The dopamine D4 receptor gene (DRD4) modulates cultural variation in emotional experience

Identifying similarities and differences in emotion recognition with EEG and eye movements among Chinese, German, and French people

OBJECTIVE

Cultures have essential influences on emotions. However, most studies on cultural influences on emotions are in the areas of psychology and neuroscience, while the existing affective models are mostly built with data from the same culture. In this paper, we identify the similarities and differences among Chinese, German, and French individuals in emotion recognition with electroencephalogram (EEG) and eye movements from an affective computing perspective.

APPROACH

Three experimental settings were designed: intraculture subject dependent, intraculture subject independent, and cross-culture subject independent. EEG and eye movements are acquired simultaneously from Chinese, German, and French subjects while watching positive, neutral, and negative movie clips. The affective models for Chinese, German, and French subjects are constructed by using machine learning algorithms. A systematic analysis is performed from four aspects: affective model performance, neural patterns, complementary information from different modalities, and cross-cultural emotion recognition.

MAIN RESULTS

From emotion recognition accuracies, we find that EEG and eye movements can adapt to Chinese, German, and French cultural diversities and that a cultural in-group advantage phenomenon does exist in emotion recognition with EEG. From the topomaps of EEG, we find that the gamma and beta bands exhibit decreasing activities for Chinese, while for German and French, theta and alpha bands exhibit increasing activities. From confusion matrices and attentional weights, we find that EEG and eye movements have complementary characteristics. From a cross-cultural emotion recognition perspective, we observe that German and French people share more similarities in topographical patterns and attentional weight distributions than Chinese people while the data from Chinese are a good fit for test data but not suitable for training data for the other two cultures.

SIGNIFICANCE

Our experimental results provide concrete evidence of the in-group advantage phenomenon, cultural influences on emotion recognition, and different neural patterns among Chinese, German, and French individuals.

The gray matter volume of the temporoparietal junction varies across cultures: a moderating role of the dopamine D4 receptor gene (DRD4)

Prior work shows that compared to European Americans, East Asians show an enhanced propensity to take the perspective of another person. In the current work, we tested whether this cultural difference might be reflected in the gray matter (GM) volume of the temporoparietal junction (TPJ), a brain region selectively implicated in perspective taking and mentalizing. We also explored whether the cultural difference in the TPJ GM volume might be moderated by dopamine D4 receptor gene (DRD4) exon 3 variable-number tandem repeat polymorphism. Structural magnetic resonance imaging of 66 European Americans and 66 East Asian-born Asians were subjected to voxel-based morphometry. It was observed that the GM volume of the right TPJ was greater among East Asians than among European Americans. Moreover, this cultural difference was significantly more pronounced among carriers of the 7- or 2-repeat allele of DRD4 than among the non-carriers of these alleles. Our findings contribute to the growing evidence that culture can shape the brain.

Oxytocin receptor gene polymorphism (rs53576) and digit ratio associates with aggression: comparison in seven ethnic groups

Background

The specific role of the oxytocin receptor (OXTR) gene polymorphisms in emotional support seeking, related to social norms and culturally normative behavior, has been discussed in several studies. Evidence on the association between aggression and OXTR polymorphisms has also been reported. The goal of the current study was to analyze the effect of the OXTR rs53576 polymorphism, prenatal testosterone effect (second-to-fourth digit ratio, or 2D:4D), and culture on aggression assessed with the Buss-Perry Aggression Questionnaire (BPAQ).

Methods

The data were collected in Russia and Tanzania and included seven ethnic groups of European, Asian, and African origin. The total sample included 1705 adults (837 males, 868 females). All the subjects were evaluated with the BPAQ. As a measure of prenatal androgenization, the second and fourth digits were measured directly from hand, and the digit ratios were calculated. All the participants provided buccal samples, from which genomic DNA was extracted, and the OXTR gene rs53576 polymorphism was genotyped. Statistical analysis was performed using SPSS version 23.0; the alpha level for all analyses was set at 0.05.

Results

The ethnic group factor was the most significant predictor of ratings on BPAQ (medium effect size for physical aggression, anger and hostility scales, and low for verbal aggression). To study the effect of sex, the OXTR polymorphism, and prenatal androgenization, we conducted the z-score transformation for BPAQ scales and 2D:4D for each ethnic group and pooled these data into new z-score variables. According to the GLM analysis after leveling the effects of culture (z-transformation), all four scales of BPAQ demonstrated association with sex (main effects), with men scoring higher on physical and verbal aggression and women scoring higher on anger and hostility. Anger and hostility scales were also associated with OXTR polymorphism and 2D:4D of the right hand. The lowest levels of anger and hostility were observed in individuals with the AA genotype, especially in men.

Conclusions

Our data suggest that both oxytocin (OXTR gene polymorphism) and fetal testosterone (2D:4D) may significantly affect emotional (anger) and cognitive (hostility) aggression in humans, given the leveling the role of culture.

DRD4 polymorphisms modulate reward positivity and P3a in a gambling task: Exploring a genetic basis for cultural learning

Prior work shows that people respond more plastically to environmental influences, including cultural influences, if they carry the 7 or 2-repeat (7/2R) allelic variant of the dopamine D4 receptor gene (DRD4). The 7/2R carriers are thus more likely to endorse the norms and values of their culture. So far, however, mechanisms underlying this moderation of cultural acquisition by DRD4 are unclear. To address this gap in knowledge, we tested the hypothesis that DRD4 modulates the processing of reward cues existing in the environment. About 72 young adults, preselected for their DRD4 status, performed a gambling task, while the electroencephalogram was recorded. Principal components of event-related potentials aligned to the Reward-Positivity (associated with bottom-up processing of reward prediction errors) and frontal-P3 (associated with top-down attention) were both significantly more positive following gains than following losses. As predicted, the gain-loss differences were significantly larger for 7/2R carriers than for noncarriers. Also, as predicted, the cultural backgrounds of the participants (East Asian vs. European American) did not moderate the effects of DRD4. Our findings suggest that the 7/2R variant of DRD4 enhances (a) the detection of reward prediction errors and (b) controlled attention that updates the context for the reward, thereby suggesting one possible mechanism underlying the DRD4 × Culture interactions.