The Psychology of Eating and Drinking PDF

6/1/22 Introduction Appetite: The psychology of eating and drinking 1 1 Introduction Who am I? (contact: dick.stevenson@mq...

6/1/22 Introduction Appetite: The psychology of eating and drinking 1 1 Introduction Who am I? (contact: [email protected]) Why am I teaching this course? Tutorials – Tutorials start next week – Please try to remain in the same tutorial class Please obtain: – The course handbook from iLearn (info about everything) Please ensure that you read the Course Handbook – You need to do so to understand how your project will work and how this is linked to the tutorials – It also contains the course timetable and other vital information which will help you to do well 2 2 1  6/1/22 Why study feeding & drinking? Eating and drinking are essential to survival Consequently, much of our behaviour, physiology and anatomy has been shaped by evolutionary forces related to ingestion Colour vision (from primates and ripe fruit) Liking for junk food (hard wired for sugar and fat) Disposition to gain weight not lose it (saving fat to survive famines) Bipedalism for predator detection and hunting (running) Gut and teeth design, and face structure (chewing) Understanding feeding behaviour (and its physiology) is important for several reasons 3 3 Why study feeding and drinking? In the developing world around 1.2 Billion (1200 million or about 60x the population of Australia) people are malnourished, underweight and hungry, yet in the West, 1.2 Billion people are overweight or obese This is important because malnourishment kills, lowers IQ, cuts earnings and entrenches poverty; Obesity shortens lifespan, induces chronic diseases and is very costly What biological, psychological, social and economic factors contribute to obesity and malnourishment? Why are some people starving whilst others are eating themselves into an early grave? 4 4 2  6/1/22 Why study feeding and drinking? In the west 15% of individuals are alcohol dependent, with 100,000 preventable alcohol related deaths/year in the US alone What biological, psychological, social and economic factors contribute to alcohol dependence? And we might now add processed food as well when we think about dependency – Mice preferring sugar to cocaine – Mice withdrawing from sugar 5 5 Why study feeding and drinking? Eating disorders - especially anorexia which is the most lethal of all psychiatric conditions - affect approximately 1-2% of college-age women in the West Eating disorders seem to be coming more common, and they are also involved in obesity, notably binge eating disorder What biological, psychological, social and economic factors contribute to eating disorders? 6 6 3  6/1/22 Answers? To study these varied conditions - obesity, alcoholism, starvation, malnutrition and eating disorders - we need to know how eating and drinking (ingestion) occur normally – Why do we choose to eat certain things and not others? Lamb chops over human chops, chips over apples…. – How do we perceive food and drink? Why is fat, fatty and chilli pepper, hot? – What starts and stops eating? How do we get hungry and full, and are we in charge of what we eat or are we physiological zombies? – What societal factors influence ingestion? Why don’t we eat‘desert shrimps’(and other insects)? – What economic factors govern eating and drinking? Fast food, dual incomes, cars, TV and obesity… – In fact as you’ll come to see, the whole structure of our society seems engineered to help us eat more and move less 7 7 Course structure Consequently… – We will start (today) by examining the basics of ingestion: Energy metabolism Food types The digestive system Water balance Eating and drinking strategies used by us and other animals 8 8 4  6/1/22 Then… Over the coming weeks we will look at: How we perceive food and drink The nature of thirst, and food-related drugs Food preferences Food taboos (why we don’t eat people and pets) The psychobiology of food intake The food system (farm gate to the plate) Finally, we will turn to obesity, starvation, eating disorders, body image, dieting and related topics 9 9 Things you need to know Format – Lectures and videos/films The lectures are all presented online via Echo360 I will try and arrange a session to watch the videos/films, as these cannot be shown via iLearn/Echo due to copyright constraints Please note that the videos/films DO NOT form part of the exam We will have one special class in the final teaching week for questions, revision etc (zoom link will be available on iLearn) – Tutorials All the tutes are online via zoom, with the class links on iLearn The tutorials are there to support your personal research project through its design and implementation to its analysis and write-up Please read the course handbook for details 10 10 5  6/1/22 Things you need to know Reading – Each week there are several compulsory pieces of reading (lecture notes, Logue chapter[s] & tutorial paper/s) – Logue is the course textbook (‘The psychology of eating and drinking’4th Edition) – There are also other supplementary references listed in the course handbook (for your interest and edification) 11 11 Things you need to know Assessment (details in Course Handbook) – End of semester exam (Multiple choice) - 50% Based upon – Lectures (but NOT the films/videos or the special class during the final week ) – Material from Logue – The exam will (as things stand) be conducted in person at Macquarie University (North Ryde campus) 12 12 6  6/1/22 The lms and videos won't be part of the examinable material but the lectures and your Logue et al. textbook will be examinable. Things you need to know Assessment (details in Course Handbook) Your personal research project (Report) – 50% – This will be a project where you serve as experimenter and participant (i.e., covid-proof) – The basics of how this will work are detailed in the course handbook – Please make sure you read the relevant material in the course handbook, and the associated tutorial papers, before your first tutorial – The first tutorial is in Week 2 Please check the course handbook to see the project timeline, when the tutorials are etc, so you are prepared 13 13 Energy metabolism The basic purpose of food is to provide energy Food provides chemical energy which the body converts into – Mechanical energy (muscles) – Electrical energy (nerves) – Heat (maintaining optimal temperature) – Other forms of chemical energy (fat; proteins) The key food constituents that provide energy are carbohydrates, proteins and fats 14 14 7  It's important to note that the body's metabolic pathway can convert energy from fats, proteins and carbohydrates 6/1/22 (macronutrients). If you're dieting a lot of diets focus on simply removing fats. However, you also have the option of limiting proteins and carbohydrates as well whilst dieting. There isn't only one way to loose weight. We haven't been able to nd a reason as to why Main metabolic pathways the brain is The liver has 100g of glycogen Liver 100g completely reliant Muscles 500g on glucose. One c. Lactic acid cycle - muscles theory is that a. Brain/CNS because if the 20-40% of body mass brain relied on other things such as proteins it could b. All other tissue damage the brain. 1. Three principal methods of generating energy – metabolic pathways (in red) a (Glycolysis), b (Kreb’s cycle, aerobic), c (Lactic acid cycle, anaerobic) Fitness determined by capacity to get oxygen to muscle (VO2 max) 2. Two principal methods of energy storage (in green) 3. Note that all energy sources can be converted to fat 15 15 It doesn't matter if your diet was completely composed of protein or carbs or fat. Any of those macronutrients can be stored by your body as fat. So you can get fat on protein, carbs or on fat. Your body is very e cient at converting these to fat. Measuring the ‘energy’ in food The measure we will use is the Kcal (kilo calorie) – To convert to the SI unit, Kilo Joule (KJ), multiply the Kcal value by 4.184 One Kcal is the energy needed to raise 1L of water by 1 degree centigrade This is measured using a bomb calorimeter The amount of energy contained per gram, differs for fats, carbohydrates and proteins – Proteins & Carbohydrate yield 4 Kcal/g – Fats yield 9 Kcal/g – (Alcohol yields 7 Kcal/g) This is why fats are called energy dense foods 16 16 8  6/1/22 Pregnancy or other demands on the body will raise What are the bodies energy needs? their BMR. Illness e.g. a fever and At rest, the body expends considerable energy - termed the basal metabolic rate (BMR) your body is in attack mode Most of the food (i.e., energy) you consume goes to maintaining your BMR – about 70-80% against the pathogen BMR includes energy for cellular physiology (pumps), breathing and blood flow, muscle tone and protein sometimes this synthesis (e.g., immune system) can triple your Women need about 0.9 Kcal per kg/hour of bodyweight to BMR. maintain BMR and men around 1.0 Kcal per Kg/hour Over 24 hours, a 70 kg man would need around 1680 Kcal Babies have a just to maintain BMR (i.e., 24x70x1.0) high BMR because they BMR varies a lot dependent upon lactation, pregnancy, muscle/fat bulk, physical fitness, illness and age need to generate 17 heat and it lowers as they age. 17 Fat is less metabolically active than muscle, muscle burns more energy. Which is why men need slightly more Kcal to maintain their Basal Metabolic Rate (BMR). Activity On top of BMR we expend additional energy on ‘doing things’ To give you some idea here is the amount of energy you would expend if you did these ‘things’ for one hour (for a 70 kg person) – Shopping 190 Kcal – Walking 300 Kcal – Running 750 Kcal (see https://healthhub.medibankhealth.com.au/calculators/energy-expenditure/) To put this in perspective… – A big mac provides 550 Kcal, a standard sized mars bar 224 Kcal, and an apple 52 Kcal – So… 3hrs of hard shopping burns away a big mac, while 5 mins of running burns away an apple 18 18 9  6/1/22 Calculating energy needs Most tables that report the caloric intake that you need are based upon calculating your BMR and then estimating a light to moderate level of activity – Very light (BMR x 1.3) – Light (men x 1.6, women x 1.5) – Moderate (men x 1.7, women x 1.6) – Heavy (men x 2.1, women x 1.9) Most westerners have activity levels that are typically in the very light to light range 19 19 Heavy would be being physically active for 7-8 hours a day) E.g. a Lumberjack Consequences According to standard tables then, an 85 kg man (Mr Average in Australia [Ms weighs in at 71kg]) would need around 3270 Kcal / day (with light levels of activity) To put this in perspective, Mr Average in Australia eats around 3400 Kcal / day At the other end of the spectrum Nazi concentration camp inmates were fed about 700 Kcal / day It is not surprising then that many Australian adults slowly gain weight and that many camp inmates died of starvation 20 20 10  There are two types of Carbohydrates divided into two groups. Monosaccharides and Discaccharides. (Simple carbohydrates) Monosaccharides Glucose 6/1/22 Fructose; it's not found in many high concentration naturally. Mostly ripe pears. Galactose Discaccharides Are two Monosaccharides joined together. Sucrose; is a People in the US combination of consume a glucose joined to a Carbohydrates approximately 30 tsp of sugar per day. fructose. Types 1lb = 0.45kg Lactose is a - Simple combination of - Monosaccharides glucose and galactose - Glucose – corn, grapes E (which is not - Fructose – honey, many fruits particularly - Galactose – avocados sweet) - Discaccharides Maltose is - Sucrose – ‘sugar’ composed of - Lactose - milk sugar two glucose "molecules" - Maltose - beer together. - Complex - Polysaccharides (starch, High fructose corn syrup (HFCS), used in cellulose) Inulin aswell soft drinks mainly in the USA. Quantities Function consumed have increased enormously. In 1955 an average soft-drink serve was – Primarily to provide energy 207ml, it is now around 600ml. 21 21 Cellulose forms bre and inulin [a complex of sugar present in the roots of various plants and used medically to test kidney function. It is a polysaccharide based on fructose] is something that we can't break down either which contributes to bre in our diet. LDL Low HDL High Density Density Lipoproteins Fats Lipoproteins Or more properly Triglycerides A glycerol with three fatty acid tails Types (These are the different types of tail the glycerol can have) - Saturated (animal, coconut, palm) – some may increase LDL (bad cholesterol) - Monounsaturated (olive oil, canola) – some may increase HDL (good cholesterol) - Polyunsaturated - Omega 6 (vegetable) - Omega 3 (deep sea fish) – may increase HDL and lower LDL - Trans-saturated They are very resistant to going rancid (they don't oxidise) - Artificially produced from Mono or Polyunsaturated fats - Have significant commercial benefit/use (storage/non-animal) - Have negative health consequences (CHD, Diabetes, Obesity) - Health controversies – fats and heart disease Function of fats – Structural (nerves), Hormone synthesis, Fat soluble vitamins, Insulation & Padding, Energy storage (fats help the myelin sheath) 22 22 You don't need to eat fat to get fat. Also, the Scienti c community is really split on whether saturated fats cause heart disease. 11  6/1/22 Essential implies that we can only get them from our diet Protein Types – All proteins built from Amino acids – Some are essential and some can be synthesised by the body (meat provides all essentials, but combinations of vegetables and legumes can do so as well) Function – Tissue maintenance & growth, Hormone, Enzyme and Protein synthesis, Fluid balance, Energy The body also needs certain Minerals and Vitamins and these are termed micronutrients… 23 23 Micronutrients - Vitamins Deficiencies relatively rare in Western nations, yet almost a third of the US population consume them (supplement sales are a 30 Billion US dollar industry) Fat soluble vitamins (A, D, E & K) – A (eyes, skin, bones, reproduction & immunity) - Night blindness, xerophthalmia – D (bone formation, hormonal control) - Rickets – E (cell membrane integrity) - Hemolytic anemia – K (blood clotting) - Infant haemorrhage (hence neonatal K shots) Vulnerabilities after obesity surgery & lipase inhibitors Water soluble vitamins (C, B1, 2, Niacin, 6, Folate,12, Pantothenic acid, Biotin) – C (collagen formation, iron absorption) - Scurvy – B1 (energy metabolism) - Beri beri (thiamine & Korsakoff’s syndrome) – B2 (energy metabolism) - Glossitis, Seborrheic dermatitis – Niacin (energy metabolism) - Pellagra – B6 (amino acid synthesis) - Anemia – Folate (DNA synthesis) - Anemia, (Neural tube defects in pregnancy) – B12 (DNA synthesis) - Renal failure – Pantothenic acid (energy metabolism) - Burning feet syndrome – Biotin (protein metabolism) - Hair loss 24 24 If you have obesity surgery one of the consequences of that is that your body becomes much less e cient at absorbing fat. Which is why in the early days, patients would develop micro nutritional de ciencies such as rickets etc. 12  6/1/22 Micronutrients - Minerals Most Westerner’s have too much sodium (as Salt [consume 10+g/day, RDA 3-6g/day]) and too little calcium Macrominerals (100mg/day+) – Calcium (osteoporosis affects 25M in USA - bones, clotting, cellular function) – Phosphorus (1% of Body Weight - metabolism) – Sodium (water balance, nerves) – Potassium (water balance, nerves) – Magnesium, Chloride & Sulphur Microminerals (100mg/day-) – Iron (5g in total - hemoglobin) – Iodine (thyroid function) – Fluoride, Selenium & Zinc (and several others…) 25 25 If you're iron de cient you may nd yourself eating ice which is a condition called Pagophagia.🧊 🧊 A desire to chew and crunch on ice. Human digestive system The basic function of the digestive system is to efficiently extract nutrients from food We can characterise the digestive system as having two major parts – Main organs (stomach, intestines) – Accessory organs (liver, pancreas, gallbladder) Food is broken down mechanically, chemically (acid) and by enzymes How does it work? 26 26 13  6/1/22 Human digestive system – gross anatomy Mouth – saliva, amylase and mechanical action Stomach Small intestine Duodenum, jejunum, ileum Accessory organs Large intestine Colon, rectum Water re/absorption & compaction The colon contains our gut microbiome. 27 27 Stomach Food is received in the upper part of the stomach (fundus) where it is mechanically ground into particles 1-2mm in diameter It is then mixed with stomach acid and enzymes to form a semi-liquid fluid called chyme, collecting in the lower part of the stomach (antrum) After the stomach discharges its content into the gut, it starts to make rhythmic contractions that you may associate with hunger 28 28 14  6/1/22 We don't know if there's a relationship between how small or large someone's small intestine is and their propensity to gain weight. Small intestine (SI) It is about 2.5-3 cm in diameter and 6-7 M long (ranges from 4-10 M) and 90% of chemical absorption from food into the body happens here Food in the SI triggers CCK release and the accessory organs release bile (500ml/day) and pancreatic juices Bile breaks down fat Pancreatic juice breaks down protein and carbohydrates (gut secretions assist too) The products of digestion move through the SI wall (up to 60M2 surface area) into the HPV (hepatic portal vein) and travel to the liver and thence to the body’s cells 29 29 Large intestine It is about 1-2m long It consists of four parts – Cecum – Receives digested matter from small intestine (appendix) – Colon – Removes remaining water and bacterial action results in the formation of B & K vitamins which are absorbed – Rectum – Temporary storage – Anal canal – As one would imagine 30 30 If you take a gram of material form the colon (it has the highest microbial density of any habitat on earth). They are extraordinarily rich viral and microorganism habitats. They a ect our chances of becoming obese and that in turn a ects our gut biome, brain and mental health. 15  6/1/22 Water balance Apart from oxygen, water is our next most important need (followed by food) You can last upwards of 28 days+ without food, but only a few days with no water (less with physical exertion and a hot climate) Function – Medium in which all chemical reactions occur Cellular & Interstitial water - 28L (for 70Kg person) Blood - 5L (for 70Kg person) Gut - 10L (for 70Kg person) – Its presence is crucial for energy release – Temperature regulation etc 31 31 Interstitial just means the spaces around cells. Water balance The body looses around 2.2 litres per day – Lungs 400ml – Sweat 600ml – Faeces 200ml – Urine 1000ml (via Kidneys filtering blood) To maintain water balance we therefore need to drink about 1 litre (thirst), with the remainder coming equally from food and the byproducts of energy release (metabolic water) 32 32 16  6/1/22 Conclusion I have covered this material with one goal in mind, so that you have all the basic concepts when we start to look in more detail at various aspects of ingestion, drinking, obesity etc We will now turn to a further introductory issue - how animals (and humans) go about the business of obtaining food and drink 33 33 Feeding strategies in animals Appetite: The psychology of eating and drinking The larger its claws are, the less poisonous it is. (The Scorpion) 34 34 17  6/1/22 Introduction The animal kingdom has managed to exploit just about every possible source of food Take the clam for example, whose muscle (meat) is well protected within its thick shell – Certain mollusks drill through its shell to get the meat – Starfish clamp to the shell and slowly prize it open – Herring gulls drop the clam on to rocks to shatter it – Otters find a rock then break the shell As you can see from this example, no food source, even one as impregnable as the clam, is safe! 35 35 Adaptive radiation The purpose of this lecture is to illustrate this diversity - that is the adaptive radiation of feeding strategies driven by the need to secure food We will do this by examining the principle types of feeding strategy that animals adopt This allows us to see where in this big picture human eating behaviour fits in and the sort of questions that we might ask about feeding behaviour in general 36 36 18  6/1/22 The need for food Obtaining energy to live and hence reproduce is a primary goal for all animals and they spend much of their time focused on feeding From the perspective of our century and our society, it is very difficult to believe the importance of food for survival Yet today, during the hour of this lecture, 350 children will die directly as a result of lack of food Industrialised countries have built an effective food system, but it is more fragile than we might care to imagine and you don’t have to go back that far in time to get to our hungry past... 37 37 What constrains feeding strategies? The animals size (Predatory mite vs Tiger) Genes (behavioural/physiological flexibility) Where it lives – In the sea & fresh water, majority of plant biomass is as algae – On land, greater variety of plant forms – In the air, primarily other animals – Water & Air offer 3-D environments, Land just 2-D 38 38 19  6/1/22 Classifying feeding strategies in animals Herbivores (e.g., Rabbit) – Eat vegetation, primary energy producers Carnivores (e.g., Lion) – Eat herbivores & carnivores, living & dead Parasites (e.g., Tape worm) – Obtain energy from a host Omnivores (e.g., Rat, roaches and us) – Eat vegetation & animals We will now look at each of these in turn 39 39 Feeding in herbivores General characteristics – Spend considerable time eating – Process large volumes of food – Food has low protein content – Retained for long periods in the gut – Long guts to maximise digestion – Have to deal with cellulose – Have to avoid being eaten Specific approaches 40 40 20  6/1/22 Grazing Grazing is one approach to feeding used by herbivores Grasses offer one source of food that is suitable for grazing Grasses are an ‘ideal’ food source – Easily accessible & widespread – Palatable – Tolerant (50% annual produce can be eaten) Most grass grazing animals are mammals Special adaptations to grazing grass include: – Teeth (cutters and grinders) – Continuous eating & coprophagy – Symbiotic cellulose digesting organisms (enzymes) – Escape strategies (numbers, camouflage, speed) 41 41 Herbivore guts for grazing 42 42 Note how long the sheep's intestines are, but also how much more complex it is in comparison to our own digestive system. 21  6/1/22 Flowers, fruits and seeds Animals specialising on these food types include pollen feeding insects, birds, bats and monkeys Many species of monkey specialise in eating fruit – Not only did this lead to the ‘re-evolving’ of colour vision it also requires considerable behavioural flexibility to exploit this food source Chimps may bite fruit that is not yet ripe to promote ripening Considerable mnemonic skills are needed to remember seasonal location of fruit and its nutritional value This information amounts to a form of ‘food culture’ which is then passed on to subsequent generations We're talking about 100,000's location and food culture which is passed on from generations so that chimps can exploit this food source. 43 43 Hummingbirds The hummingbirds are another example of this group – Some weigh 2g and so have large surface area to mass with enormous heat loss and thus need for energy – They have a heart rate of 1000/min and breath at the rate of 250/min – Many eat their own bodyweight in nectar each day and are only hours away from starvation – At night they enter a state termed ‘torpor’, where they slow their metabolism so as not to starve 44 44 22  6/1/22 Other herbivores Plant chewers and suckers – e.g., Elephants, koalas, sloths & aphids Plant burrowers – Primarily insects Deposit and suspension feeders – Marine organisms feeding on dead plant material Faeces/Rotting vegetation – 2000 species of dung beetle alone in Africa and these deserve special mention… 45 45 Dung beetles Dung beetles feed on the liquid component of faeces - herbivores being the favourite Three major types – rollers, tunnellers and burrowers – Commonest are the Rollers - balls of faeces are rolled and buried underground both as a food supply and to feed their larvae – The beetles are very strong, and can roll dung well in excess of their body weight (10x +) The beetles will also attempt to steal balls and fight over them Without these beetles fly levels would be astronomical – Dung beetles save an estimated 300 million US$/year in faeces disposal for the US livestock industry 46 46 23  6/1/22 Herbivores - conclusion A considerable focus for us in this course will be intake control and food choice Concepts such as hunger and satiety may have little meaning for animals whose ‘meals’ are continuous In addition, many feed on few plant species, yet do not apparently tire of this repetitive diet In many respects the issues of most interest to us about human diet appear irrelevant for herbivores 47 47 Feeding in carnivores General characteristics – Most spend relatively little time eating but more time attempting to obtain prey – with some very notable exceptions (filter feeders) – Preference for different prey therefore depend upon weighing the cost of the food against its benefit (note parallel to human preference for fatty and sweet foods) – Their food is higher in protein and lower in volume than herbivores (H’s), so shorter guts – Carnivores will often eat to capacity when food is available (a Wild cat can eat 1/3rd of its own body weight in 1 sitting) – Whilst H’s show adaptations to avoid being eaten, C’s show adaptations which favour catching food H's = herbivores C's = carnivores 48 48 Cost bene t trade o concerning hunting them and the amount of reward you get for catching them and we see this same parallel in humans. Most humans prefer sweet and fatty foods because they give us more bang for our buck (more high energy) and our brain is hard-wired to seek out and enjoy these foods. 24  6/1/22 Carnivore guts 49 49 Types of predator Browsing predators – Typically mollusc/sea slugs grazing colonial marine animals – Certain filter feeders E.g. Whales Hunters – Actively seek prey Stalkers (lions, leopard seals) Stealth feeders (mosquitoes, vampire bats) Carrion eaters – Dead animals or scraps Some examples… 50 50 25  6/1/22 Filter feeders These are water living organisms such as baleen whales, certain sharks and fish The baleen whales are the most interesting example of this group The blue whale (right) is the most spectacular of them all 51 51 The blue whale – An adult blue whale is the largest creature that has ever lived – It can weigh 150,000kg and be 30m in length, the same sort of size as a Boeing 737 – Yet these whales eat shrimps/krill, the largest of which is 7.5cm in length – This is accomplished by having 300 baleen plates which hang down from the mouth – Water (rich in krill) is taken into the mouth and forced out through the baleen plates leaving the krill behind – The whales stomach, when full, can hold up to 10,000kg of food 52 52 26  6/1/22 Stalking - Leopard seals Leopard seals are natives of Antarctica and hunt mainly penguins and seals Adults are about 3m and weigh around 370kg They cruise beyond the ice awaiting penguins diving in They then swim rapidly and grab the penguin’s feet beating it on the water till it is flayed alive They will also attack and kill humans 53 53 They mostly prey on cattle e.g the sleeping cow and bites into the mammal and their saliva has a potent anesthetic that also prevents clotting. Stealth - Vampire bat They hunt at night and approach their sleeping mammalian prey on the ground They detect blood vessels with heat sensors They bite and ingest blood whilst their saliva prevents clotting The bat may not be able to fly after food and has a specially adapted urinary system to off- load excess fluid The bats share food (regurgitated blood) to other (non-related or related) members of their colony who have not been able to feed 54 54 27  6/1/22 Carrion - The vulture Vultures can detect prey at many miles both by sight and smell They feed to the point where they become so full they have to rest before flying again Note the featherless head on this Kettle vulture (right) adapted for sticking into blood and guts The use of diclofenac in farm animals has led to a mass loss of vultures in Asia, leaving animal carcasses rotting where they lie It has also threatened the viability of human‘sky burial’in Tibet 55 55 Carnivores - conclusions Carnivores (with some notable exceptions) eat few meals, but when they do, they eat to repletion, diet being somewhat limited repletion; eating to excess Hunger and satiety do appear relevant concepts here, unlike with herbivores Yet the ‘meal’ concept is very different from us as large time intervals (days) may separate feeds Still carnivores share more common features with our eating behaviour than herbivores do 56 56 28  6/1/22 Feeding in parasites Definitions: When is a parasite a parasite? – The Maasai; Are they parasitic on cattle as they keep the animals alive but feed on their blood & milk (15 animals support 1 adult)? A parasite “needs its host & gains the most” Parasites are highly evolved to fill this niche – Loss of movement in adult forms – Multiple developmental stages (to assist transmission) – Redirection of resources to breeding – We will now look at the tapeworm as an example 57 57 Tapeworm Tapeworms have neither gut nor stomach, they just absorb predigested food from the host (us!) Tapeworms can reach up to 25M in length and attach themselves using their head or scolex (right) The mature tapeworm can produce 200K eggs/day And their lifecycle… 58 58 29  6/1/22 59 59 And finally, omnivores An omniverous feeding strategy is probably the most flexible and successful approach adopted by animals Three of the most ubiquitous animal species on earth are omniverous - cockroaches, rats and humans What are the advantages and disadvantages of this feeding strategy and what evolutionary‘baggage’ has it bequeathed us? 60 60 30  6/1/22 Advantages Animals that can eat many different foods can survive in all habitats where food is available As they can be flexible about what they can eat, they can… – Survive when a particular food source becomes scarce – Benefit when a particular food source becomes abundant – Rapidly adapt to changing environmental circumstances (e.g., climate change, urbanisation, farming etc) 61 61 Disadvantages (Costs) If an animal’s dietary variety is constrained, it does not face the problem of deciding what is safe to eat This leads us to what is termed the‘omnivores paradox’ - we can eat many things, but will eating those things provide energy or will they make us sick or kill us? And this is no joke… – Plants and animals can be extremely toxic and large numbers of people are STILL poisoned every year. – Just SOME examples Lathyrsm– Grass pea (10,000+) Konzo (Right) – Cassava (10,000+) Toxic hypoglycemia – Lychees (1000+) Marine neurotoxins – Shellfish, fish (500,000+) – (e.g. Domoic acid – Amnestic shellfish poisoning) 62 62 Lathysm; The Grass pea is such a hardy plant that it often survives res in Africa and a undisclosed population of African's are forced to eat it because there's nothing else. each year over 10,000 people get poisoned from digesting it and it also causes paralysis in the lower limbs. Konzo; can also come from eating the Cassava plant which didn't remove the cyanide in the washing processes. It damages the tissues in their spine and paralyses them. 31 Toxic hypoglycemia; plummets blood sugar levels and kills about 1000 people per year.  6/1/22 Consequences One way to tackle the omnivores paradox is to develop a brain and sensory systems that can… – Detect and avoid foods that are likely to make one sick or die – Learn the safety, nutritional value, and seasonal location of its many different foods – Support behavioural flexibility - hunting, gathering and utilising every feeding opportunity – including learning from others So like the omnivorous rat we… – Tend to avoid bitter tasting foods (poison!) – Tend to avoid foods that look, feel or smell rotten (with humans having evolved a special emotion for this - disgust) – Demonstrate caution to novel foods (neophobia) – Prefer sweet and/or fatty foods that signal ‘energy’ – Show extensive learning capacity relating to the foods we eat And like all animals we… – Tend to maximise energy intake and minimise energy expenditure 63 63 Conclusions In this lecture we have surveyed the many different strategies employed by animals to obtain energy - food These strategies define to a large extent the sort of questions that we might ask about eating behaviour and physiology In omnivores, key questions pertain to – The sensory apparatus (the CNS) that informs what we might eat – How we choose one food over another when so many are available – The control of ingestion - what starts and stops eating Consequently, these will form the topics for the next three sets of lectures 64 64 32  Sensory aspects of eating and drinking Reading, Logue Ch.4 Appetite: The psychology of eating and drinking 1 1 Aim This and the next lecture aim to familiarise you with the basic way in which we perceive food and drink We will start with an overview, then examine each sensory system in more depth Finally, we will return to consider the ‘big picture’ - that is how the brain integrates information from these different sensory systems into what we consciously perceive as ‘flavour’ and the consequences this has for perception 2 2  What systems? So what sensory systems are involved when we eat and drink? – Smell – many qualities (but it is the ‘hidden sense’ - case of JM [TLE & parosmia] illustrates its importance via dysfunction – vomiting & weight loss) – Taste – few qualities, but motivationally significant – Skin senses (touch) Common chemical sense – very few qualities (whole body, especially mucosa) Somatosensation/Proprioception – few qualities (static & dynamic) But be aware now that what we perceive is an integrated sensation - flavour 3 3 The ability to detect sweetness is usually the body's way of detecting a great source of carbohydrates. Some non energy chemicals can also stimulate the sweetness centre e.g. Saccharin. Cats don't have sweetness receptors because carb food sources don't relay play any role in their diet. The sense of taste It's not possible to have an allergy to The sense of taste (that results in sensations MSG we call ‘tastes’) is located primarily on the surface of the tongue We appear able to perceive several qualitatively different sensations (note hedonics-function) Sweet (e.g. sucrose, saccharine) – Energy - Pleasant Sour (e.g. acids) – Ripeness/Vitamin C, fermentation (bacteria) – Un/Pleasant Bitter (e.g. plant alkaloids) – Toxicity (LD50 correlation) - Unpleasant Salty (e.g. mineral salts) – Depletion & Preference (Miners) – Un/Pleasant Umami (e.g. MSG) – Allergy quackery (in toms, cheese, breast milk) - PleasantLD50 is the amount of the chemical needed to kill 50% of a Fat (e.g. fatty acids) – Energy – BUT may have no conscious correlate sample of rats or mice. It To determine the role of taste (independent correlates strongly with how of smell) pinch your nose whilst eating bitter something tastes. 4 4 Bitter; we only have 16 bitterness receptor but only 1 sweetness receptor.  Glutamates tend to occur the most commonly in meat based foods. The human tongue – Receptors are located in structures called taste buds – Taste buds are grouped into structures called papillae Vallate papillae (fried eggs) - 9 in adults, 250 buds/papillae (function: swallow reflex – last chance to check?) Foliate papillae (ridges) - 10 in adults, 120 buds/papillae Fungiform papillae (dots) - 30/cm2 [tip] - 8/cm2 [mid], 3 buds/pap (function: most sensitive – immediate detection of tastants?) 5 No one really knows why they (the papillae) are organised in this way 5 The front of the tongue is most receptive to all of the di erent tastes The taste bud Each bud (top right) contains cells with microvilli These cells last 2 days The bud is filled with mucus (effect of tongue scrubbing) Each bud may have more than one type of receptor located on the microvilli Taste myths (bottom right) – this diagram reproduced in many text books is wrong 6 6  Receptors There are two basic types of receptor present upon the taste bud’s microvilli – Ion gated channels Salt detectors (Na+ [sodium ions]) Acid detectors (H+ [hydrogen ions or protons]) – Protein gated channels Sweet, bitter, umami, fat It appears that each of these may occur in several forms – For bitter – may be 14 different receptors perhaps driven by selection pressure to avoid poison? – For sweet – just one receptor 7 7 For bitter there's up to 16 di erent receptors, which is bene cial because they allow you to detect poisons. And to where in the brain? After the cell depolarises an action potential passes along onto the chorda tympani nerve The first major processing point is the Nucleus of the solitary tract in the brain stem Information is then routed along two discrete pathways – To the brain stem (ingestive/protective reflexes) – To the insula and orbitofrontal cortices (perception of taste quality, intensity & hedonics) The insula is primary taste cortex, and the orbitofrontal cortex, can be thought of as secondary taste cortex Patients with discrete insula lesions are able to tell a taste is present, but have some trouble with its quality The insula also supports taste-related functions – notably the emotion of disgust 8 8  Taste and disgust Animals including humans respond with disgust to bitter tastes (see right) In humans disgust seems to occur to a much broader range of stimuli than just bitter tastes (in contrast to animals) Disease cues (body products, body envelope violations, death, spoiled food, signs of ill-health etc) Incest Perhaps even to some moral violations Disgust responding involves A characteristic facial expression (right) A particular qualia - revulsion Nausea An intense desire to withdraw If the elicitor is touched - contamination A preparatory immune response Disgust responding/perception is impaired in people with damage to their insular cortex (e.g., in Huntington’s chorea) 9 9 From a neural signal to a‘taste’ percept Crucially, for taste, we understand the‘stimulus problem’ – That is what particular physical stimulus is associated with what particular psychological state If you drip sucrose on to the tongue you will perceive a sweet taste, quinine, a bitter taste, salt….. (etc) – So we can readily address the stimulus problem for taste in a way that we can not for smell (as we will soon see) The brain appears to use two approaches to form a representation of what is stimulating the taste receptors – Labeled lines (stimulus A – receptor for A activates only A sensitive neurons – thus the presence of ‘A’ is determined) – Patterns (stimulus A – generates a unique pattern of activity across many neurons – presence of ‘A’ is determined by recognising ‘A’s’ unique neural pattern) 10 10  You have to get an electrode into the tympani which is much easier with Guinea Pigs as opposed to rats. Evidence - labeled line Labeled line – Certain fibres in the chorda tympani are selectively responsive to different tastes (i.e. fibre X is only active when salt is tasted) – On this basis we might assume that when fibre X is active, this results in a ‘salty taste’ qualia – Such selective fibres have been observed for sweet, salty, sour and bitter Firing rate (L) Salt selective (R) Sweet selective 11 11 Patterns A pattern based explanation assumes that the brain recognises a pattern of activity across many nerve fibres and that different patterns produce different taste qualities The following slide shows data from many different nerve fibres in the chorda tympani (taste nerve) of a rat… 12 12  Patterns - example Salt (NaCl) Based on these patterns of activity which tastes do you think rats have little i difficulty in telling apart (NHCL - ammonium chloride, KCL - potassium chloride, i NACL - sodium chloride [Salt])? Patterns for similar tastes can be learnt presumably based upon these activity patterns Potential to Generally similar discriminate pattern of NHCl and KCl 13 NHCl from KCl 13 So how do we ‘taste’? Basic qualities may be defined by activity within specific nerve fibres (labeled line) – For example, ‘salty’ But whether it is one sort of saltiness or another may depend upon the pattern of activity – For example, ‘metallic salty’ vs ‘mineral salty’ 14 14  Individual differences Back in the 1940’s it was first noted that some people could taste a very bitter substance called PTC (phenylthiocarbamide) and others could not This difference was genetically determined Recent research has focused on a bitter tasting chemical PROP (propylthiouracil), which is not carcinogenic (as is PTC) There are large and significant individual differences in sensitivity to PROP 15 15 Different taste worlds Recent research suggests three groups of people – Non-tasters (30%), tasters (40%) and supertasters (20%) Supertasters find PROP disgustingly bitter Supertasters appears to have more taste buds than, tasters and non-tasters. This has the following effects Greater sensitivity to sweet & bitter tastes Dislike for bitter tasting vegetables (especially sprouts and other members of the Brassicae family including cabbage, broccoli and cauliflower) Greater sensitivity to irritants such as chilli and carbonic acid (responsible for ‘fizz’ in carbonated drinks) Supertasters are often leaner as well, as they may be more sensitive to fats in food (and so need less fat to get equal ‘pleasure’) If you don't like vegetables of the cruciferous family then it's highly 16 likely that you're a super taster. 16  Taste - conclusion Taste, as you now know, is a relatively simple sensory system, with few qualities Stimulation of the taste system also stimulates the production of saliva which assists digestion and makes food more palatable Our ability to taste declines with age, but not until we are into our late 60’s – Reductions in taste sensitivity are associated with lower body weight in the elderly and with reduced appetite 17 17 The common chemical sense The primary function of the common chemical sense is to allow for the speedy identification and removal of harmful chemical irritants from the skin We will now examine how it works and then ponder the bizarre question as to why humans (unlike most animals) actively seek to add irritants to their diet Why do humans actively add irritants 18 to their diet unlike other mammals? 18  Why is it ‘common’ It is called the common chemical sense (CCS) as it is located over the whole area of the body but receptors are more densely grouped on the mucosa - mouth, eyes, genitals etc In the mouth, many CCS receptors are located around the base of taste buds, so if you have more taste buds, you have more of these receptors too When these receptors are stimulated in sufficient number the body has a reflex response – Tears, salivation, running nose, sweating 19 19 The TRPV1 receptor helps the body detect heat. capsaicin falsely binds to this receptor to tell you that there's something hot in your mouth. Menthol selectively binds to the TRPM receptor (detects cold) and if you have menthol with a cold uid that uid will appear much colder. What do we perceive? The receptors responsible for the CCS are called ‘free nerve endings’ and appear to – Detect temperature (hot/cold) - confusion studies with capsaicin and menthol – In snakes the same receptor that detects warmth (and chilli) is used to detect [visualise like a thermal camera] prey at night – Damage from excessive temperature – Chemical stimulation Many researchers believe that we can only experience the following sensory dimensions – Intensity (weak to strong) – Hot/Cold (quality; could be more - Anosmic studies) – Hedonics (pleasure to pain) If you combine a hot liquid with chilli pepper versus a cold 20 liquid with chilli pepper the hot liquid is perceived as 20 much hotter.  What do we like and why? Many foods, drinks or additives are CCS irritants, all of which have different temporal profiles – Pepper (piperine) – short acting, sharp – Ginger (zingerone) – short acting, sharp – Chilli (capsaicin) – longer lasting, burning – Fizzy drinks (carbonic acid) – Alcohol (ethanol) – Mustard (allyl-isothiocyanate) – and horseradish, onion, menthol, vinegar, salt etc 21 There's 33 million tonnes of chilli pepper produced annually! Is that world-wide or in Australia only? 21 Spice it up? People over the last 1000 years have gone to great lengths to secure irritants – Pepper shortage & price were significant financial motivators for the discovery of the America’s by Europeans (notably Columbus) – They did not find black pepper, but the chilli instead and its use rapidly spread to Europe and then to India and Asia So why do people like the burn of chilli for example? 22 22 If you add chilli pepper it increases salivation in the mouth Liking the burn Why? – Bland diets, Rice (Asia), Corn (Mexico) – salivation – Medicine effect - Vitamin C – Release of endogenous opioids – Naloxone study How? People still liked it even though they added the Naloxone – In Mexico exposure starts around 7 years – Chilli sauce is always available, but children are never forced into using it – Concentration is gradually increased – It appears that people learn to love it (i.e. they come to know that it does not harm them and this then allows them to enjoy the ‘burn’) People learn that consuming the chilli pepper isn't 23 dangerous) 23 Conclusion We have now completed our examination of taste and the common chemical sense In the next lecture we will turn our attention briefly to the other skin senses and then to our sense of smell Then we will look at how the brain integrates this information to produce the sensation of ‘flavour’ 24 24  Sensory aspects of eating and drinking II Reading, Logue Ch.4 Appetite: The psychology of eating and drinking 25 25 The brain correctly attributes the location of the smell and when it's in the mouth its of a avour which is quite di erent. Taste also seems to capture attention and olfactory location. Smell Our smell receptors are located behind the bridge of the nose and can be accessed by two separate pathways – Sniffing (orthonasal) – Via the back of the throat (retronasal) Each of these pathways is associated with its own perceived location Sniffing makes us feel that an odour is located in the environment, while when the odour is in our mouth, it is perceived as part of that food – how does this happen? – This type of question is called a‘binding problem’ and is a major issue for cognitive neuroscience – Odour location binding may be caused by nasal airflow direction and by inhibition of olfactory attention by the presence of a taste in the mouth Much of the sensation that we term ‘taste’ or ‘flavour’ when we eat and drink is in fact smell The sensations that we can experience in this modality appear to exceed the other flavour senses by many orders of magnitude 26 26  Find the Cribiform plate; the brain being jelly like slides across this in car accidents and the person can loose their sense of smell in this way. Gross anatomy I Features to notice – Frontal (anterior) nasal passages Olfactory epithelium – Receptors – olfactory epithelium – Cribiform plate and olfactory bulb (and proneness to injury) – Turbinate bones (richly vascularised to warm air and create a turbulent air flow) – Rear (posterior) nasal passages – Soft palat (velopharyngeal flap – and ability to open and close) Also referred to as the velopharyngeal ap 27 27 Freud thought that the turbinate bones were the cause of excessive masturbation.One of his colleagues William Fliess an ENT surgeon excited their turbinate bones unfortunately it's not a good idea because it leads you vulnerable to infection and loss of smell. Gross anatomy II During certain phases of eating and drinking volatiles ascend via the nasopharynx and bind to the same receptors that are stimulated during sniffing – Volatiles in food are pumped into the nasopharynx during chewing and on exhalation, when the soft palate (velopharyngeal flap) opens – This flap is normally shut during eating and drinking to stop food and drink getting into the nose – The mechanics of this process are poorly understood as it is hard to study 28 28 You're getting little pulses every time you swallow, exhale and chew. But that's not how you experience avour. Your brain intervenes to help smooth out those impulses so you can continuously experience avour. (27) Receptor surface We have about 4-6cm2 of receptor tissue - the olfactory mucosa The tissue is bathed in mucus and the ORN’s extend microvilli into this medium The mucosa has a variety of functions – Clearing ‘old’ smells away – Transport – Protection This is the olfactory epithelium (OE) 29 29 Because this is a chemical sense the body has to nd a way of getting rid of all of the chemical signals the OE receives and that's why it has a continuous smell of mucus over the OE to clear old smells. The receptors There are between 300-500 different olfactory receptors in humans and maybe 800+ in rodents Contrast this with the visual system and its 4 receptor types! Each olfactory receptor neuron on the epithelium (see right for an actual photo of the rat epithelium) expresses just one type of receptor All belong to a group called G- Proteins Chemicals bind to the G-Protein and result in depolarisation of the cell and an action potential 30 30  Other olfactory receptors? There may be other classes of receptor that are sensitive to reproductive related chemicals - Scent of symmetry - Faces vary in symmetry - More symmetrical faces are liked more - The smell from people with more symmetrical faces is liked more too - MHC (Major histocompatability complex) type – immune genes - Needs to be different between sexual partners to maximise off-spring fitness - Partners with dissimilar MHC have more kids - Partners with similar MHC have more miscarriages - Even female perfume choice seems to be selected to complement MHC type - Smell seems to be our main mode for detecting MHC type 31 31 You need to nd a partner that will have the most divergent MHC genes than you which will give your o spring the most robust immune proteins to ght o bacteria and viral infections. We seem to like the smell of people who are more dissimilar in MHC genes than us. Receptors to glomeruli As you know each ORN expresses one type of receptor The olfactory receptor types are randomly distributed across the olfactory epithelium Each receptor type is sensitive to different chemicals but there is considerable overlap in sensitivity Information from each receptor type converges on a structure called a glomeruli in the olfactory bulb There are about the same number of glomeruli (300- 500) as there are receptor types (300-500) 32 32  Schematic diagram of receptor to glomeruli relationship Three receptor types (A, B, C) on the olfactory epithelium (remember there are really 300+ types, not just 3 as here!) Each receptor type then converges on to the same glomeruli in the olfactory bulb When we sniff something there is a spatial (and temporal) pattern of activation across all of the 300-500 glomeruli – as we will see this is crucial to how we manage to perceive odours 33 33 Temporal pattern means that some smells may bind quickly and others more slowly. Here it is important to understand the di erence between paleocortex and neocortex concerning olfactory processing Information flow to/in the brain Information from the glomeruli in the olfactory bulb (OB) travels then to the olfactory cortex (PC - paleocortex), orbitofrontal cortex (OFC; neocortex), amygdala (AC; fear), mediodorsal thalamus (MD; attention role) and the hypothalamus (Hy) The neural architecture of olfaction is unique amongst the senses – Direct access to neocortex without obligatory thalamic processing – Initial paleocortical processing – Direct access to hippocampus & amygdala The olfactory system is why we have learning without awareness because it bypasses the thalamus unlike other senses. 34 34  How do we smell? In essence our sense of smell is a pattern recognition system Most odours are complex mixtures of chemicals - coffee contains 600 or so volatile (i.e. smelly) chemicals, but we just perceive ‘coffee’ The olfactory system has to recognise these complex combinations of chemicals - how? 35 35 Pattern recognition As you know each olfactory receptor type is sensitive to many different chemicals This effectively rules out ‘labeled lines’ just as the complex nature of the stimulus does too (i.e. we don’t have a ‘coffee’ receptor) Rather the brain uses the pattern of activity across the 300-500 glomeruli to recognise the odour It appears to do this by matching the glomerular pattern to patterns that have already been experienced before (and encoded in to odour memory) Crucially, it is this pattern matching process that generates our conscious perception of odour quality (that’s coffee!) 36 36  Implications What if the odour memory store is lost? – The case of Henry Molaison (HM) What if we have not smelled that odour before and so have no odour memory of its pattern? A more bizarre prediction is that we all have different smell worlds that are dependent upon our history of smelling There is strong and robust evidence for this claim as we shall see 37 37 Different smell worlds Children are poorer at telling odours apart than adults, even though they have normal acuity (they can detect whether an odour is present or absent) Different cultures perceive different culturally specific odours in different ways Japanese vs Tibetans (fish) Japanese vs Germans (soya beans & marzipan) Experience based effects can also be readily demonstrated in the laboratory… 38 38  Lab demonstration If participants, smell an odour mixture (cherry-smoky) and then later smell each component alone… – The cherry odour alone now smells somewhat smoky – The smoky odour alone now smells somewhat cherry-like – Both odours are judged to smell more alike – Both odours are less discriminable from each other The brain has encoded “Cherry-Smoky”, and so smelling either odour alone recovers the memory of the mixture Interestingly this whole process occurs without explicit knowledge – learning without awareness 39 39 Experts So in sum, smelling is based upon experience – memory that is If you loose your smell memories, like HM, a rose smells no different to coffee or petrol Before turning to our next topic, I want to briefly examine the issue of perceptual expertise in olfaction as this directly relates to our discussion of ‘experiential’ effects and it is also a big deal in the culinary world 40 40  Wine tasters Most of us probably believe that expert wine tasters have the ability to detect ‘notes’ (components) in wine that the rest of us with uneducated palates can not detect – Description of a Hunter Valley Sauvignon blanc – “It is a great wine of phenomenal length and character. The light-yellow colour and bouquet are strikingly youthful for its age, the latter showing little sign of toasty development, instead, subtle notes of lemon, herbs, beeswax and candle- wax. It’s amazingly full of fruit and richness of palate, filling up the entire mouth with flavour that lasts and lasts. All this is delivered with impeccable harmony.” Wine tasters are somewhat better, but not much – They are no better at discrimination than regular wine drinkers, but both are better than non-wine drinkers – They can match a description they gave to a particular wine about 48% of the time, compared to 28% regular wine drinkers – Their expertise lies in applying language to sensation and knowing feature clusters associated with particular varieties (and some tricks) – The phenomenon of verbal overshadowing 41 41 Is this wine description bullshit? Well sort of because back in a lab a week later they get about half of them wrong. Smell - in sum Our sense of smell is based upon recognising patterns I have not mentioned this, but there are also likely to be important genetic differences in the number and type of receptors we each have, but the full implications of this are at present unclear Both of the above mean that we probably live in relatively unique, but culturally defined, ‘smell worlds’ 42 42  Somatosensation & Proprioception We have, in the mouth, a range of receptors located in and on the tissue surface, and deep in the muscles and joints of the mouth (as with elsewhere in the body) – Somatosensation is our perception of objects (and their properties) contacting the body – it is both an active and passive sense – Proprioception is our perception of the location of our muscles and joints in ‘space’ – They are intimately related and I’ll deal with them as one‘system’ These are important in feeling – Pressure (i.e. chewing food) – Texture (i.e. crispness & fattiness) – Astringency (i.e. pinched-up & shriveled, such as tannins in wine) This is probably the most poorly explored sensory system in the context of flavour, but it is clearly important in the perception of texture and fat 43 43 Fat perception A significant component of fat perception in food involves texture Descriptive terms for fat are textural – Greasy, oily, creamy, thin, watery Fat content can be accurately gauged by the fingers alone However, this is not the whole story Smell (rat studies - Yes vs human studies – No?) Taste (as noted earlier) - currently contentious… – In rat ‘yes’, they have receptors that detect fat – Humans do appear able to discriminate fats in the absence of textural and olfactory cues, which just leaves taste (sort of) 44 44  Putting it all together So, when we go now to eat or have a coffee, how does the brain put all these pieces together (i.e. a binding problem again) to give us a unitary impression of flavour? Well we will approach this in three ways – Is flavour really a unitary sensation? i.e. homogenous – If it is, what impact does this have on our perception of food and drink? – Finally, how does the brain do it? 45 45 In putting it all together we have another "binding problem." We have taste info, olfactory info and somatosensory and proprioceptive information going into the orbitofrontal cortex somehow the brain has to put that together. Flavour No language surveyed has a term that distinguishes the olfactory from the taste component of eating & drinking – Taste and smell in the mouth seem to be treated linguistically as a single entity (contrast with ‘red’ and ‘green’ for example) When people lose their sense of smell, they typically report also having lost their sense of taste, as food now tastes bland People are poor at discriminating the components of flavours, even if trained to do so, and especially odours While children know you need eyes to see and ears to hear, most adults do not know that you need a‘nose to taste’ So we can conclude – broadly – that at least for the two major components of flavour, taste and smell, these seem to be treated as a single entity in the mouth Retronasal; is up towards the back of the throat. Not many other 46 cultures or languages have a word for this. 46 Orthonasal; is sni ng  What impact does this have One consequence of experiencing taste and smell as a unitary experience is that we seem to encode this flavour information in the same way Notably we appear to always encode flavour information irrespective of whether we wish to do so or not – unconsciously that is The most striking consequence of this is odour- taste synesthesia - sweet smelling odours 47 47 When you smell an odour like vanilla or chocolate you'll say that it smells sweet but what you're experiencing is a memory. You're smelling that cake you had earlier, that's something that a lot of us experience but we don't often recognise it as synesthesia- even though it is. Odour-taste synesthesia I Synesthesia refers to the experience of a sensation normally associated with one sensory system, when another sensory system is stimulated Most sysnesthesias (sound/word-colour; word- flavour) are rare ( 2 standard drinks/day). – Among this age group 50% of men and 20% of women have engaged in binge drinking (> 7/5 standard drinks drunk consecutively) at least once a week in the past year. – Harms from excessive intake include: Cirrhosis (liver damage) Heart disease Brain damage Road trauma Violent behaviour Relationship breakdown Lost productivity – The rate of excessive consumption in Indigenous Australians is 2-3 times higher even though fewer drink 38 38 19  7/13/22 Alcohol - impact Alcohol’s yearly adverse health impacts in Australia (averaged over the last decade) Condition Deaths Hospitalisations Cancers 1500 10,180 Cardiovascular 1150 10,700 diseases Digestive diseases 780 9,700 Injuries 1495 65,000 Neuropsychiatric 380 157,130 Total 5305 252,710 Alcohol abuse/misuse costs around 15 Billion dollars per year in Australia (and rising) 39 39 Alcohol - impact For all drug treatment services in Australia, alcohol related problems were the most common reason for referral Approximately 35% of all violent offences are committed under the influence of alcohol The yearly ABS victims of crime survey reveals around – 1.5 million people were verbally abused by someone under the influence of alcohol – 0.6 million had property damaged by someone under the influence of alcohol – 0.4 million were physically assaulted by someone under the influence of alcohol These types of statistics (and much more) can be found for every nation that consumes alcohol 40 40 20  7/13/22 The effects of alcohol Metabolism and male vs female differences – Alcohol enters the bloodstream and is rapidly absorbed by the brain, but much more slowly by muscle (women have less muscle) – Alcohol is primarily (90%) metabolised by the liver (and 10% by stomach - but women are less efficient at this) Alcohol is broken down into Acetaldehyde (women less efficient at this as well) Acetaldehyde is broken down into Acetate Acetate is then fed into the ACoa pathway yielding 7Kcal for every gram of alcohol consumed The body can metabolise a maximum of 6-8g per hour 41 41 Psychological effects General - euphoria, disinhibition, reduced anxiety, impaired motor control Specific - effects of alcohol need to be distinguished from peoples expectations of what happens on ingestion – Expectation free research designs tell us that Alcohol lengthens reaction time Alcohol narrows attention Alcohol promotes risk taking Alcohol enhances aggression – This makes for a very unfortunate cocktail when combined with a car and an inexperienced driver Expectation free research includes a placebo group that doesn't get the 42 alcohol and a group that actually does. 42 21  7/13/22 Effect on the brain Alcohol acts upon multiple brain systems, which is why it is called a promiscuous drug Its effects also vary by dose The key changes appear to be: – It acts akin to anaesthetics by increasing the permeability of nerve cell membranes (consumption of the anaesthetic agent ether is also