with inadequate extinction learning. Therefore interventions that can enhance extinction learning can be helpful in the treatment of anxiety disorders. Extinction learning can be enhanced using pharmaceutical interventions, however commonly neglected factors like diet can also exert influence on extinction. The current study is a follow-up study of Miller, Struyf, Baptist, and Van Diest (2015). The aim of this study is to further explore the influence of four different nutrients: saturated fat, alpha-linolenic acid, flavonoids (hesperidin and naringenin) and glucose on a fear based predictive learning task. These nutrients are presented in the form of milkshakes containing cream (saturated fat), walnut oil (alpha linolenic acid), orange juice combined with cream (flavonoids and saturated fat) and maltodextrin (glucose). The previous study of Miller et al. (2015) has observed a more profound and faster extinction after walnut oil intake compared to cream intake. Furthermore a higher positive mood was associated with walnut oil intake. The current study aimed to replicate these findings. Two conditions have been added: an orange juice and a maltodextrin condition. For these conditions a more profound extinction is also expected when compared to the cream condition. Finally a more negative affect is expected in the cream condition. The mechanisms thought to play a role in the influence of nutrition on cognition and mood are inflammation and brain derived neurothropic factor levels. The intake of saturated fat and glucose are associated with inflammation whereas the intake of walnut oil and orange juice have been associated with anti-inflammatory properties. Participants were asked to refrain from eating or drinking anything with calories three hours prior to the experiment. Every participant was randomly assigned to one of four conditions. After informed consent and filling in mood questionnaires and hunger related questions, they received a milkshake along with questions about the drink. To allow for digestion to start the first filler activity, anagrams, was presented 15 minutes after receiving the milkshake. After completion of the anagrams participant watch a TED lecture and filled out the mood and hunger related questions for a second time. Finally the actual task, a computerized fear-based predictive learning task was presented. The Positive and Negative Affect Scales were employed to measure mood. To accurately replicate the previous study by Miller et al. body temperature was measured three times. In the current study we failed to find any condition related effect on extinction learning or on mood. We did observe an effect in line with the hypothesis. Visual inspection of the data shows a faster extinction in the walnut oil group, followed by the orange juice and maltodextrin group. The slowest extinction was observed in the cream group. However these differences were not statistically significant. One possible reason for this could be insufficient power.