Diffusion Tensor Imaging of Pedophilia

James M. Cantor, Sophie Lafaille, Debra W. Soh, Massieh Moayedi, David J. Mikulis, Todd A. Girard

Pedophilia is a principal motivator of child molestation, incurring great emotional and financial burdens on victims and society. Even among pedophiles who never commit any offense, the condition requires lifelong suppression and control. Previous comparison using voxel-based morphometry (VBM) of MR images from a large sample of pedophiles and controls revealed group differences in white matter. The present study therefore sought to verify and characterize white matter involvement using diffusion tensor imaging (DTI), which better captures the microstructure of white matter than does VBM. Pedophilic sex offenders (n = 24) were compared with healthy, age-matched controls with no criminal record and no indication of pedophilia (n = 32). White matter microstructure was analyzed with Tract-Based Spatial Statistics, and the trajectories of implicated fiber bundles were identified by probabilistic tractography. Groups showed significant, highly focused differences in DTI parameters which related to participants' genital responses to sexual depictions of children, but not to measures of psychopathy or to childhood histories of physical abuse, sexual abuse, or neglect. Some previously reported gray matter differences were suggested under highly liberal statistical conditions (p uncorrected < .005), but did not survive ordinary statistical correction (whole brain per voxel false discovery rate of 5 %). These results confirm that pedophilia is characterized by neuroanatomical differences in white matter microstructure, over and above any neural characteristics attributable to psychopathy and childhood adversity, which show neuroanatomic footprints of their own. Although some gray matter structures were implicated previously, only few have emerged reliably.