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What makes a dish stand out? On the face of it, this question does not lend itself to an objective or scientific answer. Of course, we could talk about the quality of the products used, the chef’s expertise, an urge to take a calculated risk to surprise guests but not baffle them, or about a pleasant atmosphere in a tasteful decor... But in the end, as with aesthetic preferences, it is pretty clear that it is not easy to rationalise our culinary pleasures either, as they are often based on a je ne sais quoi or some sort of ‘alchemy in cooking’. In other words, science and gastronomy do not necessarily go hand in hand.

The origins of neurogastronomy

Yet, the connection between these two disciplines has never been stronger. It is nothing new either, as illustrated in the widely read Physiologie du goût (The Physiology of Taste) by Jean Anthelme Brillat-Savarin, !rst published in 1825 and still in print today. This book is regarded as the precursor to what we now call ‘neurogastronomy’, as Brillat-Savarin, a town lawyer, theorised on the growing interest in a scientific approach to taste, based on the premise that the human diet went far beyond its restorative role necessary for survival. The pleasure derived from a good meal not only helps unite societies, but also brings this activity akin to carnal desire and a predilection for discovery. Brillat-Savarin made no mention of psychology, nor of course of neurosciences as they barely existed at that time, but his observations brought to light a very simple fact that we all may well have noticed from time to time: Eating influences our way of thinking. “[Gastronomy] also considers the action of food or aliments on the moral of man, on his imagination, his mind, his judgment, his courage, and his perceptions, whether he is awake, sleeps, acts, or reposes.”1

From the oven to the brain

The fact that eating (well, poorly, a lot, a little or not at all) influences our behaviour, our mood and our decisions seems so self-evident that very few people have actually taken the trouble to evaluate the consequences. A study of the sentences handed out in an Israeli court, for example, found that judges were much more lenient after their lunch break than just before it (2), for which the obvious explanation lies in another quote from Brillat-Savarin: “They saw that a full stomached individual was very different from a fasting one.”3

In fact, other researchers have been able to measure the impact of food on the brain simply by showing pictures of enticing dishes to famished volunteers lying in a scanner or by wafting appetising smells around them. The results are spectacular: It is as if the mere thought of eating brings the entire brain to the boil! Under any other circumstances, we would expect such signals to cause metabolic activity to vary by 1 to 2% at most, yet here researchers observed an almost immediate increase of up to 24%.4 This could partly explain the new trend for ‘food porn’ or ‘gastropornography’, which involves taking photos of food and sharing them with the community of foodies on social media!

So, what exactly is ‘taste’? We generally use this term in its emotional, hedonistic sense, to describe the tendency of food or drink to produce a pleasant sensation, to be delicious. Here, researchers had to contend with this everyday use of the word ‘taste’, albeit somewhat ambiguous. On the one hand, we think of taste as one of the five distinct senses Aristotle classified alongside smell, touch, sight and hearing. On the other hand, the ‘taste’ of food seems to go beyond the simple activation of taste receptors embedded in our tongues, enabling us to distinguish between sweetness, saltiness, bitterness and sourness, the four ‘primary tastes’ to which we now add umami, a taste typical of Japanese food with a high glutamate content. In reality, as Brillat-Savarin rightly noted, it seems that this second aspect of ‘taste’ is primarily a result of our sense of smell, and that these two senses are inextricably linked in our appreciation of food and drinks. So as not to get bogged down in linguistics, specialists use the term ‘savour’ when referring to the perception of food based on olfaction and gustation (among others things... as we will see below).

The birth of modern neurogastronomy

This observation led Gordon Shepherd, a neurobiologist, to suggest the term neurogastronomy in 2006 (5) to refer to the specific study not of the senses as such and of how the brain depicts them, but more globally of all the neurobiological mechanisms involved in the detection and appreciation of savours, what these mechanisms teach us about human behaviour, and how we can apply them in the kitchen.

The key theory of neurogastronomy is therefore that savour originates in the brain rather than in the food itself. It also takes a multimodal approach, not only focusing on the senses of taste and smell, but all the other senses too, as well as motricity. Brillat-Savarin had already emphasised this point: Flavour is not imparted passively. We are the ones who spear food on our plates onto our forks, put it in our mouths, chew, savour and swallow it, and then appraise it. According to Gordon Shepherd, this results in the creation of ‘odour images’ in our brains, just like we have visual ‘mental images’ which enable us to recognise faces and imagine places. Furthermore, while neurological damage can impair sight, language and memory, there are also lesser-known clinical examples of brain injuries causing changes in food behaviour.

   ‘Gourmand syndrome’

There is a clinical dimension to neurogastronomy. While investigating behavioural disorders resulting from neurological conditions such as strokes, epilepsy or brain tumours, neurologists have occasionally observed changes in eating behaviour. Some specific conditions may lead to ‘classic’ disorders such as anorexia or bulimia but, in rare cases, they may also put an end to them. For example, a 36-year-old woman, who had been suffering from anorexia for a number of years, recovered normal eating habits after suffering a brain injury with a haematoma in the right frontal lobe. Stranger still, this part of the brain is associated with what neuropsychologists Marianne Regard and Theodor Landis have coined ‘gourmand syndrome’. This ‘benign’ eating disorder appears after an epileptic seizure, a traumatic brain injury, a tumour, a deformity or a stroke located in the anterior parts of the right hemisphere, and patients develop an obsession with food, and in particular gourmet food, almost overnight. They instantly become discerning foodies, developing a passion for cooking, no longer appreciating the mediocre food they used to eat but rather choosing to eat in the best restaurants, and talking incessantly about haute cuisine. One patient even resigned from his job as a political journalist to become a food columnist! Such metamorphoses are diffcult to explain, but the association between food disorders, a passion for fine food, and the right hemisphere suggests that certain regions of the brain are specialised in the vital and complex activity of eating. The frontal and temporal lobes in particular are strongly connected with the limbic system, which controls the visceral, metabolic and emotional functions enabling the body to defend itself and survive. The frontal lobe helps us resist temptation and override impulsive urges, while the right hemisphere is involved in pleasure, aesthetics and satisfaction. All these factors show not only the complexity of our eating behaviour, but also the extent to which this behaviour is dependent on a delicate balance which, if upset, can lead to various forms of impairment.

Nothing could be simpler than deciding if something tastes ‘good’ or ’bad’, yet these impressions are the fruit of an extraordinarily complex process we are only just beginning to understand. This process is based on a strange psychological illusion. We get the impression that we perceive taste, in the broadest sense of the term, in our mouths, yet we do in fact perceive taste in our nasal cavities, via a subconscious mechanism known as retronasal olfaction. When we wish to smell food, we generally place it under our noses and then sniff it, breathing in deeply. This is known as orthonasal olfaction. However, it is after we have chewed food, releasing its juices and molecules into our mouths, that as we breathe out, volatile odorous compounds are sent back to the nasal cavity through the back of the mouth. The roof of the nasal cavity has a mucous membrane called the olfactory epithelium, which comprises neurons that are sensitive to odorous molecules. These neurons are directly connected to a tiny olfactory bulb... inside the cranium, in the brain!

The olfactory bulb gathers the numerous signals sent by the epithelium receptor neurons and integrates them in a cerebral activation pattern, a sort of odour ‘map’ or ‘image’ that represents the particular mix of odorous molecules specific to each morsel of food. The olfactory bulb then projects this map towards various other structures of the brain, including the amygdala, a structure directly involved in our emotions, and the orbitofrontal cortex (located just above our eyes), a major hub grouping together bundles from other sensory systems. These include sight, touch (in our mouths too, with information about the temperature and texture of the food) and taste (which thereby takes a completely different route to that of the sense of smell), together with sensations coming from the viscera, and the homeostatic processes regulating hunger and thirst. They also include bundles from regions controlling memory and emotions, as well as the mechanisms governing inhibition and decision- making. In short, at this stage, as the episode of Marcel Proust’s madeleine so perfectly illustrates, simple odorous molecules reach and become part of an individual’s identity. Consequently, an aroma is never ‘neutral’ as it is always influenced by the context and the visual appearance of dishes, as well as by each person's preferences, appetite, mood, beliefs and memories.

We cannot see this complex layered process, so we get the impression that we perceive everything in our mouths, the place where we have put the food or drink. Yet, an important part of what we are sensing actually comes from our nasal cavities. Quite a handy evolutionary perk! After all, if we want to stay alive, we cannot just eat anything and everything: We rely on our brains sending commands to the muscles in our mouths to either spit something out or swallow it!

From neurogastronomy to gastrophysics

That’s all very well and good, but how exactly does it help us prepare the perfect risotto or choose the best appetisers? This is exactly the kind of criticism some researchers have voiced against Shepherd’s neurogastronomy. In-depth understanding of the neurophysiological processes responsible for our experience of savours may well provide an essential basis for grasping the mechanisms at play in gastronomy. It reveals, for example, how the sense of smell plays more of a role than taste, even if both remain inextricably linked, and especially how our other senses, the state of our bodies, our moods and even our beliefs can influence savour. Images of brain activity demonstrate how the price of a bottle of wine can influence our appraisal of it, or why we can be ‘tricked’ by a fizzy drink bearing the label of its competitor.

Miguel Sánchez Romera, part-neurologist, part-chef, briefly ran a restaurant in Manhattan (6) showcasing the concept of ‘neurogastronomy’, but this knowledge remains difficult to transpose into delicious recipes.(4)  Generally speaking, neurosciences have had much less of an impact on gastronomy than physics and chemistry had in their contribution to what was called ‘molecular gastronomy’. This movement emerged during a 1992 congress and focused on the science behind egg mayonnaise. It gave scientific foundation to the little tricks picked up from our grandmothers and helped improve them, and also led to the invention of all sorts of new processes – spherification, fumigation, concentration, distillation and other thermal shock treatments – designed to please, amuse, surprise and impress.7 There’s nothing ‘neuro’ about that.

The British psychologist Charles Spence preferred to call the study of the variable elements that contribute to the pleasure we feel when eating as ‘gastrophysics’. This ‘new science of eating’ strives to provide a quantitative measurement of the factors that ordinarily form a whole in our experience of savours, by separating them and experimenting with them one by one, from every possible angle.

Multimodality on the menu

Charles Spence feels the observations and applications of ‘neurogastronomy’ are too restrictive.8 In his opinion, rather than analysing the olfactory cortex of rodents or feeding liquids through a tube to people lying in a scanner, we need a science that is as close as possible to the eating experience and the reality of contemporary dining. The aim is twofold: Firstly, to gain a better understanding of the complexity of our relationships with savours and food. This involves determining how the senses differ from each other, how they interact and how they are influenced by external factors. Secondly, to use this knowledge to develop new culinary concepts, try bold new recipes and combinations and inject fresh ideas into the food industry and into marketing techniques. As far as applications are concerned, this research could also generate new ways of helping patients suffering from eating disorders and of managing the obesity epidemic currently affecting the modern world. It could also provide new tools for developing taste awareness in young children or for supporting elderly people whose perception of savours, hunger or thirst may be impaired.

That’s a tall order! So far, Charles Spence and his fellow researchers, including Michelin-starred chefs such as Heston Blumenthal, who runs the famous Fat Duck restaurant just outside London, (9) have carried out numerous experiments showing the extent to which the colour of food, the sound of its crunchy texture, the background music, the shape, weight or colour of the tableware, the names and prices of the dishes on the menu, the choice of presentation and a host of other factors can influence our judgement of savours and our culinary pleasure in general. This approach follows on from other research into multimodal perception, which for a long time focused mainly on the interactions between sight, touch and hearing, largely ignoring the senses of taste and smell.

This recent research pays particular attention to the importance of our expectations when we sit down to eat and to knowing the extent of the element of surprise. Could you be tempted by a salmon sorbet? Probably only if the conditions are right and you are up for it! Who can deny that a seafood platter tastes better when we are eating it on a seafront terrace? Heston Blumenthal’s restaurant provides guests with headphones playing the sound of seagulls and waves crashing on the beach while you eat. Scientists call this experience ‘super-additive interaction’: Taste is enhanced when it is paired with the atmosphere with which it is usually associated.

This is basically ‘sensory design’, whereby nothing is left to chance, as our brains are made in such a way that every piece of information can, even subconsciously, influence a meal, in particular within the orbitofrontal cortex, where our sensations, our expectations and beliefs, and our judgements converge and may well mislead us.

The future of eating

Will this ‘gastrophysics’ research eventually lead to the creation of the ‘perfect meal’, as Charles Spence hopes it will? Are we not in danger of moving too far away from the basic needs of ordinary people, who do not always have the means to treat themselves to such rare moments of discovery in high-end restaurants? Now is more a time for reflecting on how we can feed a growing, globalised and multicultural population healthily, against a backdrop of considerable ecological and economic challenges. There is no doubt that scientific gastronomy will also need to take these trends into account, as changes to our diet and our preferences are inevitable.

Scientists, gastronomes and chefs, from supermarkets to the Michelin-starred restaurants, will have to join forces to satisfy everybody’s needs in an uncertain future. Even if the relationship between science and gastronomy has been somewhat overcooked, let’s not forget that kitchens have always been laboratories, where creativity, experimentation and discovery are granted as much importance as in research institutes. From the invention of a new sauce to the design of a product’s packaging, a scientific and multidisciplinary approach can help rationalise and improve all sectors of the long chain of steps human food undergoes, up to the crucial point where, since the dawn of time, humans have joined together to share a good meal.