Karoline Van Den Akker
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Learned desires Citation for published version (APA): van den Akker, K. (2017). Learned desires: the acquisition and extinction of appetitive responses to food cues in humans. Maastricht University. https://doi.org/10.26481/dis.20170201kvda Document status and date: Published: 01/01/2017 DOI: 10.26481/dis.20170201kvda Document Version: Publisher's PDF, also known as Version of record Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. 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Letschert, volgens het besluit van het College van Decanen, in het openbaar te verdedigen op woensdag 1 februari 2017 om 14:00 uur door Karolien van den Akker Promotor Prof. dr. A.T.M. Jansen Co-promotor dr. R.C. Havermans Beoordelingscommissie Prof. dr. Tom R.J. Beckers (KU Leuven) Prof. dr. Marcel A. van den Hout (Universiteit Utrecht) Prof. dr. Harald L.G.J. Merckelbach (voorzitter) dr. Tom Smeets Prof. dr. Johan W.S. Vlaeyen Table of contents Chapter 1 General introduction 7 Chapter 2 Impulsivity makes more susceptible to overeating after 21 contextual appetitive conditioning Chapter 3 Appetitive conditioning to specific times of day 41 Chapter 4 Violation of eating expectancies does not reduce 57 conditioned desires for chocolate Chapter 5 Effects of occasional reinforced trials during extinction 75 on the reacquisition of conditioned responses to food cues Chapter 6 How partial reinforcement of food cues affects the 95 extinction and reacquisition of appetitive responses. A new model for dieting success? Chapter 7 Electrodermal responses during appetitive 123 conditioning are sensitive to contingency instruction ambiguity Chapter 8 General discussion 141 References 161 Summary 179 Samenvatting 185 Valorisation addendum 193 Dankwoord 201 Curriculum Vitae 207 1 Chapter 1 General introduction General introduction Background Overweight and obesity prevalence has reached dramatic proportions. It is es- timated that currently, around 2.1 billion individuals worldwide are overweight (BMI > 25), of which 600 million are obese (BMI > 30) (Ezzati, 2016; Ng et al., 2014). Given that obesity is associated with an increased risk for diabetes, car- diovascular disease, certain cancers, and various psychological illnesses (Guh et al., 2009; Luppino et al., 2010; Pulgarón, 2013; Scott et al., 2007), and societies face exploding health care costs due to obesity-associated morbidity (Cawley & Meyerhoefer, 2012; Leung, Pollack, Colditz, & Chang, 2015), halting and reversing the obesity “pandemic” has become a priority in public health. Because our genetic pool is unlikely to have changed significantly over the last decades, many researchers believe that the “obesogenic” environment is the main contributor to weight gain and obesity, for it promotes a sedentary lifestyle and provides an abundance of high-calorie foods (e.g., Goran & Weinsier, 2000; Swin- burn, Egger, & Raza, 1999). Although it may seem obvious that this food-abundant environment is associated with increased food cravings and food intake, not so much is known about the precise causal mechanism involved. Especially the role of Pavlovian learning in human eating behaviour has received very little attention in both the scientific literature and obesity treatment plans, despite the fact that several experts have emphasized its importance in overeating and obesity and its contribution to the difficulty in achieving long-term weight loss (Boggiano, Dorsey, Thomas, & Murdaugh, 2009; Bouton, 2011; Jansen, 2010; Jansen, Nederkoorn, & Havermans, 2011). This dissertation aims to address some of the links between appetitive conditioning, eating behaviour, and (un)successful dieting. In the remainder of the introduction, the role of Pavlovian (classical) condition- ing in food cue reactivity and eating behaviour is outlined, describing the main theory this dissertation builds on. Next, an overview of prior appetitive conditioning studies in the food domain is provided, and important gaps in current knowledge are identified. Finally, an outline of the dissertation is provided. Food cue reactivity and Pavlovian conditioning The obesogenic environment contains an abundance of food-associated cues, such as the sight and smell of tasty food. Exposure to these food cues activates a central appetitive state (Bouton, 2007). Responses that reflect this appetitive state consist of psychological (craving), physiological preparatory (e.g., increased salivation and insulin release), and neurocognitive components (e.g., brain activa- 9 Chapter 1 tion patterns, allocation of attentional resources). The physiologic preparatory responses (cephalic phase responses) enable the organism to better digest, ab- sorb, and metabolize nutrients (Power & Schulkin, 2008), and overall, appetitive responses motivate the organism to obtain and consume food. In line with this, increased levels of food cue reactivity (e.g., cue-elicited desires to eat) have been associated with overeating, unsuccessful dieting, higher BMI, and eating psychopathology (Boswell & Kober, 2016; Ferriday & Brunstrom, 2011; Ferriday & Brunstrom, 2008; Jansen, 1998; Jansen et al., 2003; Staiger, Dawe, & McCarthy, 2000; van den Akker, Stewart, Antoniou, Palmberg, & Jansen, 2014). Although food cue reactivity has a strong genetic component (Carnell, Haworth, Plomin, & Wardle, 2008), Pavlovian conditioning plays an important role as well. Every time palatable food is consumed, it can easily become associated with cues in the environment, and these cues can promote reactivity. In Pavlovian terms, the intake of palatable food is an unconditioned stimulus (US), and its metabolic consequences the unconditioned response (UR). Once a cue (conditioned stimu- lus; CS) has become associated with the intake of palatable food, it can stimulate appetitive responses / cue reactivity (conditioned response: CR), promoting food intake (Bouton, 2011; Jansen, 1998, Pavlov, 1927). In principle, any cue can become associated with palatable food intake; be it the sight or smell of food, a certain time of day, a hormonal state, rituals, cognitions, or a certain emotion (Bongers & Jansen, 2015; Davidson et al., 2005; Jansen, 1998; Vohs, Wang, Gino, & Norton, 2013; Wardle, 1990) – although some (more ‘natural’) food cues likely become associated with food intake more easily than others (Bouton, 2007, p. 66). This learning account of food cue reactivity has originally been proposed to explain binge eating: when a binge eater repeatedly consumes large amounts of palatable food in a specific context, this context may become a CS associated with a large US. As a result, the CS elicits a strong CR (e.g., a strong craving) and promotes a binge (Jansen, 1998; Wardle, 1990). However, this model can also explain more “normal” eating and dieting behaviour (Jansen, Havermans, & Nederkoorn, 2011). For example, consider a person who repeatedly eats crisps in the evening when watching a certain TV show. The context (watching a certain TV show in the evening) may become associated with eating crisps (US), subse- quently eliciting desires for crisps and promoting intake. Learning theory also predicts that conditioned food cue reactivity will diminish after repeated CS–noUS pairings (extinction) (Jansen et al., 2011). When a person has acquired a conditioned craving for crisps in the evening and stops eating crisps, he or she presumably practices extinction. Over time, the conditioned crisp cravings are expected to extinguish. A more successful/durable