Abstract
Behavioral studies have shown that, at a population level, women perform better on tests of social cognition and empathy than men. Furthermore Autism Spectrum Disorders (ASDs), which are characterized by impairments in social functioning and empathy, occur more commonly in males than females. These findings have led to the hypothesis that differences in the functioning of the social brain between males and females contribute to the greater vulnerability of males to ASD and the suggestion that ASD may represent an extreme form of the male brain. Here we sought to investigate this hypothesis by determining: (i) whether males and females differ in social brain function, and (ii) whether any sex differences in social brain function are exaggerated in individuals with ASD. Using fMRI we show that males and females differ markedly in social brain function when making social decisions from faces (compared to simple sex judgements) especially when making decisions of an affective nature, with the greatest sex differences in social brain activation being in the inferior frontal cortex (IFC). We also demonstrate that this difference is exaggerated in individuals with ASD, who show an extreme male pattern of IFC function. These results show that males and females differ significantly in social brain function and support the view that sex differences in the social brain contribute to the greater vulnerability of males to ASDs.
Highlights
Previous behavioural studies have suggested that women perform better in tests of social cognition and empathy than males [1,2,3,4], these findings have not been without controversy
Cross-sectional studies in adults have confirmed that females have larger relative volumes of a number of brain regions implicated in social function including the inferior frontal cortex (IFC) [10,11,12,13,14], cingulate cortex [12,15] and inferior parietal cortex [12,15,16], whilst men have larger relative volumes of the amygdala [12,17] and cerebellum [12,15]
In the present study we demonstrate sex differences in social brain function while making judgements of approachability from faces which are greatest in the left inferior frontal cortex (IFC)
Summary
Previous behavioural studies have suggested that women perform better in tests of social cognition and empathy than males [1,2,3,4], these findings have not been without controversy. Experimental evidence of sex differences in social function has been obtained from studies looking at facial emotion expression processing which have suggested a female advantage in decoding emotional expressions from faces and from the eye region alone [3,4,6,7]. There have been fewer functional imaging studies that have investigated sex differences in the social brain but investigations of face processing have suggested a degree of sexual dimorphism in brain function which depends in part on the nature of the stimuli used [18,19,20,21,22]. In view of existing evidence that men and women’s social functioning may differ at a neural level, and that those with ASD may have an exaggerated male pattern of social brain function, in the present study we sought to determine whether males and females differ in terms of social brain function while viewing faces during fMRI, and to relate these findings to brain activation in individuals with ASD
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