Serotonin transporter gene-linked polymorphic region (5-HTTLPR) influences decision making under ambiguity and risk in a large Chinese sample

Cross-species approaches to pathological gambling: a review targeting sex differences, adolescent vulnerability and ecological validity of research tools

Decision-making plays a pivotal role in daily life as impairments in processes underlying decision-making often lead to an inability to make profitable long-term decisions. As a case in point, pathological gamblers continue gambling despite the fact that this disrupts their personal, professional or financial life. The prevalence of pathological gambling will likely increase in the coming years due to expanding possibilities of on-line gambling through the Internet and increasing liberal attitudes towards gambling. It therefore represents a growing concern for society. Both human and animal studies rapidly advance our knowledge on brain-behaviour processes relevant for understanding normal and pathological gambling behaviour. Here, we review in humans and animals three features of pathological gambling which hitherto have received relatively little attention: (1) sex differences in (the development of) pathological gambling, (2) adolescence as a (putative) sensitive period for (developing) pathological gambling and (3) avenues for improving ecological validity of research tools. Based on these issues we also discuss how research in humans and animals may be brought in line to maximize translational research opportunities.

COMT val158met and 5-HTTLPR genetic polymorphisms moderate executive control in cannabis users

The adverse effects of cannabis use on executive functions are still controversial, fostering the need for novel biomarkers able to unveil individual differences in the cognitive impact of cannabis consumption. Two common genetic polymorphisms have been linked to the neuroadaptive impact of Δ9-tetrahydrocannabinol (THC) exposure and to executive functions in animals: the catechol-O-methyltransferase (COMT) gene val158met polymorphism and the SLC6A4 gene 5-HTTLPR polymorphism. We aimed to test if these polymorphisms moderate the harmful effects of cannabis use on executive function in young cannabis users. We recruited 144 participants: 86 cannabis users and 58 non-drug user controls. Both groups were genotyped and matched for genetic makeup, sex, age, education, and IQ. We used a computerized neuropsychological battery to assess different aspects of executive functions: sustained attention (CANTAB Rapid Visual Information Processing Test, RVIP), working memory (N-back), monitoring/shifting (CANTAB ID/ED set shifting), planning (CANTAB Stockings of Cambridge, SOC), and decision-making (Iowa Gambling Task, IGT). We used general linear model-based analyses to test performance differences between cannabis users and controls as a function of genotypes. We found that: (i) daily cannabis use is not associated with executive function deficits; and (ii) COMT val158met and 5-HTTLPR polymorphisms moderate the link between cannabis use and executive performance. Cannabis users carrying the COMT val/val genotype exhibited lower accuracy of sustained attention, associated with a more strict response bias, than val/val non-users. Cannabis users carrying the COMT val allele also committed more monitoring/shifting errors than cannabis users carrying the met/met genotype. Finally, cannabis users carrying the 5-HTTLPR s/s genotype had worse IGT performance than s/s non-users. COMT and SLC6A4 genes moderate the impact of cannabis use on executive functions.

Afraid to help: social anxiety partially mediates the association between 5-HTTLPR triallelic genotype and prosocial behavior

There is growing evidence that the serotonin system influences prosocial behavior. We examined whether anxiety mediated the association between variation in the serotonin transporter gene regulatory region (5-HTTLPR) and prosocial behavior. We collected self-reported tendencies to avoid certain situations and history of helping others using standard instruments and buccal cells for standard 5-HTTLPR genotyping from 398 undergraduate students. Triallelic 5-HTTLPR genotype was significantly associated with prosocial behavior and the effect was partially mediated by social anxiety, such that those carrying the S' allele reported higher levels of social avoidance and lower rates of helping others. These results are consistent with accounts of the role of serotonin on anxiety and prosocial behavior and suggest that targeted efforts to reduce social anxiety in S' allele carriers may enhance prosocial behavior.

Perceived parental rejection mediates the influence of serotonin transporter gene (5-HTTLPR) polymorphisms on impulsivity in Japanese adults

This study examined (1) the interrelationships among 5-HTTLPR genotype, perceived parental rejection, and impulsivity, and (2) meditational models in which perceived paternal/maternal rejection mediates the relationship between the 5-HTTLPR genotype and impulsive behaviour. Participants included 403 adults (152 males and 252 females, mean age = 24.20) who provided genetic data and a set of the questionnaires (BIS11; Barratt Impulsiveness Scale-11 and EMBU; Egna Minnen av Bätraffande Uppfostran). Using SEM (Structural Equation Modeling), we evaluated 3 models for both direct and indirect relationships between 5-HTTLPR (5HTT) and Impulsivity (IMP), via maternal/fraternal rejection (MAT/FAT). In model 1, the direct path from 5HTT and IMP was not significant across the mother’s and father’s analysis. Models 2 and 3 assessed the indirect influence of 5HTT on IMP through MOT/FAT. The paths of models 2 and 3 were all significant and showed a good fit between the hypothesized model and data. Furthermore, the effects of the 5-HTTLPR genotype on impulsiveness in this Japanese sample were particularly accounted for by perceived rejection from the mother or father. The effects from the parents appeared to be robust especially among males. These results may help elucidate the specific pathways of risk in relation to genetic and environment influences on impulsive phenotypes.

A critical review of sex differences in decision-making tasks: focus on the Iowa Gambling Task

It has been observed that men and women show performance differences in the Iowa Gambling Task (IGT), a task of decision-making in which subjects through exploration learn to differentiate long-term advantageous from long-term disadvantageous decks of cards: men choose more cards from the long-term advantageous decks than women within the standard number of 100 trials. Here, we aim at discussing psychological mechanisms and neurobiological substrates underlying sex differences in IGT-like decision-making. Our review suggests that women focus on both win-loss frequencies and long-term pay-off of decks, while men focus on long-term pay-off. Furthermore, women may be more sensitive to occasional losses in the long-term advantageous decks than men. As a consequence hereof, women need 40-60 trials in addition before they reach the same level of performance as men. These performance differences are related to differences in activity in the orbitofrontal cortex and dorsolateral prefrontal cortex as well as in serotonergic activity and left-right hemispheric activity. Sex differences in orbitofrontal cortex activity may be due to organisational effects of gonadal hormones early in life. The behavioural and neurobiological differences in the IGT between men and women are an expression of more general sex differences in the regulation of emotions. We discuss these findings in the context of sex differences in information processing related to evolutionary processes. Furthermore we discuss the relationship between these findings and real world decision-making.

The gambler's fallacy is associated with weak affective decision making but strong cognitive ability

Humans demonstrate an inherent bias towards making maladaptive decisions, as shown by a phenomenon known as the gambler's fallacy (GF). The GF has been traditionally considered as a heuristic bias supported by the fast and automatic intuition system, which can be overcome by the reasoning system. The present study examined an intriguing hypothesis, based on emerging evidence from neuroscience research, that the GF might be attributed to a weak affective but strong cognitive decision making mechanism. With data from a large sample of college students, we found that individuals' use of the GF strategy was positively correlated with their general intelligence and executive function, such as working memory and conflict resolution, but negatively correlated with their affective decision making capacities, as measured by the Iowa Gambling Task. Our result provides a novel insight into the mechanisms underlying the GF, which highlights the significant role of affective mechanisms in adaptive decision-making.

COMT Val158Met polymorphism interacts with stressful life events and parental warmth to influence decision making

Both genetic and environmental factors have been shown to influence decision making, but their relative contributions and interactions are not well understood. The present study aimed to reveal possible gene-environment interactions on decision making in a large healthy sample. Specifically, we examined how the frequently studied COMT Val¹⁵⁸Met polymorphism interacted with an environmental risk factor (i.e., stressful life events) and a protective factor (i.e., parental warmth) to influence affective decision making as measured by the Iowa Gambling Task. We found that stressful life events acted as a risk factor for poor IGT performance (i.e., high reward sensitivity) among Met carriers, whereas parental warmth acted as a protective factor for good IGT performance (i.e., higher IGT score) among Val/Val homozygotes. These results shed some new light on gene-environment interactions in decision making, which could potentially help us understand the underlying etiology of several psychiatric disorders associated with decision making impairment.

Sex determines which section of the SLC6A4 gene is linked to obsessive-compulsive symptoms in normal Chinese college students

Previous case-control and family-based association studies have implicated the SLC6A4 gene in obsessive-compulsive disorder (OCD). Little research, however, has examined this gene's role in obsessive-compulsive symptoms (OCS) in community samples. The present study genotyped seven tag SNPs and two common functional tandem repeat polymorphisms (5-HTTLPR and STin2), which together cover the whole SLC6A4 gene, and investigated their associations with OCS in normal Chinese college students (N = 572). The results revealed a significant gender main effect and gender-specific genetic effects of the SLC6A4 gene on OCS. Males scored significantly higher on total OCS and its three dimensions than did females (ps < .01). The 5-HTTLPR in the promoter region showed a female-specific genetic effect, with the l/l and l/s genotypes linked to higher OCS scores than the s/s genotype (ps < .05). In contrast, a conserved haplotype polymorphism (rs1042173| rs4325622| rs3794808| rs140701| rs4583306| rs2020942) covering from intron 3 to the 3' UTR of the SLC6A4 gene showed male-specific genetic effects, with the CGAAGG/CGAAGG genotype associated with lower OCS scores than the other genotypes (ps < .05). These effects remained significant after controlling for OCS-related factors including participants' depressive and anxiety symptoms as well as stressful life events, and correction for multiple tests. These results are discussed in terms of their implications for our understanding of the sex-specific role of the different sections of the SLC6A4 gene in OCD.

Distorted expectancy coding in problem gambling: is the addictive in the anticipation?

BACKGROUND

Pathologic gamblers are known to have abnormal neural responses associated with experiencing monetary wins and losses. However, neural responsiveness during reward and loss expectations in pathologic gamblers has not yet been investigated.

METHODS

We used a functional magnetic resonance imaging paradigm that allowed us to investigate the dissociable reward- and loss-related expectancies with various probabilities of winning or losing different amounts of money in 15 patients with problem gambling (PRGs) and 16 healthy control subjects (HCs).

RESULTS

Compared with HCs, PRGs showed stronger activation in the bilateral ventral striatum to 5 euro than to 1 euro trials. PRGs also showed more activation of the bilateral ventral striatum and left orbitofrontal cortex associated with gain-related expected value than HCs. In addition, regression analyses indicated a highly significant negative correlation between gambling severity scores and right amygdala activation associated with gain-related expected value coding. There were no group differences in brain activation for loss-related expected value.

CONCLUSIONS

PRGs show higher activity in the reward system during reward expectation than HCs, whereas we observed no difference between PRGs and HC in the loss value system. Furthermore, the negative relation between gambling severity and amygdala activation in gain expected value coding suggests that more severe PRGs are less likely to be risk aversive during gambling. Our study provides evidence that PRGs are characterized by abnormally increased reward expectancy coding, which may render them overoptimistic with regard to gambling outcomes.

Haplotype polymorphism in the alpha-2B-adrenergic receptor gene influences response inhibition in a large Chinese sample

Response inhibition refers to the suppression of inappropriate or irrelevant responses. It has a central role in executive functions, and has been linked to a wide spectrum of prevalent neuropsychiatric disorders. Increasing evidence from neuropharmacological studies has suggested that gene variants in the norepinephrine neurotransmission system make specific contributions to response inhibition. This study genotyped five tag single-nucleotide polymorphisms covering the whole alpha-2B-adrenergic receptor (ADRA2B) gene and investigated their associations with response inhibition in a relatively large healthy Chinese sample (N=421). The results revealed significant genetic effects of the ADRA2B conserved haplotype polymorphisms on response inhibition as measured by stop-signal reaction time (SSRT) (F(2, 418)=5.938, p=0.003). Individuals with the AAGG/AAGG genotype (n=89; mean SSRT=170.2 ms) had significantly shorter SSRTs than did those with either the CCAC/AAGG genotype (n=216; mean SSRT=182.4 ms; uncorrected p=0.03; corrected p=0.09) or the CCAC/CCAC genotype (n=116; mean SSRT=195.8 ms; corrected p<0.002, Cohen's d=0.51). This finding provides the first evidence from association research in support of a critical role of the norepinephrine neurotransmission system in response inhibition. A better understanding of the genetic basis of response inhibition would allow us to develop more effective diagnosis, treatment, and prevention of deficient or underdeveloped response inhibition as well as its related prevalent neuropsychiatric disorders.

A combination of dopamine genes predicts success by professional Wall Street traders

What determines success on Wall Street? This study examined if genes affecting dopamine levels of professional traders were associated with their career tenure. Sixty professional Wall Street traders were genotyped and compared to a control group who did not trade stocks. We found that distinct alleles of the dopamine receptor 4 promoter (DRD4P) and catecholamine-O-methyltransferase (COMT) that affect synaptic dopamine were predominant in traders. These alleles are associated with moderate, rather than very high or very low, levels of synaptic dopamine. The activity of these alleles correlated positively with years spent trading stocks on Wall Street. Differences in personality and trading behavior were also correlated with allelic variants. This evidence suggests there may be a genetic basis for the traits that make one a successful trader.

Rodent versions of the iowa gambling task: opportunities and challenges for the understanding of decision-making

Impaired decision-making is a core problem in several psychiatric disorders including attention-deficit/hyperactivity disorder, schizophrenia, obsessive–compulsive disorder, mania, drug addiction, eating disorders, and substance abuse as well as in chronic pain. To ensure progress in the understanding of the neuropathophysiology of these disorders, animal models with good construct and predictive validity are indispensable. Many human studies aimed at measuring decision-making capacities use the Iowa gambling task (IGT), a task designed to model everyday life choices through a conflict between immediate gratification and long-term outcomes. Recently, new rodent models based on the same principle have been developed to investigate the neurobiological mechanisms underlying IGT-like decision-making on behavioral, neural, and pharmacological levels. The comparative strengths, as well as the similarities and differences between these paradigms are discussed. The contribution of these models to elucidate the neurobehavioral factors that lead to poor decision-making and to the development of better treatments for psychiatric illness is considered, along with important future directions and potential limitations.

A somatic marker perspective of immoral and corrupt behavior

Individuals who engage in corrupt and immoral behavior are in some ways similar to individuals with psychopathy. Normal people refrain from engaging in such behaviors because they tie together the moral value of society and the risk of punishment when they violate social rules. What is it, then, that allows these immoral individuals to behave in this manner, and in some situations even to prosper? When there is a dysfunction of somatic markers, specific disadvantageous impairments in decision-making arise, as in moral judgment, but, paradoxically, under some circumstances, the damage can cause the patient to make optimal financial investment decisions. Interestingly, individuals with psychopathy, a personality disorder, share many of the same behavioral characteristics seen in VMPFC and amygdala lesion patients, suggesting that defective somatic markers may serve as a neural framework for explaining immoral and corrupt behaviors. While these sociopathic behaviors of sometimes famous and powerful individuals have long been discussed, primarily within the realm of social science and psychology, here we offer a neurocognitive perspective on the possible neural roots of immoral and corrupt behaviors.

Serotonin Transporter (5-HTTLPR) Genotype and Childhood Trauma are Associated with Individual Differences in Decision Making

The factors that influence individual differences in decision making are not yet fully characterized, but convergent evidence is accumulating that implicates serotonin (5-HT) system function. Therefore, both genes and environments that influence serotonin function are good candidates for association with risky decision making. In the present study we examined associations between common polymorphisms in the serotonin transporter gene (SLC6A4; 5-HTTLPR and rs25531), the experience of childhood trauma and decision making on the Iowa gambling task (IGT) in 391 (64.5% female) healthy Caucasian adults. Homozygosity for the 5-HTTLPR L allele was associated with riskier decision making in the first block of 20 trials (i.e., decision making under ambiguity, p = 0.004). In addition, mean IGT performance was significantly worse in blocks 3–5 (i.e., decision making under risk, p ≤ 0.05) for those participants who reported experiencing higher levels of childhood trauma. Our findings add to the growing evidence that genetic variation in the 5-HT system is associated with individual differences in decision making under ambiguity; and we report that the experience of childhood trauma is associated with relatively poor decision making under risk.

Contributions of serotonin in addiction vulnerability

The serotonin (5-hydroxytryptamine; 5-HT) system has long been associated with mood and its dysregulation implicated in the pathophysiology of mood and anxiety disorders. While modulation of 5-HT neurotransmission by drugs of abuse is also recognized, its role in drug addiction and vulnerability to drug relapse is a more recent focus of investigation. First, we review preclinical data supporting the serotonergic raphe nuclei and their forebrain projections as targets of drugs of abuse, with emphasis on the effects of psychostimulants, opioids and ethanol. Next, we examine the role of 5-HT receptors in impulsivity, a core behavior that contributes to the vulnerability to addiction and relapse. Finally, we discuss evidence for serotonergic dysregulation in comorbid mood and addictive disorders and suggest novel serotonergic targets for the treatment of addiction and the prevention of drug relapse.

Looking on the bright side of serotonin transporter gene variation

Converging evidence indicates an association of the short (s), low-expressing variant of the repeat length polymorphism, serotonin transporter-linked polymorphic region (5-HTTLPR), in the human serotonin transporter gene (5-HTT, SERT, SLC6A4) with anxiety-related traits and increased risk for depression in interaction with psychosocial adversity across the life span. However, genetically driven deficient serotonin transporter (5-HTT) function would not have been maintained throughout evolution if it only exerted negative effects without conveying any gain of function. Here, we review recent findings that humans and nonhuman primates carrying the s variant of the 5-HTTLPR outperform subjects carrying the long allele in an array of cognitive tasks and show increased social conformity. In addition, studies in 5-HTT knockout rodents are included that provide complementary insights in the beneficial effects of the 5-HTTLPR s-allele. We postulate that hypervigilance, mediated by hyperactivity in corticolimbic structures, may be the common denominator in the anxiety-related traits and (social) cognitive superiority of s-allele carriers and that environmental conditions determine whether a response will turn out to be negative (emotional) or positive (cognitive, in conformity with the social group). Taken together, these findings urge for a conceptual change in the current deficit-oriented connotation of the 5-HTTLPR variants. In fact, these factors may counterbalance or completely offset the negative consequences of the anxiety-related traits. This notion may not only explain the modest effect size of the 5-HTTLPR and inconsistent reports but may also lead to a more refined appreciation of allelic variation in 5-HTT function.