Don't miss the chance to reap the fruits of recent advances in behavioral genetics.

In her target article, Burt revives a by now ancient debate on nature and nurture, and the ways to measure, disentangle, and ultimately trust one or the other of these forces. Unfortunately, she largely dismisses recent advances in behavior genetics and its huge potential in contributing to a better prediction and understanding of complex traits in social sciences.

Spatio-temporal theta pattern dissimilarity in the right centro-parietal area during memory generalization.

Generalization across past events may guide our action in novel situations. Although generalization is a fundamental memory process, its neural underpinnings are not fully understood yet. In the present experiment, we combinedElectroencephalography(EEG) with multivariate representational similarity analysis (RSA) to examine in particular the role of spatio-temporal patterns of theta oscillations known to be important for associative memory processes, in memory generalization. We recorded EEG while healthy participants (n = 56) performed an acquired equivalence task. In this task, participants first acquired multiple associations among antecedent and consequent stimuli before they were required to transfer the acquired knowledge to novel stimulus pairs, thus probing memory generalization. Our behavioural data indicated that participants learned the initial associations well and transferred these associations successfully to novel test stimuli, demonstrating successful memory generalization. Our neural data revealed that, compared to mere memory retrieval, generalization was associated with significantly increased pattern dissimilarity of theta activity in the right centro-parietal area (electrodes P4 and P6). This pattern was specific to theta oscillations and not observed in other frequency bands. Our findings suggest an important role of theta oscillations in memory generalization, potentially serving the reactivation and integration of distinct events that enable the generalization across experiences.

Personality Neuroscience: An Emerging Field with Bright Prospects.

Personality neuroscience is the study of persistent psychological individual differences, typically in the general population, using neuroscientific methods. It has the potential to shed light on the neurobiological mechanisms underlying individual differences and their manifestation in ongoing behavior and experience. The field was inaugurated many decades ago, yet has only really gained momentum in the last two, as suitable technologies have become widely available. Personality neuroscience employs a broad range of methods, including molecular genetics, pharmacological assays or manipulations, electroencephalography, and various neuroimaging modalities, such as magnetic resonance imaging and positron emission tomography. Although exciting progress is being made in this young field, much remains unknown. In this brief review, we discuss discoveries that have been made, methodological challenges and advances, and important questions that remain to be answered. We also discuss best practices for personality neuroscience research and promising future directions for the field.

Examining the reliability and validity of two versions of the Effort-Expenditure for Rewards Task (EEfRT).

The Effort-Expenditure for Rewards Task (EEfRT) has gained validity evidence from several studies. However, various modifications have been applied to the original version, which have never been compared systematically. In Study 1, we tested 120 healthy participants to directly compare two versions of the EEfRT. In Study 2, we tested a larger sample of 394 healthy participants to further examine the original EEfRT. We replicated the split-half reliability of both task versions. However, self-reported personality traits (e.g., trait BAS) correlated with only some task performance parameters in Study 1, which did not replicate for the original EEfRT in Study 2. Our results indicate complex and sometimes inconsistent relations between different personality traits, task properties, and reward attributes.

Does openness/intellect predict sensitivity to the reward value of information?

A recent theory proposes that the personality trait openness/intellect is underpinned by differential sensitivity to the reward value of information. This theory draws on evidence that midbrain dopamine neurons respond to unpredicted information gain, mirroring their responses to unpredicted primary rewards. Using a choice task modelled on this seminal work (Experiment 1, N = 139, 69% female), we examined the relation between openness/intellect and willingness to pay for non-instrumental information (i.e., information with no secondary utility). We also assessed whether any such relation was moderated by the dopamine D2 receptor antagonist sulpiride (Experiment 2, N = 164, 100% male). Unexpectedly, most measures of openness/intellect were unrelated to costly information preference in both experiments, and some predicted a decreased willingness to incur a cost for information. In Experiment 2, this cost-dependent association between openness/intellect and information valuation appeared in the placebo condition but not under sulpiride. In addition, participants were more willing to pay for moderately costly information under sulpiride compared to placebo, consistent with a dopaminergic basis to information valuation. Potential refinements to the information valuation theory of openness/intellect are discussed in the light of these and other emerging findings.

The Selective Dopamine D2 Blocker Sulpiride Modulates the Relationship Between Agentic Extraversion and Executive Functions.

Initial studies suggest that agentic extraversion and executive functions (EF) are associated, because they share influences of individual differences in the dopamine (DA) system. However, it is unclear whether previously reported associations are specific to certain EFs (e.g., to updating or shifting) or due to shared variance among EF tasks. We investigated the DA-related relationship between agentic extraversion and two EF tasks in a placebo-controlled between-group design with the DA D2 receptor blocker sulpiride (200 mg) in 92 female volunteers. Our goals were to investigate whether (1) there is an association between agentic extraversion and EFs measured with two different tasks (3-back and switching), (2) this association is sensitive to a pharmacological manipulation of DA, and (3) the effects can be ascribed to shared or specific task variance. We observed the expected interaction between drug condition and agentic extraversion for both tasks in a multivariate multiple linear regression model, which supports the DA theory of extraversion. Subsequent univariate analyses revealed a highly similar interaction effect between drug condition and agentic extraversion on two of three performance measures and this effect was somewhat attenuated when we controlled for shared task variance. This pattern matches the interpretation that the association between agentic extraversion and both tasks is partly due to DA-based processes shared among the tasks. Our results, although limited by the low reliability of the switching task, suggest that variance components and measurement difficulties of EF tasks should be considered when investigating personality-related individual differences in EFs.

A low dosage of the dopamine D2-receptor antagonist sulpiride affects effort allocation for reward regardless of trait extraversion.

Dopamine (DA) is known to be involved in various aspects of reward processing and goal-directed behavior. The present preregistered study aims at directly accessing the causal influence of DA activity on reward motivation in humans, while also accounting for trait extraversion. Therefore, we examined the effect of a single dose of the DA D2 receptor antagonist sulpiride (200 mg) on effort allocation in a modified version of the Effort-Expenditure for Reward Task (EEfRT). Based on its presumably DA increasing action, we expected the low dose of sulpiride to increase participants' willingness to allocate effort during the modified EEfRT relative to placebo, especially in trials with low probability of reward attainment. Further, we expected a moderating effect of trait extraversion on the effects of sulpiride. Two hundred and three healthy male participants were tested in a randomized, double-blind between-subjects design. Contrary to our expectations, sulpiride reduced the average number of clicks within the modified EEfRT and did not interact with reward attributes, suggesting a more global and not reward-specific effect of sulpiride. Furthermore, trait extraversion did not moderate the effect of sulpiride. Our results provide initial support for the validity of the modified version of the EEfRT, suggesting a possible inhibiting effect of a low dose of sulpiride on approach motivation regardless of trait extraversion. However, given the mixed pattern of findings and the possible confounding role of motoric abilities, further studies examining these effects are clearly warranted.

Extraversion and reward-processing: Consolidating evidence from an electroencephalographic index of reward-prediction-error.

Trait extraversion has been theorized to emerge from functioning of the dopaminergic reward system. Recent evidence for this view shows that extraversion modulates the scalp-recorded Reward Positivity, a putative marker of dopaminergic signaling of reward-prediction-error. We attempt to replicate this association amid several improvements on previous studies in this area, including an adequately-powered sample (N = 100) and thorough examination of convergent-divergent validity. Participants completed a passive associative learning task presenting rewards and non-rewards that were either predictable or unexpected. Frequentist and Bayesian analyses confirmed that the scalp recorded Reward Positivity (i.e., the Feedback-Related-Negativity contrasting unpredicted rewards and unpredicted non-rewards) was significantly associated with three measures of extraversion and unrelated to other basic traits from the Big Five personality model. Narrower sub-traits of extraversion showed similar, though weaker associations with the Reward Positivity. These findings consolidate previous evidence linking extraversion with a putative marker of dopaminergic reward-processing.

Emotional and Cognitive Modulation of Cybersickness: The Role of Pain Catastrophizing and Body Awareness.

OBJECTIVE: The goal was to investigate the influence of the tendency to catastrophize somatic symptoms and body awareness on motion-related sickness. BACKGROUND: Influences of emotional and cognitive-evaluative processes on the genesis of motion sickness or cybersickness have rarely been investigated. Brain imaging studies showed activation during cybersickness, resembling the pattern found for pain processing. Two aspects often investigated in this context are pain catastrophizing and body awareness. The present two studies investigated the relationship of motion-related sickness to two tendencies involved in pain processing: pain catastrophizing and body awareness. METHOD: In the first study, 115 participants reported their motion sickness history, pain catastrophizing, and body awareness. In the second study, 40 participants were exposed to a virtual reality and reported their experience of cybersickness as well as their pain catastrophizing and body awareness. RESULTS: Pain catastrophizing was positively correlated to motion sickness history and cybersickness. Body awareness did not show a linear effect on motion sickness history or cybersickness. However, the interaction effect of pain catastrophizing and body awareness was significant in both studies. CONCLUSION: Pain catastrophizing seems to have a detrimental effect on cybersickness symptoms. Body awareness moderated the relationship in the sense that the combination of high pain catastrophizing and low body awareness lead to the highest sickness levels. APPLICATION: Affective and cognitive modulation of cybersickness symptoms should be considered when exposing risk groups to motion-related adverse stimuli.

Openness to experience predicts dopamine effects on divergent thinking.

Individual differences in trait levels of openness to experience and creativity have been theoretically linked to dopamine function. However, empirical evidence for this assumption is scarce, especially for causal connections. The present study aims to directly assess the influence of dopamine activity on the established association between openness to experience and divergent thinking (i.e., an index of creativity). We hypothesized that manipulating dopamine activity alters the relationship between self-reported openness to experience and ideational fluency and flexibility. In a placebo-controlled between-subjects design, 193 healthy male volunteers completed four divergent thinking tasks after they received either the dopamine-receptor blocker sulpiride (200 mg) or a placebo. The data revealed an interaction such that openness to experience was more positively associated with divergent thinking in the dopamine blocker group (r = 0.304) than in the placebo group (r = -0.002). Specifically, highly open individuals in the dopamine blocker group reached the highest divergent thinking scores. Thus, sulpiride administration selectively affected divergent thinking as a function of trait levels of openness to experience. Although somewhat limited by the unexpected absence of the association between openness to experience and divergent thinking in the placebo group, the present study provides novel evidence for an association between dopamine activity and both openness to experience and divergent thinking.

Frontal asymmetry predicts the incentive value of perceptual information.

Information has been suggested to convey incentive value mediated by dopaminergic systems similar to those implicated in extrinsic reward. Although the reward characteristics of information have received preliminary support by behavioral and fMRI findings, EEG correlates and individual differences have not yet been examined. In the current study, a novel perceptual paradigm was developed to probe the associations between anticipation of perceptual information and frontal electroencephalographic alpha asymmetry, i.e., a marker of approach motivation. Assuming individual differences in engaging with perceptual information, trait openness was examined as a moderator of the associations. One hundred and twenty participants viewed partly visible photos that were gradually uncovered. After they indicated state levels of confidence and curiosity, the photos were fully disclosed. During anticipation of the fully disclosed stimuli, left-lateralized asymmetry linearly increased with curiosity. Moreover, a curvilinear relationship between confidence and left-lateralized asymmetry emerged, suggesting enhanced motivational activation during medium levels of uncertainty. The curvilinear relationship was moderated by trait openness, indicating individual differences in the responsiveness to perceptual uncertainty. In summary, our findings provide novel empirical evidence for the incentive motivational value of information.

Left frontal anodal tDCS increases approach motivation depending on reward attributes.

BACKGROUND: A growing body of literature indicates a correlation between asymmetrical activity of frontal brain sites and approach vs. withdrawal motivation. Yet the causal status of this relationship is presently unclear. Here we examined the effect of anodal tDCS applied over the left dorsolateral prefrontal cortex (dlPFC) on approach motivation, operationalized as effort allocation during the Effort-Expenditure for Reward Task (EEfRT). HYPOTHESIS: We expected left frontal anodal transcranial direct current simulation (tDCS) to increase participants' willingness to allocate more effort during the EEfRT. Based on previous research, we expected this effect to be strongest on trials with low probability of reward attainment. METHODS: 60 right-handed neurologically and psychologically healthy participants (63% female) aged 18-35 were tested in a counterbalanced within-subject design. Participants were invited to our lab twice to complete two 15-min blocks of the EEfRT on each study day, randomly assigned to either an anodal tDCS or a SHAM condition. RESULTS: No main effect of stimulation condition was found, however the interactions of stimulation condition and both probability of reward attainment and reward magnitude reached significance. These interactions indicated that left frontal anodal tDCS specifically increased the percentage of hard task choices (HTC) in trials with low probability of reward attainment and in trials with high reward magnitude. DISCUSSION: The observation of an increasing effect of left frontal anodal tDCS on effort expenditure for reward as indicated by HTC supports the idea of a causal relationship between asymmetric activity of frontal brain sites and approach motivation and hints at moderating effects of task-features on the effects of tDCS.

Effects of positive emotion, extraversion, and dopamine on cognitive stability-flexibility and frontal EEG asymmetry.

The influence of positive emotions on the balance between cognitive stability and flexibility has been suggested to (a) differ among various positive emotional/motivational states (e.g., of varying approach motivation intensity), and (b) be mediated by brain dopamine (DA). Frontal EEG alpha asymmetry (ASY) is considered an indicator of approach motivational states and may be modulated by DA. The personality trait of extraversion is strongly linked to positive emotions and is now thought to reflect DA-based individual differences in incentive/approach motivation. The present study independently manipulated positive emotion (high approach wanting-expectancy [WE] vs. low approach warmth-liking [WL]) and dopamine (placebo vs. DA D2 blocker sulpiride) to examine their effects on both cognitive stability-flexibility and emotion-related ASY changes. The results showed numerically lower stability-flexibility in WE versus WL under placebo and a complete reversal of this effect under the D2 blocker, no differentiation between WE and WL groups in terms of emotion-related ASY change, but an association between self-reported WE and WL and ASY changes toward left and right frontal cortical activity, respectively. Finally, extraversion was positively associated with both stability-flexibility and ASY changes toward left frontal cortical activity under placebo, and these associations were completely reversed under the D2 blocker. The results (a) support a dopaminergic basis for frontal EEG asymmetry, extraversion, and the modulating effect of positive emotions on stability-flexibility, and (b) extend previous reports of cognitive differences between introverts and extraverts.

A Haplotype Associated with Enhanced Mineralocorticoid Receptor Expression Facilitates the Stress-Induced Shift from "Cognitive" to "Habit" Learning.

Stress induces a shift from hippocampus-dependent "cognitive" toward dorsal striatum-dependent "habit" memory. However, not all individuals are susceptible to this shift under stress. Based on pharmacological studies indicating a critical role of the mineralocorticoid receptor (MR) in the stress-induced bias toward dorsal striatal learning, we hypothesized that MR gene variants contribute to these individual differences. In two experiments, healthy participants were genotyped, exposed to a stressor or control manipulation and performed a learning task that can be solved using hippocampal or dorsal striatal systems, while electroencephalography (EEG; Experiment I) or functional magnetic resonance imaging (fMRI; Experiment II) measurements were taken. Stress led to a shift from hippocampal to dorsal striatal learning which was more pronounced in homo- and heterozygous carriers of a six single nucleotide polymorphisms (SNPs)-comprising haplotype containing the alleles of two MR SNPs associated with increased MR expression and transactivational activity (MR-2G/C C [rs2070951], MR-I180V A [rs5522]). This stress-induced shift toward habit memory was paralleled by an increased feedback-related negativity (FRN), which may reflect striatal processing, and increased caudate activation. Carriers of the MR haplotype showed a reduced P3a, an event-related potential thought to indicate cognitive processing, and reduced hippocampal activity after stress. Moreover, stress resulted in reduced amygdala-hippocampus connectivity and the decrease in amygdala connectivity to the parahippocampal cortex was particularly pronounced in MR haplotype carriers. Our findings indicate that genetic variants associated with enhanced MR expression facilitate a stress-induced shift from hippocampal toward dorsal striatal learning, most likely via impaired hippocampal processing and reduced amygdala-hippocampus cross talk, allowing the dorsal striatum to guide behavior under stress.

A Deletion Variant of the α2b-Adrenoceptor Modulates the Stress-Induced Shift from "Cognitive" to "Habit" Memory.

Stress induces a shift from hippocampus-based "cognitive" toward dorsal striatum-based "habitual" learning and memory. This shift is thought to have important implications for stress-related psychopathologies, including post-traumatic stress disorder (PTSD). However, there is large individual variability in the stress-induced bias toward habit memory, and the factors underlying this variability are completely unknown. Here we hypothesized that a functional deletion variant of the gene encoding the α2b-adrenoceptor (ADRA2B), which has been linked to emotional memory processes and increased PTSD risk, modulates the stress-induced shift from cognitive toward habit memory. In two independent experimental studies, healthy humans were genotyped for the ADRA2B deletion variant. After a stress or control manipulation, participants completed a dual-solution learning task while electroencephalographic (Study I) or fMRI measurements (Study II) were taken. Carriers compared with noncarriers of the ADRA2B deletion variant exhibited a significantly reduced bias toward habit memory after stress. fMRI results indicated that, whereas noncarriers of the ADRA2B deletion variant showed increased functional connectivity between amygdala and putamen after stress, this increase in connectivity was absent in carriers of the deletion variant, who instead showed overall enhanced connectivity between amygdala and entorhinal cortex. Our results indicate that a common genetic variation of the noradrenergic system modulates the impact of stress on the balance between cognitive and habitual memory systems, most likely via altered amygdala orchestration of these systems.SIGNIFICANCE STATEMENT Stressful events have a powerful effect on human learning and memory. Specifically, accumulating evidence suggests that stress favors more rigid dorsal striatum-dependent habit memory, at the expense of flexible hippocampus-dependent cognitive memory. Although this shift may have important implications for understanding mental disorders, such as post-traumatic stress disorder, little is known about the source of individual differences in the sensitivity for the stress-induced bias toward habit memory. We report here that a common genetic variation of the noradrenergic system, a known risk factor for post-traumatic stress disorder, modulates the stress-induced shift from cognitive to habit memory, most likely through altered crosstalk between the hippocampus and dorsal striatum with the amygdala, a key structure in emotional memory.

The COMT Val158Met polymorphism regulates the effect of a dopamine antagonist on the feedback-related negativity.

Consistent with dopamine accounts of internal and external feedback processing, prior work showed that the dopamine D2 receptor antagonist sulpiride modulates the relationship between the dopaminergic COMT Val158Met polymorphism and the error-related negativity (ERN). Here, we tested in an independent sample whether this Gene × Substance interaction generalizes to the feedback-related negativity (FRN), which presumably shares underlying dopaminergic mechanisms with the ERN. N = 83 female participants genotyped for COMT Val158Met received 200 mg sulpiride versus placebo and performed a virtual ball-catching task. The FRN to positive versus negative feedback was modulated by a significant COMT × Substance interaction. Mirroring prior work on the ERN, the tendency of the FRN to be more pronounced for VAL+ versus MET/MET carriers after placebo was reversed by sulpiride. The findings thus provide new evidence for dopaminergic models of feedback processing.

Dopamine modulates frontomedial failure processing of agentic introverts versus extraverts in incentive contexts.

The agency facet of extraversion (aE) describes individual differences in goal-directed behavior and has been linked to dopamine function in incentive contexts. Because dopamine presumably modulates the processing of negative feedback/failure, aE may relate to failure processing in incentive contexts. To test this hypothesis, N = 86 participants performed a virtual ball-catching task. An incentive context was created by displaying potential rewards and subtle manipulations of task performance, which either was (control group) or was not (incentive context group) made explicit. To probe the involvement of dopamine, participants received either placebo or the selective dopamine D2 receptor antagonist sulpiride (200 mg). Failure processing was assessed through negative-feedback-evoked differences in the frontal midline theta electroencephalogram power (DFMT) and in the feedback-related negativity event-related potential component (FRN). Before incentives were introduced, DFMT (but not the FRN) was related to neuroticism/anxiety. Importantly, once incentives were displayed, aE was associated with DFMT, FRN, task performance, and changes in self-reported positive affect, which further depended on incentive context group and/or substance group: In the incentive context group but not in the control group, agentic extraverts showed relatively blunted DFMT after placebo. Sulpiride significantly enhanced DFMT, whereas it reduced FRN amplitudes and performance in agentic extra- versus introverts. These findings provide strong support for current dopamine models of aE and failure processing, and also highlight the importance of task context. Moreover, the dissociations of FRN and DFMT suggest the existence of two nonredundant electrophysiological indices of feedback processing, both relating to dopamine and aE.

Opioid receptor blockade and warmth-liking: effects on interpersonal trust and frontal asymmetry.

The emotion 'warmth-liking' (WL) associated with feelings of affection and acceptance is regularly activated in social contexts. WL has been suggested to be more closely related to the consummatory phase of post-goal attainment positive affect than to pre-goal attainment positive affect/approach motivation and to be partly mediated by brain opioids. To validate these assumptions we employed film/imagery to induce either a neutral emotional state or WL in female participants after intake of either placebo or the opioid antagonist naltrexone. Dependent variables were emotion self-report, interpersonal trust (TRUST, i.e. a behavioral indicator of WL) and frontal asymmetry (i.e. an electroencephalogram (EEG) indicator of approach motivation/behavioral activation). We found that participants reported more WL in the placebo/WL group than in the placebo/neutral group and both naltrexone groups. In addition, TRUST increased in the WL group after placebo, but not after naltrexone, and this pattern was reversed in the neutral control groups. Consequently, opioid blockade suppressed or even reversed the effects of the WL induction on the levels of self-report and behavior, respectively. In addition, we observed reduced relative left-frontal asymmetry in the WL (vs neutral) group, consistent with reduced approach motivation. Overall, these results suggest opioidergic influences on WL and TRUST and reduced approach motivation/behavioral activation for the positive emotion WL.