Increased gray matter within temporal cortical networks in sexual sadism

Sexual sadism is an extreme, pathological manifestation of sadistic traits. While the psychological and forensic characteristics of sexual sadism have been extensively studied, the underlying neurocircuitry is far from being understood. In this study, n = 232 incarcerated men completed structural MRI scans, n = 116 of whom had been convicted of sexual offenses. Sexual offenders were assessed for the presence and severity of sadism using the Sexual Sadism Scale (SeSaS). Multivariate (source-based morphometry (SBM)) and univariate (voxel-based morphometry (VBM)) techniques were used to identify neural networks and individual regions in which gray matter volume was related to sexual sadism. Both SBM and VBM revealed associations between SeSaS scores and posterior temporal regions, including the temporoparietal junction (TPJ) and fusiform gyrus, two regions critical for social cognition and processing high-order visual information, respectively. Men with high SeSaS scores indicative of sexual sadism had enlarged gray matter volume in these regions, relative to both men with low SeSaS scores and men who had not committed sexual offenses. One of the temporal regions (right tTPJ) overlapped closely with the rTPJ region previously implicated in a functional MRI study of pain processing in sexual sadism. Overall, the results provide multi-modal evidence of the relevance of temporal cortical networks to sexual sadism.