Association study of dopamine receptor D2 TaqI A polymorphism and reward-related personality traits in healthy Korean young females

Motivational learning biases are differentially modulated by genetic determinants of striatal and prefrontal dopamine function

Dopaminergic neurotransmission plays a pivotal role in appetitively motivated behavior in mammals, including humans. Notably, action and valence are not independent in motivated tasks, and it is particularly difficult for humans to learn the inhibition of an action to obtain a reward. We have previously observed that the carriers of the DRD2/ANKK1 TaqIA A1 allele, that has been associated with reduced striatal dopamine D2 receptor expression, showed a diminished learning performance when required to learn response inhibition to obtain rewards, a finding that was replicated in two independent cohorts. With our present study, we followed two aims: first, we aimed to replicate our finding on the DRD2/ANKK1 TaqIA polymorphism in a third independent cohort (N = 99) and to investigate the nature of the genetic effects more closely using trial-by-trial behavioral analysis and computational modeling in the combined dataset (N = 281). Second, we aimed to assess a potentially modulatory role of prefrontal dopamine availability, using the widely studied COMT Val108/158Met polymorphism as a proxy. We first report a replication of the above mentioned finding. Interestingly, after combining all three cohorts, exploratory analyses regarding the COMT Val108/158Met polymorphism suggest that homozygotes for the Met allele, which has been linked to higher prefrontal dopaminergic tone, show a lower learning bias. Our results corroborate the importance of genetic variability of the dopaminergic system in individual learning differences of action-valence interaction and, furthermore, suggest that motivational learning biases are differentially modulated by genetic determinants of striatal and prefrontal dopamine function.

[The interaction effect of ANKK1/DRD2 TaqIA and HTR2C Cys23Ser on approach motivation in schizophrenic patients and normals]

AIM

To evaluate the association of the DRD2 gene and DRD2 x HTR2C interaction with hedonic and activational aspects of approach motivation in schizophrenia.

MATERIAL AND METHODS

Genotypes at polymorphic loci DRD2 rs1800497 and HTR2C rs6318 (Cys23Ser) were identified in a sample that included 174 patients with schizophrenic spectrum disorders and 268 healthy subjects without a family history of psychoses. The participants completed the BIS/BAS and Temporal Experience of Pleasure Scale (TEPS).

RESULTS AND CONCLUSION

A MANCOVA with sex and age as covariates revealed the effect of the 'DRD2 x HTR2C x diagnosis' interaction on the BAS scores (p=0.033). The effect was significant for the Fun-Seeking and Drive scales. Among patients, the carriers of the DRD2 TT/CT x HTR2C GG/G genotype showed the highest scores on the both scales, and those with the minor alleles in the two loci had the lowest ones. Differences between these groups were nominally significant for both the Fun-Seeking and Drive, but did not survive the correction for multiple comparisons. Among controls, subjects without minor alleles demonstrated the highest scores on these two scales. They differed significantly from the carriers of the DRD2 TT/CT+HTR2C GG/G genotype on the Fun-Seeking (p=0.008). No effects of DRD2 and HTR2C on TEPS scores were found. In general, the results of the study can be interpreted in favor of the hypothesis about the role of the HTR2C and DRD2 genes interaction in the variability of the activational aspects of approach motivation in schizophrenia and healthy subjects. However, the lack of differences survived correction for multiple comparisons makes it difficult to interpret the revealed effects.

Parenting and adolescents' psychological adjustment: Longitudinal moderation by adolescents' genetic sensitivity

We examined whether adolescents' genetic sensitivity, measured by a polygenic index score, moderated the longitudinal associations between parenting and adolescents' psychological adjustment. The sample included 323 mothers, fathers, and adolescents (177 female, 146 male; Time 1 [T1] average age = 12.61 years, SD = 0.54 years; Time 2 [T2] average age = 13.59 years, SD = 0.59 years). Parents' warmth and hostility were rated by trained, independent observers using videotapes of family discussions. Adolescents reported their symptoms of anxiety, depressed mood, and hostility at T1 and T2. The results from autoregressive linear regression models showed that adolescents' genetic sensitivity moderated associations between observations of both mothers' and fathers' T1 parenting and adolescents' T2 composite maladjustment, depression, anxiety, and hostility. Compared to adolescents with low genetic sensitivity, adolescents with high genetic sensitivity had worse adjustment outcomes when parenting was low on warmth and high on hostility. When parenting was characterized by high warmth and low hostility, adolescents with high genetic sensitivity had better adjustment outcomes than their counterparts with low genetic sensitivity. The results support the differential susceptibility model and highlight the complex ways that genes and environment interact to influence development.

Gene polymorphisms associated with temperament

When individuals are exposed to stressful environmental challenges, the response varies widely in one or more of three components: psychology, behavior and physiology. This variability among individuals can be defined as temperament. In recent years, an increasing large body of evidence suggests that the dimensions of temperament, as well as personality, psychological disorders and behavioral traits, are influenced by genetic factors, and much of the variation appears to involve variation in genes or gene polymorphisms in the hypothalamic-pituitary-adrenocortical (HPA) axis and the behavior-controlling neurotransmitter networks. Here, we review our current understanding of the probabilistic impact of a number of candidate gene polymorphisms that control temperament, psychological disorders and behavioral traits in animals and human, including the gene polymorphisms related to corticotrophin-releasing hormone (CRH) production and adrenal cortisol production involved in the HPA axis, and a large number of gene polymorphisms in the dopaminergic and serotonergic neurotransmitter networks. It will very likely to assist in diagnosis and treatment of human relevant disorders, and provide useful contributions to our understanding of evolution, welfare and conservation, for animals in the wild and in production systems. Additionally, investigations of gene-gene and gene-environment complex interactions in humans and animals need further clear illustration.

Effects of Mind-Body Training on Personality and Behavioral Activation and Inhibition System According to BDNF Val66Met Polymorphism

OBJECTIVE

It has been known that mind-body training (MBT) can affect personality and behavior system as well as emotional well-being, but different effects of MBT on them has not been reported according to BDNF genetic polymorphism.

METHODS

Healthy subjects consisted of 64 subjects and the MBT group who practiced meditation regularly consisted of 72 practitioners. Participants completed neuroticism-extraversion-openness (NEO) Five-Factor Inventory and Behavioral Activation System/Behavioral Inhibition System (BAS/BIS) scales. All subjects were genotyped for the BDNF Val66Met polymorphism.

RESULTS

In the same genotypes of the BDNF Val/Val+Val/Met group, MBT group showed the increased Extraversion (p=0.033) and the increased Openness to Experience (p=0.004) compared to the control group. Also, in the same Met/Met carriers, MBT group exhibited the increase of Extraversion (p=0.008), the reduction of Neuroticism (p=0.002), and the increase of Openness to Experience (p=0.008) compared to the control group. In the same genotypes of the BDNF Val/Val+Val/Met group, MBT group showed the decreased BAS-Reward Responsiveness (p=0.016) and the decrease of BIS (p=0.004) compared to the control group. In the BDNF Met/Met group, MBT group increased BAS-Fun Seeking (p=0.045) and decreased BIS (p=0.013) compared to the control group.

CONCLUSION

MBT would differently contribute to NEO personality and BAS/BIS according to BDNF genetic polymorphism, compensating for different vulnerable traits based on each genotype.

The influence of genes on "positive valence systems" constructs: A systematic review

In 2009, the U.S. National Institute of Mental Health (NIMH) proposed an approach toward the deconstruction of psychiatric nosology under the research domain criteria (RDoC) framework. The overarching goal of RDoC is to identify robust, objective measures of behavior, emotion, cognition, and other domains that are more closely related to neurobiology than are diagnoses. A preliminary framework has been constructed, which has connected molecules, genes, brain circuits, behaviors, and other elements to dimensional psychiatric constructs. Although the RDoC framework has salience in emerging studies, foundational literature that pre-dated this framework requires synthesis and translation to the evolving objectives and nomenclature of RDoC. Toward this end, we review the candidate-gene association, linkage, and genome-wide studies that have implicated a variety of loci and genetic polymorphisms in selected Positive Valence Systems (PVS) constructs. Our goal is to review supporting evidence to currently listed genes implicated in this domain and novel candidates. We systematically searched and reviewed literature based on keywords listed under the June, 2011, edition of the PVS matrix on the RDoC website (http://www.nimh.nih.gov/research-priorities/rdoc/positive-valence-systems-workshop-proceedings.shtml), which were supplemented with de novo keywords pertinent to the scope of our review. Several candidate genes linked to the PVS framework were identified from candidate-gene association studies. We also identified novel candidates with loose association to PVS traits from genome-wide studies. There is strong evidence suggesting that PVS constructs, as currently conceptualized under the RDoC initiative, index genetically influenced traits; however, future research, including genetic epidemiological, and psychometric analyses, must be performed.

A tale of two diatheses: Temperament, BIS, and BAS as risk factors for mood disorder

OBJECTIVE

Learning more about how biological traits, like temperament and sensitivity in the behavioral inhibition (BIS) and behavioral activation (BAS) systems, relate to mood pathology is consistent with the Research Domain Criteria initiative׳s goal of investigating mechanisms of risk.

METHOD

Korean young adults (n=128) and American young adults (n=630, of whom 23 has recent treatment for bipolar disorder, and 21for depression) completed self-report questionnaires, including the TEMPS-A, the BIS/BAS scales, Beck Depression Inventory (BDI), and Hypomanic Checklist (HCL-32). Linear regression quantified relations between mood symptoms, sample characteristics, temperament, and BIS/BAS.

RESULTS

Temperament styles explained 49% of the variance in BDI scores. BIS explained an additional 1% of the variance in BDI scores. BAS Fun and Reward (p<.01), in addition to cyclothymic and hyperthymic temperaments (p<.001) explained 21% of the variance in HCL-32 scores. Sample characteristics were not significant predictors in the full model.

LIMITATIONS

Differences in sample size, the cross-sectional study design, and lack of collateral report or behavioral measures of constructs are limitations.

CONCLUSIONS

Affective temperament and BIS/BAS are complementary but distinct constructs. Affective temperament, particularly cyclothymic, may represent a stronger diathesis for mood pathology, and seems potent irrespective of culture or diagnosis. Assessing temperament may help overcome some challenges in diagnosing mood disorders.

The Dopamine D2 Receptor Polymorphism (DRD2 TaqIA) Interacts with Maternal Parenting in Predicting Early Adolescent Depressive Symptoms: Evidence of Differential Susceptibility and Age Differences

Most gene-environment interaction research on depression has largely focused on negative environment and to a lesser extent on positive environment. Moreover, to date few studies have directly examined G × E at different periods in development, particularly during early adolescence. The present study addressed these issues by examining the concurrent and prospective longitudinal effects of maternal parenting, DRD2 TaqIA polymorphism, and their interaction on adolescent depressive symptoms in a sample of 1026 Chinese adolescents (Mage = 11.33 ± 0.47 years at T1, 50.3% girls) in a three-wave longitudinal study from age 11 to 13. Results indicated that maternal positive and negative parenting significantly concurrently predicted adolescent depressive symptoms at all three waves, whereas TaqIA polymorphism had no main effect on depressive symptoms. TaqIA polymorphism interacted with negative parenting in predicting concurrent depressive symptoms at age 11 and 12. A1 carriers were more susceptible to negative parenting compared to A2A2 homozygotes, such that adolescents carrying A1 alleles experiencing high negative parenting reported more depressive symptoms but fared better when experiencing low negative parenting. However, the interaction became nonsignificant at age 13, indicating the interaction of TaqIA polymorphism and maternal parenting may vary with development. Also, there was no G × E effect on longitudinal change in depression. The findings provided evidence in support of the differential susceptibility hypothesis and shed light on the potential for dynamic change in gene-environment interactions over development.

Valenced action/inhibition learning in humans is modulated by a genetic variant linked to dopamine D2 receptor expression

Motivational salience plays an important role in shaping human behavior, but recent studies demonstrate that human performance is not uniformly improved by motivation. Instead, action has been shown to dominate valence in motivated tasks, and it is particularly difficult for humans to learn the inhibition of an action to obtain a reward, but the neural mechanism behind this behavioral specificity is yet unclear. In all mammals, including humans, the monoamine neurotransmitter dopamine is particularly important in the neural manifestation of appetitively motivated behavior, and the human dopamine system is subject to considerable genetic variability. The well-studied TaqIA restriction fragment length polymorphism (rs1800497) has previously been shown to affect striatal dopamine metabolism. In this study we investigated a potential effect of this genetic variation on motivated action/inhibition learning. Two independent cohorts consisting of 87 and 95 healthy participants, respectively, were tested using the previously described valenced go/no-go learning paradigm in which participants learned the reward-associated no-go condition significantly worse than all other conditions. This effect was modulated by the TaqIA polymorphism, with carriers of the A1 allele showing a diminished learning-related performance enhancement in the rewarded no-go condition compared to the A2 homozygotes. This result highlights a modulatory role for genetic variability of the dopaminergic system in individual learning differences of action-valence interaction.

Genetic variation of the RASGRF1 regulatory region affects human hippocampus-dependent memory

The guanine nucleotide exchange factor RASGRF1 is an important regulator of intracellular signaling and neural plasticity in the brain. RASGRF1-deficient mice exhibit a complex phenotype with learning deficits and ocular abnormalities. Also in humans, a genome-wide association study has identified the single nucleotide polymorphism (SNP) rs8027411 in the putative transcription regulatory region of RASGRF1 as a risk variant of myopia. Here we aimed to assess whether, in line with the RASGRF1 knockout mouse phenotype, rs8027411 might also be associated with human memory function. We performed computer-based neuropsychological learning experiments in two independent cohorts of young, healthy participants. Tests included the Verbal Learning and Memory Test (VLMT) and the logical memory section of the Wechsler Memory Scale (WMS). Two sub-cohorts additionally participated in functional magnetic resonance imaging (fMRI) studies of hippocampus function. 119 participants performed a novelty encoding task that had previously been shown to engage the hippocampus, and 63 subjects participated in a reward-related memory encoding study. RASGRF1 rs8027411 genotype was indeed associated with memory performance in an allele dosage-dependent manner, with carriers of the T allele (i.e., the myopia risk allele) showing better memory performance in the early encoding phase of the VLMT and in the recall phase of the WMS logical memory section. In fMRI, T allele carriers exhibited increased hippocampal activation during presentation of novel images and during encoding of pictures associated with monetary reward. Taken together, our results provide evidence for a role of the RASGRF1 gene locus in hippocampus-dependent memory and, along with the previous association with myopia, point toward pleitropic effects of RASGRF1 genetic variations on complex neural function in humans.

Gene Effects and G × E Interactions in the Differential Prediction of Three Aspects of Impulsiveness

Several polymorphisms relevant to dopamine and serotonin have been identified as potential contributors to individual differences in impulsivity versus self-control. Because impulsivity is a multifaceted construct, a need remains to examine more closely how various genes relate to different aspects of impulsivity. We examined four dopamine-related polymorphisms and the serotonin transporter as predictors of three aspects of impulsivity, two bearing on impulsive reactions to emotions and one on difficulty in completing intended actions. Early adversity was also examined as a potentiator of genetic effects. Undergraduates completed measures of impulsivity and early adversity and were genotyped. COMT, BDNF, DRD4, and 5HTTLPR (the latter two in interaction with early adversity) made independent contributions to prediction of Pervasive Influence of Feelings. BDNF made a contribution to Lack of Follow-Through. ANKK1 and 5HTTLPR (both in interaction with early adversity) made independent contributions to Feelings Trigger Action. Thus, five polymorphisms contributed to predicting impulsivity, but different polymorphisms related to different aspects.

The dopaminergic reward system and leisure time exercise behavior: a candidate allele study

PURPOSE

Twin studies provide evidence that genetic influences contribute strongly to individual differences in exercise behavior. We hypothesize that part of this heritability is explained by genetic variation in the dopaminergic reward system. Eight single nucleotide polymorphisms (SNPs in DRD1: rs265981, DRD2: rs6275, rs1800497, DRD3: rs6280, DRD4: rs1800955, DBH: rs1611115, rs2519152, and in COMT: rs4680) and three variable number of tandem repeats (VNTRs in DRD4, upstream of DRD5, and in DAT1) were investigated for an association with regular leisure time exercise behavior.

MATERIALS AND METHODS

Data on exercise activities and at least one SNP/VNTR were available for 8,768 individuals aged 7 to 50 years old that were part of the Netherlands Twin Register. Exercise behavior was quantified as weekly metabolic equivalents of task (MET) spent on exercise activities. Mixed models were fitted in SPSS with genetic relatedness as a random effect.

RESULTS

None of the genetic variants were associated with exercise behavior (P>.02), despite sufficient power to detect small effects.

DISCUSSION AND CONCLUSIONS

We did not confirm that allelic variants involved in dopaminergic function play a role in creating individual differences in exercise behavior. A plea is made for large genome-wide association studies to unravel the genetic pathways that affect this health-enhancing behavior.

Motivational salience and genetic variability of dopamine D2 receptor expression interact in the modulation of interference processing

Dopamine has been implicated in the fine-tuning of complex cognitive and motor function and also in the anticipation of future rewards. This dual function of dopamine suggests that dopamine might be involved in the generation of active motivated behavior. The DRD2 TaqIA polymorphism of the dopamine D2 receptor gene (rs1800497) has previously been suggested to affect striatal function with carriers of the less common A1 allele exhibiting reduced striatal D2 receptor density and increased risk for addiction. Here we aimed to investigate the influences of DRD2 TaqIA genotype on the modulation of interference processing by reward and punishment. Forty-six young, healthy volunteers participated in a behavioral experiment, and 32 underwent functional magnetic resonance imaging (fMRI). Participants performed a flanker task with a motivation manipulation (monetary reward, monetary loss, neither, or both). Reaction times (RTs) were shorter in motivated flanker trials, irrespective of congruency. In the fMRI experiment motivation was associated with reduced prefrontal activation during incongruent vs. congruent flanker trials, possibly reflecting increased processing efficiency. DRD2 TaqIA genotype did not affect overall RTs, but interacted with motivation on the congruency-related RT differences, with A1 carriers showing smaller interference effects to reward alone and A2 homozygotes exhibiting a specific interference reduction during combined reward (REW) and punishment trials (PUN). In fMRI, anterior cingulate activity showed a similar pattern of genotype-related modulation. Additionally, A1 carriers showed increased anterior insula activation relative to A2 homozygotes. Our results point to a role for genetic variations of the dopaminergic system in individual differences of cognition-motivation interaction.

Association study on pathological gambling and polymorphisms of dopamine D1, D2, D3, and D4 receptor genes in a Korean population

Several studies have reported that some dopaminergic receptor polymorphisms are associated with pathological gambling (PG). Considering that there are major race and ethnic group difference in dopaminergic polymorphisms, the result of genetic association studies should be confirmed in more homogeneous population to avoid problems of population stratification. The present study aimed to investigate whether selected polymorphisms in the dopamine receptors genes (DRD1, DRD2, DRD3, and DRD4) are associated with PG in Korean population which is consisted of only Korean ancestry. Subjects were 104 men with a diagnosis of PG and 114 unrelated age-matched normal control men. Genotyping was performed for the DRD1 gene -48 A/G, DRD2 gene TaqI A, DRD3 gene Ser9Gly, and DRD4 gene exon III variable number tandem repeat polymorphisms. The method of multifactor dimensionality reduction (MDR) was used to analyze gene-gene interactions. There were no differences in the frequencies of any studied polymorphisms between patients with PG and normal controls. MDR analysis did not show a significant effect of the 4 dopamine receptor gene polymorphisms on susceptibility to PG (P > 0.05). The present study suggests that the analyzed polymorphisms of the dopamine receptor genes might not be associated with PG in a Korean population.

Association between the dopamine D2 receptor (DRD2) polymorphism and the personality traits of healthy Japanese participants

BACKGROUND

Dopamine neurotransmitter systems have been associated with reward-related and novelty-seeking personality traits. We investigated the possible relationship between the personality traits measured by the Temperament and Character Inventory (TCI) and the TaqI A and -141C Ins/Del polymorphisms in the dopamine D2 receptor gene (DRD2).

METHODS

The sample consisted of 1084 healthy Japanese medical students and medical staff (age=29.0±9.7 years), each of whom completed the TCI. Their genomic DNA was isolated from whole blood and genotyped using the TaqMan allele-specific assay method. The associations between gene polymorphisms and the scores for TCI were statistically analyzed by one-way analysis of covariance (ANCOVA) adjusting age. Males and females were analyzed separately. Epstatis was assesses using two-way ANCOVA between the DRD2 and ANKK1 genes.

RESULTS

Men with the Ins/Del genotype of the -141C Ins/Del polymorphism had significantly higher self-directedness scores than those with the Ins/Ins genotype (p=0.021). None of the TCI scores differed among women with regard to the three genotype groups of the -141C Ins/Del polymorphism. The DRD2/ANKK1 Taq1 A polymorphism did not affect any TCI factor for either men or women. An epistatic analysis did not reveal main effects of the two genes with regard to TCI scores, but an ANKK1×DRD2 interaction significantly predicted TCI scores.

CONCLUSION

These findings suggest the possibility that the -141C Ins/Del polymorphism and the DRD2/ANKK1 Taq1 A polymorphism are not strongly linked to personality traits directly, but influences them under the interaction between the DRD2 and ANKK1 genes.

The role of dopamine transporter (SLC6A3) and dopamine D2 receptor/ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1) gene polymorphisms in personality traits

Variations in personality traits are caused by interactions between multiple genes of small effect and environmental factors. To date, gender- and ethnicity-specific variations in personality have been established. In the present study, we aimed to test: (1) the effects of four polymorphisms of dopamine system genes: ANKK1/DRD2 Taq1A, DRD2 rs6275, SLC6A3 40-bp VNTR and rs27072, on personality traits; (2) whether these effects differ between men and women and between Russians and Tatars. A sample of 652 healthy individuals (222 men and 430 women) of Caucasian origin (233 Russians and 419 Tatars) from Russia was subjected to personality traits assessment with Eysenck Personality Inventory (EPI) and Temperament and Character Inventory-125 (TCI-125). The associations between each personality trait and polymorphisms were assessed with regression models adjusted for gender and ethnicity. There were significant effects of ANKK1/DRD2 Taq1A on Neuroticism (p=0.016) and of SLC6A3 rs27072 on Persistence (p=0.021) in both genders. The association between ANKK1/DRD2 Taq1A A2/A2-genotype and higher Novelty Seeking and lower Reward Dependence was shown in men only (p for gender interaction=0.018). In women only, there was a significant association between SLC6A3 10R*G-haplotype and higher Persistence (p=0.002). Our findings provide evidence for a modifying effect of gender on the associations between dopamine system genes and approach-related traits (in men) and Persistence (in women).

Heightened sensitivity to reward and punishment in anorexia nervosa

OBJECTIVE

The objective of this study is to test whether females with anorexia nervosa (AN) have increased sensitivity to punishing or rewarding stimuli, behaviors that could drive high self-control and anxious, avoidant behaviors.

METHOD

Sixty-four females completed the study: 33 control females (CFs, mean age 19.7 years) and 31 females with AN (mean age 19.6 years). Participants completed diagnostic exams, questionnaires for eating disorder severity and personality, and the Sensitivity to Punishment/Sensitivity to Reward Questionnaire (SPSRQ).

RESULTS

Females with AN scored higher than CFs on SPSRQ sensitivity to punishment (p < 0.00001) and sensitivity to reward (p = 0.005). Females with AN without anxiety or depression continued to have increased SPSRQ scores compared to CFs.

DISCUSSION

This is the first study comparing the SPSRQ in females with AN and CFs. Results suggest that reward and punishment sensitivity are increased in females with AN and could be potential trait markers. It is possible that harm-avoidant, anxious behaviors in females with AN are related to this heightened sensitivity.

DRD2/ANKK1 TaqI A polymorphism affects corticostriatal activity in response to negative affective facial stimuli

DRD2/ANKK1 TaqI A polymorphism has been suggested to be involved in a reward-related psychiatric disorders. However, the effect of Dopamine receptor D2 (DRD2) on emotional processing has not been investigated yet. We investigated the possible relationship between DRD2/ANKK1 TaqI A polymorphism and corticostriatal response to negative facial stimuli using functional magnetic resonance imaging. All participants were genotyped with regard to the DRD2/ANKK1 TaqI A polymorphism. Our results suggest an association between the DRD2/ANKK1 TaqI A polymorphism and activations in the putamen, the anterior cingulate cortex, and amygdala in response to negative facial stimuli. Furthermore, molecular heterosis at the TaqI polymorphism of DRD2/ANKK1 may play an important role in affective regulation by corticostriatal pathway.

A new scale for measuring reward responsiveness

Several psychological theories assume that there are two basic brain mechanisms that guide behavior: an avoidance or inhibition system, which is responsive to signals of punishment, and an approach or activation system, which is sensitive to signals of reward. Several self-report scales have been developed to assess the sensitivity to punishment and reward, and these instruments have been shown to be useful in research on personality, psychopathology, and underlying biological substrates. However, it is also true that in particular scales for measuring reward responsiveness (RR) suffer from various inadequacies. Therefore, a new RR scale was developed and subjected to an extensive psychometric evaluation. The results show that this scale measures a single factor, RR that is clearly independent of punishment sensitivity. Further, the data indicated that the internal consistency, convergent validity, discriminant validity, test–retest reliability, and predictive properties of the new scale were all adequate. It can be concluded that the RR scale is a psychometrically sound instrument that may be useful for researchers with interest in the personality construct of RR.

Epistasis of the DRD2/ANKK1 Taq Ia and the BDNF Val66Met polymorphism impacts novelty seeking and harm avoidance

Mounting evidence from animal studies show that the mesolimbic dopaminergic pathways are modulated by the brain-derived neurotrophic factor (BDNF). This study investigates in N=768 healthy Caucasian participants the influence of two prominent functional single-nucleotide polymorphisms (SNPs) on the BDNF gene (BDNF Val66Met SNP) and the ankyrin repeat and kinase domain containing 1 (ANKK1) gene (DRD2 Taq Ia/ANKK1 SNP) on the personality traits of Novelty Seeking and Harm Avoidance, which are mediated, in part, through dopaminergic mesolimbic circuitry. Carriers of the 66Met+/A1+ variant scored lowest on Novelty Seeking and highest on Harm Avoidance, compared to all other genotype groups. These participants are characterized by a relatively low D(2) receptor density in the striatum and an impaired activity-dependent secretion of BDNF. This is one of the first genetic association studies to show a modulatory role for BDNF genetic variation on genetically mediated differences in the mesolimbic dopaminergic system in the context of human personality.

Variation in DRD2 dopamine gene predicts Extraverted personality

Quantitative geneticists estimate the heritability of Extraverted personality to be around 40-60%. Theory and research which links Extraversion with variation in dopaminergic function suggests that dopaminergic genes should be a start-point for molecular genetic investigations of this trait. Recent endeavours in this area have met with some encouragement but also setbacks. In this study, we investigate the relationship between Extraversion and the DRD2 TaqIA/ANKK1 polymorphism in 224 university students. Presence of at least one copy of the A1 allele was associated with significantly higher Extraversion. The robustness of this finding was confirmed through bootstrap analysis. Findings are discussed in relation to the broader literature, in particular, methodological issues which may have obscured this finding in previous research.

The D2 dopamine receptor gene variant C957T affects human fear conditioning and aversive priming

Polymorphisms of DRD2 and ANKK1 have been associated with psychiatric syndromes where there is believed to be an underlying learning process deficit such as addiction, post-traumatic stress disorder and psychopathy. We investigated the effects of the DRD2 C957T and ANKK1 TaqIA single nucleotide polymorphism (SNP), which have been associated with psychopathic traits in alcoholic patients, on fear conditioning and aversive priming in healthy volunteers. We found that the DRD2 C957T SNP, but not the ANKK1 TaqIA SNP, was associated with both differential conditioning of the skin conductance response and the aversive priming effect. There were no differences between the genotype groups with respect to the extinction of the skin-conductance conditioned response. These results suggest that the C957T SNP could be related to learning differences associated with the risk of developing psychiatric disorders in individuals that are carriers of the C homozygous genotype. Our genetic data raise the possibility that the dopaminergic system functional variations determined by this SNP could affect fear learning.