Distinct brain representations of processed and unprocessed foods

Automatic engagement of limbic and prefrontal networks in response to food images reflects distinct information about food hedonics and inhibitory control

Adaptive regulation of food consumption involves both identifying food as well as evaluating whether it should be eaten, a process that requires assessing relevant properties such as healthfulness and hedonic value. In order to identify how these fine-grained food properties are represented in the brain, we analyzed functional Magnetic Resonance Imaging data from 43 participants who viewed images of 36 different foods. A data-driven clustering approach based on Representational Similarity Analysis partitioned food-responsive brain regions into two sub-networks based on their multivariate response to food pictures: a Prefrontal network composed of fronto-parietal brain regions and a Limbic network composed of cortico-limbic and sub-cortical brain regions. Further analysis, using similarity judgments of those foods from a large online sample, revealed that the Prefrontal network predominantly represented information related to food healthfulness or processing, the key factor underlying food similarity. In another imaging task, we found that responses in the Prefrontal network were strongly influenced by judgments of food-related self-control, while the Limbic network responses were more affected by hedonic food judgments. These results suggest that, upon viewing food images, behaviorally relevant information is automatically retrieved from distinct brain networks that act as opponent processes in guiding food consumption.

Origins of food selectivity in human visual cortex

Several recent studies, enabled by advances in neuroimaging methods and large-scale datasets, have identified areas in human ventral visual cortex that respond more strongly to food images than to images of many other categories, adding to our knowledge about the broad network of regions that are responsive to food. This finding raises important questions about the evolutionary and developmental origins of a possible food-selective neural population, as well as larger questions about the origins of category-selective neural populations more generally. Here, we propose a framework for how visual properties of food (particularly color) and nonvisual signals associated with multimodal reward processing, social cognition, and physical interactions with food may, in combination, contribute to the emergence of food selectivity. We discuss recent research that sheds light on each of these factors, alongside a broader account of category selectivity that incorporates both visual feature statistics and behavioral relevance.

The Impact of Artificial and Natural Additives in Meat Products on Neurocognitive Food Perception: A Narrative Review

The holistic sensory experience creates a unified perception that influences consumer memory. Consumer interest in clean label products underlines an accelerated trend towards products without artificial additives. From a sensory point of view, food appeal is significantly influenced by how additives actively participate in the organoleptic properties of the final product. This research aims to shed light on the impact of artificial and natural additives in meat products on neurocognitive food perception, which is essential for understanding how they influence the consumer's final decision and direct food trends. Different neural mechanisms involved in multimodal sensory integration confirm differences in perception of meat products containing artificial and natural additives. Analysis confirms that neurocognitive perception integrates organoleptic sensations to form a complete sensory experience. The encephalon simultaneously processes multimodally integrated stimuli from organoleptic properties, reaching the orbitofrontal cortex and other regions involved in the neuroprocessing of the final product. The reformulation and development of meat products need a detailed analysis of the impact of additives on sensory properties contributing to the shaping of consumption trends.

Positive serial dependence in ratings of food images for appeal and calories

Food is fundamental to survival, and our brains are highly attuned to rapidly process food stimuli. Neural signals show that foods can be discriminated as edible or inedible as early as 85 ms after stimulus onset,1 distinguished as processed or unprocessed beginning at 130 ms,2 and as high or low density from 165 ms.3 Recent evidence revealed specialized processing of food stimuli in the ventral visual pathway,4,5,6 an area that underlies perception of faces and other important objects. For many visual objects, perception can be biased toward recent perceptual history (known as serial dependence7,8). We examined serial dependence for food in two large samples (n > 300) who rated sequences of food images for either "appeal" or "calories." Ratings for calories were highly correlated between participants and were similar for males and females. Appeal ratings varied considerably between participants, consistent with the idiosyncratic nature of food preferences, and tended to be higher for males than females. High-calorie ratings were associated with high appeal, especially in males. Importantly, response biases showed clear positive serial dependences: higher stimulus values in the previous trials led to positive biases, and vice versa. The effects were similar for males and females and for calories and appeal ratings and were remarkably consistent across participants. These findings square with recently found food selectively in the visual temporal cortex, reveal a new mechanism influencing food decision-making, and suggest a new sensory-level component that could complement cognitive strategies in diet intervention.

Graspable foods and tools elicit similar responses in visual cortex

The extrastriatal visual cortex is known to exhibit distinct response profiles to complex stimuli of varying ecological importance (e.g. faces, scenes, and tools). Although food is primarily distinguished from other objects by its edibility, not its appearance, recent evidence suggests that there is also food selectivity in human visual cortex. Food is also associated with a common behavior, eating, and food consumption typically also involves the manipulation of food, often with hands. In this context, food items share many properties with tools: they are graspable objects that we manipulate in self-directed and stereotyped forms of action. Thus, food items may be preferentially represented in extrastriatal visual cortex in part because of these shared affordance properties, rather than because they reflect a wholly distinct kind of category. We conducted functional MRI and behavioral experiments to test this hypothesis. We found that graspable food items and tools were judged to be similar in their action-related properties and that the location, magnitude, and patterns of neural responses for images of graspable food items were similar in profile to the responses for tool stimuli. Our findings suggest that food selectivity may reflect the behavioral affordances of food items rather than a distinct form of category selectivity.

The Time-Course of Food Representation in the Human Brain

Humans make decisions about food every day. The visual system provides important information that forms a basis for these food decisions. Although previous research has focused on visual object and category representations in the brain, it is still unclear how visually presented food is encoded by the brain. Here, we investigate the time-course of food representations in the brain. We used time-resolved multivariate analyses of electroencephalography (EEG) data, obtained from human participants (both sexes), to determine which food features are represented in the brain and whether focused attention is needed for this. We recorded EEG while participants engaged in two different tasks. In one task, the stimuli were task relevant, whereas in the other task, the stimuli were not task relevant. Our findings indicate that the brain can differentiate between food and nonfood items from ∼112 ms after the stimulus onset. The neural signal at later latencies contained information about food naturalness, how much the food was transformed, as well as the perceived caloric content. This information was present regardless of the task. Information about whether food is immediately ready to eat, however, was only present when the food was task relevant and presented at a slow presentation rate. Furthermore, the recorded brain activity correlated with the behavioral responses in an odd-item-out task. The fast representation of these food features, along with the finding that this information is used to guide food categorization decision-making, suggests that these features are important dimensions along which the representation of foods is organized.

Graspable foods and tools elicit similar responses in visual cortex

Extrastriatal visual cortex is known to exhibit distinct response profiles to complex stimuli of varying ecological importance (e.g., faces, scenes, and tools). The dominant interpretation of these effects is that they reflect activation of distinct "category-selective" brain regions specialized to represent these and other stimulus categories. We sought to explore an alternative perspective: that the response to these stimuli is determined less by whether they form distinct categories, and more by their relevance to different forms of natural behavior. In this regard, food is an interesting test case, since it is primarily distinguished from other objects by its edibility, not its appearance, and there is evidence of food-selectivity in human visual cortex. Food is also associated with a common behavior, eating, and food consumption typically also involves the manipulation of food, often with the hands. In this context, food items share many properties in common with tools: they are graspable objects that we manipulate in self-directed and stereotyped forms of action. Thus, food items may be preferentially represented in extrastriatal visual cortex in part because of these shared affordance properties, rather than because they reflect a wholly distinct kind of category. We conducted fMRI and behavioral experiments to test this hypothesis. We found that behaviorally graspable food items and tools were judged to be similar in their action-related properties, and that the location, magnitude, and patterns of neural responses for images of graspable food items were similar in profile to the responses for tool stimuli. Our findings suggest that food-selectivity may reflect the behavioral affordances of food items rather than a distinct form of category-selectivity.

Ultra-Processed Food, Reward System and Childhood Obesity

Obesity and overweight are a major public health problem globally. Diet quality is critical for proper child development, and an unhealthy diet is a preventable risk factor for noncommunicable diseases (NCDs), such as obesity. Consumption of sugar-sweetened beverages and ultra-processed foods (UPFs) in childhood may increase the BMI/BMI z-score, body fat percentage, or likelihood of overweight. A strict feeding regulation system allows for sufficient food to be consumed to meet ongoing metabolic demands while avoiding overconsumption. This narrative review explores the issues of obesity and the regulation of food intake related to reward systems and UPF consumption. Nutrient composition alone cannot explain the influence of UPFs on the risk of obesity. Furthermore, the non-nutritional properties of UPFs may explain the mechanisms underlying the relationship with obesity and NCDs. UPFs are designed to be highly palatable, appealing, and energy dense with a unique combination of the main taste enhancer ingredients to generate a strong rewarding stimulus and influence the circuits related to feeding facilitation. How individual UPF ingredients influence eating behavior and reward processes remains not fully elucidated. To increase the knowledge on the relationship between UPFs and pediatric obesity, it may be useful to limit the rapid growth in the prevalence of obesity and subsequent related complications, and to develop new strategies for appropriate food and nutrition policies.

Changes in food cue reactivity through affective and nonaffective touch: An event-related potential study

Affective touch (gentle/slow brushing of the skin) can facilitate the allocation of processing resources to simultaneously present stimuli from different modalities. The present event-related potential (ERP) study investigated whether affective touch can enhance attention to visual cues of healthy food. Female participants (n = 117) were randomly assigned to three different groups that either received affective touch, nonaffective touch (fast brushing of the skin), or no touch during the presentation of pictures of healthy food (fruits and vegetables) and non-food. Electrocortical markers of motivated attention (frontal/parietal P300, late positive potential: LPP) and reported appetite for the depicted food items were compared between the three groups. Nonaffective touch was associated with reduced amplitudes of the frontal P300/LPP (300-1000 ms) for food pictures indexing reduced motivated attention. Affective touch did not influence food cue reactivity (P300/LPP, appetite). Effects of affective touch may be restricted to specific stimuli, e.g. those with social relevance.

Impact of textual warnings on emotional brain responses to ultra-processed food products

Background and objectives

Ultra-processed food products (UPF) have been associated with numerous non-communicable diseases. Despite this, the addictive nature of UPF, and the aggressive marketing strategies used to promote them, has created a strong emotional connection between UPF and consumers, and supports their increasing UPF global consumption. In view of the emotional link that consumers often have with UPF, modulating emotional reactions to UPF (by using strategies such as textual warnings) is important in changing consumers' behavior. Since emotions are better understood by assessing individuals' implicit reactions, we conducted an electroencephalographic study applying the event-related potential technique to investigate whether textual warnings were able to modulate the brain responses to UPF stimuli.

Materials and methods

Twenty-six participants (19 women) viewed pictures of UPF preceded by a warning sentence about the health risks of consuming UPF or a control sentence while the electroencephalogram was recorded. In addition, the participants rated the picture in respect of pleasantness, arousal, and intention to consume. As emotions are associated with motivational circuits in the brain, we focused on a well-known event-related potential brain marker of the motivational relevance associated with emotional stimuli, namely late positive potential (LPP).

Results

The late positive potential amplitude was larger for pictures depicting UPF under the warning condition compared to the control condition, a result that was accompanied by lower pleasantness ratings during the warning condition (compared to the control).

Conclusion

Textual warnings about the negative health consequences of consuming UPF changed the emotional responses toward UPF, possibly increasing the motivation to avoid UPF. These results shed new light on the impact of textual warnings on UPF-evoked emotions.

Tears for pears: Influence of children’s neophobia on categorization performance and strategy in the food domain

Preschoolers’ neophobic dispositions mainly target fruits and vegetables. They received a great deal of attention in the past decades as these dispositions represent the main psychological barrier to dietary variety. Recently, children’s food neophobia has been found to be negatively correlated with their categorization performance (i.e., the accuracy to discriminate between food categories). We investigated categorization strategies among neophobic children, tendencies to favor one type of error over the other (misses over false alarms), in order to compensate for their poor categorization performance. To capture children’s categorization strategies, we used the Signal Detection Theory framework. A first experiment assessed 120 3-to-6-years old children’ sensitivity to discriminate between foods and nonfoods as well as their decision criterion (i.e., response strategy). In a second experiment, we manipulated the influence of food processing. The hypothesis was that food processing acts as a sign of human interventions that decreases uncertainty about edibility and thus promotes feelings of safety in the food domain. 137 children were tested on a food versus nonfood categorization task contrasting whole and sliced stimuli. In both experiments, increased levels of food neophobia were significantly associated with poorer categorization sensitivity and with a more conservative decision criterion (i.e., favoring “it is inedible” errors). Additionally, results from Experiment 2 revealed that food processing did not influence neophobic children, whereas their neophilic counterparts adopted a more liberal decision criterion for sliced stimuli than for whole stimuli. These findings are the first demonstration of a relationship between a decision criterion and food neophobia in young children. These results have strong implications for theories of food neophobia and laid the groundwork for designing novel types of food education interventions.

Implicit and explicit safety evaluation of foods: The importance of food processing

Identifying beneficial foods in the environment, while avoiding ingesting something toxic, is a crucial task humans face on a daily basis. Here we directly examined adults' implicit and explicit safety evaluations of the same foods presented with different degrees of processing, ranging from unprocessed (raw) to processed (cut or cooked). Moreover, we investigated whether individual characteristics (e.g., Body Mass Index, food neophobia and hunger) modulated their evaluations. We hypothesized that adults would associate the processed form of a food with safety more than its unprocessed form since processing techniques, which are ubiquitously applied in different cultures, often reduce the toxicity of foods, and signal previous human intervention and intended consumption. Adults (N = 109, 43 females) performed an implicit Go/No-Go association task (GNAT) online, assessing the association between safety attributes and food images differing on their degree of processing, both unfamiliar and familiar foods were used. Then each food was explicitly evaluated. Results revealed that individual self-reported characteristics affected both implicit and explicit evaluations. Individuals with excess weight and obesity had a strong and positive implicit association between processed foods and safety attributes, but explicitly rated cooked foods as the least safe overall, this latter result was found in highly neophobic individuals as well. Yet, at the explicit level, when looking at unfamiliar foods only, processed foods were rated safer than unprocessed foods by all participants. Our results are the first evidence that directly highlights the relevance of the degree of processing in food safety evaluation and suggest that thinking of the important tasks humans face regarding food selection enriches our understanding of food behaviors.

The role of associative learning in healthy and sustainable food evaluations: An event-related potential study

Individuals in industrialized societies frequently include processed foods in their diet. However, overconsumption of heavily processed foods leads to imbalanced calorie intakes as well as negative health consequences and environmental impacts. In the present study, normal-weight healthy individuals were recruited in order to test whether associative learning (Evaluative Conditioning, EC) could strengthen the association between food-types (minimally processed and heavily processed foods) and concepts (e.g., healthiness), and whether these changes would be reflected at the implicit associations, at the explicit ratings and in behavioral choices. A Semantic Congruency task (SC) during electroencephalography recordings was used to examine the neural signature of newly acquired associations between foods and concepts. The accuracy after EC towards minimally processed food (MP-food) in the SC task significantly increased, indicating strengthened associations between MP-food and the concept of healthiness through EC. At the neural level, a more negative amplitude of the N400 waveform, which reflects semantic incongruency, was shown in response to MP-foods paired with the concept of unhealthiness in proximity of the dorsal lateral prefrontal cortex (DLPFC). This implied the possible role of the left DLPFC in changing food representations by integrating stimuli's features with existing food-relevant information. Finally, the N400 effect was modulated by individuals' attentional impulsivity as well as restrained eating behavior.

Sinful Foods: Measuring Implicit Associations Between Food Categories and Moral Attributes in Anorexic, Orthorexic, and Healthy Subjects

Recently, neurocognitive studies have shown that food categorization is sensitive to both the properties of the food stimuli (e.g., calorie content) and the individual characteristics of subjects (e.g., BMI, eating disorders) asked to categorize these stimuli. Furthermore, groups of patients with eating disorders (ED) were described as relying more on moral criteria to form food categories than were control subjects. The present studies built on these seminal articles and aimed to determine whether certain food properties might trigger moral categories preferentially in subjects suffering from ED and in the general population. Using a Go/No-Go Association Task, Study 1 focused on the extent to which food categories are laden with moral attributes in ED patients compared to control subjects. Study 2 was a follow-up with a different design (an Implicit Association Test), another food variable (calorie content), and two non-clinical subgroups (orthorexic and healthy control subjects). Results revealed for the first time implicit associations between food variables cueing for energy density and moral attributes in the general population, the population suffering from anorexia nervosa, and subjects suffering from disordered eating such as orthorexia nervosa. These findings suggest that moralization of food is a pervasive phenomenon that can be measured with methods reputed to be less vulnerable to self-presentation or social desirability biases.

Strength or Nausea? Children's Reasoning About the Health Consequences of Food Consumption

Children’s reasoning on food properties and health relationships can contribute to healthier food choices. Food properties can either be positive (“gives strength”) or negative (“gives nausea”). One of the main challenges in public health is to foster children’s dietary variety, which contributes to a normal and healthy development. To face this challenge, it is essential to investigate how children generalize these positive and negative properties to other foods, including familiar and unfamiliar ones. In the present experiment, we hypothesized that children might rely on cues of food processing (e.g., signs of human intervention such as slicing) to convey information about item edibility. Furthermore, capitalizing on previous results showing that food rejections (i.e., food neophobia and picky eating) are a significant source of inter-individual variability to children’s inferences in the food domain, we followed an individual approach. We expected that children would generalize the positive properties to familiar foods and, in contrast, that they would generalize more often the negative properties to unfamiliar foods. However, we expected that children would generalize more positive and less negative properties to unfamiliar sliced foods than to whole unfamiliar foods. Finally, we expected that children displaying higher levels of food rejections would generalize more negative properties than children displaying lower levels of food rejections. One-hundred and twenty-six children, aged 3–6 years, performed an induction task in which they had to generalize positive or negative health-related properties to familiar or unfamiliar foods, whole or sliced. We measured children’s probability of generalization for positive and negative properties. The children’s food rejection score was assessed on a standardized scale. Results indicated that children evaluated positively familiar foods (regardless of processing), whereas they tend to view unfamiliar food negatively. In contrast, children were at chance for processed unfamiliar foods. Furthermore, children displaying higher levels of food rejections were more likely to generalize the negative properties to all kinds of foods than children displaying lower levels of food rejections. These findings entitle us to hypothesize that knowledge-based food education programs should take into account the valence of the properties taught to children, as well as the state of processing of the food presented. Furthermore, one should take children’s interindividual differences into account because they influence how the knowledge gained through these programs may be generalized.

Image database of Japanese food samples with nutrition information

Background

Visual processing of food plays an important role in controlling eating behaviors. Several studies have developed image databases of food to investigate visual food processing. However, few databases include non-Western foods and objective nutrition information on the foods.

Methods

We developed an image database of Japanese food samples that has detailed nutrition information, including calorie, carbohydrate, fat and protein contents. To validate the database, we presented the images, together with Western food images selected from an existing database and had Japanese participants rate their affective (valence, arousal, liking and wanting) and cognitive (naturalness, recognizability and familiarity) appraisals and estimates of nutrition.

Results

The results showed that all affective and cognitive appraisals (except arousal) of the Japanese food images were higher than those of Western food. Correlational analyses found positive associations between the objective nutrition information and subjective estimates of the nutrition information, and between the objective calorie/fat content and affective appraisals.

Conclusions

These data suggest that by using our image database, researchers can investigate the visual processing of Japanese food and the relationships between objective nutrition information and the psychological/neural processing of food.