White Matter Correlates of Psychopathic Traits in a Japanese Community Sample: Sex Matters!

Abstract

Psychopathy is a personality disorder marked by distinct interpersonal, affective and behavioural abnormalities. Relatively little is known about associations between psychopathic traits and white matter (WM) microstructure among community samples, as most diffusion tensor imaging (DTI) research has focused on small clinical and forensic samples. These studies are also often limited to males from Western populations, leaving gaps in the understanding of females and non-Western populations. This study uses DTI data from a large community sample (n = 97) of well-functioning Japanese adults (45 males, aged 21-39 years). We used tract-based spatial statistics to investigate WM microstructural integrity (whole brain corrected using threshold-free cluster enhancement (TFCE), p < 0.05). Psychopathy traits were measured using the Self-Report Psychopathy Scale (SRP-SF). Region of interest analysis showed that callous affect scores negatively correlated with fractional anisotropy and axial diffusivity in the left cingulum. Furthermore, analysis across the entire white matter skeleton revealed that sex acted as a moderator in the association between psychopathy trait scores and mean diffusivity (MD) in the right superior longitudinal fasciculus, anterior thalamic radiation, and corpus callosum. The interaction showed that psychopathy trait scores were positively associated with MD in females, whereas the opposite pattern was observed in males. Our findings offer novel insights into the white matter correlates of psychopathic traits.

Keywords: diffusion tensor imaging; psychopathy; sex differences; tract‐based spatial statistics; white matter.

FIGURE 1

Sex interactions in white matter microstructure. (A) voxels within the right superior longitudinal fasciculus (x, y, z = 43, −31, 33) in which total psychopathy scores interacted with sex to predict mean diffusivity and voxels within the right (B) superior longitudinal fasciculus (x, y, z = 32, −47, 34), (C) anterior thalamic radiation (x, y, z = 18, 38, −1), (D) corpus callosum (x, y, z = 16, 5, 31) in which callous affect scores interacted with sex to predict mean diffusivity. For viewing purposes, skeletonised clusters have been ‘thickened’ using TBSSfill. Findings are overlaid onto the mean FA skeleton (green) in MNI space.

FIGURE 2

White matter microstructure in left cingulum. (A) voxels within the left cingulum (x, y, z = −17, −36, 35) in which callous affect scores were significantly negatively correlated with fractional anisotropy. (B) Voxels within the left cingulum (x, y, z = −17, −36, 35) in which callous affect scores significantly negatively correlated with axial diffusivity. For viewing purposes, skeletonised clusters have been ‘thickened’ using TBSSfill. Findings are overlaid onto the mean FA skeleton (green) in MNI space and cingulum mask (blue).