Serotonin and dopamine play complementary roles in gambling to recover losses

Effect of Dopaminergic Therapy on Impulse Control Disorders in Patients With a Prolactinoma

BACKGROUND

Studies have reported an increase in the incidence of impulse control disorders (ICDs) in patient groups treated with dopamine agonists (DAAs), especially in Parkinson disease (PD). However, very few studies have reported on ICDs in individuals with a prolactinoma who were treated with DAAs.

OBJECTIVE

To see whether a DAA by itself causes ICDs in individuals with a prolactinoma by controlling the susceptibility to impulsivity by excluding individuals with other risk factors for ICDs.

METHOD

We compared the performance of 31 individuals with a prolactinoma receiving DAA therapy (DAA+) on various behavioral scales and the Iowa gambling task (IGT), a neuropsychological instrument that measures risky decision-making, with the performance of 20 individuals with a prolactinoma who were not on DAA therapy (DAA-) and 30 healthy controls (HC).

RESULTS

There was no significant difference among the groups concerning performance on the Zuckerman Sensation Seeking Scale-V, Minnesota Impulse Disorders Interview, Barratt Impulsiveness Scale-11, or IGT. No correlation was found between the scores on these scales and the duration or dose of DAA in the DAA+ group. The incidence of ICDs was 25.8% in the DAA+ group, 15% in the DAA- group, and 16.7% in the HC. The differences among the groups did not reach statistical significance.

CONCLUSION

Individuals who are under treatment with low-dose, D 2 -selective DAAs for a prolactinoma do not face an increased risk for ICDs, especially when they are carefully screened for any psychiatric comorbidity that may also display impulsivity.

Vulnerability and fraud: evidence from the COVID-19 pandemic

This study examines consumer fraud at the onset of the COVID-19 pandemic and provides novel evidence for the opportunity model of predatory victimization. Scammers have taken advantage of the COVID-19 pandemic shock to exploit victims who are already vulnerable and suffering. The number of fraud cases has greatly increased as COVID-19 spread across the U.S., consistent with the vulnerable-to-become-victimization hypothesis based on the opportunity model of predatory victimization. A Google Trends analysis shows that the increase in fraud and scams is attributable to victims' increased vulnerability rather than to their awareness of fraud and increased motivation to report scams. An improvement in financial literacy is associated with the reduction of finance-related fraud and scams. Finally, we provide important policy implications to protect people from fraud victimization.

Serotonin modulates asymmetric learning from reward and punishment in healthy human volunteers

Instrumental learning is driven by a history of outcome success and failure. Here, we examined the impact of serotonin on learning from positive and negative outcomes. Healthy human volunteers were assessed twice, once after acute (single-dose), and once after prolonged (week-long) daily administration of the SSRI citalopram or placebo. Using computational modelling, we show that prolonged boosting of serotonin enhances learning from punishment and reduces learning from reward. This valence-dependent learning asymmetry increases subjects’ tendency to avoid actions as a function of cumulative failure without leading to detrimental, or advantageous, outcomes. By contrast, no significant modulation of learning was observed following acute SSRI administration. However, differences between the effects of acute and prolonged administration were not significant. Overall, these findings may help explain how serotonergic agents impact on mood disorders.

Two factors can drive learning: punishment of failures and reward of successes. Serotonin induces a valence-dependent learning asymmetry, as revealed by prolonged administering of SSRIs to healthy participants in a gambling task.

Influences of social uncertainty and serotonin on gambling decisions

In many instances in life, our decisions’ outcomes hinge on someone else’s choices (i.e., under social uncertainty). Behavioral and pharmacological work has previously focused on different types of uncertainty, such as risk and ambiguity, but not so much on risk behaviors under social uncertainty. Here, in two different studies using a double-blind, placebo-controlled, within-subject design, we administrated citalopram (a selective-serotonin-reuptake inhibitor) to male participants and investigated decisions in a gambling task under social and nonsocial uncertainty. In the social condition, gamble outcomes were determined by another participant. In the nonsocial condition, gamble outcomes were determined by a coin toss. We observed increased gamble acceptance under social uncertainty, especially for gambles with lower gains and higher losses, which might be indicative of a positivity bias in social expectations in conditions of high uncertainty about others’ behaviors. A similar effect was found for citalopram, which increased overall acceptance behavior for gambles irrespective of the source of uncertainty (social/nonsocial). These results provide insights into the cognitive and neurochemical processes underlying decisions under social uncertainty, with implications for research in risk-taking behaviors in healthy and clinical populations.

Towards a Unifying Account of Dopamine’s Role in Cost-Benefit Decision Making

Dopamine is thought to play a crucial role in cost-benefit decision making, but so far there is no consensus on the precise role of dopamine in decision making. Here, we review the literature on dopaminergic manipulations of cost-benefit decision making in humans and evaluate how well different theoretical accounts explain the existing body of evidence. Reduced D₂ stimulation tends to increase the willingness to bear delay and risk costs (i.e., wait for later rewards, take riskier options), while increased D₁ and D₂ receptor stimulation increases willingness to bear effort costs. We argue that the empirical findings can best be explained by combining the strengths of two theoretical accounts: in cost-benefit decision making, dopamine may play a dual role both in promoting the pursuit of psychologically close options (e.g., sooner and safer rewards) and in computing which costs are acceptable for a reward at stake. Moreover, we identify several limiting factors in the study designs of previous investigations that prevented a fuller understanding of dopamine's role in value-based choice. Together, the proposed theoretical framework and the methodological suggestions for future studies may bring us closer to a unifying account of dopamine in healthy and impaired cost-benefit decision making.

Neuromodulation of prefrontal cortex cognitive function in primates: the powerful roles of monoamines and acetylcholine

The primate prefrontal cortex (PFC) subserves our highest order cognitive operations, and yet is tremendously dependent on a precise neurochemical environment for proper functioning. Depletion of noradrenaline and dopamine, or of acetylcholine from the dorsolateral PFC (dlPFC), is as devastating as removing the cortex itself, and serotonergic influences are also critical to proper functioning of the orbital and medial PFC. Most neuromodulators have a narrow inverted U dose response, which coordinates arousal state with cognitive state, and contributes to cognitive deficits with fatigue or uncontrollable stress. Studies in monkeys have revealed the molecular signaling mechanisms that govern the generation and modulation of mental representations by the dlPFC, allowing dynamic regulation of network strength, a process that requires tight regulation to prevent toxic actions, e.g., as occurs with advanced age. Brain imaging studies in humans have observed drug and genotype influences on a range of cognitive tasks and on PFC circuit functional connectivity, e.g., showing that catecholamines stabilize representations in a baseline-dependent manner. Research in monkeys has already led to new treatments for cognitive disorders in humans, encouraging future research in this important field.

When Helping Is Risky: The Behavioral and Neurobiological Trade-off of Social and Risk Preferences

Helping other people can entail risks for the helper. For example, when treating infectious patients, medical volunteers risk their own health. In such situations, decisions to help should depend on the individual's valuation of others' well-being (social preferences) and the degree of personal risk the individual finds acceptable (risk preferences). We investigated how these distinct preferences are psychologically and neurobiologically integrated when helping is risky. We used incentivized decision-making tasks (Study 1; N = 292 adults) and manipulated dopamine and norepinephrine levels in the brain by administering methylphenidate, atomoxetine, or a placebo (Study 2; N = 154 adults). We found that social and risk preferences are independent drivers of risky helping. Methylphenidate increased risky helping by selectively altering risk preferences rather than social preferences. Atomoxetine influenced neither risk preferences nor social preferences and did not affect risky helping. This suggests that methylphenidate-altered dopamine concentrations affect helping decisions that entail a risk to the helper.

An Experimental Medicine Investigation of the Effects of Subacute Pramipexole Treatment on Emotional Information Processing in Healthy Volunteers

Treatment with the dopamine D2/D3 receptor agonist pramipexole has demonstrated promising clinical effects in patients with depression. However, the mechanisms through which pramipexole might alleviate depressive symptoms are currently not well understood. Conventional antidepressant drugs are thought to work by biasing the processing of emotional information in favour of positive relative to negative appraisal. In this study, we used an established experimental medicine assay to explore whether pramipexole treatment might have a similar effect. Employing a double-blind, parallel-group design, 40 healthy volunteers (aged 18 to 43 years, 50% female) were randomly allocated to 12 to 15 days of treatment with either pramipexole (at a peak daily dose of 1.0 mg pramipexole salt) or placebo. After treatment was established, emotional information processing was assessed on the neural level by measuring amygdala activity in response to positive and negative facial emotional expressions, using functional magnetic resonance imaging (MRI). In addition, behavioural measures of emotional information processing were collected at baseline and on drug, using an established computerized task battery, tapping into different cognitive domains. As predicted, pramipexole-treated participants, compared to those receiving placebo, showed decreased neural activity in response to negative (fearful) vs. positive (happy) facial expressions in bilateral amygdala. Contrary to our predictions, however, pramipexole treatment had no significant antidepressant-like effect on behavioural measures of emotional processing. This study provides the first experimental evidence that subacute pramipexole treatment in healthy volunteers modifies neural responses to emotional information in a manner that resembles the effects of conventional antidepressant drugs.

Selective effects of serotonin on choices to gather more information

BACKGROUND

Gathering and evaluating information leads to better decisions, but often at cost. The balance between information seeking and exploitation features in neurodevelopmental, mood, psychotic and substance-related disorders. Serotonin's role has been highlighted by experimental reduction of its precursor, tryptophan.

AIMS

We tested the boundaries and applicability of this role by asking whether changes to information sampling would be observed following acute doses of serotonergic and catecholaminergic clinical treatments. We used a variant of the Information Sampling Task (IST) to measure how much information a person requires before they make a decision. This task allows participants to sample information until satisfied to make a choice.

METHODS

In separate double-blind placebo-controlled experiments, we tested 27 healthy participants on/off 20 mg of the serotonin reuptake inhibitor (SRI) citalopram, and 22 participants on/off 40 mg of the noradrenergic reuptake inhibitor atomoxetine. The IST variant minimised effects of temporal impulsivity and loss aversion. Analyses used a variety of participant prior expectations of sampling spaces in the IST, including a new prior that accounts for learning of likely states across trials. We analysed behaviour by a new method that also accounts for baseline individual differences of risk preference.

RESULTS

Baseline preferences demonstrated risk aversion. Citalopram decreased the expected utility of choices and probability of being correct based on informational content of samples collected, suggesting participants collected less useful information before making a choice. Atomoxetine did not influence information seeking.

CONCLUSION

Acute changes of serotonin activity by way of a single SRI dose alter information-seeking behaviour.

Eating to dare - Nutrition impacts human risky decision and related brain function

Macronutrient composition modulates plasma amino acids that are precursors of neurotransmitters and can impact brain function and decisions. Neurotransmitter serotonin has been shown to regulate not only food intake, but also economic decisions. We investigated whether an acute nutrition-manipulation inducing plasma tryptophan fluctuation affects brain function, thereby affecting risky decisions. Breakfasts differing in carbohydrate/protein ratios were offered to test changes in risky decision-making while metabolic and neural dynamics were tracked. We identified that a high-carbohydrate/protein breakfast increased plasma tryptophan/LNAA (large neutral amino acids) ratio which mapped to individual risk propensity changes. The nutrition-manipulation and tryptophan/LNAA fluctuation effects on risk propensity changes were further modulated by individual differences in body fat mass. Using fMRI, we further identified activation in the parietal lobule during risk-processing, of which activities 1) were sensitive to the tryptophan/LNAA fluctuation, 2) were modulated by individual's body fat mass, and 3) predicted the risk propensity changes in decision-making. Our results provide evidence for a personalized nutrition-driven modulation on human risky decision and its metabolic and neural mechanisms.

Human complex exploration strategies are enriched by noradrenaline-modulated heuristics

An exploration-exploitation trade-off, the arbitration between sampling a lesser-known against a known rich option, is thought to be solved using computationally demanding exploration algorithms. Given known limitations in human cognitive resources, we hypothesised the presence of additional cheaper strategies. We examined for such heuristics in choice behaviour where we show this involves a value-free random exploration, that ignores all prior knowledge, and a novelty exploration that targets novel options alone. In a double-blind, placebo-controlled drug study, assessing contributions of dopamine (400 mg amisulpride) and noradrenaline (40 mg propranolol), we show that value-free random exploration is attenuated under the influence of propranolol, but not under amisulpride. Our findings demonstrate that humans deploy distinct computationally cheap exploration strategies and that value-free random exploration is under noradrenergic control.

Using pharmacological manipulations to study the role of dopamine in human reward functioning: A review of studies in healthy adults

Dopamine (DA) plays a key role in reward processing and is implicated in psychological disorders such as depression, substance use, and schizophrenia. The role of DA in reward processing is an area of highly active research. One approach to this question is drug challenge studies with drugs known to alter DA function. These studies provide good experimental control and can be performed in parallel in laboratory animals and humans. This review aimed to summarize results of studies using pharmacological manipulations of DA in healthy adults. 'Reward' is a complex process, so we separated 'phases' of reward, including anticipation, evaluation of cost and benefits of upcoming reward, execution of actions to obtain reward, pleasure in response to receiving a reward, and reward learning. Results indicated that i) DAergic drugs have different effects on different phases of reward; ii) the relationship between DA and reward functioning appears unlikely to be linear; iii) our ability to detect the effects of DAergic drugs varies depending on whether subjective, behavioral, imaging measures are used.

The Role of Tryptophan and Tyrosine in Executive Function and Reward Processing

The serotonergic precursor tryptophan and the dopaminergic precursor tyrosine have been shown to be important modulators of mood, behaviour and cognition. Specifically, research on the function of tryptophan has characterised this molecule as particularly relevant in the context of pathological disorders such as depression. Moreover, a large body of evidence has now been accumulated to suggest that tryptophan may also be involved in executive function and reward processing. Despite some clear differentiation with tryptophan, the data reviewed in this paper illustrates that tyrosine shares similar functions with tryptophan in the regulation of executive function and reward, and that these processes in turn, rather than acting in isolation, causally influence each other.

The role of dopamine pharmacotherapy and addiction-like behaviors in Parkinson's disease

Addictions involve a spectrum of behaviors that encompass features of impulsivity and compulsivity, herein referred to as impulsive-compulsive spectrum disorders (ICSDs). The etiology of ICSDs likely involves a complex interplay among neurobiological, psychological and social risk factors. Neurobiological risk factors include the status of the neuroanatomical circuits that govern ICSDs. These circuits can be altered by disease, as well as exogenous influences such as centrally-acting pharmacologics. The 'poster child' for this scenario is Parkinson's disease (PD) medically managed by pharmacological treatments. PD is a progressive neurodegenerative disease that involves a gradual loss of dopaminergic neurons largely within nigrostriatal projections. Replacement therapy includes dopamine receptor agonists that directly activate postsynaptic dopamine receptors (bypassing the requirement for functioning presynaptic terminals). Some clinically useful dopamine agonists, e.g., pramipexole and ropinirole, exhibit high affinity for the D2/D3 receptor subtypes. These agonists provide excellent relief from PD motor symptoms, but some patients exhibit debilitating ICSD. Teasing out the neuropsychiatric contribution of PD-associated pathology from the drugs used to treat PD motor symptoms is challenging. In this review, we posit that modern clinical and preclinical research converge on the conclusion that dopamine replacement therapy can mediate addictions in PD and other neurological disorders. We provide five categories of evidences that align with this position: (i) ICSD prevalence is greater with D2/D3 receptor agonist therapy vs PD alone. (ii) Capacity of dopamine replacement therapy to produce addiction-like behaviors is independent of disease for which the therapy is being provided. (iii) ICSD-like behaviors are recapitulated in laboratory rats with and without PD-like pathology. (iv) Behavioral pathology co-varies with drug exposure. (v) ICSD Features of ICSDs are consistent with agonist pharmacology and neuroanatomical substrates of addictions. Considering the underpinnings of ICSDs in PD should not only help therapeutic decision-making in neurological disorders, but also apprise ICSDs in general.

Dopamine and reward hypersensitivity in Parkinson's disease with impulse control disorder

Impulse control disorders in Parkinson's disease are common neuropsychiatric complications associated with dopamine replacement therapy. Some patients treated with dopamine agonists develop pathological behaviours, such as gambling, compulsive eating, shopping, or disinhibited sexual behaviours, which can have a severe impact on their lives and that of their families. In this study we investigated whether hypersensitivity to reward might contribute to these pathological behaviours and how this is influenced by dopaminergic medication. We asked participants to shift their gaze to a visual target as quickly as possible, in order to obtain reward. Critically, the reward incentive on offer varied over trials. Motivational effects were indexed by pupillometry and saccadic velocity, and patients were tested ON and OFF dopaminergic medication, allowing us to measure the effect of dopaminergic medication changes on reward sensitivity. Twenty-three Parkinson's disease patients with a history of impulse control disorders were compared to 26 patients without such behaviours, and 31 elderly healthy controls. Intriguingly, behavioural apathy was reported alongside impulsivity in the majority of patients with impulse control disorders. Individuals with impulse control disorders also exhibited heightened sensitivity to exogenous monetary rewards cues both ON and OFF (overnight withdrawal) dopamine medication, as indexed by pupillary dilation in anticipation of reward. Being OFF dopaminergic medication overnight did not modulate pupillary reward sensitivity in impulse control disorder patients, whereas in control patients reward sensitivity was significantly reduced when OFF dopamine. These effects were independent of cognitive impairment or total levodopa equivalent dose. Although dopamine agonist dose did modulate pupillary responses to reward, the pattern of results was replicated even when patients with impulse control disorders on dopamine agonists were excluded from the analysis. The findings suggest that hypersensitivity to rewards might be a contributing factor to the development of impulse control disorders in Parkinson's disease. However, there was no difference in reward sensitivity between patient groups when ON dopamine medication, suggesting that impulse control disorders may not emerge simply because of a direct effect of dopaminergic drug level on reward sensitivity. The pupillary reward sensitivity measure described here provides a means to differentiate, using a physiological measure, Parkinson's disease patients with impulse control disorder from those who do not experience such symptoms. Moreover, follow-up of control patients indicated that increased pupillary modulation by reward can be predictive of the risk of future emergence of impulse control disorders and may thereby provide the potential for early identification of patients who are more likely to develop these symptoms.

Dopaminergic signaling of uncertainty and the aetiology of gambling addiction

Although there is increasing clinical recognition of behavioral addictions, of which gambling disorder is the prototype example, there is a limited understanding of the psychological properties of (non-substance-related) behaviors that enable them to become 'addictive' in a way that is comparable to drugs of abuse. According to an influential application of reinforcement learning to substance addictions, the direct effects of drugs to release dopamine can create a perpetual escalation of incentive salience. This article focusses on reward uncertainty, which is proposed to be the core feature of gambling that creates the capacity for addiction. We describe the neuro-dynamics of the dopamine response to uncertainty that may allow a similar escalation of incentive salience, and its relevance to behavioral addictions. We review translational evidence from both preclinical animal models and human clinical research, including studies in people with gambling disorder. Further, we describe the evidence for 1) the effects of the omission of expected reward as a stressor and to promote sensitization, 2) the effect of the resolution of reward uncertainty as a source of value, 3) structural characteristics of modern Electronic Gaming Machines (EGMs) in leveraging these mechanisms, 4) analogies to the aberrant salience hypothesis of psychosis for creating and maintaining gambling-related cognitive distortions. This neurobiologically-inspired model has implications for harm profiling of other putative behavioral addictions, as well as offering avenues for enhancing neurological, pharmacological and psychological treatments for gambling disorder, and harm reduction strategies for EGM design.

Effects of 5-HT2C, 5-HT1A receptor challenges and modafinil on the initiation and persistence of gambling behaviours

RATIONALE

Problematic patterns of gambling are characterised by loss of control and persistent gambling often to recover losses. However, little is known about the mechanisms that mediate initial choices to begin gambling and then continue to gamble in the face of losing outcomes.

OBJECTIVES

These experiments first assessed gambling and loss-chasing performance under different win/lose probabilities in C57Bl/6 mice, and then investigated the effects of antagonism of 5-HT_2CR with SB242084, 5-HT_1AR agonism with 8-OH-DPAT and modafinil, a putative cognitive enhancer.

RESULTS

As seen in humans and other species, mice demonstrated the expected patterns of behaviour as the odds for winning were altered increasing gambling and loss-chasing when winning was more likely. SB242084 decreased the likelihood to initially gamble, but had no effects on subsequent gambling choices in the face of repeated losses. In contrast, 8-OH-DPAT had no effects on choosing to gamble in the first place, but once started 8-OH-DPAT increased gambling choices in a dose-sensitive manner. Modafinil effects were different to the serotonergic drugs in both decreasing the propensity to initiate gambling and chase losses.

CONCLUSIONS

We present evidence for dissociable effects of systemic drug administration on different aspects of gambling behaviour. These data extend and reinforce the importance of serotonergic mechanisms in mediating discrete components of gambling behaviour. They further demonstrate the ability of modafinil to reduce gambling behaviour. Our work using a novel mouse paradigm may be of utility in modelling the complex psychological and neurobiological underpinnings of gambling problems, including the analysis of genetic and environmental factors.

An fMRI study of decision-making under sunk costs in gambling disorder

The sunk cost effect is the tendency to continue an investment, or take an action, even though it has higher future costs than benefits, if costs of time, money, or effort were previously incurred. This type of decision bias is pervasive in real life and has been studied in various disciplines. Previous studies and clinical observations suggest that decision-making under sunk costs is altered in gambling disorder (GD). However, the neural mechanisms of decision-making under sunk costs in GD remain largely unknown, and so is their association with the clinical characteristics of this patient group. Here, by combining functional magnetic resonance imaging and the task that demonstrated a clear example of the sunk cost effect, we investigated the neural correlates during decision-making under sunk costs in GD. We found no significant differences in the strength of the sunk cost effect between the GD and healthy control (HC) groups. However, the strength of the sunk cost effect in patients with GD showed a significant negative correlation with abstinence period and a marginally significant positive correlation with the duration of illness. We also found a reduction in the neural activation in the dorsal medial prefrontal cortex during decision-making under sunk costs for the GD group compared with the HC group. Furthermore, in patients with GD, the levels of activation in this area negatively correlated with the duration of illness. These findings have important clinical implications. This study will contribute to a better understanding of the mechanisms underlying altered decision-making abilities in GD.

The β-adrenoceptor blocker propranolol ameliorates compulsive-like gambling behaviour in a rodent slot machine task: implications for iatrogenic gambling disorder

Previous work has shown that chronic administration of the dopamine D_2/3 receptor agonist ropinirole invigorates performance on a rodent slot machine task (rSMT). This behavioural change appears superficially similar to the iatrogenic gambling disorder (GD) observed in a sub-set of patients with Parkinson's disease (PD), and has been associated with increased activation of the intra-cellular signalling proteins GSK3β and CREB in the striatum. Here, we wanted to determine whether this response to ropinirole could be attenuated by targeting these signalling proteins, and if the loss of dopaminergic innervation characteristic of PD would alter ropinirole's effects on the rSMT. Male Long Evans rats were trained on the rSMT. Dopaminergic terminals innervating the dorsolateral striatum were then lesioned bilaterally using the neurotoxin 6-hydroxydopamine hydrochloride (6-OHDA). Subsequently animals were implanted with osmotic mini-pumps delivering ropinirole. Lastly, animals were given dietary lithium (Li⁺ ), to inhibit the activation of GSK3β, or injections of the ß-adrenoceptor antagonist propranolol, which potently inhibits CREB as a secondary mechanism of action, and any changes in ropinirole-induced increases in compulsive-like engagement in the rSMT evaluated. Chronic ropinirole increased the number of trials animals completed, reproducing our original finding. This increase in task engagement was not altered in animals with 6-OHDA lesions, a putative model of early PD. In addition, the effects of ropinirole were not attenuated by administration of Li⁺ , but were ameliorated by propranolol. These data suggest that propranolol may represent a potential pharmacotherapy for the treatment of iatrogenic gambling.

Dopamine Receptor-Specific Contributions to the Computation of Value

Dopamine is thought to play a crucial role in value-based decision making. However, the specific contributions of different dopamine receptor subtypes to the computation of subjective value remain unknown. Here we demonstrate how the balance between D1 and D2 dopamine receptor subtypes shapes subjective value computation during risky decision making. We administered the D2 receptor antagonist amisulpride or placebo before participants made choices between risky options. Compared with placebo, D2 receptor blockade resulted in more frequent choice of higher risk and higher expected value options. Using a novel model fitting procedure, we concurrently estimated the three parameters that define individual risk attitude according to an influential theoretical account of risky decision making (prospect theory). This analysis revealed that the observed reduction in risk aversion under amisulpride was driven by increased sensitivity to reward magnitude and decreased distortion of outcome probability, resulting in more linear value coding. Our data suggest that different components that govern individual risk attitude are under dopaminergic control, such that D2 receptor blockade facilitates risk taking and expected value processing.

Alterations in functional brain networks associated with loss-chasing in gambling disorder and cocaine-use disorder

BACKGROUND

Continued, persistent gambling to recover accumulating losses, or 'loss-chasing', is a behavioral pattern linked particularly closely to gambling disorder (GD) but may reflect impaired decision-making processes relevant to drug addictions like cocaine-use disorder (CUD). However, little is known regarding the neurocognitive mechanisms of this complex, maladaptive behavior, particularly in individuals with addictive disorders.

METHODS

Seventy participants (25 GD, 18 CUD, and 27 healthy comparison (HC)) completed a loss-chase task during fMRI. Engagement of functional brain networks in response to losing outcomes and during decision-making periods preceding choices to loss-chase or to quit chasing losses were investigated using independent component analysis (ICA). An exploratory factor analysis was performed to examine patterns of coordinated engagement across identified networks.

RESULTS

In GD relative to HC and CUD participants, choices to quit chasing were associated with greater engagement of a medial frontal executive-processing network. By comparison, CUD participants exhibited altered engagement of a striato-amygdala motivational network in response to losing outcomes as compared to HC, and during decision-making as compared to GD. Several other networks were differentially engaged during loss-chase relative to quit-chasing choices, but did not differ across participant groups. Exploratory factor analysis identified a system of coordinated activity across prefrontal executive-control networks that was greater in GD and CUD relative to HC participants and was associated with increased chasing persistence across all participants.

CONCLUSIONS

Results provide evidence of shared and distinct neurobiological mechanisms in substance and behavioral addictions, and lend insight into potential cognitive interventions targeting loss-chasing behavior in GD.

Similarities and Differences in Neurobiology

Substance addiction is a chronic, relapsing brain disease characterized by compulsive drug seeking and use despite harmful consequences. Non-substance addiction is defined recently that people may compulsively engage in an activity despite any negative consequences to their lives. Despite differences with respect to their addictive object, substance addiction and non-substance addiction may share similarities with respect to biological, epidemiological, clinical, genetic and other features. Here we review the similarities and differences in neurobiology between these two addictions with a focus on dopamine, serotonin, opioid, glutamate and norepinephrine systems. Studies suggest the involvement of all these systems in both substance addiction and non-substance addiction while differences may exist with respect to their contributions.

Winning and losing: Effects on impulsive action

In the present study, we examined the effect of wins and losses on impulsive action in gambling (Experiments 1-3) and nongambling tasks (Experiments 4-5). In each experiment, subjects performed a simple task in which they had to win points. On each trial, they had to choose between a gamble and a nongamble. The gamble was always associated with a higher amount but a lower probability of winning than the nongamble. After subjects indicated their choice (i.e., gamble or not), feedback was presented. They had to press a key to start the next trial. Experiments 1-3 showed that, compared to the nongambling baseline, subjects were faster to initiate the next trial after a gambled loss, indicating that losses can induce impulsive actions. In Experiments 4 and 5, subjects alternated between the gambling task and a neutral decision-making task in which they could not win or lose points. Subjects were faster in the neutral decision-making task if they had just lost in the gambling task, suggesting that losses have a general effect on action. Our results challenge the dominant idea that humans become more cautious after suboptimal outcomes. Instead, they indicate that losses in the context of potential rewards are emotional events that increase impulsivity. (PsycINFO Database Record

Single dose testosterone administration reduces loss chasing in healthy females

Testosterone has been linked to modulation of impulsivity and risky choice, potentially mediated by changes in reward or punishment sensitivity. This study investigated the effect of testosterone on risk-taking and the adjustment of risk-taking on trials following a gain or a loss. Loss chasing is operationalized herein as the propensity to recover losses by increasing risky choice. Healthy female participants (n=26) received a single-dose of 0.5mg sublingual testosterone in a double-blind, placebo-controlled crossover design. At 240min post-administration, participants performed a gambling task with a high and a low risk option. In the placebo condition, participants were more likely to choose the high risk option following losses compared to wins. This effect was abolished on the testosterone session. Ignoring prior outcomes, no overall changes in risk-taking were observed. Our data indicate that testosterone affects human decision-making via diminishing sensitivity to punishment.

Alterations in DNA-methylation of the dopamine-receptor 2 gene are associated with abstinence and health care utilization in individuals with a lifetime history of pathologic gambling

BACKGROUND

Several studies point towards a role for dopaminergic circuits in the pathophysiology of problematic gambling behavior. The aim of the present study was to investigate alterations of DNA methylation in the dopamine D2 receptor (DRD2)-gene in participants with pathologic gambling behavior.

RESULTS

The study was part of a large epidemiological study on pathologic gambling in Germany. DNA methylation of the DRD2-gene was analyzed from oral mucosa using next generation bisulfite sequencing. The final sample included 77 participants. The study showed significantly lower methylation levels of the DRD2-gene in abstinent patients over the last 12 or 30months compared to non-abstinent participants. Furthermore, participants without any treatment utilization regarding gambling behavior showed higher DRD2-gene methylation levels compared to treatment-seeking participants.

CONCLUSIONS

DNA-methylation patterns in the DRD2-gene were altered in respect to abstinence over a 12-month or a 30-month period and to treatment utilization with higher methylation levels in non-abstinent and participants without treatment-seeking behavior. These results point towards a pathophysiologic relevance of altered DRD2-expression due to changes of DNA methylation in pathologic gambling behavior.

Stress psychobiology in the context of addiction medicine: from drugs of abuse to behavioral addictions

In this chapter, we briefly review the basic biology of psychological stress and the stress response. We propose that psychological stress and the neurobiology of the stress response play in substance use initiation, maintenance, and relapse. The proposed mechanisms for this include, on the one hand, the complex interactions between biological mediators of the stress response and the dopaminergic reward system and, on the other hand, mediators of the stress response and other systems crucial in moderating key addiction-related behaviors such as endogenous opioids, the sympathetic-adrenal-medullary system, and endocannabinoids. Exciting new avenues of study including genomics, sex as a moderator of the stress response, and behavioral addictions (gambling, hypersexuality, dysfunctional internet use, and food as an addictive substance) are also briefly presented within the context of stress as a moderator of the addictive process.

Behavioral addictions in addiction medicine: from mechanisms to practical considerations

Recent progress has been made in our understanding of nonsubstance or "behavioral" addictions, although these conditions and their most appropriate classification remain debated and the knowledge basis for understanding the pathophysiology of and treatments for these conditions includes important gaps. Recent developments include the classification of gambling disorder as a "Substance-Related and Addictive Disorder" in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and proposed diagnostic criteria for Internet Gaming Disorder in Section 3 of DSM-5. This chapter reviews current neuroscientific understandings of behavioral addictions and the potential of neurobiological data to assist in the development of improved policy, prevention, and treatment efforts.

No Evidence of Association between Toxoplasma gondii Infection and Financial Risk Taking in Females

Background

Past research linked Toxoplasma gondii (TG) infection in humans with neurological and mental disorders (e.g., schizophrenia, Alzheimer’s disease and attention disorders), irregularities of the dopaminergic and testosterone system, and increased likelihood of being involved in traffic accidents.

Methodology/Principal Findings

We test for an association between TG infection and financial decision-making (DM) using a case-control design in a sample of female Czech students (n = 79). We estimate each subject's risk attitude and loss aversion using an experimental economic task involving real monetary incentives. We find no significant evidence that either measure of decision-making is associated with TG infection.

Conclusion

We were unable to find evidence of an association between TG infection and financial decision-making in females.

Dissociable effects of basolateral amygdala lesions on decision making biases in rats when loss or gain is emphasized

Individuals switch from risk seeking to risk aversion when mathematically identical options are described in terms of loss versus gains, as exemplified in the reflection and framing effects. Determining the neurobiology underlying such cognitive biases could inform our understanding of decision making in health and disease. Although reports vary, data using human subjects have implicated the amygdala in such biases. Animal models enable more detailed investigation of neurobiological mechanisms. We therefore tested whether basolateral amygdala (BLA) lesions would affect risk preference for gains or losses in rats. Choices in both paradigms were always between options of equal expected value-a guaranteed outcome, or the 50:50 chance of double or nothing. In the loss-chasing task, most rats exhibited strong risk seeking preferences, gambling at the risk of incurring double the penalty, regardless of the size of the guaranteed loss. In the betting task, the majority of animals were equivocal in their choice, irrespective of bet size; however, a wager-sensitive subgroup progressively shifted away from the uncertain option as the bet size increased, which is reminiscent of risk aversion. BLA lesions increased preference for the smaller guaranteed loss in the loss-chasing task, without affecting choice on the betting task, which is indicative of reduced risk seeking for losses, but intact risk aversion for gains. These data support the hypothesis that the amygdala plays a more prominent role in choice biases related to losses. Given the importance of the amygdala in representing negative affect, the aversive emotional reaction to loss, rather than aberrant estimations of probability or loss magnitude, may underlie risk seeking for losses.

Co-occurrence of alcohol use disorder and behavioral addictions: relevance of impulsivity and craving

PURPOSE

The aims of the study were to evaluate the occurrence of behavioral addictions (BAs) in alcohol use disorder (AUD) subjects and to investigate the role of impulsivity, personality dimensions and craving.

METHODS

95 AUD outpatients (DSM-5) and 140 homogeneous controls were assessed with diagnostic criteria and specific tests for gambling disorder, compulsive buying, sexual, internet and physical exercise addictions, as well as with the Barratt Impulsiveness Scale (BIS-11) and Temperamental and Character Inventory-Revised (TCI-R). The Obsessive Compulsive Drinking Scale (OCDS) and Visual Analogue Scale for craving (VASc) were also administered to the AUD sample.

RESULTS

28.4% (n=27) of AUD subjects had at least one BA, as compared to 15% (n=21) of controls (χ(2)=6.27; p=.014). In AUD subjects, direct correlations between BIS-11 and Compulsive Buying Scale (CBS), Internet Addiction Disorder test (IAD), Exercise Addiction Inventory-Short Form (EAI-SF) scores (p<.01), between OCDS obsessive and CBS and VASc and CBS, IAD scores (p<.003), were found. BIS-11 (t=-2.36; p=.020), OCDS obsessive (Z=-4.13; p<.001), OCDS compulsive (Z=-2.12; p=.034) and VASc (Z=-4.94; p<.001) scores were higher in AUD subjects with co-occurring BAs. The occurrence of BAs was associated with higher impulsivity traits (BIS-11 scores; OR=1.08; p=.012) and higher craving levels (VASc scores; OR=2.48; p<.001).

CONCLUSIONS

Our findings emphasize a significant rate of co-occurrence of BAs in AUD. High levels of impulsivity and craving for alcohol seem to be associated with other addictive behaviors.

The role of serotonin in reward, punishment and behavioural inhibition in humans: insights from studies with acute tryptophan depletion

Deakin and Graeff proposed that forebrain 5-hydroxytryptamine (5-HT) projections are activated by aversive events and mediate anticipatory coping responses including avoidance learning and suppression of the fight-flight escape/panic response. Other theories proposed 5-HT mediates aspects of behavioural inhibition or reward. Most of the evidence comes from rodent studies. We review 36 experimental studies in humans in which the technique of acute tryptophan depletion (ATD) was used to explicitly address the role of 5-HT in response inhibition, punishment and reward. ATD did not cause disinhibition of responding in the absence of rewards or punishments (9 studies). A major role for 5-HT in reward processing is unlikely but further tests are warranted by some ATD findings. Remarkably, ATD lessened the ability of punishments (losing points or notional money) to restrain behaviour without affecting reward processing in 7 studies. Two of these studies strongly indicate that ATD blocks 5-HT mediated aversively conditioned Pavlovian inhibition and this can explain a number of the behavioural effects of ATD.

Citalopram-associated gambling: a case report

Pathological gambling behaviour is a side effect of dopaminergic drugs used in Parkinson's disease, but has seldom been reported with selective serotonin reuptake inhibitors. A 58-years-old woman with somatisation disorder since the age of 20 and recent-onset major depression (at 54 years) received 40 mg/day intravenous citalopram, thereafter switching to the same dose of oral citalopram to treat her comorbid psychiatric disorders after showing poor response to paroxetine for one year. Her anxious and depressive symptoms were moderately reduced after 7 months of oral citalopram, but simultaneously, the patient admitted gambling. We gradually discontinued citalopram and introduced pregabalin and alprazolam; this was followed by a reduction of gambling compulsions, but the somatisation and depressive symptoms did not further improve. Pathological gambling may be mediated by an interplay of 5-HT1A serotonergic and D2 dopaminergic mechanisms. Citalopram affects both these mechanisms in areas that were shown to be involved in gambling behaviour, but while dopaminergic effects of citalopram appear to be consistent with the induction of gambling, its serotonergic mechanisms are rather inconsistent. In our patient, mood destabilisation induced by citalopram may have contributed to the first onset of pathological gambling.

The role of dopamine in risk taking: a specific look at Parkinson's disease and gambling

An influential model suggests that dopamine signals the difference between predicted and experienced reward. In this way, dopamine can act as a learning signal that can shape behaviors to maximize rewards and avoid punishments. Dopamine is also thought to invigorate reward seeking behavior. Loss of dopamine signaling is the major abnormality in Parkinson’s disease. Dopamine agonists have been implicated in the occurrence of impulse control disorders in Parkinson’s disease patients, the most common being pathological gambling, compulsive sexual behavior, and compulsive buying. Recently, a number of functional imaging studies investigating impulse control disorders in Parkinson’s disease have been published. Here we review this literature, and attempt to place it within a decision-making framework in which potential gains and losses are evaluated to arrive at optimum choices. We also provide a hypothetical but still incomplete model on the effect of dopamine agonist treatment on these value and risk assessments. Two of the main brain structures thought to be involved in computing aspects of reward and loss are the ventral striatum (VStr) and the insula, both dopamine projection sites. Both structures are consistently implicated in functional brain imaging studies of pathological gambling in Parkinson’s disease.

Individual differences in impulsive and risky choice: effects of environmental rearing conditions

The present experiment investigated early-rearing environment modulation of individual differences in impulsive and risky choice. Rats were reared in an isolated condition (IC; n=12), in which they lived alone without novel stimuli, or an enriched condition (EC; n=11), in which they lived among conspecifics with novel stimuli. The impulsive choice task involved choices between smaller-sooner (SS) versus larger-later (LL) rewards. The risky choice task involved choices between certain-smaller (C-S) versus uncertain-larger (U-L) rewards. Following choice testing, incentive motivation to work for food was measured using a progressive ratio task and correlated with choice behavior. HPLC analyses were conducted to determine how monoamine concentrations within the prefrontal cortex (PFC) and nucleus accumbens (NAC) related to behavior in different tasks. IC rats were more impulsive than EC rats, but they did not differ in risky choice behavior. However, choice behavior across tasks was significantly correlated (i.e., the more impulsive rats were also riskier). There were no group differences in monoamine levels, but noradrenergic and serotonergic concentrations were significantly correlated with impulsive and risky choice. Furthermore, serotonin and norepinephrine concentrations in the NAC significantly correlated with incentive motivation and the timing of the reward delays within the choice tasks. These results suggest a role for domain general processes in impulsive and risky choice and indicate the importance of the NAC and/or PFC in timing, reward processing, and choice behavior.

Update on the Pharmacological Treatment of Pathological Gambling

This is an update to a previously published article discussing the neuropsychopharmacology of pathological gambling (PG) (1). In the prior manuscript, we described how cortico-limbic circuitry and neurotransmitter systems (norepinephrine, serotonin, dopamine, opioids, glutamate, and gamma-aminobutyric acid (GABA)) have been implicated in PG. These systems represent potential targets for psychopharmacological treatments for PG, with opioid antagonists arguably showing the most consistent benefit in RCTs. In the past year and half since this publication was prepared, there has been one additional randomized clinical trial (RCT) published along with a single case study. Our original manuscript did not describe in detail findings from case studies or open-label studies so in addition to the new RCT data and a new case report involving naltrexone, here we describe case and open-label findings. A PubMed search was conducted using terms such as "pathological gambling treatment", "clinical trials and gambling", and "gambling psychopharmacology." Using these search terms, numerous results were obtained, necessitating further search modifiers. For example, using just "pathological gambling treatment" results in over 1600 hits. In order to focus in on the search modalities, we searched within the initial results for specific phrases such as "psychopharmacology, clinical trial, medication, serotonergic, dopaminergic, etc." in addition to searching for specific medications. Results not directly related to the treatment of pathological gambling were not included. The study of pathological gambling is relatively new. As such, our search did not exclude any studies due to age of material, but with a few exceptions, the majority of the studies discussed were published later than 2000. This resulted in 24 case studies and/or RCTs not previously included in our original review article. These findings in conjunction with our prior publication provide a comprehensive overview of controlled investigations and exploratory reports of pharmacotherapies for PG.

Pathological choice: the neuroscience of gambling and gambling addiction

Gambling is pertinent to neuroscience research for at least two reasons. First, gambling is a naturalistic and pervasive example of risky decision making, and thus gambling games can provide a paradigm for the investigation of human choice behavior and "irrationality." Second, excessive gambling involvement (i.e., pathological gambling) is currently conceptualized as a behavioral addiction, and research on this condition may provide insights into addictive mechanisms in the absence of exogenous drug effects. This article is a summary of topics covered in a Society for Neuroscience minisymposium, focusing on recent advances in understanding the neural basis of gambling behavior, including translational findings in rodents and nonhuman primates, which have begun to delineate neural circuitry and neurochemistry involved.

Effects of pramipexole on the processing of rewarding and aversive taste stimuli

RATIONALE

Pramipexole, a D2/D3 dopamine receptor agonist, has been implicated in the development of impulse control disorders in patients with Parkinson's disease. Investigation of single doses of pramipexole in healthy participants in reward-based learning tasks has shown inhibition of the neural processing of reward, presumptively through stimulation of dopamine autoreceptors.

OBJECTIVES

This study aims to examine the effects of pramipexole on the neural response to the passive receipt of rewarding and aversive sight and taste stimuli.

METHODS

We used functional magnetic resonance imaging to examine the neural responses to the sight and taste of pleasant (chocolate) and aversive (mouldy strawberry) stimuli in 16 healthy volunteers who received a single dose of pramipexole (0.25 mg) and placebo in a double-blind, within-subject, design.

RESULTS

Relative to placebo, pramipexole treatment reduced blood oxygen level-dependent activation to the chocolate stimuli in the areas known to play a key role in reward, including the ventromedial prefrontal cortex, the orbitofrontal cortex, striatum, thalamus and dorsal anterior cingulate cortex. Pramipexole also reduced activation to the aversive condition in the dorsal anterior cingulate cortex. There were no effects of pramipexole on the subjective ratings of the stimuli.

CONCLUSIONS

Our results are consistent with an ability of acute, low-dose pramipexole to diminish dopamine-mediated responses to both rewarding and aversive taste stimuli, perhaps through an inhibitory action of D2/3 autoreceptors on phasic burst activity of midbrain dopamine neurones. The ability of pramipexole to inhibit aversive processing might potentiate its adverse behavioural effects and could also play a role in its proposed efficacy in treatment-resistant depression.

Systemic administration of 8-OH-DPAT and eticlopride, but not SCH23390, alters loss-chasing behavior in the rat

Gambling to recover losses is a common gaming behavior. In a clinical context, however, this phenomenon mediates the relationship between diminished control over gambling and the adverse socioeconomic consequences of gambling problems. Modeling loss-chasing through analogous behaviors in rats could facilitate its pharmacological investigation as a potential therapeutic target. Here, rats were trained to make operant responses that produced both food rewards, and unpredictably, imminent time-out periods in which rewards would be unavailable. At these decision points, rats were offered choices between waiting for these time-out periods to elapse before resuming responding for rewards ('quit' responses), or selecting risky options with a 0.5 probability of avoiding the time-outs altogether and a 0.5 probability of time-out periods twice as long as signaled originally ('chase' responses). Chasing behavior, and the latencies to chase or quit, during sequences of unfavorable outcomes were tested following systemic administration of the 5-HT1A receptor agonist, 8-OH-DPAT, the D2 receptor antagonist, eticlopride, and the D1 receptor antagonist, SCH23390. 8-OH-DPAT and eticlopride significantly reduced the proportion of chase responses, and the mean number of consecutive chase responses, in a dose-dependent manner. 8-OH-DPAT also increased latencies to chase. Increasing doses of eticlopride first speeded, then slowed, latencies to quit while SCH23390 had no significant effects on any measure. Research is needed to identify the precise cognitive mechanisms mediating these kinds of risky choices in rats. However, our data provide the first experimental demonstration that 5-HT1A and D2, but not D1, receptor activity influence a behavioral analog of loss-chasing in rats.

Effects of the 5HT2C antagonist SB242084 on the pramipexole-induced potentiation of water contrafreeloading, a putative animal model of compulsive behavior

RATIONALE

In rats, quinpirole, a dopaminergic D2/D3 receptor agonist, elicits both hyperdipsia and water "contrafreeloading" (CFL), a putative model of compulsivity. The role of D3 receptors in this effect remains unclear. Clomipramine (CIM) was found to contrast both hyperdipsia and CFL, but the role of serotonin in this effect requires further investigation.

OBJECTIVES

We studied the effects of the preferential D3 agonist pramipexole (PPX) in both models. Furthermore, we tested the sensitivity of PPX-induced CFL to CIM and to the 5HT2c antagonist SB242084.

METHODS

In experiment 1, drinking was measured at 2 and 5 h after eight daily injections of PPX (0 to 1.0 mg/kg intraperitoneally). In the CFL study, every other third lever press, the rat was reinforced by the delivery of water. On days 1-6, water was only available upon lever pressing. On days 7-15, choice between response-contingent and free access was provided. PPX doses as in the experiment 1 were given. In two further experiments, PPX (0.5 mg/kg) was administered alone or in combination with CIM (5 or 10 mg/kg) or SB242084 (0.3 or 1.0 mg/kg).

RESULTS

PPX did not produce hyperdipsia but enhanced spontaneous CFL. SB242084 attenuated PPX-induced CFL more effectively than CIM, restoring the preference for free access to water.

CONCLUSIONS

CFL, but not polydipsia, was induced by preferential D3 activation, an effect prevented by 5HT2c receptor blockade. Since PPX interferes with decision making and 5HT2c receptor supersensitivity is involved in the expression of compulsive behaviors, this study supports the compulsive nature of dopaminergic-induced CFL.

Serotonin 1B receptor imaging in pathological gambling

Abstract Objectives. Although serotonergic mechanisms have been implicated in pathological gambling (PG), no ligand-based imaging studies have assessed serotonin receptors in individuals with PG. Given its role in substance addictions and its abundance in brain regions implicated in PG, we evaluated serotonin 1B receptors (5-HT1BRs) in PG. Methods. Ten medication-free subjects with PG (mean ± SD age = 36.3 ± 9.4 years, nine men) and ten control comparison (CC) subjects (mean ± SD age = 35.8 ± 9.9 years, nine men) underwent [(11)C]P943 positron emission scanning on a high resolution research tomograph. Results. 5-HT1BR BPND values were similar in PG and CC subjects (P > 0.1). Among PG subjects, scores on the South Oaks Gambling Screen (SOGS) correlated positively with 5-HT1BR BPND values in the ventral striatum (r = 0.66; P = 0.04), putamen (r = 0.67; P = 0.03) and anterior cingulate cortex (r = 0.73; P = 0.02). Conclusions. These findings provide the first evidence that PG severity in humans is linked to increased levels of 5-HT1BRs in regions previously implicated in functional neuroimaging studies of PG. These findings indicate a potential role for serotonergic function in the ventral striatum and anterior cingulate cortex contributing to problem gambling severity and warrant further studies to investigate whether numbers of available 5-HT1BRs might represent a vulnerability factor for PG or develop in relationship to problem gambling.

In for a penny, in for a pound: methylphenidate reduces the inhibitory effect of high stakes on persistent risky choice

Methylphenidate (MPH) is a stimulant that increases extracellular levels of dopamine and noradrenaline. It can diminish risky decision-making tendencies in certain clinical populations. MPH is also used, without license, by healthy adults, but the impact on their decision-making is not well established. Previous work has found that dopamine receptor activity of healthy adults can modulate the influence of stake magnitude on decisions to persistently gamble after incurring a loss. In this study, we tested for modulation of this effect by MPH in 40 healthy human adults. In a double-blind experiment, 20 subjects received 20 mg of MPH, while 20 matched controls received a placebo. All were provided with 30 rounds of opportunities to accept an incurred loss from their assets or opt for a "double-or-nothing" gamble that would either avoid or double it. Rounds began with a variable loss that would double with every failed gamble until it was accepted, recovered, or reached a specified maximum. Probability of recovery on any gamble was low and ambiguous. Subjects receiving placebo gambled less as the magnitude of the stake was raised and as the magnitude of accumulated loss escalated over the course of the task. In contrast, subjects treated with MPH gambled at a consistent rate, well above chance, across all stakes and trials. Trait reward responsiveness also reduced the impact of high stakes. The findings suggest that elevated catecholamine activity by MPH can disrupt inhibitory influences on persistent risky choice in healthy adults.

Prospect theory does not describe the feedback-related negativity value function

Humans handle uncertainty poorly. Prospect theory accounts for this with a value function in which possible losses are overweighted compared to possible gains, and the marginal utility of rewards decreases with size. fMRI studies have explored the neural basis of this value function. A separate body of research claims that prediction errors are calculated by midbrain dopamine neurons. We investigated whether the prospect theoretic effects shown in behavioral and fMRI studies were present in midbrain prediction error coding by using the feedback-related negativity, an ERP component believed to reflect midbrain prediction errors. Participants' stated satisfaction with outcomes followed prospect theory but their feedback-related negativity did not, instead showing no effect of marginal utility and greater sensitivity to potential gains than losses.

Extrastriatal dopaminergic abnormalities of DA homeostasis in Parkinson's patients with medication-induced pathological gambling: a [11C] FLB-457 and PET study

Impulse control disorders such as pathological gambling (PG) are a serious and common adverse effect of dopamine (DA) replacement medication in Parkinson's disease (PD). Patients with PG have increased impulsivity and abnormalities in striatal DA, in common with behavioural and substance addictions in the non-PD population. To date, no studies have investigated the role of extrastriatal dopaminergic abnormalities in PD patients with PG. We used the PET radiotracer, [11C] FLB-457, with high-affinity for extrastriatal DA D2/3 receptors. 14 PD patients on DA agonists were imaged while they performed a gambling task involving real monetary reward and a control task. Trait impulsivity was measured with the Barratt Impulsivity Scale (BIS). Seven of the patients had a history of PG that developed subsequent to DA agonist medication. Change in [11C] FLB-457 binding potential (BP) during gambling was reduced in PD with PG patients in the midbrain, where D2/D3 receptors are dominated by autoreceptors. The degree of change in [11C] FLB-457 binding in this region correlated with impulsivity. In the cortex, [11C] FLB-457 BP was significantly greater in the anterior cingulate cortex (ACC) in PD patients with PG during the control task, and binding in this region was also correlated with impulsivity. Our findings provide the first evidence that PD patients with PG have dysfunctional activation of DA autoreceptors in the midbrain and low DA tone in the ACC. Thus, altered striatal and cortical DA homeostasis may incur vulnerability for the development of PG in PD, linked with the impulsive personality trait.