Temporal Unfolding of Racial Ingroup Bias in Neural Responses to Perceived Dynamic Pain in Others.

In this study, we investigated how empathic neural responses unfold over time in different empathy networks when viewing same-race and other-race individuals in dynamic painful conditions. We recorded magnetoencephalography signals from Chinese adults when viewing video clips showing a dynamic painful (or non-painful) stimulation to Asian and White models' faces to trigger painful (or neutral) expressions. We found that perceived dynamic pain in Asian models modulated neural activities in the visual cortex at 100 ms-200 ms, in the orbitofrontal and subgenual anterior cingulate cortices at 150 ms-200 ms, in the anterior cingulate cortex around 250 ms-350 ms, and in the temporoparietal junction and middle temporal gyrus around 600 ms after video onset. Perceived dynamic pain in White models modulated activities in the visual, anterior cingulate, and primary sensory cortices after 500 ms. Our findings unraveled earlier dynamic activities in multiple neural circuits in response to same-race (vs other-race) individuals in dynamic painful situations.

Are women more empathetic than men? Questionnaire and EEG estimations of sex/gender differences in empathic ability.

The debate regarding whether women are more empathetic than men has broad scientific, social and clinical implications. However, previous independent questionnaires and brain imaging studies that tested different samples reported inconsistent results regarding sex/gender differences in empathic ability. We conducted three studies to investigate sex/gender differences in empathic ability using large-sample questionnaires and electroencephalography (EEG) measures. We showed that the estimation of empathic ability using the Interpersonal Reactivity Index questionnaire showed higher rating scores in women than in men in all studies. However, our EEG measures of empathy, indexed by both phase-locked and non-phased-locked neural responses to others' painful (vs neutral) facial expressions, support a null hypothesis of the sex/gender difference in empathic ability. In addition, we showed evidence that priming social expectations of women and men's ability to share and care about others' feelings eliminated the sex/gender difference in questionnaire measures of empathic ability. Our large-sample EEG results challenge the notion of women's superiority in empathy that is built based on subjective questionnaire measures that are sensitive to social desirability. Our findings indicate that whether the notion of women's superiority in empathic ability reflects a biological/social difference between women and men or a gender-role stereotype remains an open question.

Effect of lemon essential oil on halitosis.

OBJECTIVES: To evaluate the effect of lemon essential oil (LEO) on salivary bacteria and volatile sulfur compound (VSC) production of patients with halitosis. MATERIALS AND METHODS: Saliva of five patients with halitosis was collected, after adding different concentrations (0.563-9 mg/ml) of LEO, detecting the growth of salivary bacteria, the formation of biofilm, and VSC production, and compare the difference of different concentrations of LEO on bacterial growth and VSC production. 48 volunteers were randomly divided into 4 groups. After gargling with LEO, cetylpyridinium chloride (CPC), chlorhexidine (CHX), and hydrogen peroxide (H2 O2 ) separately measure changes of VSC production and pH values at 30, 45, 60, 90, and 120 min and then compare the differences at different time points within group. RESULTS: Compared with the negative control group, under subinhibitory concentrations of LEO (0.563-2.25 mg/ml), the biofilm formation and VSC production of salivary bacteria in LEO group were significantly inhibited (p < 0.05). Compared with the baseline, the VSC production of subjects decreased after rinsing with the LEO in 60 min (p < 0.05). After gargling with LEO, the pH value rose significantly in 30 min and reverted to the baseline level at 120 min (p < 0.05). CONCLUSIONS: Lemon essential oil can inhibit the growth of salivary bacteria and reduce VSC production of patients with halitosis.

Racial outgroup favoritism in neural responses to others' pain emerges during sociocultural interactions.

Racial ingroup favoritism in empathic brain activity has been widely observed and is associated with biased behavior toward same-race and other-race individuals. We investigated whether racial outgroup favoritism in neural responses to others' pain - an objective measure of empathy - may emerge during sociocultural interactions in a new social environment. We recorded magnetoencephalography to pain and neutral expressions of Asian and White faces from White students who had stayed in China for 6-36 weeks (Experimental group) or 2-4 weeks (Control group). The experimental group showed better neural decoding of and greater insular/sensorimotor responses to pain vs. neutral expressions of Asian compared to White faces. By contrast, the control group showed better neural decoding of pain vs. neutral expressions of White than Asian faces. In addition, participants of the experimental group who had stayed longer in China showed greater sensorimotor responses to pain (vs. neutral) expressions of Asian faces but weaker sensorimotor responses to pain (vs. neutral) expressions of White faces. Our findings revealed emerging racial outgroup favoritism in brain activities associated with sensorimotor resonance and affective sharing of others' pain during sociocultural interactions.

A neurobiological association of revenge propensity during intergroup conflict.

Revenge during intergroup conflict is a human universal, but its neurobiological underpinnings remain unclear. We address this by integrating functional MRI and measurements of endogenous oxytocin in participants who view an ingroup and an outgroup member's suffering that is caused mutually (Revenge group) or by a computer (Control group). We show that intergroup conflict encountered by the Revenge group is associated with an increased level of oxytocin in saliva compared to that in the Control group. Furthermore, the medial prefrontal activity in response to ingroup pain in the Revenge group but not in the Control group mediates the association between endogenous oxytocin and the propensity to give painful electric shocks to outgroup members, regardless of whether they were directly involved in the conflict. Our findings highlight an important neurobiological correlate of revenge propensity, which may be implicated in conflict contagion across individuals in the context of intergroup conflict.