The catecholamine precursor Tyrosine reduces autonomic arousal and decreases decision thresholds in reinforcement learning and temporal discounting.

Supplementation with the catecholamine precursor L-Tyrosine might enhance cognitive performance, but overall findings are mixed. Here, we investigate the effect of a single dose of tyrosine (2g) vs. placebo on two catecholamine-dependent trans-diagnostic traits: model-based control during reinforcement learning (2-step task) and temporal discounting, using a double-blind, placebo-controlled, within-subject design (n = 28 healthy male participants). We leveraged drift diffusion models in a hierarchical Bayesian framework to jointly model participants' choices and response times (RTS) in both tasks. Furthermore, comprehensive autonomic monitoring (heart rate, heart rate variability, pupillometry, spontaneous eye blink rate) was performed both pre- and post-supplementation, to explore potential physiological effects of supplementation. Across tasks, tyrosine consistently reduced participants' RTs without deteriorating task-performance. Diffusion modeling linked this effect to attenuated decision-thresholds in both tasks and further revealed increased model-based control (2-step task) and (if anything) attenuated temporal discounting. On the physiological level, participants' pupil dilation was predictive of the individual degree of temporal discounting. Tyrosine supplementation reduced physiological arousal as revealed by increases in pupil dilation variability and reductions in heart rate. Supplementation-related changes in physiological arousal predicted individual changes in temporal discounting. Our findings provide first evidence that tyrosine supplementation might impact psychophysiological parameters, and suggest that modeling approaches based on sequential sampling models can yield novel insights into latent cognitive processes modulated by amino-acid supplementation.

Hypnotic suggestions of safety reduce neuronal signals of delay discounting.

Waiting for delayed rewards is important to reach long-term goals, yet most people prefer immediate rewards. This tendency is called delay discounting. Evidence shows that people are more willing to wait for delayed rewards when they believe that the delayed reward is certain. We hypothesized that feeling safe makes delayed outcomes subjectively more certain, which should in turn reduce neuronal signals of delay discounting. We hypnotized 24 highly suggestible participants and gave them a suggestion to feel safe. We then used EEG to measure their brain responses to immediate and delayed rewards while they played a delayed gratification game. As compared to a control condition without hypnosis, participants that were suggested to feel safe under hypnosis reported feeling significantly safer. Further, their reward-related brain activity differentiated less between immediate and delayed rewards. We conclude that feeling safe makes delayed outcomes subjectively more certain and therefore reduces neuronal signals of delay discounting.

Hypothalamic-Extended Amygdala Circuit Regulates Temporal Discounting.

Choice behavior is characterized by temporal discounting, i.e., preference for immediate rewards given a choice between immediate and delayed rewards. Agouti-related peptide (AgRP)-expressing neurons located in the arcuate nucleus of the hypothalamus (ARC) regulate food intake and energy homeostasis, yet whether AgRP neurons influence choice behavior and temporal discounting is unknown. Here, we demonstrate that motivational state potently modulates temporal discounting. Hungry mice (both male and female) strongly preferred immediate food rewards, yet sated mice were largely indifferent to reward delay. More importantly, selective optogenetic activation of AgRP-expressing neurons or their axon terminals within the posterior bed nucleus of stria terminalis (BNST) produced temporal discounting in sated mice. Furthermore, activation of neuropeptide Y (NPY) type 1 receptors (Y1Rs) within the BNST is sufficient to produce temporal discounting. These results demonstrate a profound influence of hypothalamic signaling on temporal discounting for food rewards and reveal a novel circuit that determine choice behavior.SIGNIFICANCE STATEMENT Temporal discounting is a universal phenomenon found in many species, yet the underlying neurocircuit mechanisms are still poorly understood. Our results revealed a novel neural pathway from agouti-related peptide (AgRP) neurons in the hypothalamus to the bed nucleus of stria terminalis (BNST) that regulates temporal discounting in decision-making.

Acute and extended exposure to episodic future thinking in a treatment seeking addiction sample: A pilot study.

Individuals with addictive disorders commonly exhibit a shortened temporal window (shortened period of time an individual can imagine into their own future), which interferes with treatment focusing on long-term sobriety or reductions in use. Episodic future thinking (EFT) involves generating personalized cues related to anticipated, positive future events. EFT has been shown to reduce impulsive decision-making and the reinforcing value of addictive substances; however, this has only been shown in nontreatment samples. The current study examined the feasibility and impact of a 1-week EFT protocol on decision-making and alcohol motivation in a sample of individuals receiving treatment for alcohol use disorder. We randomly assigned twenty-eight individuals currently enrolled in community-based alcohol use disorder treatment to either an EFT protocol or a control episodic recent thinking (ERT) protocol. Participants completed assessments of delay discounting, alcohol demand, craving, self-efficacy, consideration of consequences, and mindfulness at baseline, after 1 week of EFT practice, and at 1-week follow-up. We observed patterns of reductions in alcohol demand indices, delay discounting rates, and an increase in mindfulness after both acute (1 session) and extended (4 sessions) exposure to EFT. These proof-of-concept findings lay the foundation for a randomized controlled trial of EFT as a supplement to addictions treatment.

Episodic future thinking, delay discounting, and exercise during weight loss maintenance: The PACE trial.

OBJECTIVES: Weight loss maintenance (WLM) is the next major challenge in obesity treatment. While most individuals who lose weight intend to keep their weight off, weight regain is common. Temporal Self-Regulation Theory posits that whether intentions lead to behavior depends on self-regulatory capacity, including delay discounting (DD; the tendency to discount a larger future reward in favor of a smaller immediate reward). Episodic Future Thinking (EFT; mental imagery of a future event for which a health goal is important) may improve DD and promote behavior change. Described herein is a trial protocol designed to examine whether EFT improves DD within the context of weight loss maintenance. METHOD: Participants who lose ≥5% of initial body weight in an online behavioral weight loss intervention will be randomly assigned to a standard weight loss maintenance program (WLM-STD) or a weight loss maintenance program plus EFT (WLM + EFT). Both interventions involve periodic phone and in-person treatment sessions. Participants in WLM + EFT will engage in daily EFT training via smartphone. To control for contact, participants in WLM-STD will engage in daily Healthy Thinking (reviewing strategies for weight management) on their smartphone. Our primary hypothesis is that WLM + EFT will yield better improvements in DD compared to WLM-STD. We will also explore whether DD mediates the relationship between intervention allocation and physical activity (secondary outcome). Weight and contextual variables will be explored. CONCLUSIONS: This study is the first to test whether EFT improves DD within the context of weight loss maintenance; results from this experimental medicine approach could have important implications for understanding the impact of both EFT and DD on sustained behavior change. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Targeting cognitive and emotional regulatory skills for smoking prevention in low-SES youth: A randomized trial of mindfulness and working memory interventions.

Research to date provides striking evidence that youth from low socio-economic status (SES) households are at an increased risk for smoking. Converging evidence from developmental studies, psychopathology studies, intervention studies, and basic research on self-control abilities have identified working memory and distress tolerance as potential crucial modifiable risk factors to prevent smoking onset in this cohort. To confirm the value of these mechanistic targets, this randomized trial was designed to evaluate the influence of working memory and distress tolerance interventions on risk of smoking initiation. Recruiting primarily from low-income community afternoon programs, we randomized 93 adolescents to one of three intervention conditions, all of which were a prelude to a smoking-prevention informational intervention: (1) a working memory intervention, (2) a mindfulness training intervention to target distress tolerance, and (3) a wellness-focused control condition. Despite a number of adherence efforts, engagement in treatment was limited, and under these conditions no significant evidence was found either for differential efficacy for smoking prevention or for intervention effects on mechanistic targets. However, working memory capacity and distress tolerance were found to be negatively related to smoking propensity. As such, our mechanistic targets-working memory and distress tolerance--may well be processes undergirding smoking, despite the fact that our interventions did not adequately engage these targets.

Vagal signaling and the somatic marker hypothesis: The effect of transcutaneous vagal nerve stimulation on delay discounting is modulated by positive mood.

Controlling impulsivity and delaying gratifications are key features of effective self-control. Delay Discounting (DD) indexes the ability to delay rewards and previous research has shown that discounting is influenced by affective states such as mood. According to the Somatic Marker Hypothesis (SMH), afferent somatic signals, such as mood, are carried by the vagus and can influence decision making. In the current study, we employed transcutaneous vagus nerve stimulation (tVNS), a novel non-invasive brain stimulation technique that stimulates the auricular branch of the afferent vagus nerve (located in the outer ear), to assess its effects on decision impulsivity, while taking into account individuals' mood and resting-state HRV as a possible confounding factor. Employing a within-subjects cross-over design, 94 participants received active or sham tVNS while performing delay discounting in two separate sessions. As compared to sham, active tVNS increased discounting, but only for individuals reporting lower positive mood, regardless of the level of negative mood reported. We evidence that the effect of tVNS on reward discounting depends on the level of positive mood. This result suggests that positive mood state might be a proxy of task-relevant arousal, likely influencing the effectiveness of afferent vagal stimulation on self-control processes, as temporal discounting.

Behavioral trainings and manipulations to reduce delay discounting: A systematic review.

In everyday decision-making, individuals make trade-offs between short-term and long-term benefits or costs. Depending on many factors, individuals may choose to wait for larger delayed reward, yet in other situations they may prefer the smaller, immediate reward. In addition to within-subject variation in the short-term versus long-term reward trade-off, there are also interindividual differences in delay discounting (DD), which have been shown to be quite stable. The extent to which individuals discount the value of delayed rewards turns out to be associated with important health and disorder-related outcomes: the more discounting, the more unhealthy or problematic choices. This has led to the hypothesis that DD can be conceptualized as trans-disease process. The current systematic review presents an overview of behavioral trainings and manipulations that have been developed to reduce DD in human participants aged 12 years or older. Manipulation studies mostly contain one session and measure DD directly after the manipulation. Training studies add a multiple session training component that is not per se related to DD, in between two DD task measurements. Ninety-eight studies (151 experiments) were identified that tested behavioral trainings and manipulations to decrease DD. Overall, results indicated that DD can be decreased, showing that DD is profoundly context dependent and changeable. Most promising avenues to pursue in future research seem to be acceptance-based/mindfulness-based trainings, and even more so manipulations involving a future orientation. Limitations and recommendations are discussed to identify the mechanistic processes that allow for changes in discount rate and behavior accordingly.

Cuing both positive and negative episodic foresight reduces delay discounting but does not affect risk-taking.

Humans frequently create mental models of the future, allowing outcomes to be inferred in advance of their occurrence. Recent evidence suggests that imagining positive future events reduces delay discounting (the devaluation of reward with time until its receipt), while imagining negative future events may increase it. Here, using a sample of 297 participants, we experimentally assess the effects of cued episodic simulation of positive and negative future scenarios on decision-making in the context of both delay discounting (monetary choice questionnaire) and risk-taking (balloon-analogue risk task). Participants discounted the future less when cued to imagine positive and negative future scenarios than they did when cued to engage in control neutral imagery. There were no effects of experimental condition on risk-taking. Thus, although these results replicate previous findings suggesting episodic future simulation can reduce delay discounting, they indicate that this effect is not dependent on the valence of the thoughts, and does not generalise to all other forms of "impulsive" decision-making. We discuss various interpretations of these results, and suggest avenues for further research on the role of prospection in decision-making.

Enacting rituals to improve self-control.

Rituals are predefined sequences of actions characterized by rigidity and repetition. We propose that enacting ritualized actions can enhance subjective feelings of self-discipline, such that rituals can be harnessed to improve behavioral self-control. We test this hypothesis in 6 experiments. A field experiment showed that engaging in a pre-eating ritual over a 5-day period helped participants reduce calorie intake (Experiment 1). Pairing a ritual with healthy eating behavior increased the likelihood of choosing healthy food in a subsequent decision (Experiment 2), and enacting a ritual before a food choice (i.e., without being integrated into the consumption process) promoted the choice of healthy food over unhealthy food (Experiments 3a and 3b). The positive effect of rituals on self-control held even when a set of ritualized gestures were not explicitly labeled as a ritual, and in other domains of behavioral self-control (i.e., prosocial decision-making; Experiments 4 and 5). Furthermore, Experiments 3a, 3b, 4, and 5 provided evidence for the psychological process underlying the effectiveness of rituals: heightened feelings of self-discipline. Finally, Experiment 5 showed that the absence of a self-control conflict eliminated the effect of rituals on behavior, demonstrating that rituals affect behavioral self-control specifically because they alter responses to self-control conflicts. We conclude by briefly describing the results of a number of additional experiments examining rituals in other self-control domains. Our body of evidence suggests that rituals can have beneficial consequences for self-control. (PsycINFO Database Record

The Attention Training Technique improves Children's ability to delay gratification: A controlled comparison with progressive relaxation.

The ability to delay gratification at a young age is a predictor of psychological, cognitive, health, and academic later-life outcomes. This study aimed to extend earlier research and explore whether a metacognitive intervention, Wells' (1990) Attention Training Technique (ATT), could improve young children's ability to delay gratification compared to an active-control (Progressive Muscle Relaxation: PMR), and no-intervention group. One hundred and one children aged 5-6 years old were recruited from schools. Classes of children were randomly allocated to receive the ATT, PMR or no-intervention and tested at pre- and post-intervention on measures of delay of gratification (the Marshmallow Test) and verbal inhibition (Day/Night Task). Results showed that, even when covariates were controlled for, following ATT, children delayed gratification significantly longer than after PMR or no-intervention. ATT also improved verbal inhibition compared with the no-intervention group, whilst PMR did not. The results add to earlier findings; ATT appears to provide a simple and effective way of improving young children's ability to delay gratification which has previously been shown to predict positive outcomes in later-life.

A Bird in the Hand Isn't Good for Long.

Folk wisdom tells us that additional time to make a decision helps us to refrain from the first impulse to take the bird in the hand. However, the question why the time to decide plays an important role is still unanswered. Here we distinguish two explanations, one based on a bias in value accumulation that has to be overcome with time, the other based on cognitive control processes that need time to set in. In an intertemporal decision task, we use mouse tracking to study participants' responses to options' values and delays which were presented sequentially. We find that the information about options' delays does indeed lead to an immediate bias that is controlled afterwards, matching the prediction of control processes needed to counter initial impulses. Hence, by using a dynamic measure, we provide insight into the processes underlying short-term oriented choices in intertemporal decision making.

Impulsivity predicts poorer improvement in quality of life during early treatment for people with methamphetamine dependence.

BACKGROUND AND AIMS: Methamphetamine dependence is associated with heightened impulsivity and diminished quality of life, but the link between impulsivity and changes in quality of life during treatment has not been examined. We aimed to investigate how different elements of impulsivity predict change in quality of life in the 6 weeks after engaging in treatment. DESIGN: Longitudinal, observational cohort study. SETTING: Public and private detoxification and rehabilitation facilities in metropolitan Melbourne, Australia. PARTICIPANTS: One hundred and eight individuals with methamphetamine dependence (81 male) tested within 3 weeks of commencing treatment; 80 (74%) were followed-up at 6 weeks. MEASUREMENTS: The Continuous Performance Test-2 measured impulsive action (cognitive and motor impulsivity); the Delay Discounting Task measured impulsive choice. Quality of life was measured with the World Health Organization Quality of Life Scale-Brief, which includes social, psychological, physical and environment domains. Control variables included age, gender, estimated IQ, depression severity score, methamphetamine dependence severity score, cannabis dependence severity score and treatment modality. FINDINGS: We found that all three forms of impulsivity were significant predictors of change in the social domain: motor impulsivity (ß = -0.54, P = 0.013), cognitive impulsivity (ß = -0.46, P = 0.029) and impulsive choice (ß = -0.26, P = 0.019). Change in the psychological domain was predicted significantly by motor impulsivity (ß = -0.45, P = 0.046). Control variables of age and depression were associated significantly with changes in the physical domain. CONCLUSIONS: In Australian methamphetamine-dependent individuals, elevated impulsivity predicts lower improvement of social and psychological quality of life in the first 6-9 weeks of treatment.

Distinct Roles of Dopamine Receptors in the Lateral Thalamus in a Rat Model of Decisional Impulsivity.

The thalamus and central dopamine signaling have been shown to play important roles in high-level cognitive processes including impulsivity. However, little is known about the role of dopamine receptors in the thalamus in decisional impulsivity. In the present study, rats were tested using a delay discounting task and divided into three groups: high impulsivity (HI), medium impulsivity (MI), and low impulsivity (LI). Subsequent in vivo voxel-based magnetic resonance imaging revealed that the HI rats displayed a markedly reduced density of gray matter in the lateral thalamus compared with the LI rats. In the MI rats, the dopamine D1 receptor antagonist SCH23390 or the D2 receptor antagonist eticlopride was microinjected into the lateral thalamus. SCH23390 significantly decreased their choice of a large, delayed reward and increased their omission of lever presses. In contrast, eticlopride increased the choice of a large, delayed reward but had no effect on the omissions. Together, our results indicate that the lateral thalamus is involved in decisional impulsivity, and dopamine D1 and D2 receptors in the lateral thalamus have distinct effects on decisional impulsive behaviors in rats. These results provide a new insight into the dopamine signaling in the lateral thalamus in decisional impulsivity.

Positive autobiographical memory retrieval reduces temporal discounting.

People generally prefer rewards sooner rather than later. This phenomenon, temporal discounting, underlies many societal problems, including addiction and obesity. One way to reduce temporal discounting is to imagine positive future experiences. Since there is overlap in the neural circuitry associated with imagining future experiences and remembering past events, here we investigate whether recalling positive memories can also promote more patient choice. We found that participants were more patient after retrieving positive autobiographical memories, but not when they recalled negative memories. Moreover, individuals were more impulsive after imagining novel positive scenes that were not related to their memories, showing that positive imagery alone does not drive this effect. Activity in the striatum and temporo parietal junction during memory retrieval predicted more patient choice, suggesting that to the extent that memory recall is rewarding and involves perspective-taking, it influences decision-making. Furthermore, representational similarity in the ventromedial prefrontal cortex between memory recall and decision phases correlated with the behavioral effect across participants. Thus, we have identified a novel manipulation for reducing temporal discounting-remembering the positive past-and have begun to characterize the psychological and neural mechanisms behind it.

Mindful eating reduces impulsive food choice in adolescents and adults.

OBJECTIVE: The present study tested the extent to which age and obesity predicted impulsive choices for food and monetary outcomes and tested how a brief mindful-eating training would alter delay discounting for food and money choices compared with control groups. METHOD: First, 172 adolescents (Mage = 13.13 years) and 176 (Mage = 23.33 years) adults completed the Food Choice Questionnaire (FCQ) and Monetary Choice Questionnaire (MCQ) as measures of food and money delay discounting, respectively. Then, participants returned to the lab and were randomly assigned to complete a brief mindful-eating training, watch a DVD on nutrition, or serve as a control. Participants completed the FCQ and MCQ again as a postmanipulation measure. RESULTS: Participants with high percent body fat (PBF) were more impulsive for food than those with low PBF. Adults with high PBF were also more impulsive for money compared with adults with low PBF; no PBF-related differences were found for adolescents. Participants in the mindful-eating group exhibited more self-controlled choices for food, but not for money. The control conditions did not exhibit changes. CONCLUSION: The study suggests that individuals with high PBF make more impulsive food choices relative to those with low PBF, which could increase the risk of obesity over time. It also is the first to demonstrate shifts in choice patterns for food and money using a brief mindful-eating training with adolescents. Mindful eating is a beneficial strategy to reduce impulsive food choice, at least temporarily, that may impede weight gain. (PsycINFO Database Record

The influence of episodic foresight on delay discounting and demand for alcohol.

BACKGROUND: There is a near-universal tendency to discount the value of delayed rewards relative to those available in the here and now. The rate at which future rewards become devalued over time, delay discounting, is an important individual difference variable related to impulsivity and is elevated in externalising disorders, including alcohol use disorders. Recent research suggests that vividly imagining personally relevant future events (episodic foresight) during an intertemporal choice task can attenuate the rate at which delayed rewards are discounted. OBJECTIVES: The present study sought to extend these findings by examining the effect of episodic foresight on both delay discounting and alcohol-related decision-making. METHODS: Forty-eight college students were administered both modified intertemporal choice and hypothetical alcohol purchase tasks during which personally relevant episodic future event cues or control imagery cues were presented. RESULTS: Engaging in episodic foresight reduced both the rate at which delayed monetary rewards were discounted and initial alcohol demand intensity (but not other demand indices) relative to control imagery. CONCLUSIONS: Findings suggest that the attenuating effect of episodic foresight on impulsivity may be limited to particular aspects of impulsive choice.

Serotonergic modulation of orbitofrontal activity and its relevance for decision making and impulsivity.

BACKGROUND: The orbitofrontal cortex seems to play a crucial role in reward-guided learning and decision making, especially for impulsive choice procedures including delayed reward discounting. The central serotonergic system is closely involved in the regulation of impulsivity, but how the serotonergic firing rate and release, best investigated by the loudness dependence of auditory evoked potentials (LDAEP), interact with orbitofrontal activity is still unknown. METHODS: Twenty healthy volunteers (11 males, 9 females, 31.3 ± 10.6 years old) were studied in a 3T MRI scanner (Philips, Hamburg, Germany) during a delay discounting task, after their LDAEP was recorded using a 32 electrodes EEG machine (Brain Products, Munich, Germany). RESULTS: Significant positive correlations were only found between the LDAEP and the medial orbitofrontal part of the superior frontal gyrus (SFG/MO) [Δ immediate reward - delayed reward] for the right (r = 0.519; P = 0.019) and left side (r = 0.478; P = 0.033). This relationship was stronger for females compared with males. Orbitofrontal activity was also related to the Barratt Impulsivity Scale. CONCLUSIONS: This study revealed that low serotonergic activity as measured by a strong LDAEP was related to a high fMRI signal intensity of SFG/MO during immediate reward behavior which is related to impulsivity. Since this relationship was only found for the infralimbic medial and not for the middle or lateral part of the orbitofrontal cortex, an exclusive projection tract of the serotonergic system to this cortical region can be assumed to regulate impulsive reward-orientated decision making. Hum Brain Mapp 38:1507-1517, 2017. © 2016 Wiley Periodicals, Inc.

Focus on the future: Episodic future thinking reduces discount rate and snacking.

Obesity seems related to a preference for immediate gratification. By changing this focus on short term benefits to a more future-oriented outlook, delay discounting (impulsive decision making) can be changed by a manipulation of episodic future thinking (EFT). EFT comprises a vivid mental simulation of general future experiences. EFT may also affect consumption of unhealthy foods, which can be seen as a choice for immediate gratification. Recent research shows that future orientation should be tailored to the behavior at outcome. We therefore hypothesize that the effectiveness of EFT on food intake could be enhanced by making the content food-related. We conducted a 2 (future vs past thinking) by 2 (food vs non-food related thoughts) between-subject design experiment in female undergraduates (N = 94), to compare the efficacy of EFT versus the recalling of episodic past events in reducing discount rate and caloric intake. Content of imagery was either unrestricted or food-related. Participants engaged in EFT or control episodic imagery while snacks were offered to freely consume, and next the Monetary Choice Questionnaire was completed as a measure of delay discounting, while again being engaged in EFT or control imagery. Both types of EFT reduced delay discounting, however, only food-related EFT lead to more restricted caloric consumption. Thus, we found evidence that EFT reduced discount rate during decision making. However, in order to restrict caloric intake, EFT should entail food-related imagery. As discount rate and caloric intake were not related in the current sample, the underlying mechanism remains to be discovered. Results however suggest that EFT is a promising technique to resist immediate gratification.

The Stomach-Derived Hormone Ghrelin Increases Impulsive Behavior.

Impulsivity, defined as impaired decision making, is associated with many psychiatric and behavioral disorders, such as attention-deficit/hyperactivity disorder as well as eating disorders. Recent data indicate that there is a strong positive correlation between food reward behavior and impulsivity, but the mechanisms behind this relationship remain unknown. Here we hypothesize that ghrelin, an orexigenic hormone produced by the stomach and known to increase food reward behavior, also increases impulsivity. In order to assess the impact of ghrelin on impulsivity, rats were trained in three complementary tests of impulsive behavior and choice: differential reinforcement of low rate (DRL), go/no-go, and delay discounting. Ghrelin injection into the lateral ventricle increased impulsive behavior, as indicated by reduced efficiency of performance in the DRL test, and increased lever pressing during the no-go periods of the go/no-go test. Central ghrelin stimulation also increased impulsive choice, as evidenced by the reduced choice for large rewards when delivered with a delay in the delay discounting test. In order to determine whether signaling at the central ghrelin receptors is necessary for maintenance of normal levels of impulsive behavior, DRL performance was assessed following ghrelin receptor blockade with central infusion of a ghrelin receptor antagonist. Central ghrelin receptor blockade reduced impulsive behavior, as reflected by increased efficiency of performance in the DRL task. To further investigate the neurobiological substrate underlying the impulsivity effect of ghrelin, we microinjected ghrelin into the ventral tegmental area, an area harboring dopaminergic cell bodies. Ghrelin receptor stimulation within the VTA was sufficient to increase impulsive behavior. We further evaluated the impact of ghrelin on dopamine-related gene expression and dopamine turnover in brain areas key in impulsive behavior control. This study provides the first demonstration that the stomach-produced hormone ghrelin increases impulsivity and also indicates that ghrelin can change two major components of impulsivity-motor and choice impulsivity.