Healthiness or calories? Side biases in food perception and preference.

The visual perception of a product and the ability to categorize it play a central role in food choice. People's opinion of the healthiness and caloric content of a food is influenced substantially by its appearance. Despite that, few studies have analyzed i) which one of the two dimensions of caloric content and healthiness is preferred to categorize food, ii) if these dimensions are mapped on the individuals' horizontal space, and iii) if such biases could influence food preferences. Therefore, through 4 experiments, we investigated which dimension, healthiness or caloric content, is more often used to categorize foods. We also evaluated whether a healthiness/caloric content side bias could be able to influence food preferences. We found that foods were mainly categorized as "Healthy" or "High-calorie" and the latter label was used more often when presented on the right of a foodstuff. Also, foods were categorized as healthier when the "Healthy" label was anchored to the left and the "Unhealthy" one to the right side of a visual analogue scale. Then, we found a more positive evaluation of transformed food when the key assigned to the "Pleasant" choice was on the right compared to the left. Lastly, we found that when presented on the left side, low-calorie was preferred compared to high-calorie food. Our findings shed light on both the fields of food categorization and side biases in food perception and preferences, suggesting the possibility to use these biases to promote a healthy diet and emphasizing the importance of considering this potential confounder in experimental setups.

Two days of calorie deprivation impairs high level cognitive processes, mood, and self-reported exertion during aerobic exercise: A randomized double-blind, placebo-controlled study.

Military personnel and emergency responders perform cognitively-demanding tasks during periods of sustained physical exertion and limited caloric intake. Cognitive function is preserved during short-term caloric restriction, but it is unclear if preservation extends to combined caloric restriction and physical exertion. According to the "reticular-activating hypofrontality" model, vigorous exertion impairs prefrontal cortex activity and associated functions. This double-blind, placebo-controlled, crossover study examined cognitive function during sustained exertion while volunteers were calorically-deprived. Twenty-three volunteers were calorie-depleted for two days on one occasion and fully-fed on another. They completed intermittent bouts of exercise at 40-65% VO2peak while prefrontal cortex-dependent tasks of cognitive control, mood, and perceived exertion were assessed. Calorie deprivation impaired accuracy on the task-switching task of set-shifting (p < .01) and decreased sensitivity on the go/no-go task of response inhibition (p < .05). Calorie deprivation did not affect risk taking on the Rogers risk task. During exercise, calorie deprivation, particularly on day 2, increased perceived exertion (p < .05) and impaired mood states of tension, depression, anger, vigor, fatigue, and confusion (all p < .01). Physical exertion during severe calorie deprivation impairs cognitive control, mood, and self-rated exertion. Reallocation of cerebral metabolic resources from the prefrontal cortex to structures supporting movement may explain these deficits.

Cognitive aids and food choice: Real-time calorie counters reduce calories ordered and correct biases in calorie estimates.

Studies of the effect of calorie information on food choices in food-away-from-home settings have identified minor to insignificant changes in calories ordered. An element of the choice process that may play an important role in influencing the total caloric content of a meal has received little attention: how individuals track the total number of calories selected when choosing multiple items. We study the effects of automating this potentially costly cognitive process using technology. We compare the number of calories ordered in a sequential food choice task in two conditions: one in which participants have access to calorie information for all options available and a second in which they are also exposed to automatically updating information about the number of calories they have ordered. Participants with access to calorie summation ordered significantly fewer calories than those without access to calorie summation. Participants without access to calorie summation significantly underestimated the number of calories they had ordered, while those in the calorie summation condition did not. The calorie summation seems to work in part through adjustment of sequential choices: calories ordered in the first choice category were very similar in the two conditions but diverged increasingly in later categories. Technologies that help individuals keep track of the nutritional consequences of cumulative choices may help promote healthier diets.

Change in self-efficacy, eating behaviors and food cravings during two years of calorie restriction in humans without obesity.

Calorie restriction (CR) enhances longevity in humans who are normal weight, overweight and obese. While dietary regimens can change self-efficacy, eating behaviors, and food cravings in individuals with obesity, the responses of these measures to prolonged CR in individuals who are exclusively not obese is unknown. The aim of this analysis was to test the effects of a two-year CR intervention on self-efficacy and eating attitudes and behaviors in humans without obesity by analyzing data from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy Phase 2 (CALERIE 2) study. Participants (n = 218, BMI range = 21.3-29.0 kg/m2) were randomized to a 25% CR group or an ad libitum (AL) group. Eating attitudes and behaviors and self-efficacy were assessed using validated questionnaires at baseline, month 12, and month 24. Dietary restraint and self-efficacy increased in the CR compared to the AL group (ES ≥ 0.32). Increased self-efficacy was negatively related to weight change (ρ < -0.24). In the CR group, males showed a reduction in cravings for carbohydrates and fats at month 24, whereas females did not. The CR group showed elevations in state hunger, which were transient, and disinhibited eating (ES ≥ 0.37). In individuals without obesity, dietary restraint and self-efficacy could be important in promoting long-term CR for individuals looking to use CR as a tool to improve longevity.

Naïve models of dietary splurges: Beliefs about caloric compensation and weight change following non-habitual overconsumption.

The mechanisms that lead to overeating and the consumption of tempting, unhealthy foods have been studied extensively, but the compensatory actions taken afterwards have not. Here we describe the naïve models individuals hold around dietary splurges (single bouts of overeating) and associated weight changes. Across six online experiments, we found that, following a hypothetical dietary splurge, participants did not plan to adequately adjust calorie consumption to account for the additional calories consumed (Studies 1 and 2), and this pattern was worse following hypothetical splurges characterized by a large amount of food consumed in a single bout (Study 3). Participants expected weight changes to happen faster than they do in reality (Study 4) and they expected that weight gained from a dietary splurge would disappear on its own without explicit compensation attempts through diet or exercise (Study 5). Similarly, participants expected that when compensation attempts were made through calorie restriction, the rate of weight loss would be faster following a dietary splurge compared to normal eating (Study 6). This research contributes novel data demonstrating an important mechanism that likely contributes to weight gain and failed weight loss attempts.

Personal relative deprivation increases self-selected portion sizes and food intake.

Cues and experiences of the deprivation of financial/material resources have been associated with increased caloric intake and risk for overweight/obesity. Given that social comparisons may serve as a powerful reference for the adequacy of one's standing and resources, the present research tested whether subjective feelings of personal relative deprivation (PRD) or "losing out" to others stimulates calorie selection and intake. Study 1 demonstrated that self-reported chronic experiences of PRD positively predicted calories selected for a portion and consumed during an ad-libitum meal. Study 2 revealed that experimentally-induced PRD resulted in an increase in the amount of calories selected on a portion selection task and a stronger desire to consume the foods. Consequently, these findings demonstrate that chronic and acute subjective deprivation of non-food resources may contribute to socioeconomic gradients in obesity, and that perceived social inequality may have inherently obesogenic properties that promote excess calorie intake.

Do Food Preferences Change After Bariatric Surgery?

PURPOSE OF REVIEW: Insights into physiological mechanisms responsible for weight loss after bariatric surgery (BS) have challenged the traditional view that mechanical restriction and caloric malabsorption are major drivers of weight loss and health benefits after BS. Altered diet selection with an increased postoperative preference for low-sugar and low-fat food has also been implicated as a potential mechanism beyond mere reduction of calorie intake. However, the empirical support for this phenomenon is not uniform and evidence is largely based on indirect measurements, such as self-reported food intake data, which are prone to inaccuracy due to their subjective character. RECENT FINDINGS: Most studies indicate that patients not only reduce their caloric intake after BS, but also show a reduced preference of food with high sugar and high fat content. So far, standard behavioral tests to directly measure changes in food intake behavior after BS have been mainly used in animal models. It remains unclear whether there are fundamental shifts in the palatability of high-fat and sugary foods after BS or simply a decrease in the appetitive drive to ingest them. Studies of appetitive behavior in humans after BS have produced equivocal results. Learning processes may play a role as changes in diet selection seem to progress with time after surgery. So far, direct measures of altered food selection in humans after BS are rare and the durability of altered food selection as well as the role of learning remains elusive.

Acceptability of a very-low-energy diet in Type 2 diabetes: patient experiences and behaviour regulation.

AIMS: To evaluate the acceptability of an 8-week very-low-energy diet for remission of Type 2 diabetes, and to identify barriers and facilitators of adherence and behaviour-regulation strategies used by participants in the Counterbalance study. METHODS: Eighteen of 30 participants in the Counterbalance study (ISRCTN88634530) took part in semi-structured interviews. Of these, 15 participants were interviewed before and after the 8-week very-low-energy diet intervention. Thematic analysis was used to analyse the narratives. RESULTS: The prospect of diabetes remission, considerable weight loss, and long-term health improvement provided participants with substantial initial motivation. This motivation was sustained through the experience of rapid weight loss, improvements in blood glucose levels, social support and increased physical and psychological well-being. Overall, adherence to the very-low-energy diet for 8 weeks was perceived as much easier than anticipated, but required personal effort. Participants addressed challenges by removing food from the environment, planning, avoidance of tempting situations or places, and self-distraction. Weight loss and improvements in blood glucose levels lead to a sense of achievement and improvements in physical and psychological wellbeing. CONCLUSIONS: Dietary treatment for reversal of Type 2 diabetes is acceptable and feasible in motivated participants, and the process is perceived as highly gratifying. Research outside of controlled trial settings is needed to gauge the generalisability of these findings.

Ecological Momentary Assessment of Dietary Lapses Across Behavioral Weight Loss Treatment: Characteristics, Predictors, and Relationships with Weight Change.

BACKGROUND: Adherence to dietary prescriptions is critical for successful weight loss and weight loss maintenance. However, research on specific instances of inadherence (lapses) is limited, and findings regarding the frequency, nature, and causes of lapses are mixed. Additionally, no studies have examined lapses over the course of a weight loss program. PURPOSE: In the context of a reduced calorie diet prescribed as part of a behavioral treatment, we aimed to characterize lapse occurrence, examine lapse frequency across treatment, examine predictors of lapses, and assess the relationship between lapses and weight loss. METHODS: Adults (n = 189) enrolled in a 12-month behavioral weight loss program completed ecological momentary assessment (EMA) at baseline, mid-treatment, and end of treatment. At each EMA survey, participants indicated whether a lapse had occurred, and responded to questions assessing situational, environmental, and affective states. RESULTS: Lapse frequency showed a curvilinear relationship over time, such that frequency first decreased and then increased. Lapse frequency at baseline was negatively associated with early and overall weight loss. Lapses most often occurred at home, in the evenings, on the weekends, and entailed eating a forbidden food. Greater overall levels of assessed affective and environmental triggers predicted lapses, and greater momentary hunger and deprivation, and the presence of palatable food, also prospectively predicted lapses. CONCLUSIONS: In addition to characterizing lapse frequency, the current study identified prospective predictors of lapses across treatment. These findings support the importance of lapses to weight control and provide insight for potential targets of intervention to prevent lapse occurrence.

Food cravings in everyday life: An EMA study on snack-related thoughts, cravings, and consumption.

Food craving refers to an intense desire to consume a specific food and is regularly experienced by the majority of individuals. Yet, there are interindividual differences in the frequency and intensity of food craving experiences, which is often referred to as trait food craving. The characteristics and consequences of trait and state food craving have mainly been investigated in questionnaire-based and laboratory studies, which may not reflect individuals' behavior in daily life. In the present study, sixty-one participants completed the Food Cravings Questionnaire-Trait-reduced (FCQ-T-r) as measure of trait food craving, followed by seven days of Ecological Momentary Assessment (EMA), during which they reported snack-related thoughts, craving intensity, and snack consumption at five times per day. Results showed that 86 percent of reported snacks were high-caloric, with chocolate-containing foods being the most often reported snacks. Individuals with high FCQ-T-r scores (high trait food cravers, HCs) thought more often about high-calorie than low-calorie snacks whereas no differences were found in individuals with low FCQ-T-r scores (low trait food cravers, LCs). Further, the relationship between craving intensity and snack-related thoughts was stronger in HCs than in LCs. Higher craving intensity was associated with more consumption of snacks and again this relationship was stronger in HCs than in LCs. Finally, more snack-related thoughts were related to more frequent consumption of snacks, independent of trait food craving. Thus, HCs are more prone to think about high-calorie snacks in their daily lives and to consume more snack foods when they experience intense cravings, which might be indicative of a heightened responding towards high-calorie foods. Thus, trait-level differences as well as snack-related thoughts should be targeted in dietary interventions.

Cultural factors influencing dietary and fluid restriction behaviour: perceptions of older Chinese patients with heart failure.

AIMS AND OBJECTIVES: To explore the cultural factors related to dietary and fluid restriction behaviours among older Chinese patients. BACKGROUND: Excess dietary sodium and fluid intake are risk factors contributing to the worsening and rehospitalisation for heart failure in older patients. Managing the complex fluid and diet requirements of heart failure patients is challenging and is made more complicated by cultural variations in self-management behaviours in response to a health threat. DESIGN: Qualitative study using semi-structured in interviews and framework analysis. METHODS: The design of this study is qualitative descriptive. Semi-structured in-depth interviews were conducted with 15 heart failure patients. Data were analysed through content analysis. RESULTS: Seven cultural themes emerged from the qualitative data: the values placed on health and illness, customary way of life, preference for folk care and the Chinese healthcare system, and factors related to kinship and social ties, religion, economics and education. CONCLUSIONS: Dietary change and management in response to illness, including heart failure, is closely related to individuals' cultural background. Healthcare providers should have a good understanding of cultural aspects that can influence patients' conformity to medical recommendations. RELEVANCE TO CLINICAL PRACTICE: Heart failure patients need support that considers their cultural needs. Healthcare providers must have a good understanding of the experiences of people from diverse cultural backgrounds.

Daily exposure to a touchscreen-paradigm and associated food restriction evokes an increase in adrenocortical and neural activity in mice.

The translational assessment of mechanisms underlying cognitive functions using touchscreen-based approaches for rodents is growing in popularity. In these paradigms, daily training is usually accompanied by extended food restriction to maintain animals' motivation to respond for rewards. Here, we show a transient elevation in stress hormone levels due to food restriction and touchscreen training, with subsequent adaptation effects, in fecal corticosterone metabolite concentrations, indicating effective coping in response to physical and psychological stressors. Corticosterone concentrations of experienced but training-deprived mice revealed a potential anticipation of task exposure, indicating a possible temporary environmental enrichment-like effect caused by cognitive challenge. Furthermore, the analyses of immediate early gene (IEG) immunoreactivity in the hippocampus revealed alterations in Arc, c-Fos and zif268 expression immediately following training. In addition, BDNF expression was altered as a function of satiation state during food restriction. These findings suggest that standard protocols for touchscreen-based training induce changes in hippocampal neuronal activity related to satiation and learning that should be considered when using this paradigm.

A daily diary study of perceived social isolation, dietary restraint, and negative affect in binge eating.

Negative affect and dietary restraint are key predictors of binge eating, yet less is known about the impact of social factors on binge eating. The study sought to replicate and extend research on the relationships between negative affect, dietary restraint, perceived social isolation and binge eating using a daily diary methodology. College women (N = 54) completed measures of dietary restraint, negative affect, perceived social isolation, and binge eating daily for 14 days. Participants completed the measures nightly each day. A series of generalized estimating equations showed that dietary restraint was associated with less binge eating while controlling for negative affect and for perceived social isolation separately. Negative affect and perceived social isolation were associated with greater binge eating while controlling for restraint in separate analyses, but only perceived social isolation was significant when modeled simultaneously. All two-way interactions between negative affect, dietary restraint, and perceived social isolation predicting binge eating were nonsignificant. This study furthers our understanding of predictors of binge eating in a nonclinical sample. Specifically, these data suggest perceived social isolation, negative affect, and dietary restraint are important variables associated with binge eating in daily life and warrant further research.

A prime a day keeps calories away: The effects of supraliminal priming on food consumption and the moderating role of gender and eating restraint.

The link between intentions and action in weight control is weaker than previously thought, so recent research has called for further investigation of ways to improve weight control that bypass conscious intentions. Priming has been shown to have effects on individual behavior in a variety of contexts by influencing subconscious cognition. This paper investigates the effects of semantic priming using healthy body image, goal-oriented words on food consumption. The moderating role of both restrained eating and gender is investigated. 161 participants were involved in an experiment using a novel version of a scrambled sentence priming game. The outcome measure was the number of kilocalories consumed, examined using a between subjects ANCOVA with priming, gender, restrained eating index, self-reported BMI, and two interaction terms (primingxgender, and primingxrestrained eating index). There was no main effect of priming but there was an interaction of priming with gender. Females consumed significantly fewer kilocalories after being exposed to priming words related to a healthy body image (i.e. "slim", "fit,") compared to females receiving the neutral prime, with a medium effect size (d = 0.58). The body image prime did not significantly affect food intake for males, nor did it have a differential effect on restrained eaters. This study shows that priming can be an effective method for influencing females to reduce food intake, regardless of whether they are restrained or unrestrained eaters. Future studies could investigate whether different priming words related to a male's healthy body image goal (i.e. "buff," "muscles," etc.) would similarly reduce food intake for males.

Brain regions involved in ingestive behavior and related psychological constructs in people undergoing calorie restriction.

Human food intake is regulated by physiological energy homeostatic mechanisms and hedonic mechanisms. These are affected by both very short-term and longer-term calorie restriction (CR). To date, there are parallel discussions in the literature that fail to integrate across these disciplines and topics. First, much of the available neuroimaging research focusses on specific functional paradigms (e.g. reward, energy homeostasis). These paradigms often fail to consider more complex and inclusive models that examine how potential brain regions of interest interact to influence ingestion. Second, the paradigms used focus primarily on short-term CR (fasting) which has limited generalizability to clinical application. Finally, the behavioral literature, while frequently examining longer-term CR and related psychological constructs in the context of weight management (e.g. hedonic restraint, 'liking', 'wanting' and food craving), fails to adequately tie these phenomena to underlying neural mechanisms. The result is a less than complete picture of the brain's role in the complexity of the human experience of ingestion. This disconnect highlights a major limitation in the CR literature, where attempts are persistently made to exert behavioral control over ingestion, without fully understanding the complex bio behavioral systems involved. In this review we attempt to summarize all potential brain regions important for human ingestion, present a broad conceptual overview of the brain's multifaceted role in ingestive behavior, the human (psychological) experiences related to ingestion and to examine how these factors differ according to three forms of CR. These include short-term fasting, extended CR, and restrained eating. We aim to bring together the neuroimaging literature with the behavioral literature within a conceptual framework that may inform future translational research.

The association of eating styles with weight change after an intensive combined lifestyle intervention for children and adolescents with severe obesity.

UNLABELLED: The main purpose of this prospective intervention study was to determine whether eating styles after an intensive, partly inpatient, one year combined lifestyle intervention are associated with weight change in the following year in severely obese children and adolescents. A total of 120 participants (8-19 years) with an average SDS-BMI of 3.41 (SD = 0.38) was included. Measurements were conducted at baseline (T0), at the end of treatment (T12) and at the end of follow up two years after baseline (T24). The primary outcome measurement was the ΔSDS-BMI between T12 and T24. As primary determinant of weight change after treatment, the participants eating styles were evaluated with the Dutch Eating Behavior Questionnaire - child report that measures external, emotional and restraint eating. The association between outcome and determinant was assessed in linear regression analyses. Complete data were available for 76 of the 120 participants. This study shows that for girls a higher score on restraint eating at T12 and a higher score on external eating at T12 were associated with more weight (re)gain in the year after treatment. No statistically significant association with emotional eating at T12 was found. In addition for girls a higher score on external eating at T0 was associated with more weight (re)gain in the year after treatment. Furthermore, the observed changes in eating styles suggest that on average it is possible to influence these with treatment, although the detected changes were different for girls and boys and for the different eating styles. More generally, this study indicates that for girls the levels of restraint and external eating after treatment were associated with the weight change during the following year. TRIAL REGISTRATION: Netherlands Trial Register (NTR1678, registered 20-Feb-2009).

The portion size effect on food intake is robust to contextual size information.

Larger portion sizes have consistently been shown to lead to greater food intake. However, studies of the portion size effect typically provided participants with a single portion of food at a time without any objective information about the size of the portion, and hence failed to consider the potential significance of contextual size information. In order to investigate whether contextual size information moderates the portion size effect, participants were served small or large portions of pasta for lunch in the presence or absence of contextual size information. Study 1 found that the portion size effect on food intake was robust to contextual size information. Study 2 replicated this finding in an online paradigm, showing that contextual size information also had no influence on prospective intake, even when participants chose the portion size they preferred. Both studies also showed that participants' perceptions of how much was appropriate to eat mediated the effect of portion size on intake. A practical implication of our findings is that modifying consumption norms may be an effective way to promote healthier consumer food decisions.

Impulse control and restrained eating among young women: Evidence for compensatory cortical activation during a chocolate-specific delayed discounting task.

Theory and associated research indicate that people with elevated restrained eating (RE) scores have higher risk for binge eating, future bulimic symptom onset and weight gain. Previous imaging studies have suggested hyper-responsive reward brain area activation in response to food cues contributes to this risk but little is known about associated neural impulse control mechanisms, especially when considering links between depleted cognitive resources related to unsuccessful RE. Towards illuminating this issue, we used a chocolate-specific delayed discounting (DD) task to investigate relations between RE scores, behavior impulsivity, and corresponding neural impulse control correlates in a functional magnetic resonance imaging (fMRI) study of 27 young women. Specifically, participants were required to choose between more immediate, smaller versus delayed, larger hypothetical chocolate rewards following initial consumption of a chocolate. As predicted, RE scores were correlated positively with behavior impulse control levels. More critically, higher RE scores were associated with stronger activation in impulse control region, the dorsal-lateral prefrontal cortex (DLPFC) during the completion of difficult decision trials reflecting higher cognitive demands and resource depletion relative to easy decision trials. Exploratory analyses revealed a positive correlation between RE scores and activity in a reward system hub, the right striatum. Moreover, a positive correlation between left DLPFC and striatum activation was posited to reflect, in part, impulse control region compensation in response to stronger reward signal among women with RE elevations. Findings suggested impulse control lapses may contribute to difficulties in maintaining RE, particularly when cognitive demands are high.

Directive and non-directive food-related parenting practices: Associations between an expanded conceptualization of food-related parenting practices and child dietary intake and weight outcomes.

This study examines associations between an expanded conceptualization of food-related parenting practices, specifically, directive and non-directive control, and child weight (BMI z-score) and dietary outcomes [Healthy Eating Index (HEI) 2010, daily servings fruits/vegetables] within a sample of parent-child dyads (8-12 years old; n = 160). Baseline data from the Healthy Home Offerings via the Mealtime Environment (HOME Plus) randomized controlled trial was used to test associations between directive and non-directive control and child dietary outcomes and weight using multiple regression analyses adjusted for parental education. Overall variance explained by directive and non-directive control constructs was also calculated. Markers of directive control included pressure-to-eat and food restriction, assessed using subscales from the Child Feeding Questionnaire; markers of non-directive control were assessed with a parental role modeling scale and a home food availability inventory in which an obesogenic home food environment score was assigned based on the types and number of unhealthful foods available within the child's home food environment. DIRECTIVE CONTROL: Food restriction and pressure-to-eat were positively and negatively associated with BMI z-scores, respectively, but not with dietary outcomes. NON-DIRECTIVE CONTROL: An obesogenic home food environment was inversely associated with both dietary outcomes; parental role modeling of healthful eating was positively associated with both dietary outcomes. Neither non-directive behavioral construct was significantly associated with BMI z-scores. TOTAL VARIANCE: Greater total variance in BMI-z was explained by directive control; greater total variance in dietary outcomes was explained by non-directive control. Including a construct of food-related parenting practices with separate markers for directive and non-directive control should be considered for future research. These concepts address different forms of parental control and, in the present study, yielded unique associations with child dietary and weight outcomes.

Combining restricted diet with forced or voluntary exercises improves hippocampal BDNF and cognitive function in rats.

Dietary restriction (RDt) and exercise (Ex) enhances cognitive function due, at least in part, levels of neurotrophins such as brain-derived neurotrophic factor (BDNF). This study examined changes in BDNF levels and data acquisition and retention following every-other-day RDt alone, and combined with either voluntary wheel (VxRDt) or forced swimming Exs (FxRDt) in rats. Hippocampal BDNF was measured using ELISA while learning and memory formation were assessed with the radial arm water maze (RAWM) paradigm. After 6 weeks, VxRDt and FxRDt enhanced BDNF levels, and short- and long-term memories (p < 0.05). The magnitude of the increase in BDNF was significantly higher in VxRDt group than in other groups (p < 0.05). However, no differences were found in learning and memory formation between the Ex regiments (VxRDt versus FxRDt). Additionally, RDt alone neither modulated BDNF level nor enhanced learning and memory formation (p > 0.05). These results suggest more important role of Ex, as opposed to RDt, in enhancing learning and memory formation. In addition, VxRDt appears to be more potent in enhancing brain BDNF levels than FxRDt, when combined with RDt in rats.