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Previous research on how stereotypes affect perceptions of intimate partner violence and domestic homicide has found that violence committed by men is perceived as more severe and judged more harshly than violence committed by women. The present mock jury study investigated how perpetrator sex (male or female), crime type (familicide or filicide), and relatedness between perpetrator and child victims (biological or step) affect laypeople's perceptions of the appropriate consequence of the crime, the reason for the offense, responsibility of the perpetrator, the likelihood of certain background factors being present, and the risk of future violence. One hundred sixty-seven university students read eight fictive descriptions of cases of multiple-victim domestic homicides, in which the sex of the perpetrator, the crime type, and the relatedness between the perpetrator and the child victims were manipulated. We found that participants recommended equally severe punishments to and placed the same amount of responsibility on male and female offenders. Female offenders were, however, regarded as mentally ill to a larger extent and perceived more likely to have been victims of domestic violence compared with male offenders. Male offenders were seen as more likely to have committed domestic violence in the past, having been unemployed, have substance abuse, hold aggressive attitudes, and commit violent acts in the future. Participants also perceived offenders killing biological children as more mentally ill than those killing stepchildren. The present study extends the literature on the possible effect of stereotypes on decision making in psychiatric and judicial contexts.

The endogenous mu-opioid receptor (MOR) system modulates a multitude of social and reward-related functions, and exogenous opiates also influence sex drive in humans and animals. Sex drive shows substantial variation across humans, and it is possible that individual differences in MOR availability underlie interindividual of variation in human sex drive. We measured healthy male subjects’ (n = 52) brain’s MOR availability with positron emission tomography (PET) using an agonist radioligand, [11C]carfentanil, that has high affinity for MORs. Sex drive was measured using self-reports of engaging in sexual behaviour (sex with partner and masturbating). Bayesian hierarchical regression analysis revealed that sex drive was positively associated with MOR availability in cortical and subcortical areas, notably in caudate nucleus, hippocampus, and cingulate cortices. These results were replicated in full-volume GLM analysis. These widespread effects are in line with high spatial autocorrelation in MOR expression in human brain. Complementary voxel-based morphometry analysis (n = 108) of anatomical MR images provided limited evidence for positive association between sex drive and cortical density in the midcingulate cortex. We conclude that endogenous MOR tone is associated with individual differences in sex drive in human males.

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The endogenous mu-opioid receptor (MOR) system modulates a multitude of social and reward-related functions, and exogenous opiates also influence sex drive in humans and animals. However, there is no in vivo evidence for the contribution of MOR system on human sex drive. Here we measured healthy male subjects’ (n=52) brain’s MOR availability with positron emission tomography (PET) using an agonist radioligand, [11C]carfentanil, that has high affinity for MORs. Sex drive was measured using self-reports of engaging in sexual behaviour (sex with partner and masturbating). Bayesian hierarchical regression analysis revealed that sex drive was positively associated with MOR availability in cortical and subcortical areas, notably in caudate nucleus, hippocampus, and cingulate cortices. These results were replicated in full-volume GLM analysis. Complementary voxel-based morphometry analysis (n=108) provided limited evidence for association between sex drive and cortical density in the midcingulate cortex. We conclude that MOR system modulates individual differences in sex drive in human males.

IntroductionCentral μ-opioid receptors (MORs) modulate affective responses to physical exercise. Individuals with higher aerobic fitness report greater exercise-induced mood improvements than those with lower fitness, but the link between cardiorespiratory fitness and the MOR system remains unresolved. Here we tested whether maximal oxygen uptake (V̇O2peak) and physical activity level are associated with cerebral MOR availability and whether these phenotypes predict endogenous opioid release after a session of exercise.MethodsWe studied 64 healthy lean men who performed a maximal incremental cycling test for V̇O2peak determination, completed a questionnaire assessing moderate-to-vigorous physical activity (MVPA; in minutes per week), and underwent positron emission tomography with [11C]carfentanil, a specific radioligand for MOR. A subset of 24 subjects underwent additional positron emission tomography scan also after a 1-h session of moderate-intensity exercise and 12 of them also after a bout of high-intensity interval training.ResultsHigher self-reported MVPA level predicted greater opioid release after high-intensity interval training, and both V̇O2peak and MVPA level were associated with a larger decrease in cerebral MOR binding after aerobic exercise in the ventral striatum, orbitofrontal cortex, and insula. That is, more trained individuals showed greater opioid release acutely after exercise in brain regions especially relevant for reward and cognitive processing. Fitness was not associated with MOR availability.ConclusionsWe conclude that regular exercise training and higher aerobic fitness may induce neuroadaptation within the MOR system, which might contribute to improved emotional and behavioral responses associated with long-term exercise.

Previous research on how stereotypes affect perceptions of intimate partner violence and domestic homicide has found that violence committed by men is perceived as more severe and judged more harshly than violence committed by women. The present mock jury study investigated how perpetrator sex (male or female), crime type (familicide or filicide), and relatedness between perpetrator and child victims (biological or step) affect laypeople’s perceptions of the appropriate consequence of the crime, the reason for the offence, responsibility of the perpetrator, the likelihood of certain background factors being present, and the risk of future violence. One hundred sixty-seven university students read eight fictive descriptions of cases of multiple-victim domestic homicides, in which the sex of the perpetrator, the crime type, and the relatedness between the perpetrator and the child victims were manipulated. We found that participants recommended equally severe punishments to and placed the same amount of responsibility on male and female offenders. Female offenders were, however, regarded as mentally ill to a larger extent and perceived more likely to have been victims of domestic violence compared to male offenders. Male offenders, on the other hand, were seen as more likely to have committed domestic violence in the past, having been unemployed, have substance abuse, hold aggressive attitudes, and commit violent acts in the future. Participants also perceived offenders killing biological children as more mentally ill than offenders killing stepchildren. The present study extends the literature on the possible effect of stereotypes on decision making in psychiatric and judicial contexts.

BACKGROUND: The dopamine system contributes to a multitude of functions ranging from reward and motivation to learning and movement control, making it a key component in goal-directed behavior. Altered dopaminergic function is observed in neurological and psychiatric conditions. Numerous factors have been proposed to influence dopamine function, but due to small sample sizes and heterogeneous data analysis methods in previous studies their specific and joint contributions remain unresolved. METHODS: In this cross-sectional register-based study we investigated how age, sex, body mass index (BMI), as well as cerebral hemisphere and regional volume influence striatal type 2 dopamine receptor (D2R) availability in the human brain. We analyzed a large historical dataset (n=156, 120 males and 36 females) of [11C]raclopride PET scans performed between 2004 and 2018. RESULTS: Striatal D2R availability decreased through age for both sexes and was higher in females versus males throughout age. BMI and striatal D2R availability were weakly associated. There was no consistent lateralization of striatal D2R. The observed effects were independent of regional volumes. These results were validated using two different spatial normalization methods, and the age and sex effects also replicated in an independent sample (n=135). CONCLUSIONS: D2R density is dependent on age and sex, which may contribute to the vulnerability of neurological and psychiatric conditions involving altering D2R expression.