Week 7-Appetite Flashcards

Question

What is the Anhedonia Theory? (Wise, 1982)

Answer 1

Dopamine mediates pleasure, based on observation of rat behaviour: -Disruption of brain dopamine systems lead to failure to eat or drink -Dopamine receptor antagonists reduce working for food (i.e., reduced ability and motivation to do as dopamine mediates this) -It's argued that the apparent loss of motivation to eat is due to loss of reward or hedonic (pleasure) consequences - that are normally mediated by dopamine

Answer 2

1. Dopamine blockade prevents animals from attending to food, and working to obtain it - but this reflects motor incapacity NOT a motivational deficit -Stimulating dopamine activity can increase responding for food BUT doesn't increase how much is eaten -Critical experiments show that dopamine IS NOT required for the experience of pleasure from eating (Berridge, 1996) If something is pleasurable, shouldn't rats eat more of it?

Answer 3

-Food reward contains distinguishable psychological components that are controlled by separate neurobiological systems -The key distinction is between processes associated with affective vs motivational consequences of consuming food -Core processes of LIKING and WANTING (Anhedonia theory just assumes reward is pleasure)

Answer 4

Liking represents the pleasure or affective aspects of food. Liking may activate, but does not require wanting (Berridge & Robinson, 2003) -Explicit="This food tastes really good!" -"It's nice, but it doesn't grab me" (may like chocolate but may not want to eat it in the morning)

Answer 5

Wanting is the motivational component also known as "incentive salience" (Berridge et al., 2009). Wanting without liking adds the compulsive element to eating -Implicit="I just have to have it, I don't know why." -"Why do I keep eating this?"

Answer 6

Chemical lesions of brain dopamine systems using 6-hydroxydopamine (6-OHDA): -Aphagia (rejection of food) -Adipsia (absence of thirst) -BUT NORMAL taste reactivity -Hedonic evaluation of food ("liking") is therefore independent of dopamine -Chemical lesions are why we can't do it in humans (so we do it on rats) -Rats react to taste normally (reacts hedonically)

Answer 7

Dopamine plays a role in: -Recognising motivationally important stimuli -Energising of goal-directed behaviour -Learning of associations between psychological state/experience, environmental stimuli and behaviour -Effort Dopamine thus serves alerting and activating functions related to WANTING

Answer 8

-Natural opioid (opiate-like) chemicals occur in the brain. -Morphine (opioid agonist) increases food intake -Opioid antagonist drugs reduce food intake: Naloxone reduced hedonic preference for sweet, high-fat foods in humans (Drewnowski et al., 1992) -Evidence for a specific role for opioids in liking (but NOT wanting)

Answer 9

-Learned associations between food cues (e.g., the sight and smell of food) and the rewarding consequences of eating These cues elicit conditioned responses such as: -Increased desire and craving for food -Attentional bias (drawn to food) -Physiological changes (e.g., increased salivation) -Food-seeking behaviours (reminded of a tasty treat means people may go out to get it despite not being hungry/actually needing it)

Answer 10

An intense desire which is directed towards a particular food, drink or taste (Hill, 2007) -Top 10 most "problematic foods"=chocolate, ice cream, french fries, pizza, cookie, chips, cake, popcorn (buttered), cheeseburger, muffin (Schulte et al., 2016) -People typically crave energy dense foods with high fat

Answer 11

-Chocolate cravers vs non-cravers (Half participants habitually craved chocolate, the other half didn’t) -Sight and flavour of chocolate, plus their combination -fMRI found greater activation in medial OFC and ventral striatum in cravers (these are key brain areas involved in reward)

Answer 12

-Exposure to sight and smell of pizza increased desire to eat and salivary response (getting ready to eat) in participants with obesity relative to participants who were healthy weight (Ferriday & Brunstrom, 2011) --> increased motivation to consume food. -People with obesity showed a greater attentional bias to food images, but only when they were satiated (Castellanos et al., 2009). Because when hungry everyone has an attentional bias to food

Answer 13

Rothemund et al (2007): -fMRI study - responses to pictures of high-calorie foods, low-calorie foods, eating-related utensils and neutral images, following abstinence from eating for at least 1.5h -Women with obesity (BMI>30) - greater activation to high-calorie foods vs. neutral images in the caudate/putamen (reward/motivation), anterior insula (taste, interception, emotion), hippocampus (memory) and parietal cortex (spatial attention) -In relation to control group of women who were lean (BMI 19-24)

Answer 14

-Without higher level control/executive control, we would be slaves to our reward system (Our reward system has a constant drive and want to consume food - what would happen if we were slaves to it) -But we do not always respond to the presence of food cues by initiating eating. Some individuals are very successful at controlling their food intake -An appetitive response to a tasty food may be inhibited if the individual has a long term goal for health (for empirical support see Yokum & Slice, 2013 who did an fMRI)

Answer 15

Cognitive: -Goals and values (vegan, vegetarian) -Expectations (taste of food) -Inhibitory control (i.e., self-control) -Memories Brain: -Involvement of ventromedial-prefrontal cortex (vmPFC) and network that includes dorsolateral prefrontal cortex (dIPFC). -Obesity is characterised by lower gray matter volume in brain areas important for executive function (suggests brain areas are not working as well as they could do) -Genetic vulnerability to higher body weight is expressed in brain areas important for cognitive function García-García et al. (2019). International Journal of Obesity, 43, 943–951. Higgs et al. (2017). Journal of Psychopharmacology, 31(11), 1460–1474 Vainik et al. (2018). Proceedings of the National Academy of Sciences 115(37), 9312-9317

Answer 16

Thomas et al (2015): -16 healthy participants were scanned on 2 separate test days, before and after eating a meal to satiation or after not eating for 4 h. -Satiation reduced activity in reward-related brain regions. -Satiation increased activity in the dorsolateral prefrontal cortex (dlPFC), (seen by an fMRI done by Nutr (2015) → “top down” cognitive influence on satiation.

Answer 17

-R.H. had bilateral damage to the medial temporal lobes which resulted in severe amnesia. He was able to eat multiple meals: -Ate three meals in a short space of time. Rejected a fourth meal because his “stomach was a little tight”. → R.H was unable to remember his recent eating and continued to eat as a result. -A large number of studies with neurologically intact participants indicate that memories about recent eating episodes are an important determinant of food intake (Higgs, 2005, Physiology & Behavior, 85, 67-72). -Stretch receptor still intact but couldn’t link that to their eating due to damage in medial temporal lobes