Sexual arousal is a dynamical, highly coordinated neurophysiological process that is often induced by visual stimuli. Numerous studies have proposed that the cognitive processing stage of responding to sexual stimuli is the first stage, in which sex differences occur, and the divergence between men and women has been attributed to differences in the concerted activity of neural networks. The present comprehensive metaanalysis challenges this hypothesis and provides robust quantitative evidence that the neuronal circuitries activated by visual sexual stimuli are independent of biological sex. Sixty-one functional magnetic resonance imaging studies (1,850 individuals) that presented erotic visual stimuli to men and women of different sexual orientation were identified. Coordinate-based activation likelihood estimation was used to conduct metaanalyses. Sensitivity and clustering analyses of averaged neuronal response patterns were performed to investigate robustness of the findings. In contrast to neutral stimuli, sexual pictures and videos induce significant activations in brain regions, including insula, middle occipital, anterior cingulate and fusiform gyrus, amygdala, striatum, pulvinar, and substantia nigra. Cluster analysis suggests stimulus type as the most, and biological sex as the least, predictor for classification. Contrast analysis further shows no significant sex-specific differences within groups. Systematic review of sex differences in gray matter volume of brain regions associated with sexual arousal (3,723 adults) did not show any causal relationship between structural features and functional response to visual sexual stimuli. The neural basis of sexual arousal in humans is associated with sexual orientation yet, contrary to the widely accepted view, is not different between women and men.

Sex differences in behavioural patterns of drug abuse and dependence have been hypothesized to be a consequence of sexual dimorphisms in brain pathways, particularly within the dopaminergic reward circuitry. Yet, how potential sex differences are manifested at a neurochemical level remains unclear. Here, we use a meta‐analysis approach to investigate whether animal studies robustly indicate a different regulation of striatal dopamine transmission in males and females. Data from 39 microdialysis experiments on female rats (n = 676) were extracted and statistically compared with data from 1523 male rats. All drugs of abuse, independent of their molecular mechanisms of action, notably increase extracellular dopamine concentrations in the nucleus accumbens (NAc) and caudate putamen (CPu). No significant sex differences in basal levels or in dopaminergic response to drugs of abuse were found. However, basal dopamine levels in CPu (but not NAc) were significantly altered by ovariectomy. In conclusion, there are no sex‐dependent differences in basal dopamine levels within the NAc and CPu. Previously reported sex differences in the CPu seem to be a result of ovariectomy and may only to a lesser, non‐significant degree be attributed to a sexual duality.

Highlights d Bistable evolution of rat behavior during development and depends on sex and strain d Big data analysis reveals circatidal-like rhythms in locomotor activity d Thigmotaxic behavior in home-cage may be driven by random walk and not stress