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PubMed2006

The present values of delayed rewards are approximately additive.

In two experiments, human subjects were asked to estimate their present values of single delayed rewards and their present values of temporal sequences of three rewards. Present values were solicited by asking subjects to indicate an amount of money v for which they would be indifferent between receiving v at the end of the session and receiving the delayed reward(s). A procedure was used for which responding the true value of v was the optimal strategy, and the actual payoff that each subject received was determined by one randomly selected trial. In Experiment 1 (n=29) each delayed reward was 9.90 dollars in cash. In Experiment 2 (n=19) the delayed rewards were dated 15 dollars gift certificates to a local restaurant. In both experiments, the present values of the sequences were approximately equal to the sums of the present values of their component rewards. The presence of outliers suggests that a few subjects may have valued sequences less than the sums of their single rewards. Effects of a preference for uniform sequences, if any, were too small to be detected. Discounting of sequences was well fit by a parallel hyperbolic discounting equation, consistent with Mazur's [Mazur, J.E., 1986. Choice between single and multiple delayed reinforcers. J. Exp. Anal. Behav. 46 (1), 67-77] results using multiple reinforcers.

Adult↗
PubMed2004

Event-related functional magnetic resonance imaging of reward-related brain circuitry in children and adolescents.

BACKGROUND: Functional disturbances in reward-related brain systems are thought to play a role in the development of mood, impulse, and substance-abuse disorders. Studies in nonhuman primates have identified brain regions, including the dorsal/ventral striatum and orbital-frontal cortex, in which neural activity is modulated by reward. Recent studies in adults have concurred with these findings by observing reward-contingent blood oxygen level-dependent (BOLD) responses in these regions during functional magnetic resonance imaging (fMRI) paradigms; however, no previous studies indicate whether comparable modulations of neural activity exist in the brain reward systems of children and adolescents. METHODS: We used event-related fMRI and a behavioral paradigm modeled on previous work in adults to study brain responses to monetary gains and losses in psychiatrically healthy children and adolescents as part of a program examining the neural substrates of anxiety and depression in youth. RESULTS: Regions and time-courses of reward-related activity were similar to those observed in adults with condition-dependent BOLD changes in the ventral striatum and lateral and medial orbital-frontal cortex; specifically, these regions showed larger responses to positive than to negative feedback. CONCLUSIONS: These results provide further evidence for the value of event-related fMRI in examining reward systems of the brain, demonstrate the feasibility of this approach in children and adolescents, and establish a baseline from which to understand the pathophysiology of reward-related psychiatric disorders in youth.

Adolescent↗
PubMed2005

The effect of reward magnitude differences on choosing disadvantageous decks in the Iowa Gambling Task.

In the Iowa Gambling Task, participants have to develop a long-term profitable monetary scenario in a situation of uncertainty and a conflict between the chance of encountering an immediate large reward (100 US dollars) in two long-term loosing decks (A and B; -250 US dollars per 10 cards) and the chance of encountering an immediate small reward (50 US dollars) in two long-term winning decks (C and D; +250 US dollars per 10 cards). The ratio of the immediate rewards in decks A/B and C/D is thus 2:1. Here, we manipulated these differences in reward magnitude between the advantageous (C/D) and disadvantageous (A/B) decks, while keeping the net gains and losses per 10 cards the same, to assess the impact of the conflict between immediate and distant pay-off on choice behaviour. Participants selected less cards from disadvantageous decks and won more money when the reward magnitude difference was decreased, A/B:C/D=1:1, while they selected more cards from disadvantageous decks and lost more money when reward magnitude differences were increased, A/B:C/D=4:1 and 6:1. This study shows that the outcome in the Iowa Gambling Task is sensitive to differences between the magnitude of immediate rewards in the advantageous and disadvantageous decks.

Adult↗
PubMed2026

Smoking Cue Reactivity in Relation to Uncertain-Threat and Reward-Anticipation Networks: A Coordinate-Based fMRI Meta-Analysis.

BACKGROUND: Smoking is a concerning medical and social problem, yet how the brain links stress to continued smoking is still not well understood. This coordinate-based meta-analysis identified convergent activations for smoking cues, uncertain threat, and reward anticipation, and examined co-activation patterns to clarify whether smoking-cue activity in smokers relates to threat and reward activity in non-addicted controls. METHODS: We conducted a coordinate-based activation likelihood estimation (ALE) meta-analysis of 102 fMRI studies (N = 3,068), including 30 studies on smoking cue reactivity (n = 945), 48 on reward anticipation (n = 1,413), and 24 on uncertain threat processing (n = 1,621). We performed single, conjunction, and contrast analyses, followed by meta-analytic connectivity modeling (MACM) of key regions. RESULTS: Single analysis revealed smoking engaged bilateral ACC (-1.1, 46.2, -1.1), uncertain threat engaged bilateral insula (left = -33.6, 22, 4.3, right = 41.3, 22, 1), reward anticipation activated thalamus (0.9, 1.3, -3.1) and medial frontal gyrus (2.7, 6.6, 52.1). Conjunction and contrast analyses showed shared or unique activation for each task in its respective regions. MACM showed ACC co-activation with thalamus and medial frontal gyrus, while insula co-activated with ACC and inferior frontal gyrus. CONCLUSIONS: Each process converged in a separate region, with no overlap between the smoking-cue map and either the threat or reward map. The ACC nonetheless co-activated with reward-related regions and shared network membership with the threat-related insula. On this basis we hypothesize a shift in motivation from stress-driven reward toward cue-driven craving, to be tested within subjects, and identify candidate neuromodulation targets for preventing stress-precipitated relapse.

fMRI↗
PubMed2005

The neuroscience of investing: fMRI of the reward system.

Functional magnetic resonance imaging (fMRI) has proven a useful tool for observing neural BOLD signal changes during complex cognitive and emotional tasks. Yet the meaning and applicability of the fMRI data being gathered is still largely unknown. The brain's reward system underlies the fundamental neural processes of goal evaluation, preference formation, positive motivation, and choice behavior. fMRI technology allows researchers to dynamically visualize reward system processes. Experimenters can then correlate reward system BOLD activations with experimental behavior from carefully controlled experiments. In the SPAN lab at Stanford University, directed by Brian Knutson Ph.D., researchers have been using financial tasks during fMRI scanning to correlate emotion, behavior, and cognition with the reward system's fundamental neural activations. One goal of the SPAN lab is the development of predictive models of behavior. In this paper we extrapolate our fMRI results toward understanding and predicting individual behavior in the uncertain and high-risk environment of the financial markets. The financial market price anomalies of "value versus glamour" and "momentum" may be real-world examples of reward system activation biasing collective behavior. On the individual level, the investor's bias of overconfidence may similarly be related to reward system activation. We attempt to understand selected "irrational" investor behaviors and anomalous financial market price patterns through correlations with findings from fMRI research of the reward system.

Behavioral Sciences↗
PubMed2005

Individual differences in extraversion and dopamine genetics predict neural reward responses.

Psychologists have linked the personality trait extraversion both to differences in reward sensitivity and to dopamine functioning, but little is known about how these differences are reflected in the functioning of the brain's dopaminergic neural reward system. Here, we show that individual differences in extraversion and the presence of the A1 allele on the dopamine D2 receptor gene predict activation magnitudes in the brain's reward system during a gambling task. In two functional MRI experiments, participants probabilistically received rewards either immediately following a behavioral response (Study 1) or after a 7.5 s anticipation period (Study 2). Although group activation maps revealed anticipation- and reward-related activations in the reward system, individual differences in extraversion and the presence of the D2 Taq1A allele predicted a significant amount of inter-subject variability in the magnitudes of reward-related, but not anticipation-related, activations. These results demonstrate a link between stable differences in personality, genetics, and brain functioning.

Alleles↗
PubMed2006

Interactive effects of the mGlu5 receptor antagonist MPEP and the mGlu2/3 receptor antagonist LY341495 on nicotine self-administration and reward deficits associated with nicotine withdrawal in rats.

Stimulatory actions of nicotine on mesocorticolimbic dopamine transmission are partly mediated by nicotine-induced glutamate release acting on ionotropic and metabotropic glutamate (mGlu) receptors. Because both presynaptic inhibitory mGlu2/3 and postsynaptic excitatory mGlu5 receptors provide potential targets for treatment of aspects of nicotine dependence, we examined interacting effects of mGlu5 (2-methyl-6-(phenylethynyl)-pyridine, MPEP) and mGlu2/3 (LY341495) receptor antagonists on nicotine self-administration and brain reward threshold elevations associated with spontaneous nicotine withdrawal in rats. We hypothesized that increasing glutamate transmission by blocking presynaptic inhibitory mGlu2/3 autoreceptors would antagonize MPEP-induced decreases in nicotine self-administration. We also hypothesized that blocking postsynaptic actions of glutamate on mGlu5 receptors would exacerbate nicotine withdrawal-induced reward deficits, and that this effect would be attenuated by co-administration of the mGlu2/3 receptor antagonist LY341495. MPEP selectively decreased nicotine, but not food, self-administration in rats. LY341495 slightly decreased both nicotine and food self-administration. Co-administration of LY341495 with MPEP attenuated the effectiveness of MPEP in decreasing nicotine intake, although MPEP was still effective. Spontaneous nicotine withdrawal induced somatic signs of withdrawal and reward threshold elevations indicating reward deficits. MPEP increased somatic signs and reward deficits in both nicotine- and saline-withdrawing rats. Thus, while mGlu5 receptor antagonists may be therapeutically useful in decreasing tobacco smoking, they worsen nicotine withdrawal. Co-administration of LY341495 reduced MPEP-induced reward deficits in both nicotine- and saline-withdrawing rats. Thus, increasing glutamate transmission via mGlu2/3 autoreceptor blockade reduces the effects of mGlu5 receptor blockade on nicotine self-administration and MPEP-induced exacerbation of brain reward deficits associated with nicotine withdrawal.

Amino Acids↗
PubMed2004

Reward, memory and substance abuse: functional neuronal circuits in the nucleus accumbens.

The firing patterns of neurons in the nucleus accumbens (NA) are examined and discussed with respect to different types of rewards and reward conditions. Comparisons and contrasts between individually identified NA neuron responses to cocaine self-administration and water reinforcement are presented with an emphasis on the fact that the same neurons do not respond in a phasic manner to both types of rewards. However, the phasic firing patterns, even though segregated for each reinforcer, are quite similar, suggesting that the method of differentiation between rewarding stimuli in the NA is by sorting cell populations into distinct ensembles or networks for each type of reinforcer. These neural networks appear to be 'tuned' to respond to particular associative behavioral contexts that couple response execution to reward delivery, and in the process acquire a reciprocity to firing within reward contexts. This maintains the specificity of each reinforcer for the response and associated stimuli that produce it and, makes it possible to attach different NA networks to different reinforcing circumstances. Comparisons of cocaine and water reinforced NA cell firing patterns during rapid switching between these two reinforcers suggests that the networks are negatively coupled and mutually inhibit each other to maintain accurate encoding of immediately experienced, as well as expected (i.e. future) reward contingencies.

Action Potentials↗
PubMed2005

Reward-related FMRI activation of dopaminergic midbrain is associated with enhanced hippocampus-dependent long-term memory formation.

Long-term potentiation in the hippocampus can be enhanced and prolonged by dopaminergic inputs from midbrain structures such as the substantia nigra. This improved synaptic plasticity is hypothesized to be associated with better memory consolidation in the hippocampus. We used a condition that reliably elicits a dopaminergic response, reward anticipation, to study the relationship between activity of dopaminergic midbrain areas and hippocampal long-term memory in healthy adults. Pictures of object drawings that predicted monetary reward were associated with stronger fMRI activity in reward-related brain areas, including the substantia nigra, compared with non-reward-predicting pictures. Three weeks later, recollection and source memory were better for reward-predicting than for non-reward-predicting pictures. FMRI activity in the hippocampus and the midbrain was higher for reward-predicting pictures that were later recognized compared with later forgotten pictures. These data are consistent with the hypothesis that activation of dopaminergic midbrain regions enhances hippocampus-dependent memory formation, possibly by enhancing consolidation.

Adult↗
PubMed2005

Midbrain dopamine neurons encode a quantitative reward prediction error signal.

The midbrain dopamine neurons are hypothesized to provide a physiological correlate of the reward prediction error signal required by current models of reinforcement learning. We examined the activity of single dopamine neurons during a task in which subjects learned by trial and error when to make an eye movement for a juice reward. We found that these neurons encoded the difference between the current reward and a weighted average of previous rewards, a reward prediction error, but only for outcomes that were better than expected. Thus, the firing rate of midbrain dopamine neurons is quantitatively predicted by theoretical descriptions of the reward prediction error signal used in reinforcement learning models for circumstances in which this signal has a positive value. We also found that the dopamine system continued to compute the reward prediction error even when the behavioral policy of the animal was only weakly influenced by this computation.

Algorithms↗
PubMed2004

Choice selection and reward anticipation: an fMRI study.

We examined neural activations during decision-making using fMRI paired with the wheel of fortune task, a newly developed two-choice decision-making task with probabilistic monetary gains. In particular, we assessed the impact of high-reward/risk events relative to low-reward/risk events on neural activations during choice selection and during reward anticipation. Seventeen healthy adults completed the study. We found, in line with predictions, that (i) the selection phase predominantly recruited regions involved in visuo-spatial attention (occipito-parietal pathway), conflict (anterior cingulate), manipulation of quantities (parietal cortex), and preparation for action (premotor area), whereas the anticipation phase prominently recruited regions engaged in reward processes (ventral striatum); and (ii) high-reward/risk conditions relative to low-reward/risk conditions were associated with a greater neural response in ventral striatum during selection, though not during anticipation. Following an a priori ROI analysis focused on orbitofrontal cortex, we observed orbitofrontal cortex activation (BA 11 and 47) during selection (particularly to high-risk/reward options), and to a more limited degree, during anticipation. These findings support the notion that (1) distinct, although overlapping, pathways subserve the processes of selection and anticipation in a two-choice task of probabilistic monetary reward; (2) taking a risk and awaiting the consequence of a risky decision seem to affect neural activity differently in selection and anticipation; and thus (3) common structures, including the ventral striatum, are modulated differently by risk/reward during selection and anticipation.

Adult↗
PubMed2004

Testosterone shifts the balance between sensitivity for punishment and reward in healthy young women.

Animal research has demonstrated reductions in punishment sensitivity and enhanced reward dependency after testosterone administration. In humans, elevated levels of testosterone have been associated with violent and antisocial behavior. Interestingly, extreme forms of violent and antisocial behavior can be observed in the psychopath. Moreover, it has been argued that reduced punishment sensitivity and heightened reward dependency are crucially involved in the etiology and maintenance of psychopathy. A task that has been proven to be capable of simulating punishment-reward contingencies is the IOWA gambling task. Decisions to choose from decks of cards become motivated by punishment and reward schedules inherent in the task. Importantly, clinical and subclinical psychopaths demonstrate a risky, disadvantageous pattern of decision-making in the task, indicating motivational imbalance (insensitivity for punishment and enhanced reward dependency). Here, in a double-blind placebo-controlled crossover design (n = 12), whether a single administration of testosterone would shift the motivational balance between the sensitivity for punishment and reward towards this tendency to choose disadvantageously was investigated. As hypothesized, subjects showed a more disadvantageous pattern of decision-making after testosterone compared to placebo administration. These findings not only provide the first direct evidence for the effects of testosterone on punishment-reward contingencies in humans, but they also give further insights into the hypothetical link between testosterone and psychopathy.

Administration, Sublingual↗
PubMed1996

Ibotenic acid lesions of the amygdala basolateral complex or central nucleus differentially effect the response to reductions in reward.

The present study examined the role of the amygdala in the acquisition and expression of the Crespi effect (Crespi, L.P., Quantitative variation in incentive and performance in the white rat, Am. J. Psychol., 55 (1942) 467-517), also known as successive negative behavioral contrast. In Experiment One rats with bilateral amygdala cannulae were trained to run a straight alley for either a large (ten pellet) or small (one pellet) food reward. After 8 days of training, half of the rats in each reward condition received vehicle or ibotenic acid administered bilaterally into the amygdala. After 4 days of recovery from the induction of the lesions, training resumed. On Day 12 of training, the reward for rats in the large reward condition was shifted to one pellet and this reward level was maintained for the next 4 days of training. Both the lesioned and unlesioned shifted rats exhibited increased latencies to the reduction. However, shifted lesioned rats displayed a more persistent increase in latencies than shifted unlesioned rats, exhibiting significantly longer latencies than those of unlesioned rats by Day 15. This finding suggests that large amygdala lesions may impair learning of the appetitive value of the small reward. Experiment Two examined the effects of discrete ibotenic acid lesions of either the central nucleus or basolateral/lateral complex of the amygdala. Lesions of the central nucleus produced results similar to those of Experiment One. However, in Experiment Two the performance of shifted unlesioned and lesioned groups diverged significantly 1 day earlier, on Day 14. In contrast, lesions of the basolateral/lateral complex reduced the duration of the contrast effect. Shifted lesioned rats exhibited significantly lower latencies than shifted unlesioned rats by the first postshift day, Day 13. This finding suggests that the basolateral/lateral complex may be involved in learning about, or expressing the response to, the aversiveness of reward reduction.

Amygdala↗
PubMed1998

Dopamine D1-like receptors and reward-related incentive learning.

There now is general agreement that dopaminergic neurons projecting from ventral mesencephalic nuclei to forebrain targets play a critical role in reward-related incentive learning. Many recent experiments evaluate the role of dopamine (DA) receptor subtypes in various paradigms involving this type of learning. The first part of this paper reviews evidence from these studies that use antagonists or agonists relatively specific for D1- or D2-like receptors in operant paradigms with food, brain stimulation, self-administered stimulant or conditioned rewards or place conditioning. The focus is on studies that directly compare agents acting at the two DA receptor families, especially those studies where the agents produce differential actions. Results support the conclusion that D1-like receptors play a more critical role in reward-related learning than D2-like receptors. D1-like receptors initiate a cascade of intracellular events including cyclic adenosine monophosphate (cAMP) formation and activation of cAMP-dependent protein kinase (PKA). The final section of this paper reviews evidence from a wide range of neuroscience experiments that implicates the cAMP/PKA pathway in learning in general and in reward-related incentive learning in particular. We conclude that the molecular mechanism underlying DA-mediated incentive learning may involve DA release in association with reward, stimulation of D1-like receptors, activation of the cAMP/PKA cascade and additional intracellular events leading to modification of cortico-striatal glutamatergic synapses activated by stimuli encountered in close temporal contiguity with reward. Thus, when reward-related incentive learning takes place, it may be the action of DA acting at D1-like receptors that leads to plastic changes in the striatum that form the substrate of that learning.

Animals↗
PubMed2001

Repeated exposure to rewarding brain stimulation downregulates GluR1 expression in the ventral tegmental area.

There is considerable evidence that drug reward and brain stimulation reward (BSR) share common neural substrates. Although it is known that exposure to drugs of abuse causes a variety of molecular changes in brain reward systems, little is known about the molecular consequences of BSR. We report that repeated exposure to rewarding stimulation of the medial forebrain bundle (MFB) selectively decreases expression of GluR1 (an AMPA receptor subunit) in the VTA, without effect on expression of several other proteins (GluR2, NMDAR1, tyrosine hydroxylase). This effect of BSR on GluR1 expression is opposite of that caused by intermittent exposure to cocaine and morphine, which are known to elevate GluR1 expression in the VTA. Considering that elevated GluR1 expression in the VTA has been associated with increased sensitivity to drug reward, the finding that BSR and drugs of abuse have opposite effects on GluR1 expression in this region may provide an explanation for why the reward-related effects of many drugs (cocaine, morphine, amphetamine, PCP, nicotine) do not sensitize with repeated testing in BSR procedures that quantify reward strength.

Animals↗
PubMed1987

Critical self-reflection and self-perceived altruism: when self-reward fails.

Social learning theory has produced a three-step model of prosocial development: In the young child, prosocial behavior is elicited by material rewards; in the older child, it is elicited also by social rewards; and in the morally mature adult, it is elicited by self-rewards based on an internalized perception of oneself as a kind, caring, altruistic individual. Self-perception theory has complicated this social learning model by demonstrating that once the third step is reached, the continued presence of material and social rewards may undermine intrinsic prosocial motivation based on self-rewards, producing moral regression. We propose a further complication. Critical self-reflection--the desire to know thyself, warts and all--may introduce a self-deprecating attributional bias that can undermine self-perceived altruism, even following helping for which one receives only intrinsic self-rewards. Two experiments are reported in which we manipulated critical self-reflection on one's reasons for helping. Results indicated that self-reflection undermined self-perceived altruism, especially when the salience of the self-rewards for helping was high. Experiment 2 also provided evidence that, as predicted, this self-reflection effect was most apparent for individuals who valued self-knowledge more highly than concern for others. Moral consequences of critical self-reflection are discussed.

Altruism↗
PubMed1997

Can salient reward increase creative performance without reducing intrinsic creative interest?

Two experiments, involving 416 preadolescent school children, investigated the effects of monetary reward on generalized creative performance and intrinsic creative interest. In Experiment 1, the explicit requirement of novel performance in 1 task (generating unusual uses for physical objects) produced greater subsequent creative performance in an entirely different task (picture drawing) when a large reward was used rather than a small reward or no reward. In Experiment 2, reward for novel performance increased subsequent intrinsic creative interest, measured here by the choice to produce original drawings rather than copy a familiar drawing. Intrinsic creative interest was reduced only by reward for uncreative performance. These findings suggest that the explicit requirement of novel performance for salient reward enhances generalized creativity without any loss of intrinsic creative interest.

Child↗
PubMed2003

Impulsivity and rapid discounting of delayed hypothetical rewards in cocaine-dependent individuals.

In this study, crack/cocaine-dependent (CD) and non-drug-using matched control (MC) participants were presented with hypothetical immediate and delayed rewards, with 16 delay conditions ranging from 5 min to 25 years. All participants were presented with hypothetical monetary rewards; however, the CD group was also presented with hypothetical crack/cocaine rewards. The objective value of the rewards ranged from $1 to $1,000. Hyperbolic discounting functions provided a good fit of the data. The CD group discounted monetary rewards at a higher rate than the MC group did, and the CD group discounted crack/cocaine rewards at a higher rate than it did monetary rewards. Moreover, scores on self-report measures indicated greater impulsivity in the CD group when compared with the MC group.

Adult↗