Neural Representations of the Committed Romantic Partner in the Nucleus Accumbens.

Having an intimate romantic relationship is an important aspect of life. Dopamine-rich reward regions, including the nucleus accumbens (NAcc), have been identified as neural correlates for both emotional bonding with the partner and interest in unfamiliar attractive nonpartners. Here, we aimed to disentangle the overlapping functions of the NAcc using multivoxel pattern analysis, which can decode the cognitive processes encoded in particular neural activity. During functional MRI scanning, 46 romantically involved men performed the social-incentive-delay task, in which a successful response resulted in the presentation of a dynamic and positive facial expression from their partner and unfamiliar women. Multivoxel pattern analysis revealed that the spatial patterns of NAcc activity could successfully discriminate between romantic partners and unfamiliar women during the period in which participants anticipated the target presentation. We speculate that neural activity patterns within the NAcc represent the relationship partner, which might be a key neural mechanism for committed romantic relationships.

Reduced orbitofrontal cortical volume is associated with interdependent self-construal.

Interdependent self-construal refers to a view of the self as embedded in relationships with others. Prior work suggests that this construal is linked to a strong value placed on social obligations and duties. Interdependent people are therefore cognitively attuned to others and various social events in their surroundings while down-regulating their personal goals. In the present work, we examined whether structural properties of the brain predict interdependent self-construal. We performed a structural magnetic resonance imaging on 135 Japanese young adults while assessing (i) independent and interdependent self-construals and (ii) the degree to which individuals form vivid images of external objects (object imagery). The cortical volume of the orbitofrontal cortex (OFC) (a core cortical region responsible for value-based decisionmaking and, thus, inherently involved in personal goals and desires) inversely predicted interdependent self-construal. Further analysis found that the highest level of interdependent self-construal is achieved when those who are relatively low in the OFC volume are simultaneously high in object imagery, consistent with previous evidence that interdependence, as realized via obligation and duty, requires both the reduced self-interest and vigilant cognitive attunement to environmental context.

Executive control and faithfulness: only long-term romantic relationships require prefrontal control.

Individuals in the early stages of a romantic relationship generally express intense passionate love toward their partners. This observation allows us to hypothesize that the regulation of interest in extra-pair relationships by executive control, which is supported by the function of the prefrontal cortex, is less required in individuals in the early stages of a relationship than it is in those who are in a long-term relationship. To test this hypothesis, we asked male participants in romantic relationships to perform a go/no-go task during functional magnetic resonance imaging (fMRI), which is a well-validated task that can measure right ventrolateral prefrontal cortex (VLPFC) activity implicated in executive control. Subsequently, the participants engaged in a date-rating task in which they rated how much they wanted to date unfamiliar females. We found that individuals with higher right VLPFC activity better regulated their interest in dates with unfamiliar females. Importantly, this relationship was found only in individuals with long-term partners, but not in those with short-term partners, indicating that the active regulation of interest in extra-pair relationships is required only in individuals in a long-term relationship. Our findings extend previous findings on executive control in the maintenance of monogamous relationships by highlighting the role of the VLPFC, which varies according to the stage of the romantic relationship.

Trading of dynamic interaural time and level difference cues and its effect on the auditory motion-onset response measured with electroencephalography.

Interaural time (ITD) and level differences (ILD) constitute the two main cues for sound localization in the horizontal plane. Despite extensive research in animal models and humans, the mechanism of how these two cues are integrated into a unified percept is still far from clear. In this study, our aim was to test with human electroencephalography (EEG) whether integration of dynamic ITD and ILD cues is reflected in the so-called motion-onset response (MOR), an evoked potential elicited by moving sound sources. To this end, ITD and ILD trajectories were determined individually by cue trading psychophysics. We then measured EEG while subjects were presented with either static click-trains or click-trains that contained a dynamic portion at the end. The dynamic part was created by combining ITD with ILD either congruently to elicit the percept of a right/leftward moving sound, or incongruently to elicit the percept of a static sound. In two experiments that differed in the method to derive individual dynamic cue trading stimuli, we observed an MOR with at least a change-N1 (cN1) component for both the congruent and incongruent conditions at about 160-190 ms after motion-onset. A significant change-P2 (cP2) component for both the congruent and incongruent ITD/ILD combination was found only in the second experiment peaking at about 250 ms after motion onset. In sum, this study shows that a sound which - by a combination of counter-balanced ITD and ILD cues - induces a static percept can still elicit a motion-onset response, indicative of independent ITD and ILD processing at the level of the MOR - a component that has been proposed to be, at least partly, generated in non-primary auditory cortex.

Implicit attitudes and executive control interact to regulate interest in extra-pair relationships.

Do we actively maintain monogamous relationships by force of will, or does monogamy flow automatically? During functional magnetic resonance imaging (fMRI), male participants in a romantic relationship performed the Implicit Association Test (IAT) to evaluate implicit attitudes toward adultery and a go/no-go task to measure prefrontal activity implicated in explicit executive control. Subsequently, they were engaged in a date-rating task in which they rated how much they wanted to date unfamiliar females. We found that the individuals with higher prefrontal activity during go/no-go task could regulate the interest for dates with unattractive females; moreover, the individuals with both a stronger negative attitude toward adultery and higher prefrontal activity could regulate their interest for dates with attractive females, and such individuals tended to maintain longer romantic relationships with a particular partner. These results indicate that regulation of amorous temptation via monogamous relationship is affected by the combination of automatic and reflective processes.

Neural Processing of Facial Attractiveness and Romantic Love: An Overview and Suggestions for Future Empirical Studies.

Romantic love is universally observed in human communities, and the manner in which a person chooses a long-term romantic partner has been a central question in studies on close relationships. Numerous empirical psychological studies have demonstrated that facial attractiveness greatly impacts initial romantic attraction. This close link was further investigated by neuroimaging studies showing that both viewing attractive faces and having romantic thoughts recruit the reward system. However, it remains unclear how our brains integrate perceived facial attractiveness into initial romantic attraction. In addition, it remains unclear how our brains shape a persistent attraction to a particular person through interactions; this persistent attraction is hypothesized to contribute to a long-term relationship. After reviewing related studies, I introduce methodologies that could help address these questions.

Automatic honesty forgoing reward acquisition and punishment avoidance: a functional MRI investigation.

Recent neuroimaging investigations into human honesty suggest that honest moral decisions in individuals who consistently behave honestly occur automatically, without the need for active self-control. However, it remains unclear whether this observation can be applied to two different types of honesty: honesty forgoing dishonest reward acquisition and honesty forgoing dishonest punishment avoidance. To address this issue, a functional MRI study, using an incentivized prediction task in which participants were confronted with real and repeated opportunities for dishonest gain leading to reward acquisition and punishment avoidance, was conducted. Behavioral data revealed that the frequency of dishonesty was equivalent between the opportunities for dishonest reward acquisition and for punishment avoidance. Reaction time data demonstrated that two types of honest decisions in the opportunity for dishonest reward acquisition and punishment avoidance required no additional cognitive control. Neuroimaging data revealed that honest decisions in the opportunity for dishonest reward acquisition and those for punishment avoidance required no additional control-related activity compared with a control condition in which no opportunity for dishonest behavior was given. These results suggest that honesty flows automatically, irrespective of the concomitant motivation for dishonesty leading to reward acquisition and punishment avoidance.

The neural basis of individual differences in mate poaching.

This study tested the hypothesis that individual differences in the activity of the orbitofrontal cortex, a region implicated in value-based decision-making, are associated with the preference for a person with a partner, which could lead to mate poaching. During functional magnetic resonance imaging (fMRI), male participants were presented with facial photographs of (a) attractive females with a partner, (b) attractive females without a partner, (c) unattractive females with a partner, and (d) unattractive females without a partner. The participants were asked to rate the degree to which they desired a romantic relationship with each female using an 8-point scale. The participants rated attractive females higher than unattractive females, and this effect was associated with ventral striatum activation. The participants also indicated lower ratings for females with a partner than for females without a partner, and this effect was associated with parietal cortex activation. As predicted, the participants characterized by higher orbitofrontal activity demonstrated a greater willingness to engage in a romantic relationship with females who have a partner compared with females who do not have a partner. These results are the first to provide a possible neural explanation for why certain individuals are willing to engage in mate poaching.

Auditory Mismatch Negativity in Response to Changes of Counter-Balanced Interaural Time and Level Differences.

Interaural time differences (ITD) and interaural level differences (ILD) both signal horizontal sound source location. To achieve a unified percept of our acoustic environment, these two cues require integration. In the present study, we tested this integration of ITD and ILD with electroencephalography (EEG) by measuring the mismatch negativity (MMN). The MMN can arise in response to spatial changes and is at least partly generated in auditory cortex. In our study, we aimed at testing for an MMN in response to stimuli with counter-balanced ITD/ILD cues. To this end, we employed a roving oddball paradigm with alternating sound sequences in two types of blocks: (a) lateralized stimuli with congruently combined ITD/ILD cues and (b) midline stimuli created by counter-balanced, incongruently combined ITD/ILD cues. We observed a significant MMN peaking at about 112-128 ms after change onset for the congruent ITD/ILD cues, for both lower (0.5 kHz) and higher carrier frequency (4 kHz). More importantly, we also observed significant MMN peaking at about 129 ms for incongruently combined ITD/ILD cues, but this effect was only detectable in the lower frequency range (0.5 kHz). There were no significant differences of the MMN responses for the two types of cue combinations (congruent/incongruent). These results suggest that-at least in the lower frequency ranges (0.5 kHz)-ITD and ILD are processed independently at the level of the MMN in auditory cortex.