Abstract
A growing body of work offers compelling evidence for theory of mind impairments in individuals with traumatic brain injury (TBI). However, little is known about the neural correlates of theory of mind impairments following TBI. Deeper knowledge of the neural underpinnings of theory of mind impairments in individuals with TBI can aid in the development of more accurate diagnostic and prognostic tools, and shed light on the mechanisms that lead to social dysfunction following TBI. The present study aimed to examine differences in performance on the Reading the Mind in the Eyes (Eyes) task in individuals with moderate to severe TBI (n=30) and demographically matched healthy comparison participants (n=23). We also sought to further examine the relationship between diffusion tensor imaging (DTI) scalars, in particular (fractional anisotropy (FA) and mean diffusivity (MD), and performance on the Eyes task. We executed an ROI analysis, focusing on three white matter tracts shown to be implicated in theory of mind: the superior longitudinal fasciculus (SLF), the inferior longitudinal fasciculus (ILF), and the uncinate fasciculus (UF). Mixed effect logistic regression was used to determine group differences in individuals with TBI and demographically matched comparison participants in Eyes task performance, and revealed that individuals with TBI were significantly more likely to make mistakes in emotion and state of mind attribution than healthy comparison participants (p<.05). Neuroimaging analysis revealed a significant positive association between white matter FA in the bilateral uncinate fasciculi and performance on the Eyes task, as well as a significantly negative association between the MD in the left uncinate fasciculus the Eyes task. There were no significant relationships between performance on the Eyes task and other ROIs. Further analysis of the DTI data revealed lower FA, and higher MD, of the bilateral uncinate fasciculi in individuals with TBI. These findings suggest that the structural integrity of the uncinate fasciculus is related to performance on a well-established task of theory of mind, and expand our knowledge on the white matter correlates of Theory of Mind and the neural mechanisms leading to social dysfunction following moderate to severe TBI.