Hedonic Reactions Research Articles

The nature of training in flavor preference learning determines the underlying associative structure

Pairing a palatable flavor (US) with an initially neutral flavor cue (CS) results in an acquired conditioned preference for the latter. Two main associations have been proposed to explain the acquisition of flavor preferences: Flavor-Flavor and Flavor-Nutrient learning. Although the hedonic reaction triggered by US consumption has also been suggested as a possible additional component underlying acquired flavor preference, this issue has received little attention. Here we explored whether the amount of training to the CS-US compound can favor the formation of a Flavor-Hedonic reaction association using rats as subjects and sucrose as the US. We expected that the more exposure to the CS-US compound, the stronger the S-R type association. Since S-R associations are not sensitive to devaluation procedures, we used a Sensory-Specific Satiety procedure to devalue the US after conditioning and then measured preferences for the CS. On Experiment 1 with a short restrictive training (classic procedure), preference for the CS was decreased after devaluation of the US compared to the control condition. On Experiment 2, with short unrestrictive training, preference for the CS was again weakened. Experiment 3 with a long unrestrictive training, rats expressed preference for the CS regardless of the devaluation procedure. These results suggest that, as with an instrumental paradigm, extensive training in flavor preference learning undermines the US devaluation effect.

Global reward processing deficits predict negative symptoms transdiagnostically and transphasically in a severe mental illness-spectrum sample.

Reward processing impairments are a key factor associated with negative symptoms in those with severe mental illnesses. However, past findings are inconsistent regarding which reward processing components are impaired and most strongly linked to negative symptoms. The current study examined the hypothesis that these mixed findings may be the result of multiple reward processing pathways (i.e., equifinality) to negative symptoms that cut across diagnostic boundaries and phases of illness. Participants included healthy controls (n = 100) who served as a reference sample and a severe mental illness-spectrum sample (n = 92) that included psychotic-like experiences, clinical high-risk for psychosis, bipolar disorder, and schizophrenia participants. All participants completed tasks measuring four RDoC Positive Valence System constructs: value representation, reinforcement learning, effort-cost computation, and hedonic reactivity. A k-means cluster analysis of the severe mental illness-spectrum samples identified three clusters with differential reward processing profiles that were characterized by: (1) global reward processing deficits (22.8%), (2) selective impairments in hedonic reactivity alone (40.2%), and (3) preserved reward processing (37%). Elevated negative symptoms were only observed in the global reward processing cluster. All clusters contained participants from each clinical group, and the distribution of these groups did not significantly differ among the clusters. Findings identified one pathway contributing to negative symptoms that was transdiagnostic and transphasic. Future work further characterizing divergent pathways to negative symptoms may help to improve symptom trajectories and personalized treatments.

Distinct neurofunctional alterations during motivational and hedonic processing of natural and monetary rewards in depression - a neuroimaging meta-analysis.

Reward processing dysfunctions are considered a candidate mechanism underlying anhedonia and apathy in depression. Neuroimaging studies have documented that neurofunctional alterations in mesocorticolimbic circuits may neurally mediate these dysfunctions. However, common and distinct neurofunctional alterations during motivational and hedonic evaluation of monetary and natural rewards in depression have not been systematically examined. Here, we capitalized on pre-registered neuroimaging meta-analyses to (1) establish general reward-related neural alterations in depression, (2) determine common and distinct alterations during the receipt and anticipation of monetary v. natural rewards, and, (3) characterize the differences on the behavioral, network, and molecular level. The pre-registered meta-analysis (https://osf.io/ay3r9) included 633 depressed patients and 644 healthy controls and revealed generally decreased subgenual anterior cingulate cortex and striatal reactivity toward rewards in depression. Subsequent comparative analyses indicated that monetary rewards led to decreased hedonic reactivity in the right ventral caudate while natural rewards led to decreased reactivity in the bilateral putamen in depressed individuals. These regions exhibited distinguishable profiles on the behavioral, network, and molecular level. Further analyses demonstrated that the right thalamus and left putamen showed decreased activation during the anticipation of monetary reward. The present results indicate that distinguishable neurofunctional alterations may neurally mediate reward-processing alterations in depression, in particular, with respect to monetary and natural rewards. Given that natural rewards prevail in everyday life, our findings suggest that reward-type specific interventions are warranted and challenge the generalizability of experimental tasks employing monetary incentives to capture reward dysregulations in everyday life.

An evaluation of hedonic responses in taste-potentiated odor aversion using the analysis of licking microstructure and orofacial reactivity

Two experiments examined the hedonic responses conditioned to odor cues in the phenomenon of taste-potentiated odor aversion. Experiment 1 analyzed the microstructure of licking behavior during voluntary consumption. A tasteless odor (amyl acetate) was delivered to rats either diluted in water or mixed with saccharin before being injected with LiCl. At test, subjects which had received the odor-taste compound during conditioning showed both lower odor consumption and lick cluster size, a result indicating an increased negative evaluation of the odor. Experiment 2 examined the orofacial reactions elicited by the odor as index of its hedonic impact. During conditioning, the rats were intraorally infused with either the odor alone or the odor-saccharin compound before being injected with LiCl. At test, they were infused with the odor and their orofacial responses video recorded. More aversive orofacial responses were elicited by the odor cue in rats that had compound conditioning, again a result indicating a strengthened negative hedonic reactivity compared to animals experiencing odor aversion conditioning alone. Taken together, these results indicate that taste-mediated potentiation of odor aversion conditioning impacts on the acquisition of conditioned hedonic reactions as well as consumption.

Involvement of the Receptor for Advanced Glycation End Products (RAGE) in high fat-high sugar diet-induced anhedonia in rats

Clinical and basic science investigation indicates a link between insulin resistance and anhedonia. Previous results of this laboratory point to impaired nucleus accumbens (NAc) insulin signaling as an underpinning of diet-induced anhedonia, based on use of a glucose lick microstructure assay. The present study evaluated whether advanced glycation end products (AGEs) and their receptor (RAGE), known to mediate obesogenic diet-induced inflammation and pathological metabolic conditions, are involved in this behavioral change. Six weeks maintenance of male and female rats on a high fat-high sugar liquid diet (chocolate Ensure) increased body weight gain, and markedly increased circulating insulin and leptin, but induced anhedonia (decreased first minute lick rate and lick burst size) in males only. In these subjects, anhedonia correlated with plasma concentrations of insulin. Although the diet did not alter plasma or NAc AGEs, or the expression of RAGE in the NAc, marginally significant correlations were seen between anhedonia and plasma content of several AGEs and NAc RAGE. Importantly, a small molecule RAGE antagonist, RAGE229, administered twice daily by oral gavage, prevented diet-induced anhedonia. This beneficial effect was associated with improved adipose function, reflected in the adiponectin/leptin ratio, and increased pCREB/total CREB in the NAc, and a shift in the pCREB correlation with pThr34-DARPP-32 from near-zero to strongly positive, such that both phospho-proteins correlated with the rescued hedonic response. This set of findings suggests that the receptor/signaling pathway and cell type underlying the RAGE229-mediated increase in pCREB may mediate anhedonia and its prevention. The possible role of adipose tissue as a locus of diet-induced RAGE signaling, and source of circulating factors that target NAc to modify hedonic reactivity are discussed.

The role of opioid transmission in music-induced pleasure.

Studies conducted in rodents indicate a crucial role of the opioid circuit in mediating objective hedonic reactions to primary rewards. However, it remains unclear whether opioid transmission is also essential to experience pleasure with more abstract rewards, such as music. We addressed this question using a double-blind within-subject pharmacological design in which opioid levels were up- and downregulated by administering an opioid agonist (oxycodone) and antagonist (naltrexone), respectively, before healthy participants (n = 21) listened to music. Participants also performed a monetary incentive delay (MID) task to control for the effectiveness of the treatment and the specificity of the effects. Our results revealed that the pharmacological intervention did not modulate subjective reports of pleasure, nor the occurrence of chills. On the contrary, psychophysiological (objective) measures of emotional arousal, such as skin conductance responses (SCRs), were bidirectionally modulated in both the music and MID tasks. This modulation specifically occurred during reward consumption, with greater pleasure-related SCR following oxycodone than naltrexone. These findings indicate that opioid transmission does not modulate subjective evaluations but rather affects objective reward-related psychophysiological responses. These findings raise new caveats about the role of the opioidergic system in the modulation of pleasure for more abstract or cognitive forms of rewarding experiences, such as music.

Perceptual learning after rapidly alternating exposure to taste compounds: Assessment with different indices of generalization.

Exposure to two similar stimuli (AX and BX; e.g., two tastes) reduces the extent to which a conditioned response later established to BX generalizes to AX. This example of perceptual learning is more evident when AX and BX are exposed in an alternating manner (AX, BX, AX, BX,…) than when AX and BX occur in separate blocks (e.g., AX, AX,…BX, BX,…). We examined in male rats (N = 126) the impact of rapid alternation to AX and BX on generalization of a taste aversion from BX to AX. Experiment 1 showed that such alternating presentations (with 5-min intervals between AX and BX) reduced generalization relative to blocked exposure; but only as assessed by consumption levels and not by lick cluster size (an index of hedonic reactions). Experiment 1 also showed that the nature of exposure did not affect how A influenced performance to a novel conditioned taste, Y. Experiment 2 replicated the pattern of results involving the different influences of rapidly alternating and blocked exposure on generalization from BX to AX, and showed that this effect was only evident when rats received access to water during the 5-min intervals between AX and BX. These results reinforce parallels between perceptual learning effects in rats and humans, both at empirical and theoretical levels. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Differential Contributions of Ventral Striatum Subregions to the Motivational and Hedonic Components of the Affective Processing of Reward.

The ventral striatum is implicated in the affective processing of reward, which can be divided into a motivational and a hedonic component. Here, we examined whether these two components rely on distinct neural substrates within the ventral striatum in humans (11 females and 13 males). We used a high-resolution fMRI protocol targeting the ventral striatum combined with a pavlovian-instrumental task and a hedonic reactivity task. Both tasks involved an olfactory reward, thereby allowing us to measure pavlovian-triggered motivation and sensory pleasure for the same reward within the same participants. Our findings show that different subregions of the ventral striatum are dissociable in their contributions to the motivational versus the hedonic component of the affective processing of reward. Parsing the neural mechanisms of the interplay between pavlovian incentive and hedonic processes may have important implications for understanding compulsive reward-seeking behaviors such as addiction, binge eating, or gambling.

Opioid-blunted cortisol response to stress is associated with increased negative mood and wanting of social reward

Animal research suggests a central role of the μ-opioid receptor (MOR) system in regulating affiliative behaviors and in mediating the stress-buffering function of social contact. However, the neurochemistry of stress-related social contact seeking in humans is still poorly understood. In a randomized, double-blind, between-subjects design, healthy female volunteers (N = 80) received either 10 mg of the µ-opioid agonist morphine sulfate, or a placebo. Following a standardized psychosocial stress induction, participants engaged in a social reward task, in which the motivation to obtain skin-to-skin social touch and the hedonic reactions elicited by such touch were assessed. Morphine prevented the increase of salivary cortisol typically observed following acute stress exposure. Notably, this altered HPA axis responsivity was associated with increased negative affect in response to psychosocial stress, and with enhanced subjective wanting of highly rewarding social contact. These findings provide novel evidence on the effect of exogenous opioids administration on the reactions to psychosocial stress and point to a state-dependent regulation of social motivation.

Behavioural and molecular characterisation of the Dlg2 haploinsufficiency rat model of genetic risk for psychiatric disorder.

Genetic studies implicate disruption to the DLG2 gene in copy number variants as increasing risk for schizophrenia, autism spectrum disorders and intellectual disability. To investigate psychiatric endophenotypes associated with DLG2 haploinsufficiency (and concomitant PSD‐93 protein reduction) a novel clinically relevant Dlg2 +/− rat was assessed for abnormalities in anxiety, sensorimotor gating, hedonic reactions, social behaviour, and locomotor response to the N‐Methyl‐D‐aspartic acid receptor antagonist phencyclidine. Dlg gene and protein expression were also investigated to assess model validity. Reductions in PSD‐93 messenger RNA and protein were observed in the absence of compensation by other related genes or proteins. Behaviourally Dlg2 +/− rats show a potentiated locomotor response to phencyclidine, as is typical of psychotic disorder models, in the absence of deficits in the other behavioural phenotypes assessed here. This shows that the behavioural effects of Dlg2 haploinsufficiency may specifically relate to psychosis vulnerability but are subtle, and partially dissimilar to behavioural deficits previously reported in Dlg2 +/− mouse models demonstrating issues surrounding the comparison of models with different aetiology and species. Intact performance on many of the behavioural domains assessed here, such as anxiety and reward processing, will remove these as confounds when continuing investigation into this model using more complex cognitive tasks.

Characterizing Hedonic Responses to Flavors Paired with Internal Pain and Nausea through the Taste Reactivity Test in Rats.

Feeding behavior is a complex experience that involves not only sensory (i.e., visual, odor, taste, or texture) but also affective or emotional aspects (i.e., pleasure, palatability, or hedonic value) of foods. As such, behavioral tests that assess the hedonic impact of foods are necessary to fully understand the factors involved in ingestive behavior. In this protocol, we use the taste reactivity (TR) test to characterize the hedonic responses of rats to flavors paired with either lithium chloride-induced nausea or internal pain produced by hypertonic NaCl, two treatments that reduce voluntary consumption. This application of the TR test demonstrates how emetic and non-emetic (somatic pain in particular) treatments produce dissociable patterns of hedonic reactions to fluids: only emetic treatments result in the production of aversive orofacial responses, reflecting conditioned nausea, whereas somatic pain produces immobility, reflecting conditioned fear. Other methods, such as the microstructural analysis of licking behavior, do not reliably distinguish conditioned nausea and fear, a key advantage of the more selective TR procedure. This protocol also contains guidance for adaptation to other species and designs.

Consumer Acceptability and Sensory Profile of Three New Celery (Apium graveolens) Hybrids and Their Parental Genotypes

Celery is a stalky green vegetable that is grown and consumed globally and used in many cuisines for its distinctive taste and flavour. Previous investigations identified the aroma composition of celery and profiled its sensory characteristics using a trained panel; however, evaluation of the sensory characteristics of celery combined with a consumer panel, where consumer preferences and acceptability are determined, is novel. In this study, three parental genotypes (12, 22 and 25) and three new hybrids (12x22, 22x12 and 25x12) were presented to a trained sensory panel (n = 12) for profiling and a consumer panel (n = 118), where liking and preference were assessed. Celery samples were analysed by SPME GC–MS and significant differences in aroma composition between all samples were identified, causing significant differences in the sensory profile. Furthermore, significant differences in attributes assessed for liking (appearance, aroma, texture and overall) were identified. Consumer segmentation identified three groups of consumers exhibiting differences in the hedonic reaction to the samples. Sweet and bitter taste along with overall flavour were identified as drivers of liking. Hybrid 25x12 was found to be the hybrid that exhibited high intensities for most of the attributes assessed.

Unraveling factors affecting consumers' liking of novel Uruguayan mandarins

Mandarin cultivars show a great diversity on fruit-quality and sensory characteristics, together with an extended harvest season. Citrus breeding is focused on exploiting season niches for higher prices as well as nutritional and sensory aspects, among others. In this context, the sensory characterization of new hybrids and the identification of key characteristics of consumers´ liking provide valuable information towards breeding efforts and marketing strategies. Previous works showed that sensory characteristics, and specially flavor, play a key role in consumer acceptance of mandarins. Two studies were carried out during mandarin harvest season (mid and late) applying “check all that apply” (CATA) questions with at least 100 consumers. Overall liking scores of the most liked hybrids and cultivars ranged between 6.5 to 7.7 in the 9-point hedonic scale, evidencing a positive hedonic reaction. Local hybrids showed similar or higher values than the reference cultivars Tango, Gold Nugget, Murcott and Ortanique. Results showed that orange color, regular shape, smoothness, sweetness, juiciness, intense and typical flavor are the key drivers of consumer's liking of mandarins, and that external appearance is not a good predictor of mandarin tasting experience. Hybrids F3P8, F5P8 and F2P3 were described using terms related to positive sensory characteristics and received liking scores similar or higher to reference cultivars such as Tango, stressing the importance of sensory and consumer science as an integral part of breeding strategies.

The impact of problematic Facebook use and Facebook context on empathy for pain processing: An event-related potential study

Deficits in the individuals’ functioning manifesting as a specific Internet addiction may be revealed during contact with the cue associated with addiction. In this context, frequent Facebook users presented spontaneous hedonic reactions following Facebook stimuli compared to less frequent Facebook users. Additionally, a tool like Facebook, created for social connection, may be reducing connective capacities (“media-empathy paradox”). In our study, we wanted to examine the relation between nonproblematic and problematic Facebook use as well as the influence of a cue associated with Facebook on empathy. We used the most common stimuli that were presented in the empathy paradigm (painful and nonpainful stimuli) with Facebook and neutral context. We found that painful stimuli elicited greater neural responses than nonpainful stimuli at a time point of 220 ms (N2) over frontocentral brain regions. Also, we registered the interaction between context and painful stimulation. The difference in N2 amplitude was shown between painful and nonpainful pictures, but only for the neutral context. There were no differences in the Facebook context. At the later stage of 300–400 ms (P3) over centroparietal regions, painful stimuli elicited significantly greater neural responses than nonpainful stimuli. The present study extends the findings of previous research about specific Internet addiction.

Consumer Acceptability and Sensory Profile of Sustainable Paper-Based Packaging.

Sustainability appears to be increasingly important to consumers. In order for companies to reach their sustainability targets and offer more environmentally friendly solutions to consumers, food producers and retailers have begun to change their packaging to more recyclable, bio-based and biodegradable packaging. This study evaluated the sensory characteristics of paper-based prototype packages developed for two product categories (biscuit and meat packages) using a trained sensory panel. Consumer liking, preference and purchase intent were assessed by 130 participants. For the biscuit packages, no significant differences were observed for the liking of any of the four dimensions assessed (appearance, design, feel or overall liking). However, consumer segmentation identified three relatively homogeneous groups of consumers exhibiting differences in the hedonic reaction to the three packages. For the meat packages, significant differences and preference were observed between the original and paper-based packages. For both categories, the purchase intent was low, indicating that further work needed to be done to improve several quality characteristics (e.g., design, size and strength of the package), which would lead to better consumer acceptability.

Influence of wine traits and context on liking, intention to consume, wine-evoked emotions and perceived sensory sensations

Wine consumption is a sensory experience that can evoke a wide range of emotional responses and heterogeneous hedonic reactions, that also depend on the circumstances in which the product is consumed. The recent literature has extensively addressed emotions elicited by wine consumption; however little research has been done on the effect of the context of consumption. This study focuses on how testing contexts and Chianti wine traits impact on liking, desire to consume again, wine-evoked emotions and perceived flavour, by comparing measurements recorded in a standard sensory laboratory (CLT), in an evoked consumption situation (images and self-description of their own habitual context of consumption) (CLT-evoked) and in a home use test in natural testing conditions (HUT), on commercial Chianti wine samples by regular consumers of red wine.The results of this study show that liking and intention to consume did not vary significantly among the test settings. This finding would suggest that the testing conditions have low relevance compared to the wine samples. However, the context influenced emotion and sensory terms. In the home use test a lowering of scores was found, both for positive and negative emotions and for sensory terms. In the HUT context a longer time for testing resulted in a better product separation.Pleasure of Chianti wine was associated with the emotions: pleasant, peaceable, joyful, amusing, and best correlated with the sensory attribute sweet. Unpleasantness was associated to the emotions: aggressive, disgusting, and overwhelming, and with the sensory terms acid, dry, astringent. Level of arousal was positively associated with euphoric, passionate, and keen, and well correlated with spicy and persistent as sensory characteristics.

Ventral arkypallidal neurons inhibit accumbal firing to promote reward consumption.

The shell of the nucleus accumbens (NAcSh) and ventral pallidum (VP) are critical for reward processing, although how coordinated activity within these nuclei orchestrates reward valuation and consumption remains unclear. Inhibition of NAcSh firing is necessary for reward consumption, but the source of this inhibition remains unknown. Here, we report that a subpopulation of VP neurons, the ventral arkypallidal (vArky) neurons, project back to the NAcSh, where they inhibit NAcSh neurons in vivo in mice. Consistent with this pathway driving reward consumption via inhibition of the NAcSh, calcium activity of vArky neurons scaled with reward palatability and predicted the subsequent drinking behavior during a free-access paradigm, which was dissociable from reward seeking. Activation of the VP to NAchSh pathway increased on-going reward consumption while amplifying hedonic reactions to reward. Our results establish a pivotal role of vArky neurons in promoting reward consumption, through modulating NAcSh firing in a value-dependent manner.

Healthy snacking in the school environment: Exploring children and mothers' perspective using projective techniques

Snacks consumed at school are an important source of energy and nutrients in children's diets. Understanding the factors that underlie children and mothers' choices of school snacks can contribute to the development of strategies to promote healthier eating patterns. In this context, the aims of the present work were: i) to explore children's conceptualization of school snacking, and ii) to identify children and mothers' perceived barriers and facilitators to healthy snacking in the school environment. Two studies with 518 children and 1183 mothers were carried out. In Study 1, children (n = 255) were asked to draw a child eating a snack at school. In Study 2, five incomplete dialogues about school snacks were presented to participants (263 children and 1183 mothers), who had to complete them using their own words. Data were analyzed using content analysis. The drawings showed that school snacking frequently occurs during the recess while children do other activities, such as playing football or other games. Fruit, sandwiches, cookies and juices were the foods and beverages most frequently included in the drawings. Responses to the dialogues enabled the identification of barriers to healthy snacking in the school environment, which were related to children's positive hedonic reaction towards unhealthy foods, the sales of unhealthy products in the school canteen, lack of time to prepare home-made snacks and mothers' perception that children can eat unhealthy snacks once in a while. In addition, the existence of a school snacking policy was mentioned as a facilitator for healthy snacking. Potential additional actions to promote healthy snacking habits in the school environment were identified.

Significant sugar-reduction in dairy products targeted at children is possible without affecting hedonic perception

The objective of the present study was to evaluate children's hedonic sensitivity to sugar reduction in three dairy products: vanilla milk desserts, chocolate-flavoured milk, and vanilla yoghurt. For each product, a regular sample and five samples with different reduction in added-sugar content were formulated. The regular sample contained the sugar content of commercial products available in the marketplace. The reduction in added-sugar content ranged between 10.0 and 41.0%. A total of 126 children (8–13 years old) participated in the study. An A-not A test was used to evaluate children's hedonic sensitivity to sugar reduction. Sugar reductions up to 27% in chocolate flavoured milk and vanilla yoghurt, and up to 19% in vanilla milk desserts, did not cause significant changes in children's hedonic reaction. These results confirm that sugar-reduction strategies can be easily implemented in the dairy industry without significant risk of affecting sample appreciation and market share.

The role of sex and femininity in preferences for unfamiliar infants among Chinese adults.

Guided by parental investment theory and social role theory, this study aimed to understand current contradictory results regarding sex differences in response to infant faces by considering the effect of gender role orientation. We recruited 300 adults in China and asked them to complete an Interest in Infants questionnaire and a Bem Sex Role Inventory and then administered a behavioral assessment that used unfamiliar infant faces with varying expressions (laughing, neutral, and crying) as stimuli to gauge three components of motivation towards infants (i.e., liking, representational responding, and evoked responding). The results demonstrated that sex differences emerged only in self-reported interest in infants, but no difference was found between the sexes in terms of their hedonic reactions to infant faces. Furthermore, femininity was found to correlate with preferences for infants in both verbal and visual tests, but significant interactive effects of feminine traits and sex were found only in the behavioral test. The findings indicated that men's responses to infants were influenced more by their feminine traits than were women's responses, potentially explaining the greater extent to which paternal (vs. maternal) investment is facultative.