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De voornaamste doelstellingen van deze masterproef waren het vertalen en valideren van de “Smith Mindfulness State Questionnaire” (SMSQ; Smith, 2014), een relaxatievragenlijst met 43 items die 17 “mindfulness states” beoogt te meten. Deze “mindfulness states” beschrijven subjectieve ervaringen die samengaan met relaxatie en kunnen gegroepeerd worden in “premindful relaxation”, “core mindfulness” en “mindful engagement and transcendence”. De vertaling werd uitgevoerd door drie perfect tweetalige psychologen en bestond uit een procedure die gebruik maakte van cross-vertaling. Na de vertaling werd een pilootstudie (n = 15) uitgevoerd om mogelijke fouten en/of onduidelijkheden bij de instructie na te gaan. De uiteindelijke vragenlijst vroeg de participanten om terug te denken aan de meest effectieve en belonende relaxatieactiviteit uit de voorbije twee weken en vervolgens op een 4-likert schaal aan te duiden in welke mate hun ervaring paste bij de vragen. De Nederlandstalige SMSQ werd afgenomen bij 269 eerstejaarsstudenten uit de richting psychologie. Aan de hand van de Shapiro-Wilk test werd aangetoond dat de data scheef verdeeld waren. Vervolgens werden met Mplus vijf exploratieve factoranalyses uitgevoerd gaande van een één tot een vijf factoren oplossing met oblieke rotatie (oblimin). Vanwege de scheve verdeling werd gebruik gemaakt van het WLSMV schattingsalgoritme. Op basis van deze analyses en rekening houdend met de interpreteerbaarheid van de factoren, werd gekozen voor een oplossing met vijf factoren. Deze vijf factoren werden vervolgens gereduceerd tot vier schalen, met name slaap (n = 4), fysieke en mentale relaxatie (n = 13), transcendentie en positieve emotie (n = 16) en acceptatie en flow (n = 5). De vier schalen vertoonden ondanks de verschillen met de voorgestelde factorstructuur van Smith een goede betrouwbaarheid met Cronbach’s alfa coëfficiënten tussen .78 en .92. Met uitzondering van de schaal slaap, vertoonden de gemiddelde scores van de schalen bovendien matige tot hoge correlaties met de gemiddelde score van de “fysical tension” schaal van de Relaxation Inventory, wat een teken is van een goede convergente validiteit. De gevonden verschillen tussen de schalen en de factorstructuur van Smith (2014) kunnen samenhangen met de aard van “mindfulness states”, welke afhankelijk zijn van de relaxatieactiviteit die beoefend wordt. Ondanks de verschillen tussen de schalen uit dit onderzoek en de originele factorenstructuur van Smith waren we in staat om vier valide en betrouwbare schalen af te leiden van de SMSQ. Verder onderzoek dat in staat is om de factorstructuur te vergelijken tussen twee populaties of tussen data die reeds bestaan uit onderzoek met vorige versies van de SMSQ is nodig om de validiteit van de Nederlandstalige SMSQ verder aan te tonen.

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Many studies have already addressed the effects of slow deep breathing (SDB) on pain and blood pressure (BP), but the underlying mechanism is still unclear. No studies however looked at the gradual effect of SDB over time. The aim of this study was to investigate the evolution of pain and systolic blood pressure (BP) over the trial during instructed SDB. Forty-one participants performed three trials of SDB, each trial lasting ten minutes. In each SDB trial, participants received 30 electrocutaneous stimuli, with an individually tailored intensity rated as 'moderate pain' at the start of the study. Participants had to rate their perceived pain caused by each stimulus on a numeric scale and beat-to-beat blood pressure was continuously recorded. A Repeated Measures ANOVA with two within subject factors, number of trial (1, 2, 3) and time within trial (minutes 1-10), was applied to the pain ratings and the systolic blood pressure data. As expected, BP decreased over time during SDB, but this effect became less strong through repeated trials. Unexpectedly, also an increase in pain over time was observed during SDB. The increase in pain can potentially be explained by the decrease in BP, which possibly influenced the pain via the central branch of the baroreflex system. Alternative explanations for the increase in pain over time during SDB may involve (1) a decreasing effect over time of distraction from pain during instructed SDB, or, (2) central sensitization. The present findings suggest that to maximize a potential pain-reducing effect of SDB, SDB should be applied only for a short time (e.g. 1 minute).

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A healthy diet consists of a balance between three primary macronutrients: carbohydrates, protein and fats. These may influence executive control, an important brain function for success and well-being in daily life. However, little is known about the mechanism whereby nutrients affect the brain. Previous research has shown that nutrients activate receptors in the gut via digestive hormones activating afferent fibers of the vagus nerve that signal to brain areas such as the prefrontal cortex (important for executive control). We proposed that fatty acids with chain lengths longer than 12 carbons affect the vagus nerve through release of cholecystokinin, thereby differentially affecting executive control and heart rate variability (HRV), a measure of efferent vagal activation. It was expected that long chain fatty acids C12 (lauric acid) and C16 (palmitic acid) improve performance on executive control tasks and elevate heart rate variability compared to control conditions saline and C10 (capric acid). To investigate this hypothesis, a randomized, within-subject double-blind, placebo-controlled experiment was conducted. Participants completed four sessions and received a different solution each session (saline, C10, C12 and C16). Solutions were administered intragastrically before participants completed executive control tasks, including an immediate word recall task, the Trail Making Test, the Forward Digit Span Task and a delayed word recognition task. Heart rate variability was measured before and after nutrient manipulation. Since previous research shows that fatty acids can have an attenuating effect on induced negative emotion, we controlled for mood effects in this study. Participants filled out several mood and satiety questionnaires including the Positive and Negative Affect Scale (PANAS), Visual Analogue Scale (VAS), and Self-Assessment Manikin (SAM). Preliminary results of 20 participants did not show a significant effect of the administered long chain fatty acids on executive control. However, for the mood and satiety ratings, some significant effects were found. Valence scores tended to be higher post-infusion compared to pre-infusion in all conditions. A similar result was found for feelings of control in all conditions except for C10. Also nausea and fullness scores increased significantly post-infusionw. This study was innovative in two ways. Firstly, this study contributes to existing literature by investigating the effects of isolated nutrients on executive control. Secondly, fatty acids were directly infused in the stomach, thereby bypassing taste and expectation effects. This study contributes to a better understanding of mechanisms involved in gut-brain interactions, such as the effects of nutrients on executive control. Since executive control is correlated with success in several life areas such as social relationships and job performance, it is of crucial importance to better understand which manipulations might influence this cognitive function.

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A healthy diet consists of a balance between three primary macronutrients: carbohydrates, protein and fats. These may influence executive control, an important brain function for success and well-being in daily life. However, little is known about the mechanism whereby nutrients affect the brain. Previous research has shown that nutrients activate receptors in the gut via digestive hormones activating afferent fibers of the vagus nerve that signal to brain areas such as the prefrontal cortex (important for executive control). We proposed that fatty acids with chain lengths longer than 12 carbons affect the vagus nerve through release of cholecystokinin, thereby differentially affecting executive control and heart rate variability (HRV), a measure of efferent vagal activation. It was expected that long chain fatty acids C12 (lauric acid) and C16 (palmitic acid) improve performance on executive control tasks and elevate HRV compared to control conditions saline and C10 (capric acid). To investigate this hypothesis, a randomized, within-subject, double-blind, placebo-controlled experiment was conducted. Participants completed four sessions and received a different solution each session (saline, C10, C12, and C16). Solutions were administered intragastrically before participants completed executive control tasks, including an immediate word recall task, the Trail Making Test, the Forward Digit Span Task, and a delayed word recognition task. HRV was assumed to measure efferent vagal activity and was measured before and after the nutrient manipulations. Since previous research showed that fatty acids have an attenuating effect on induced negative emotion, we controlled for mood effects in this study. Participants filled out several mood and satiety questionnaires, including the Positive and Negative Affect Scale, Visual Analogue Scale, and Self-Assessment Manikin. Preliminary results of 20 participants did not show a significant effect of the administered long chain fatty acids on executive control performance. However, for the mood and satiety ratings, some significant effects were found. Valence scores tended to be higher post-infusion compared to pre-infusion in all conditions. A similar result was found for feelings of control in all conditions except for C10. Also nausea and fullness scores increased significantly post-infusion. This study was innovative in two ways. Firstly, this study contributes to existing literature by investigating the effects of isolated nutrients on executive control. Secondly, fatty acids were directly infused in the stomach, thereby bypassing taste and expectation effects. This study contributes to a better understanding of mechanisms involved in gut-brain interactions, such as the effects of nutrients on executive control. Since executive control is correlated with success in several life areas such as social relationships and job performance, it is of crucial importance to better understand which manipulations might influence this cognitive funtion.