A neural signature of food semantics is associated with body-mass index

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.

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.

Longitudinal geo-referenced field evidence for the heightened BMI responsiveness of obese women to price discounts on carbonated soft drinks

There is increasing interest in the effect that food environments may have on obesity, particularly through mechanisms related to the marketing and consumption of calorie-dense, nutrient-poor foods and sugary beverages. Price promotions, such as temporary price discounts, have been particularly effective in the marketing of carbonated soft drinks (CSDs) among consumers. Research has also suggested that the purchasing behavior of consumer groups may be differentially sensitive to price discounts on CSDs, with obese women particularly sensitive. In addition, the intensity of price discount in a person's food environment may also vary across geography and over time. This study examines whether the weight change of obese women, compared to overweight or normal BMI women, is more sensitive to the intensity of price discounts on CSDs in the food environment. This study used longitudinal survey data from 1622 women in the Montreal Neighborhood Networks and Health Aging (MoNNET-HA) Panel. Women were asked to report their height and weight in 2008, 2010 and 2013 in order to calculate women's BMI in 2008 and their change of weight between 2008 and 2013. Women's exposure to an unhealthy food environment was based on the frequency in which their neighborhood food stores placed price discounts on CSDs in 2008. The price discount frequency on CSDs within women's neighborhoods was calculated from Nielsen point-of sales transaction data in 2008 and geocoded to participant's forward sortation area. The prevalence of obesity and overweight among MoNNET-HA female participants was 18.3% in 2008, 19.9% in 2010 and 20.7% in 2013 respectively. Results showed that among obese women, exposure to unhealthy food environments was associated with a 3.25 kilogram (SE = 1.35, p-value = 0.02) weight gain over the five-year study period. Exposure to price discounts on CSDs may disproportionately affect and reinforce weight gain in women who are already obese.

How to do Better N400 Studies: Reproducibility, Consistency and Adherence to Research Standards in the Existing Literature

Given the complexity of ERP recording and processing pipeline, the resulting variability of methodological options, and the potential for these decisions to influence study outcomes, it is important to understand how ERP studies are conducted in practice and to what extent researchers are transparent about their data collection and analysis procedures. The review gives an overview of methodology reporting in a sample of 132 ERP papers, published between January 1980 – June 2018 in journals included in two large databases: Web of Science and PubMed. Because ERP methodology partly depends on the study design, we focused on a well-established component (the N400) in the most commonly assessed population (healthy neurotypical adults), in one of its most common modalities (visual images). The review provides insights into 73 properties of study design, data pre-processing, measurement, statistics, visualization of results, and references to supplemental information across studies within the same subfield. For each of the examined methodological decisions, the degree of consistency, clarity of reporting and deviations from the guidelines for best practice were examined. Overall, the results show that each study had a unique approach to ERP data recording, processing and analysis, and that at least some details were missing from all papers. In the review, we highlight the most common reporting omissions and deviations from established recommendations, as well as areas in which there was the least consistency. Additionally, we provide guidance for a priori selection of the N400 measurement window and electrode locations based on the results of previous studies.

Investigating salience strategies to counteract obesity

The investigation of the characteristics and attributes that make a brand prominent for shoppers is known as salience research. This line of study concentrates on influencing buying behaviors via the manipulation of shopping environments and food products. Such promotional strategies successfully attract massive food sales and therefore have been associated with changes in dietary patterns and the epidemic expansion of non-communicable diseases, like obesity. Marketers have empirically proven that global buying patterns are influenced by their salience strategies and techniques. However, despite the significance of such methods, empirical salience investigations have rarely been extended beyond their primary business focus to the field of health promotion. Therefore, this study is presenting a way of transferring the salience knowledge to the health promotion field in order to track dietary choices and possibly gain information to identify buying and eating behaviors connected to obesity. The salience literature from various disciplines permits to hypothesize that consumers are more likely to have unhealthy diets when food-choices and conditions are saliently manipulated. A quasi-experimental method (combining salience measures with Bayesian analysis) was used to test this proposition. The results support the hypothesis and endorse the introduced research tool. As predicted, data reflect the latest national overweight and obesity statistics and suggest that habitual unhealthy diets are more likely when salience strategies link food products to taste, social and emotional attributes. These preliminary findings encourage further investigation to enhance the method as a possible epidemiological tool.

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.

Distinct brain representations of processed and unprocessed foods

Among all of the stimuli surrounding us, food is arguably the most rewarding for the essential role it plays in our survival. In previous visual recognition research, it has already been demonstrated that the brain not only differentiates edible stimuli from non-edible stimuli but also is endowed with the ability to detect foods' idiosyncratic properties such as energy content. Given the contribution of the cooked diet to human evolution, in the present study we investigated whether the brain is sensitive to the level of processing food underwent, based solely on its visual appearance. We thus recorded visual evoked potentials (VEPs) from normal-weight healthy volunteers who viewed color images of unprocessed and processed foods equated in caloric content. Results showed that VEPs and underlying neural sources differed as early as 130 ms post-image onset when participants viewed unprocessed versus processed foods, suggesting a within-category early discrimination of food stimuli. Responses to unprocessed foods engaged the inferior frontal and temporal regions and the premotor cortices. In contrast, viewing processed foods led to the recruitment of occipito-temporal cortices bilaterally, consistently with other motivationally relevant stimuli. This is the first evidence of diverging brain responses to food as a function of the transformation undergone during its preparation that provides insights on the spatiotemporal dynamics of food recognition.

Food knowledge depends upon the integrity of both sensory and functional properties: a VBM, TBSS and DTI tractography study

Food constitutes a fuel of life for human beings. It is therefore of chief importance that their recognition system readily identifies the most relevant properties of food by drawing on semantic memory. One of the most relevant properties to be considered is the level of processing impressed by humans on food. We hypothesized that recognition of raw food capitalizes on sensory properties and that of transformed food on functional properties, consistently with the hypothesis of a sensory-functional organization of semantic knowledge. To test this hypothesis, patients with Alzheimer’s disease, frontotemporal dementia, primary progressive aphasia, and healthy controls performed lexical-semantic tasks with food (raw and transformed) and non-food (living and nonliving) stimuli. Correlations between task performance and local grey matter concentration (VBM) and white matter fractional anisotropy (TBSS) led to two main findings. First, recognition of raw food and living things implicated occipital cortices, typically involved in processing sensory information and, second, recognition of processed food and nonliving things implicated the middle temporal gyrus and surrounding white matter tracts, regions that have been associated with functional properties. In conclusion, the present study confirms and extends the hypothesis of a sensory and a functional organization of semantic knowledge.

A hierarchical-drift diffusion model of the roles of hunger, caloric density and valence in food selection

Decisions based on affectively relevant stimuli, such as food items, hardly follow strictly rational rules. Being hungry, the food's caloric density, and the subjective valence attributed to various foods are known factors that modulate food choices. Yet, how these factors relatively and altogether contribute to the food choice process is still unknown. In this study, we showed 16 healthy young adults low- and high-calorie food when hungry or fed, and we asked them to evaluate the valence of each visually-presented food. To compute the relative influence of hunger, caloric density and valence on food choice, we applied a hierarchical drift diffusion model (HDDM). Results indicated that hunger, caloric density and valence affected how fast participants accumulated information in favor of the chosen item over the other. When fed, participants were faster in choosing low-calorie foods and foods with a higher valence. Conversely, when hungry, participants were faster in choosing high-calorie foods, including food items with lower subjective valence. All in all, these findings confirm the complex nature of food choices and the usefulness of nuanced computational models to address the multifaceted nature of decision-making and value assessment processes affecting food selection.

Neural correlates of the energetic value of food during visual processing and response inhibition

Previous research showed that human brain regions involved in reward and cognitive control are responsive to visually presented food stimuli, in particular high-energy foods. However, it is still to be determined whether the preference towards high-energy foods depends on their higher energy density (kcal/gram), or is based on the difference in energy content of the food items (total amount of kcal). Here we report the results of an fMRI study in which normal-weight healthy participants processed food images during a one-back task or were required to inhibit their response towards food stimuli during a Go/No-Go task. High-energy density (HD) and low-energy density (LD) foods were matched for energy content displayed. Food-related kitchen objects (OBJ) were used as control stimuli. The lateral occipital complex and the orbitofrontal cortex showed consistent higher activity in response to HD than LD foods, both during visual processing and response inhibition. This result suggests that images of HD foods, even when the amount of food shown is not associated with a higher energy content, elicit preferential visual processing - possibly involving attentional processes - and trigger a response from the reward system. We conclude that the human brain is able to distinguish food energy densities of food items during both active visual processing and response inhibition.

Episodic memory for natural and transformed food

It has been proposed that the conceptual knowledge of food and its putative subdivision into natural (i.e., fruit/vegetables) and transformed (i.e., food that underwent thermic or non-thermic processing) may follow the living/non-living distinction. In the present study, we investigated whether the advantage for living things compared to non-living things observed in episodic memory (the so-called animacy effect) extends to natural foods and transformed foods respectively. We pursued this issue in two experiments. In Experiment 1, we measured episodic memory for natural and transformed foods in young participants. In Experiment 2, we enrolled dementia-free centenarians, patients with Alzheimer's disease (DAT), Progressive primary aphasia (PPA), and healthy controls whose episodic memory was also tested for living/non-living things. Results showed that young participants had better recognition memory for transformed foods compared to natural foods. This difference disappeared in centenarians and patients. However, centenarians and PPA exhibited enhanced levels of false alarms (FA) with natural food, and DAT patients with both natural and transformed food. As far as the living/non-living distinction is concerned, the episodic memory for the living category appears more resilient to the decline compared to the non-living category in patients, particularly those with PPA. In conclusion, our study shows that transformed food is better remembered than natural food, suggesting that it is more salient and possibly relevant from an evolutionary perspective. The natural/transformed distinction appears susceptible to erosion only in the presence of a high degree of episodic memory impairment. These results offer novel insight on episodic memory of food, and also extend the current knowledge on the animacy effect in episodic memory.

How experience modulates semantic memory for food: evidence from elderly adults and centenarians

In order to make sense of the objects we encounter in everyday life we largely rely on previous knowledge stored in our semantic memory. Semantic memory is considered dependent on lifelong experience and cultural knowledge. So far, a few studies have investigated the role of expertise on the organization of semantic memory, whereas life-long experience has largely been overlooked. In this study, we investigated this issue using food concepts. In particular, we administered different semantic tasks using food (natural and transformed) and non-food (living and non-living things) as stimuli to participants belonging to three different age cohorts (56–74, 75–91, 100–108), who were also asked to report on the dietary habits held throughout their life. In addition, we investigated to what extent psycholinguistic variables influence the semantic performance of different age cohorts. Results showed that Centenarians recognized natural food better than transformed food, while the other two groups showed the opposite pattern. According to our analyses, experience is responsible for this effect in Centenarians, as their dietary habits seem to suggest. Moreover, significant correlations between picture naming and age of acquisition, familiarity and frequency were observed. This study indicates that lifelong experience can shape conceptual knowledge of food concepts, and that semantic memory is less resilient to aging than initially thought.

Body weight and its association with impulsivity in middle and old age individuals

Impulsivity, conceptualized as impulsive personality trait, poor inhibitory control and enhanced reward sensitivity, has been strongly linked to obesity. In particular, a disequilibrium between cognitive control and reward sensitivity has been observed in obese individuals in both behavioural and imaging studies. While this issue has been widely investigated in children and adults, it has received little attention in older adults. Here, obese and non-obese participants aged between 40 and 70 years completed the Barratt Impulsiveness scale (assessing motor, non-planning and attentional impulsiveness), a Go/no-go task with foods and non-foods (assessing inhibitory control) and a reward sensitivity battery with high and low caloric foods (assessing liking, wanting, tastiness and frequency of consumption). We observed that participants with higher BMI reported increased wanting for high calorie foods, but did not show poorer inhibitory control. Interestingly, participants who scored lower on the MMSE reported to consume high calorie more than low calorie foods. Finally, those who presented low scores on non-planning and motor impulsiveness subscales reported higher tastiness ratings for low calorie foods. These results show that increased reward sensitivity but not reduced inhibitory control may characterize higher BMI during aging. Importantly, they also highlight new findings concerning food preferences among older adults.