Effects of distraction on taste-related neural processing: a cross-sectional fMRI study

The impact of cognitive distraction on gustatory perception in volunteers with obesity

Obesity, a global health challenge, is influenced by biological, behavioral, socioeconomical, and environmental factors. In our technology-driven world, distracted eating is prevalent, yet neurocognitive mechanisms behind it remain poorly understood. This study targets individuals with overweight and obesity, exploring taste perception under distraction comprehensively. Participants formed two distinct groups based on their Body Mass Index (BMI), lean and overweight/obese. During the experiment participants received gustatory stimuli while playing a Tetris game of various difficulty levels. Participants rated taste intensity and pleasantness, with linear mixed models analyzing distraction effects. Results confirmed that high distraction levels reduced perception of taste intensity (p = 0.017) and taste pleasantness (p = 0.022), with variations influenced by gender and weight status. Individuals in the overweight/obese group exhibited most profound intensity changes during distraction (p = 0.01). Taste sensitivity ratings positively correlated with BMI interacting with gender (male r = 0.227, p < 0.001; female r = 0.101, p < 0.001). Overall across both groups, female participants demonstrated higher taste sensitivity compared to male participants (p < 0.001). This study highlights the impact of cognitive distraction during consumption on taste perception, particularly in relation to weight status and gender, underscoring their significant roles in this interplay.

Distraction suppresses high-fat flavor perception

Distraction during eating contributes to overeating, and when habitually eating with distraction, this may contribute to the development of obesity. One of the proposed mediating mechanisms is the suppression of intensity perception in odor and taste. The effect of distraction on fat intensity perception in flavor, the multisensory combination of odor, taste, and other sensory aspects, is still unknown. In this study, 32 participants (22 women) performed a flavor perception task while also performing a distracting working memory task. In each trial, participants were instructed to observe and memorize a string of 3 (low cognitive load) or 7 (high cognitive load) consonants. Then they received a small quantity of a high- or low-fat chocolate drink, and after that, they were asked to select the string they tried to memorize from three answer options. Last, they rated the intensity and fattiness of the flavor. As intended, in the working memory task, we observed that with a high cognitive load (relative to a low cognitive load), accuracy decreased and response times increased. Regarding perception of the flavors, we observed that overall, high-fat drinks were rated as more intense and fattier. Cognitive load and fat content interacted, such that for the low-fat drink, intensity and fattiness ratings were similar under both cognitive loads; however, under the high cognitive load (relative to the low cognitive load), intensity and fattiness ratings for the high-fat drink were lower. Our results show that distraction can impact the perception of fat in high-fat drinks. If distraction primarily reduces perception of high-fat foods, this may pose a particular risk of overeating high-calorie foods.

The effect of cognitive load on preference and intensity processing of sweet taste in the brain

Distracted eating can cause overconsumption. Whereas previous work has shown that cognitive load suppresses perceived taste intensity and increases subsequent consumption, the mechanism behind distraction-induced overconsumption remains unclear. To elucidate this, we performed two event-related fMRI experiments that examined how cognitive load affects neural responses and perceived intensity and preferred intensity, respectively, to solutions varying in sweetness. In Experiment 1 (N = 24), participants tasted weak sweet and strong sweet glucose solutions and rated their intensity while we concurrently varied cognitive load using a digit-span task. In Experiment 2 (N = 22), participants tasted five different glucose concentrations under varying cognitive load and then indicated whether they wanted to keep, decrease or increase its sweetness. Participants in Experiment 1 rated strong sweet solutions as less sweet under high compared to low cognitive load, which was accompanied by attenuated activation the right middle insula and bilateral DLPFC. Psychophysiological interaction analyses showed that cognitive load moreover altered connectivity between the middle insula and nucleus accumbens and DLPFC and middle insula while tasting strong sweet solutions. In Experiment 2, cognitive load did not affect participants' preferred sweetness intensity. fMRI results revealed that cognitive load attenuated DLPFC activation for the strongest sweet solutions in the study. In conclusion, our behavioral and neuroimaging results suggest that cognitive load dampens the sensory processing of strong sweet solutions in particular, which may indicate higher competition for attentional resources for strong sweet than weak sweet solutions under high cognitive load. Implications for future research are discussed.

Caregiver perceptions of snacks for young children: A thematic synthesis of qualitative research

Snacks are inconsistently defined in nutrition research and dietary guidelines for young children, challenging efforts to improve diet quality. Although some guidelines suggest that snacks include at least two food groups and fit into an overall health promoting dietary pattern, snacks high in added sugars and sodium are highly marketed and frequently consumed. Understanding how caregivers perceive "snacks" for young children may aid in development of effective nutrition communications and behaviourally-informed dietary interventions for obesity prevention. We aimed to synthesize caregivers' perceptions of snacks for young children across qualitative studies. Four databases were searched for peer-reviewed qualitative articles including caregiver perceptions of "snacks" for children ≤5 years. We conducted thematic synthesis of study findings, concluding with the development of analytical themes. Data synthesis of fifteen articles from ten studies, conducted in the U.S., Europe, and Australia, revealed six analytical themes that captured food type, hedonic value, purpose, location, portion size, and time. Caregivers perceived snacks as both "healthy" and "unhealthy" foods. Less healthy snacks were described as highly liked foods, which required restriction and were consumed outside the home. Caregivers used snacks to manage behavior and curb hunger. Snack portions were described as "small", although caregivers reported various methods to estimate child portion size. Caregivers' perceptions of snacks revealed opportunities for targeted nutrition messaging, especially supporting responsive feeding and nutrient-dense food choices. In high-income countries, expert recommendations should consider caregivers' perceptions of snacks, more clearly defining nutrient-dense snacks that are enjoyable, achieve dietary requirements, reduce hunger, and promote healthy weight.

Encouraging (Nudging) People to Increase Their Fluid Intake

This narrative historical review considers the various routes to nudging consumers towards drinking more, given self-reported evidence that many people are often not adequately hydrated. This review builds on the related notion of 'visual hunger'. Interestingly, however, while many desirable foods are associated with distinctive sensory qualities (such as an appetizing smell), that may capture the consumer's (visual) attention, it is less clear that there is an equivalent sensory attentional capture by hydration-related cues. One of the other important differences between satiety and thirst is that people tend to overconsume if they use interoceptive satiety cues to decide when to stop eating, while the evidence suggests that people typically stop drinking prior to being adequately hydrated. What is more, the increasing amount of time we spend in consistently warm indoor environments may also be exacerbating our need to drink more. A number of concrete suggestions are made concerning how people may be encouraged (or nudged) to imbibe sufficient water.

Sensory emotion regulation

Decades of evidence reveal intimate links between sensation and emotion. Yet, discussion of sensory experiences as tools that promote emotion regulation is largely absent from current theorizing on this topic. Here, we address this gap by integrating evidence from social-personality, clinical, cognitive-neuroscience, and animal research to highlight the role of sensation as a tool that can be harnessed to up- or downregulate emotion. Further, we review evidence implicating sensation as a rapid and relatively effortless emotion regulation modality and highlight future research directions. Notably, we emphasize the need to examine the duration of sensory emotion regulation effects, the moderating role of individual and cultural differences, and how sensory strategies interact with other strategies.

Room for Feelings: A “Working Memory” Account of Affective Processing

In the past decades, affective science has overwhelmingly demonstrated the unique properties of affective information to bias our attention, memory, and decisions. At the same time, accumulating evidence suggests that neutral and affective representations rely on the same working memory substrates for the selection and computation of information and that they are therefore restricted by the same capacity limitations that these substrates impose. Here, we integrate these insights into a working memory model of affective processing (WMAP). Drawing on competitive access models of working memory, we discuss its role in the various stages of affective processing, from attentional selection to maintenance and memory storage, and resulting feelings and actions. We end our overview with some open questions and future directions.

A true response of the brain network during electroacupuncture stimulation at scalp acupoints: An fMRI with simultaneous EAS study

OBJECTIVES

The aim of this study was to explore simultaneous brain network responses to electroacupuncture stimulation (EAS) at scalp acupoints by accounting for placebo effects.

MATERIALS AND METHODS

Sixty healthy subjects were recruited and randomly divided into two groups: Group 1 and Group 2. Functional magnetic resonance imaging (fMRI) was performed in Group 1 with sham acupuncture stimulation at acupoints Shenting (GV24) and Touwei (ST8) without EAS. Group 2 underwent verum EAS at the same acupoints during fMRI. Independent component analysis was used to analyze the fMRI data. Full-factor statistical analysis was used to compare the differences in fMRI data between the two groups and evaluate the changes in functional connectivity in brain networks after verum electrical stimulation (Group 1 [after sham electrical current stimulation - before sham electrical current stimulation] - Group 2 [after verum electrical current stimulation - before verum electrical current stimulation]) (p <.001, extent threshold k = 20 voxels).

RESULTS

Six brain networks were identified. Significant increased functional connectivity was observed in the right and left executive control networks, sensorimotor network, and attention network, while decreased functional connectivity was mainly found in the default mode network. There were no statistically significant differences in the salience network.

CONCLUSIONS

fMRI with simultaneous EAS provides a method to explore brain network responses due to EAS at scalp acupoints. The networks responsible for cognition are differentially activated by EAS in a coordinated manner.

Functional Connectivity of the Chemosenses: A Review

Functional connectivity approaches have long been used in cognitive neuroscience to establish pathways of communication between and among brain regions. However, the use of these analyses to better understand how the brain processes chemosensory information remains nascent. In this review, we conduct a literature search of all functional connectivity papers of olfaction, gustation, and chemesthesis, with 103 articles discovered in total. These publications largely use approaches of seed-based functional connectivity and psychophysiological interactions, as well as effective connectivity approaches such as Granger Causality, Dynamic Causal Modeling, and Structural Equation Modeling. Regardless of modality, studies largely focus on elucidating neural correlates of stimulus qualities such as identity, pleasantness, and intensity, with task-based paradigms most frequently implemented. We call for further "model free" or data-driven approaches in predictive modeling to craft brain-behavior relationships that are free from a priori hypotheses and not solely based on potentially irreproducible literature. Moreover, we note a relative dearth of resting-state literature, which could be used to better understand chemosensory networks with less influence from motion artifacts induced via gustatory or olfactory paradigms. Finally, we note a lack of genomics data, which could clarify individual and heritable differences in chemosensory perception.

Daily distracted consumption patterns and their relationship with BMI

The rapidly increasing prevalence of overweight and obesity has heightened the need for a better understanding of obesity-related eating patterns and dietary behaviours. Recent work suggests that distracted eating is causally related to increased immediate and later food, pushing the need for a better understanding of the prevalence of distracted consumption and how this relates to body weight. To extract insights in the relationship between demographics, daily consumption settings, and BMI, we performed secondary data analyses on data from 1011 individuals representative of the Dutch population (adults, 507F, BMI 17-50 kg/m²). The most commonly reported distractions were talking to others (32.7%) and watching television (21.7%). Only 18.4% of respondents reported no distractions during meals. To examine how different distractions related to BMI, we performed OLS regression which showed, among other things, that watching tv while eating lunch (η² = 0.37) and working during dinner were associated with a higher BMI (η² = 1.63). To examine the robustness of these findings, machine learning techniques were used. A random forest analysis (RMSE = 4.09) showed that next to age and education level, distraction during lunch and snack was amongst the largest predictors of BMI. Multiple linear regression with lasso penalty (RMSE = 4.13) showed that specifically watching tv while eating lunch or snacks was associated with a higher BMI. In conclusion, our analyses confirmed the assumption that people are regularly distracted during their daily meals, with distinct distractors relating to BMI. These findings provide a starting point for evidence-based recommendations on which consumption settings are associated with healthier eating patterns and body weight.

Ingested but not perceived: Response to satiety cues disrupted by perceptual load

Selective attention research has shown that when perceptual demand is high, unattended sensory information is filtered out at early stages of processing. We investigated for the first time whether the sensory and nutrient cues associated with becoming full (satiety) would be filtered out in a similar manner. One-hundred and twenty participants consumed either a low-satiety (75 kcal) or high-satiety (272 kcal plus thicker texture) beverage, delivered via an intra-oral infusion device while participants simultaneously completed a task which was either low or high in perceptual demand. Among participants who performed the low perceptual load task, ingestion of the high-satiety beverage increased rated satiety and reduced consumption at a subsequent snack test. However, both effects were eliminated by the high perceptual load task. Therefore, the processing of satiety cues was dependent on the availability of attention, identifying a novel perceptual load mechanism of inattentive eating and supporting more recent cognitive models of appetite control.

Distraction decreases rIFG-putamen connectivity during goal-directed effort for food rewards

Distracted eating can lead to increased food intake, but it is unclear how. We aimed to assess how distraction affects motivated, goal-directed responses for food reward after satiation. Thirty-eight healthy normal-weight participants (28F; 10M) performed a visual detection task varying in attentional load (high vs. low distraction) during fMRI. Simultaneously, they exerted effort for sweet and savory food rewards by repeated button presses. Two fMRI runs were separated by sensory-specific satiation (outcome devaluation) of one of the (sweet or savory) reward outcomes, to assess outcome-sensitive, goal-directed, responses (valued vs. devalued reward, post vs. pre satiation). We could not verify our primary hypothesis that more distraction leads to less activation in ventromedial prefrontal cortex (vmPFC) during goal-directed effort. Behaviorally, distraction also did not affect effort for food reward following satiation across subjects. For our secondary hypothesis, we assessed whether distraction affected other fronto-striatal regions during goal-directed effort. We did not obtain such effects at our whole-brain corrected threshold, but at an exploratory uncorrected threshold (p < 0.001), distraction decreased goal-directed responses (devalued vs. valued) in the right inferior frontal gyrus (rIFG). We continued with this rIFG region for the next secondary hypothesis; specifically, that distraction would reduce functional connectivity with the fronto-striatal regions found in the previous analyses. Indeed, distraction decreased functional connectivity between the rIFG and left putamen for valued versus devalued food rewards (pFWE(cluster) < 0.05). In an exploratory brain-behavior analysis, we showed that distraction-sensitive rIFG-responses correlated negatively (r = - 0.40; p = 0.014) with the effect of distraction on effort. Specifically, decreased distraction-related rIFG-responses were associated with increased effort for food reward after satiation. We discuss the absence of distraction effects on goal-directed responses in vmPFC and in behavior across participants. Moreover, based on our significant functional connectivity and brain-behavior results, we suggest that distraction might attenuate the ability to inhibit responses for food reward after satiation by affecting the rIFG and its connection to the putamen.