Hedonic Responses Research Articles

What the eyes reveal about (reading) poetry

This study investigated how rhyme and meter affect eye movements and subjective aesthetic evaluations while reading poems. Earlier findings suggest that the effects might include prosodic predictability-driven cognitive and affective rewards from increased processing fluency (Blohm, Wagner, Schlesewsky and Menninghaus, 2018, McGlone and Tofighbakhsh, 2000), but also semantic and syntactic disfluency, as rhyme and meter are often implemented at the expense of unusual word forms and word order (Menninghaus et al., 2015, Wallot and Menninghaus, 2018). This study set out to investigate the extent to which eye movements might reveal not only distinct effects of fluency and disfluency at the same time, but potentially also hedonic responses that are associated with longer rather than shorter self-motivated exposure, in line with the hypothesis of “savoring” (Frijda and Sundararajan, 2007). The results reveal several fluency-enhancing effects of rhyme and meter on reading times for more global features of the poems, but also increased disfluency effects on gaze durations for some more local features of the poems. Moreover, some of the latter effects are readily interpretable in terms of the savoring hypothesis. Eye movement characteristics that were predictive of higher aesthetic evaluation—irrespective of the presence or absence of rhyme and meter—similarly resulted in increased fluency, disfluency, and savoring effects. Our study thus reveals, for the first time, a complex picture of effects that co-occur while reading poetic prosody, based on analyzing different dimensions of a single psychophysiological variable, namely, eye movements.

Physicochemical characterization of sous vide cooked squid (Loligo forbesii and Loligo vulgaris) and the relationship to selected sensory properties and hedonic response

The present study aims at promoting the use of squid in Scandinavia, a currently unexploited, and possible sustainable source of protein, available in the local waters. By a gastrophysical approach, the effects of sous vide cooking time and temperature on the mantle of squid (Loligo forbesii and Loligo vulgaris) were quantitatively assessed to obtain good eating quality, evaluated by Danish consumers (n = 141) coupled to physicochemical characterisation by texture analysis (TA) using the Warner-Bratzler shear blade and by differential scanning calorimetry (DSC). Consumers rated the squid samples well above neutral for the most liked samples, indicating a possible market for squid among Danish consumers. A positive hedonic rating of squid was found to be independent of gender and familiarity with eating squid, but some dependence of age was identified where the “younger” half of the consumers (<50 years) rated the squid higher in hedonic response with regards to taste. According to Danish consumers, squid mantle meat should be cooked long enough for it to be tender, but not too long, resulting in an extensive softness and compromised taste. A desirable texture and taste were obtained at the expense of cooking loss, which increased with extended cooking, which may negatively impact juiciness. However, it was found that cooking at lower temperatures (46–55 °C) significantly decreased cooking loss, while in some cases, possessed similar physicochemical textural attributes (55 °C) as squid cooked at a higher temperature of 77 °C. Indicatively, a sous vide cooking temperature of 55 °C seems to be an acceptable compromise to obtain both a pleasant texture and sufficient juiciness.

Gut microbes participate in food preference alterations during obesity

ABSTRACT Hypothalamic regulations of food intake are altered during obesity. The dopaminergic mesocorticolimbic system, responsible for the hedonic response to food intake, is also affected. Gut microbes are other key players involved in obesity. Therefore, we investigated whether the gut microbiota plays a causal role in hedonic food intake alterations contributing to obesity. We transferred fecal material from lean or diet-induced obese mice into recipient mice and evaluated the hedonic food intake using a food preference test comparing the intake of control and palatable diets (HFHS, High-Fat High-Sucrose) in donor and recipient mice. Obese mice ate 58% less HFHS during the food preference test (p < 0.0001) than the lean donors, suggesting a dysregulation of the hedonic food intake during obesity. Strikingly, the reduction of the pleasure induced by eating during obesity was transferable through gut microbiota transplantation since obese gut microbiota recipient mice exhibited similar reduction in HFHS intake during the food preference test (40% reduction as compared to lean gut microbiota recipient mice, p < 0.01). This effect was associated with a consistent trend in modifications of dopaminergic markers expression in the striatum. We also pinpointed a highly positive correlation between HFHS intake and Parabacteroides (p < 0.0001), which could represent a potential actor involved in hedonic feeding probably through the gut-to-brain axis. We further demonstrated the key roles played by gut microbes in this paradigm since depletion of gut microbiota using broad-spectrum antibiotics also altered HFHS intake during food preference test in lean mice. In conclusion, we discovered that gut microbes regulate hedonic aspects of food intake. Our data demonstrate that gut microbiota modifications associated with obesity participate in dysregulations of the reward and hedonic components of the food intake. These data provide evidence that gut microbes could be an interesting therapeutic target to tackle hedonic disorders related to obesity.

Insulin resistance is associated with deficits in hedonic, self-reported cognitive, and psychosocial functional response to antidepressant treatment in individuals with major depressive disorder

BackgroundTo assess the effect of insulin resistance (IR) on treatment response to the antidepressant, vortioxetine, in patients with Major Depressive Disorder (MDD). MethodsThis is a secondary analysis of an 8-week, open-label clinical trial. Ninety-five adults in a primary care setting experiencing a major depressive episode were included. Response to vortioxetine was measured using the THINC-integrated tool, Montgomery Åsberg Depression Rating Scale (MADRS), the Snaith-Hamilton Pleasure Scale (SHAPS), the Perceived Deficits Questionnaire (PDQ-5), and the Sheehan Disability Scale (SDS). Generalized estimating equation models were utilized for data analysis. ResultsWhen adjusted for age, gender, dose, and BMI, there was a significant baseline IR by time interaction for SHAPS (p = 0.022), PDQ-5 (p = 0.037), and SDS (p = 0.013). Higher baseline IR predicted decreased early improvements in anhedonia. It also predicted poorer subjective assessments of cognition and increased functional impairment at the endpoint of treatment. For functional capacity (i.e. SDS) other covariates including severity of symptoms, illness course, other metabolic factors (e.g. cholesterol), and physical activity were included with no changes to the moderating effect of baseline IR. LimitationsThis was a post-hoc analysis of a primarily non-diabetic sample. Also, only one agent was assessed. ConclusionsIR was a predictor of response to vortioxetine. This persisted after controlling for other factors including, but not limited to, BMI. These findings strengthen the link between depression and IR and may point to another novel metabolic predictor of response. These findings should be replicated using other antidepressants.

Animal welfare information affects consumers’ hedonic and emotional responses towards milk

This research aimed to explore the effects of animal welfare information on consumers’ hedonic and emotional responses towards milk. Two studies were conducted. For Study 1, participants (N = 101) were asked to fill out a questionnaire on attitudes towards animal welfare, in which a variety of factors including raising methods, quality of life, emotions, quality of the product, nutrition, price, and environment, were tested. For Study 2, participants (N = 63) tasted a milk sample (2% fat, standardized and homogenized) in two different conditions: [1] blind (without any previous information), and [2] informed (with information stating that the milk was obtained from a farm with an animal welfare system in place). For Study 1, participants with higher milk consumption per week showed a higher agreement with positive animal welfare statements. For Study 2, the overall liking for the milk in the informed condition was significantly higher than that of the milk in the blind condition (7.4 vs. 6.8, using a 9-point hedonic scale). Participants had higher penalizations for the milk in the blind condition as they suggested that the milk’s flavor, sweetness, aroma, and mouthfeel were not enough in the product. This research showed that animal welfare can be an important extrinsic factor in the consumers’ hedonic and emotional responses towards milk. These findings can be useful for understanding consumers’ behaviors towards animal welfare.

Memorable, Meaningful, Pleasurable: An Exploratory Examination of Narrative Character Deaths.

The current manuscript presents a study that examines contextual factors that can explain two distinct types of viewer responses to death in narratives. Using procedures developed in past research, we explore why some narrative character deaths elicit poignant, eudaimonic responses while others elicit joyful, hedonic responses. We incorporate a control group to examine whether freely-recalled memorable deaths are more closely associated with feelings of meaning or pleasure. Results suggest that meaningful deaths lead to appreciation; befall liked, moral characters; and elicit mixed/negative affect, whereas pleasurable deaths lead to enjoyment; befall disliked, immoral characters, and elicit positive affect. In addition, freely-recalled character death is more closely aligned with meaningful death and its correlates than pleasurable death and its correlates. We conclude with a discussion of how the current findings can improve the use of mediated death in clinical settings, particularly as a strategy for approaching instances of disenfranchised grief.

Consumption Context Effects on Fine Wine Consumer Segments' Liking and Emotions.

Wine consumer lifestyle segmentation has been widely studied; however, most studies have solely utilised online surveys. This work investigated the impact of context on wine consumer segments’ liking and emotions while consuming wines in different environments. Two studies were conducted with regular wine consumers segmented based on their fine wine behaviour using the Fine Wine Instrument. Study 1 (n = 122) investigated the effects of wine variety and product information, and Study 2 (n = 346) the effects of wine quality and consumption context, on hedonic and emotional responses of the segments. Within both studies, three segments were identified and named: Wine Enthusiasts, Aspirants and No Frills. The Wine Enthusiast segment generally liked the wines more and perceived more intense positive emotions when consuming wine compared to the No Frills segment, with the Aspirant’s likes and emotion intensities ranging in between. Wine Enthusiasts were more discriminative of their preferred wines and reported stronger positive emotions when tasting higher quality (Study 1) and more complex (Study 2) wines. The consistent results across the two studies showed for the first time that consumer segments, based on lifestyle segmentation, differ in their hedonic and emotional responses towards wine when actually tasting wines, demonstrating that the Fine Wine Instrument has practical implications and can identify wine consumers displaying different wine consumption behaviours.

Hypothetical Roles of the Olfactory Tubercle in Odor-Guided Eating Behavior.

Olfaction plays an important role in the evaluation, motivation, and palatability of food. The chemical identity of odorants is coded by a spatial combination of activated glomeruli in the olfactory bulb, which is referred to as the odor map. However, the functional roles of the olfactory cortex, a collective region that receives axonal projections from the olfactory bulb, and higher olfactory centers in odor-guided eating behaviors are yet to be elucidated. The olfactory tubercle (OT) is a component of the ventral striatum and forms a node within the mesolimbic dopaminergic pathway. Recent studies have revealed the anatomical domain structures of the OT and their functions in distinct odor-guided motivated behaviors. Another component of the ventral striatum, the nucleus accumbens, is well known for its involvement in motivation and hedonic responses for foods, which raises the possibility of functional similarities between the OT and nucleus accumbens in eating. This review first summarizes recent findings on the domain- and neuronal subtype-specific roles of the OT in odor-guided motivated behaviors and then proposes a model for the regulation of eating behaviors by the OT.

Interference with the renin-angiotensin system reduces the palatability of 0.3 M NaCl in sodium-deplete rats

The renin-angiotensin system (RAS) controls hypertonic NaCl intake driven by sodium appetite. Here we investigated whether the antagonism of RAS interferes with hedonic and aversive orofacial motor responses, or palatability, to intraoral infusion of 0.3 M NaCl (hNaCl). Adult rats were depleted of sodium by combined sc injection of furosemide and 24 h removal of ambient sodium. In experiment 1, losartan (AT1 angiotensin II receptor antagonist, intracerebroventricular, 200 μg/μl), produced a three-fold increase in aversive orofacial motor responses to hNaCl. Losartan also suppressed hNaCl intake recorded immediately thereafter. In experiment 2, each animal had repeated recordings of hNaCl intake and orofacial responses to hNaCl distributed for 180 min. Paired recordings of intake and orofacial responses occurred within five successive blocks after the recordings of only orofacial responses when the animals were still sodium deplete (block zero). Captopril (angiotensin converting enzyme blocker, intraperitoneal, 30 mg/kg) inhibited by 75% the hedonic orofacial responses to hNaCl in blocks zero and 1. The hedonic responses to captopril remained the same throughout blocks, but became similar to vehicle from blocks 2 to 5. There was no difference in aversive responses to 0.3 M NaCl between captopril and vehicle. Captopril produced a 70–100% inhibition of hNaCl intake in blocks 1 to 5. The results suggest that angiotensin II acts in the brain increasing the palatability of hypertonic sodium during the consummatory phase of sodium appetite.

Does portion size matter? Dynamic changes in hedonic and emotional responses to foods varying in portion size

Does portion size matter? Dynamic changes in hedonic and emotional responses to foods varying in portion size

Individual differences in responsiveness to oral sensations and odours with chemesthetic activity: Relationships between sensory modalities and impact on the hedonic response

Independent sensory modalities are related and showed covariations in prior literature. However, little is known on the relationship between oral sensations and nasal chemesthesis. This large-scale study aims (I.) to test the hypothesis that response to oral stimuli is related to responsiveness to odours with chemesthetic activity; and (II.) to explore the implications of these relationships on liking.Oral and olfactory responsiveness of 2205 Italians (18–65 years, men = 41%) were evaluated. Intensities of tastes, astringency and pungency were collected in water solutions and in four foods modulated for target sensations. Responses to bitterness of 6-n-propylthiouracil (PROP) was measured. Odour intensity and irritation were assessed for three pure odorants (L-Menthol, trans-anethole, (+)-α-Terpineol) stimulating nasal chemesthesis (respectively: TRPM8, TRPA1, TRPA1). Liking for odours and foods was measured. Specific intensity indices were developed for each sensation.Three clusters were identified based on taste intensity responses (Cl1, Cl2, Cl3). Cl1 (38%) was the most responsive to tastes, astringency, pungency, PROP and odours’ intensity and irritation. This hyper-responsive cluster showed the highest hedonic variation (the span of liking ratings for stimuli with varied tastant concentrations). Cl2 (24%) was intermediate for oral responsiveness (apart for sourness) and Cl3 (38%) was the least responsive. Cl2 and Cl3 did not differ in odours’ responsiveness (neither for perceived intensity nor for irritation). All sensory modalities were correlated but cross-correlations were higher when stimulating the same peripherical areas (oral vs oral more correlated than oral vs nasal). Results corroborate the idea of an overall high ‘sensory responsiveness’ covering different sensory modalities. Practical implications of the study are that less responsive subjects might require greater modifications in products formulations to modify their liking.

A tale of 3 scales: How do the 9-pt, Labeled Affective Magnitude, and unstructured Visual Analog scales differentiate real product sets of fresh berries?

Selection of scales for measuring liking remains an active area of discussion in sensory science, but there is still no real consensus on which scale a sensory scientist working in industry should use to measure actual hedonic responses to food products. Key criteria for a hedonic scale are whether it sensitively and efficiently discriminates among consumer responses to products. Therefore, the key question this study investigates is whether the use of different scales by the same subjects on the same products in a real-world situation would provide different results for the sensory analyst. To address this question, this study comprises the evaluation of 6 for-market varieties each of 4 berries—raspberry, strawberry, blackberry, and blueberry—by the same N = 147 untrained subjects using 3 popular scales—the 9-pt hedonic scale, the Labeled Affective Magnitude Scale (LAM), and the unstructured Visual Analog Scale (VAS). Data were analyzed by mixed-effects ANOVA with subsequent scale-performance and post-hoc measures, and by bootstrapping simulation studies to estimate the empirical power of each scale to detect differences. For each berry type, significant differences in liking were detected by at least one scale, but scale performance differed. The 9-pt scale was the only one of the three to detect differences among the blueberry samples, and examination of ANOVA and post-hoc results for all berries showed that the 9-pt scale consistently discriminated among samples as well or better than the other two scales. In simulation studies, the 9-pt scale showed reliable detection of differences at sample sizes smaller or equal to the other two scales. It is apparent that—in terms of real-world applications and expected detection of differences—the 9-pt scale discriminates consumer liking for different products as well or better than two continuous scales and can be retained in industry research programs.

3D Biomimetic Tongue-Emulating Surfaces for Tribological Applications.

Oral friction on the tongue surface plays a pivotal role in mechanics of food transport, speech, sensing, and hedonic responses. The highly specialized biophysical features of the human tongue such as micropapillae-dense topology, optimum wettability, and deformability present architectural challenges in designing artificial tongue surfaces, and the absence of such a biomimetic surface impedes the fundamental understanding of tongue–food/fluid interaction. Herein, we fabricate for the first time, a 3D soft biomimetic surface that replicates the topography and wettability of a real human tongue. The 3D-printed fabrication contains a Poisson point process-based (random) papillae distribution and is employed to micromold soft silicone surfaces with wettability modifications. We demonstrate the unprecedented capability of these surfaces to replicate the theoretically defined and simulated collision probability of papillae and to closely resemble the tribological performances of human tongue masks. These de novo biomimetic surfaces pave the way for accurate quantification of mechanical interactions in the soft oral mucosa.

Hedonic Responses to Touch are Modulated by the Perceived Attractiveness of the Caresser

Previous research has shown that a specific type of C fiber, the C tactile afferents, are involved in detecting gentle, dynamic tactile stimuli on the skin, giving rise to affective responses in the central nervous system. Despite building on such bottom-up information flow, the hedonic perception and the physiological consequences of affective touch are influenced by various sources of top-down information. In the present study we investigated how perception of affective touch is influenced by the attractiveness of hypothetical caressers. Participants were stroked on the arm and the palm while looking at photos of high attractive and low attractive opposite-gender faces, and were instructed to imagine those people as the caressers. In a control condition no photo was paired with the touch. The stroking stimulation was delivered with a soft brush either on the forearm or on the palm, and either with a slower or faster speed. Participants rated the pleasantness of each stimulation, while electrocardiographic recordings were made to extract heart rate variability data. Results showed that participants preferred touch stimuli paired with high attractive faces; they also preferred palm stroking and slower stroking speed. Like subjective pleasantness ratings, heart rate variability responses to affective touch (slow) were higher for high attractive than for low attractive caressers, but were not selective for arm or palm stroking. Overall, the present study confirms that contextual social information plays a major role in affective touch experiences, influencing not only the hedonic quality of the experience but also the physiological state of the body.

Childhood trauma is associated with elevated anhedonia and altered core reward circuitry in major depression patients and controls.

Childhood trauma (CT) is a well‐established risk factor for major depressive disorder (MDD). However, the underlying mechanism linking CT and MDD remains not fully understood. The present study tested the hypothesis that CT have effects on specific types of anhedonia in depression via reward system. To do so, we evaluated different aspects of anhedonia and resting‐state functional connectivity (FC) in reward system among 66 patients with MDD (44 with moderate‐to‐severe and 22 with no or low CT), and 57 healthy controls (HC; 23 with moderate‐to‐severe and 34 with no or low CT). Results showed that MDD patients with moderate‐to‐severe CT suffered more severe state anhedonic depression than patients with no or low level of CT. Individuals with moderate‐to‐severe CT, irrespective of MDD diagnosis, had elevated physical, social and anticipatory but not consummatory trait anhedonia, and demonstrated decreased left nucleus accumbens (NAcc)‐right orbital frontal cortex (OFC) and left ventral caudate‐left OFC connectivity compared to those with no or low exposure. Left NAcc‐right OFC connectivity mediated relationship between CT and state anhedonia in MDD. The total altered ventral striatum (VS)‐OFC connectivity mediated links between CT and physical trait anhedonia in HC. These findings highlight specific types of anhedonia and the core reward system as targets of CT. Blunted hedonic responses via decreased coupling within core reward system may be involved in the mechanism of depression following CT. Implications for clinical interventions are also discussed.

Kappa-opioid receptor-dependent changes in dopamine and anxiety-like or approach-avoidance behavior occur differentially across the nucleus accumbens shell rostro-caudal axis

Neural circuit engagement within the nucleus accumbens (NAc) shell is implicated in the regulation of both negative and positive affect. Classically, the dynorphin/kappa opioid receptor (KOR) system in the NAc was believed to promote aversion, while dopamine was viewed as interacting with reward behavior, and KOR activation was known to inhibit dopamine release. Recently, however, both the KOR and dopamine systems have, separately, been shown to have differential effects across the rostro-caudal axis of the NAc shell on hedonic responses. Whether or not this is due to interactions between KORs and dopamine, and if it extends to anxiety-like or approach-avoidance behaviors, remains to be determined. In this study, we examined in rats the relationship between the KOR and dopamine systems in both the rostral and caudal NAc shell using ex vivo fast scan cyclic voltammetry and the impact of KOR activation on affective behavior using exploration-based tasks. We report here that activation of KORs in the caudal NAc shell significantly inhibits dopamine release, stimulates rearing behavior in a novel environment, increases anxiety-like or avoidance behavior, and reduces locomotor activity. In contrast, activation of KORs in the rostral NAc shell inhibits dopamine release to a lesser extent and instead reduces anxiety-like behavior or increases approach behavior. Taken together, these results indicate that there is heterogeneity across the rostro-caudal axis of the NAc shell in the effects of KOR stimulation on affective behaviors, and they suggest that this might be due to differences in KOR control over dopamine release.

Fructose and Uric Acid as Drivers of a Hyperactive Foraging Response: A Clue to Behavioral Disorders Associated with Impulsivity or Mania?

Several behavioral disorders, including attention deficit hyperactivity disorder (ADHD), bipolar disorder, and aggressive behaviors are linked with sugar intake and obesity. The reason(s) for this association has been unclear. Here we present a hypothesis supporting a role for fructose, a component of sugar and high fructose corn syrup (HFCS), and uric acid (a fructose metabolite), in increasing the risk for these behavioral disorders. Recent studies have shown that the reason fructose intake is strongly associated with development of metabolic syndrome is that fructose intake activates an evolutionary-based survival pathway that stimulates foraging behavior and the storage of energy as fat. While modest intake may aid animals that would like to store fat as a protective response from food shortage or starvation, we propose that high intake of sugar and HFCS causes a hyperactive foraging response that stimulates craving, impulsivity, risk taking and aggression that increases the risk for ADHD, bipolar disease and aggressive behavior. High glycemic carbohydrates and salty foods may also contribute as they can be converted to fructose in the body. Some studies suggest uric acid produced during fructose metabolism may mediate some of these effects. Chronic stimulation of the pathway could lead to desensitization of hedonic responses and induce depression. In conclusion, a hyperactive foraging response driven by high glycemic carbohydrates and sugars may contribute to affective disorders.

Sensory and chemical characteristics of tomato juice from fresh market cultivars with comparison to commercial tomato juice

AbstractFlorida tomatoes are primarily produced for the fresh market and have not been widely used in processed tomato products. This study tested six Florida fresh market tomato cultivars (FLA 8083, FLA 8297, FLA 8344, FLA 8570, FLA 8924 and Garden Gem) to determine suitability for juice production. Genetic and environmental‐induced variation was studied, and analyses identified metabolites that influenced the perceptual and hedonic responses of tomato juice. Each cultivar was processed into juice by hot breaking at 86 ˚C for 3.5 minutes and then pasteurization at 121 ˚C for 42 seconds for a shelf stable product. Among the six pilot products, FLA 8344 cultivar had significantly higher soluble solids content and titratable acidity in all three experiments. The pH of each of the tomato juices made from fresh market tomatoes was within or below the typical range for tomato juice. Garden Gem was consistently rated significantly (P ≤ .05) higher for aroma, overall liking, tomato flavour, texture and overall flavour. In all three experiments, tomato juice from a fresh market cultivar simultaneously had the greatest abundance of green‐note volatiles (hexanal, 1‐hexanol, (Z)‐3‐hexen‐1‐ol, etc) and the lowest abundance of cooked‐note volatiles (dimethyl sulphide, methional and furfural). Consumer acceptance increased as salt concentration increased and while season had minor effects on the chemical composition of the juice, consumers preferred the Spring processed tomato juice over Fall.

The effects of contexts on consumer emotions and acceptance of a domestic food and an unfamiliar ethnic food: a cross-cultural comparison between Chinese and Korean consumers.

Contexts are known to affect hedonic and emotional responses to various food products. This study was conducted to investigate the effects of context on consumer acceptance and emotion of a domestic food and an unfamiliar ethnic food. Here, 97 Chinese and 83 Koreans rated hedonic and emotional responses to Korean shallot-seafood pancake (Haemul-pajeon) and Chinese shallot pancake (Cōngyóubĭng), in a sensory or ethnic context. Context did not significantly influence liking, but the Koreans' liking for Cōngyóubĭng significantly decreased in ethnic context compared to sensory context. Context significantly influenced eliciting positive emotions to domestic foods, whereas the context that increased positive emotions differed by the nationality of the panel. Ethnic food evaluated in ethnic context elicited emotions with negative valence or high arousal, whereas actual tasting significantly reduced these emotions. The results suggest that previous experiences and associations moderate the effect of context on emotions and acceptance.

Memantine effects on ingestion microstructure and the effect of administration time: A within-subject study.

In a between-subject comparison of two memantine administration schedules we observed that treatment with the NMDA receptor antagonist memantine before testing sessions reduced ingestion of a 10% sucrose solution in rats, due to reduced licking burst size, thus suggesting a blunted hedonic response. Conversely, daily post-session administration reduced burst number, indicating a reduced level of behavioural activation, likely due to the development of conditioned taste aversion (CTA). In this study, the effect of pre-session and post-session memantine administration was investigated within-subjects. Memantine was administered in daily intraperitoneal injections for 13 days, on alternate days, either 1-h before-"before testing" sessions-or immediately after a 30-min session-"after testing" sessions. The effects on the microstructure of licking for a 10% sucrose solution were examined in the course of treatment and for 21 days after treatment discontinuation. The results show reduced burst size in the "before testing" sessions, without effects on the intra-burst lick rate, an index of motoric effects. Moreover, burst number was reduced since the third session of both administration conditions until the end of treatment. Interestingly, the effect of memantine of reducing the activation of ingestive behaviour was less pronounced in this study with respect to that observed with the previous study post-session administration schedule, in spite of the longer treatment. This apparent paradox might be explained if one considers these effects as instances of a memory-related effect, such as the development of CTA. In the framework of this hypothesis, the "before testing" sessions, not being followed by memantine administration, can be considered as extinction sessions performed every other day. Moreover, the animals treated with memantine at the highest dose failed to recover to pre-treatment ingestion levels 21 days after treatment discontinuation, while the animals treated after testing sessions in the previously published study showed a complete recovery well before the 15th day test. Within the same interpretative framework, this might depend by the reduced number and frequency of the extinction trials-i.e. the number of the sessions run after treatment discontinuation-in the present study. These results provide further support to the conclusion that memantine administration before sessions reduce burst size, an effect which is likely due to blockade of NMDA receptors occurring during behavioural testing. The observation that this effect can be obtained even in absence of a reduced intra-burst lick rate, which rules out the involvement of motor impairment, provides an important piece of evidence in support to the interpretation of this effect as a blunted hedonic response. Moreover, these results provide further evidence that burst number reduction is due to a memory-related effect induced by memantine administration after sessions.