Transcranial Direct Current Stimulation over the Medial Prefrontal Cortex and Left Primary Motor Cortex (mPFC-lPMC) Affects Subjective Beauty but Not Ugliness

Beauty affects fairness: facial attractiveness alters neural responses to unfairness in the ultimatum game

Human faces consist of rich information for social interactions and facial attractiveness is a key dimension affecting social decisions. Previous studies have indicated that human players are less likely to refuse an unfair offer from proposers with high facial attractiveness in the Ultimatum Game (UG). However, the neural mechanisms underlying such beauty premium effect remain unclear. In this study, we used functional magnetic resonance imaging (fMRI) and examined the effects of facial attractiveness on brain responses to fair and unfair offers in the UG. Behavioral data showed that subjects were overall prone to refuse unfair offers across conditions but were more likely to accept unfair offers from higher facial attractive proposers than those from lower facial attractive proposers. Imaging data showed that unfair offers induced greater activity in the anterior insula and medial prefrontal cortex (MePFC) compared to those in fair offers condition for both high and low facial attractive proposers. Moreover, the acceptance rate of unfair offers positively correlated with the MePFC activity for high facial attractive proposers and negatively correlated with the anterior insula activity for low facial attractive proposers. These findings suggest that facial attractiveness modulates brain responses to unfairness through altering the roles of emotion and cognitive motivation in social interactions.

Testing the Reproducibility of the Effects of Transcranial Direct Current Stimulation: Failure to Modulate Beauty Perception by Brain Stimulation

Transcranial direct current stimulation (tDCS) has been recognized as a promising tool for investigating the causal relationship between specific brain areas of interest and behavior. However, the reproducibility of previous tDCS studies is often questioned because of failures in replication. This study focused on the effects of tDCS on one cognitive domain: beauty perception. To date, the modulation of beauty perception by tDCS has been shown in two studies: Cattaneo et al. (2014) and Nakamura and Kawabata (2015). Here, we aimed at replicating their studies and investigating the effects of tDCS on beauty perception using the following parameters: (1) cathodal stimulation over the medial prefrontal cortex (mPFC) (Nakamura and Kawabata, 2015); (2) anodal stimulation over the left dorsolateral prefrontal cortex (lDLPFC) (Cattaneo et al., 2014). We also performed a more focal stimulation targeting the orbitofrontal cortex (OFC) to determine the optimal stimulation site for modulating beauty perception (3). Participants rated the subjectively-perceived beauty of the images before and after the tDCS administration. We divided images into four clusters according to the obtained scores in our preliminary study and examined changes in beauty ratings in each image cluster separately to exclude factors, such as stimuli attributions that may reduce tDCS effects. The results showed no strong effects of tDCS with the same parameters as in previous studies on beauty rating scores in any image cluster. Likewise, anodal stimulation over the OFC did not result in a change in rating scores. In contrast to previous studies, the current study did not corroborate the effects of tDCS on beauty perception. Our findings provide evidence regarding the recent reproducibility issue of tDCS effects and suggest the possible inflation of its effects on cognitive domains.

How the Cerebellum and Prefrontal Cortex Cooperate During Trace Eyeblinking Conditioning

Several data have demonstrated that during the widely used experimental paradigm for studying associative learning, trace eye blinking conditioning (TEBC), there is a strong interaction between cerebellum and medial prefrontal cortex (mPFC). Despite this evidence, the neural mechanisms underlying this interaction are still not clear. Here, we propose a neurophysiologically plausible computational model to address this issue. The model is constrained on the basis of two critical anatomo-physiological features: (i) the cerebello-cortical organization through two circuits, respectively, targeting M1 and mPFC; (ii) the different timing in the plasticity mechanisms of these parallel circuits produced by the granule cells time sensitivity according to which different subpopulations are active at different moments during conditioned stimuli. The computer simulations run with the model suggest that these features are critical to understand how the cooperation between cerebellum and mPFC supports motor areas during TEBC. In particular, a greater trace interval produces greater plasticity changes at the slow path synapses involving mPFC with respect to plasticity changes at the fast path involving M1. As a consequence, the greater is the trace interval, the stronger is the mPFC involvement. The model has been validated by reproducing data collected through recent real mice experiments.

Tracking two pleasures

Can people track several pleasures? In everyday life, pleasing stimuli rarely appear in isolation. Yet, experiments on aesthetic pleasure usually present only one image at a time. Here, we ask whether people can reliably report the pleasure of either of two images seen in a single glimpse. Participants (N = 13 in the original; +25 in the preregistered replication) viewed 36 Open Affective Standardized Image Set (OASIS) images that span the entire range of pleasure and beauty. On each trial, the observer saw two images, side by side, for 200 ms. An arrow cue pointed, randomly, left, right, or bidirectionally. Left or right indicated which image (the target) to rate while ignoring the other (the distractor); bidirectional requested rating the combined pleasure of both images. In half the blocks, the cue came before the images (precuing). Otherwise, it came after (postcuing). Precuing allowed the observer to ignore the distractor, while postcuing demanded tracking both images. Finally, we obtained single-pleasure ratings for each image shown alone. Our replication confirms the original study. People have unbiased access to their felt pleasure from each image and the average of both. Furthermore, the variance of the observer's report is similar whether reporting the pleasure of one image or the average pleasure of two. The undiminished variance for reports of the average pleasure of two images indicates either that the underlying pleasure variances are highly correlated, or, more likely, that the variance arises in the common reporting process. In brief, observers can faithfully track at least two visual pleasures.

Transcranial direct current stimulation (tDCS) over vmPFC modulates interactions between reward and emotion in delay discounting

Delay discounting requires computing trade-offs between immediate-small rewards and later-larger rewards. Negative and positive emotions shift decisions towards more or less impulsive responses, respectively. Models have conceptualized this trade-off by describing an interplay between “emotional” and “rational” processes, with the former involved during immediate choices and relying on the ventromedial prefrontal cortex (vmPFC), and the latter involved in long-term choices and relying on the dorsolateral prefrontal cortex (dlPFC). Whether stimulation of the vmPFC modulates emotion-induced delay discounting remains unclear. We applied tDCS over the vmPFC in 20 healthy individuals during a delay discounting task following an emotional (positive, negative) or neutral induction. Our results showed that cathodal tDCS increased impulsivity after positive emotions in high impulsivity trials. For low impulsivity trials, anodal tDCS decreased impulsivity following neutral induction compared with emotional induction. Our findings demonstrate that the vmPFC integrates reward and emotion most prominently in situations of increased impulsivity, whereas when higher cognitive control is required the vmPFC appears to be less engaged, possibly due to recruitment of the dlPFC. Understanding how stimulation and emotion influence decision-making at the behavioural and neural levels holds promise to develop interventions to reduce impulsivity.

Neural correlates of visual aesthetic appreciation: insights from non-invasive brain stimulation

During the last decade, non-invasive brain stimulation techniques have been increasingly employed in the field of neuroaesthetics research to shed light on the possible causal role of different brain regions contributing to aesthetic appreciation. Here, I review studies that have employed transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to investigate neurocognitive mechanisms mediating visual aesthetic appreciation for different stimuli categories (faces, bodies, paintings). The review first considers studies that have assessed the possible causal contribution of cortical regions in mediating aesthetic appreciation along the visual ventral and dorsal pathways (i.e., the extrastriate body area, the motion-sensitive region V5/MT+ , the lateral occipital complex and the posterior parietal cortex). It then considers TMS and tDCS studies that have targeted premotor and motor regions, as well as other areas involved in body and facial expression processing (such as the superior temporal sulcus and the somatosensory cortex) to assess their role in aesthetic evaluation. Finally, it discusses studies that have targeted medial and dorsolateral prefrontal regions leading to significant changes in aesthetic appreciation for both biological stimuli (faces and bodies) and artworks. Possible mechanisms mediating stimulation effects on aesthetic judgments are discussed. A final section considers both methodological limitations of the reviewed studies (including levels of statistical power and the need for further replication) and the future potential for non-invasive brain stimulation to significantly contribute to the understanding of the neural bases of visual aesthetic experiences.

Intense Beauty Requires Intense Pleasure

At the beginning of psychology, Fechner (1876) claimed that beauty is immediate pleasure, and that an object’s pleasure determines its value. In our earlier work, we found that intense pleasure always results in intense beauty. Here, we focus on the inverse: Is intense pleasure necessary for intense beauty? If so, the inability to experience pleasure (anhedonia) should prevent the experience of intense beauty. We asked 757 online participants to rate how intensely they felt beauty from each image. We used 900 OASIS images along with their available valence (pleasure vs. displeasure) and arousal ratings. We then obtained self-reports of anhedonia (TEPS), mood, and depression (PHQ-9). Across images, beauty ratings were closely related to pleasure ratings (r = 0.75), yet unrelated to arousal ratings. Only images with an average pleasure rating above 4 (of a possible 7) often achieved (>10%) beauty averages exceeding the overall median beauty. For normally beautiful images (average rating > 4.5), the beauty ratings were correlated with anhedonia (r ∼−0.3) and mood (r ∼ 0.3), yet unrelated to depression. Comparing each participant’s average beauty rating to the overall median (5.0), none of the most anhedonic participants exceeded the median, whereas 50% of the remaining participants did. Thus, both general and anhedonic results support the claim that intense beauty requires intense pleasure. In addition, follow-up repeated measures showed that shared taste contributed 19% to beauty-rating variance, only one third as much as personal taste (58%). Addressing age-old questions, these results indicate that beauty is a kind of pleasure, and that beauty is more personal than universal, i.e., 1.7 times more correlated with individual than with shared taste.

Neuropsychopharmacological aesthetics: A theoretical consideration of pharmacological approaches to causative brain study in aesthetics and art

Recent developments in neuroaesthetics have heightened the need for causative approaches to more deeply understand the mechanism underlying perception, emotion, and aesthetic experiences. This has recently been the topic for empirical work, employing several causative methods for changing brain activity, as well as comparative assessments of individuals with brain damage or disease. However, one area of study with high potential, and indeed a long history of often nonscientific use in the area of aesthetics and art, employing psychopharmacological chemicals as means of changing brain function, has not been systematically utilized. This chapter reviews the literature on this topic, analyzing neuroendocrinological (neurochemical) approaches and mechanisms that might be used to causatively study the aesthetic brain. We focus on four relevant neuromodulatory systems potentially related to aesthetic experience: the dopaminergic, serotonergic, cannabinoid, and the opioidergic system. We build a bridge to psychopharmacological methods and review drug-induced behavioral and neurobiological consequences. We conclude with a discussion of hypotheses and suggestions for future research.

Transcranial Direct Current Stimulation of the Medial Prefrontal Cortex Affects Judgments of Moral Violations

Previous studies show that neural activities in the medial prefrontal cortex (mPFC) are correlated with moral processing during picture viewing tasks. In this study, we applied transcranial direct current stimulation (tDCS) to determine whether this non-invasive brain stimulation technique could modulate the evaluation of moral violations. Sixty-four subjects were randomly recruited, separated into different groups and tested with 42 pairs of pictures depicting moral violations. Each subject was required to rate the pictures two separate times, i.e., before and after tDCS intervention. We found that anodal tDCS (atDCS) increases cortical excitability over the mPFC (between the Fpz and Fp1 positions) as well as the sense of morality and emotional arousal of the subjects. In conclusion, this study indicated that the mPFC plays an important role in moral judgments while modulating ratings of moral violations under tDCS intervention conditions.

The experience of beauty derived from sorrow

We studied the neural mechanisms that are engaged during the experience of beauty derived from sorrow and from joy, two experiences that share a common denominator (beauty) but are linked to opposite emotional valences. Twenty subjects viewed and rerated, in a functional magnetic resonance imaging scanner, 120 images which each had classified into the following four categories: beautiful and sad; beautiful and joyful; neutral; ugly. The medial orbito‐frontal cortex (mOFC) was active during the experience of both types of beauty. Otherwise, the two experiences engaged different parts of the brain: joyful beauty engaged areas linked to positive emotions while sorrowful beauty engaged areas linked to negative experiences. Separate regions of the cerebellum were engaged during experience of the two conditions. A functional connectivity analysis indicated that the activity within the mOFC was modulated by the supplementary motor area/middle cingulate cortex, known to be engaged during empathetic experiences provoked by other peoples' sadness. Hum Brain Mapp 38:4185–4200, 2017. © 2017 Wiley Periodicals, Inc.