The temporoparietal junction (TPJ) is a key component of a right-lateralized ventral attention network (VAN) that also includes structures such as the anterior insula (aINS), and the inferior frontal gyrus (IFG) 
. Functional MRI (fMRI) studies have consistently shown that these right-lateralized regions are activated by salient stimuli in visual, auditory and somatosensory modalities including prolonged pain, with a preference for behaviourally-relevant stimuli 
. Lesions to areas within the VAN and their surrounding white matter are a common neural substrate of left unilateral spatial neglect, suggesting that regions in this right-lateralized network play a specialized role in spatial awareness 
. Transcranial magnetic stimulation of the right TPJ results in abnormal orienting of stimulus-driven attention 
. Furthermore, resting state BOLD studies demonstrate that areas within the VAN, particularly the TPJ and aINS/IFG, have correlated intrinsic fluctuations in activity in the right hemisphere 
. However, despite extensive fMRI, lesion and stimulation studies on the VAN, the anatomical basis of this network's right-lateralized properties remains poorly investigated.
In recent years, diffusion-weighted MRI (DW-MRI) has emerged as an invaluable tool for investigating in vivo
connectional anatomy in the human brain 
. In DW-MRI, the signal is sensitized to anisotropic diffusion of water, which occurs in brain white matter and is characterized by greater diffusion along an axon compared to across an axon. If the diffusion profile in each voxel is fit to a tensor model, principal diffusion directions can be estimated and white matter pathways can be traced. This method of deterministic “streamline tractography,” however, is limited in that tracing is poor near gray matter, where anisotropy is low but white matter is still present. Thus alternative techniques such as probabilistic tractography 
have been developed to improve sensitivity. In probabilistic tractography, a probability distribution representing uncertainty in fiber orientation is modeled at each voxel. A large number (usually thousands) of streamlines are drawn between two points to build up a connectivity distribution, and the number of successful connections is counted. This approach is advantageous because pathway tracing does not stop near gray matter, multiple fiber populations can be modeled 
, and quantitative measures of connection likelihood can be obtained. Despite inherent limitations of probabilistic tractography (reviewed in 
), the technique is useful especially when a priori
connections are known.
Anatomical connections between regions of the VAN have been identified in the monkey and human. The arcuate fasciculus (AF) and subcomponent III of the superior longitudinal fasciculus (SLF III) connects the TPJ with the IFG 
, and the extreme capsule connects the TPJ with the insula 
. DW-MRI studies indicate that temporoparietal regions are also connected with the aINS and pars triangularis of the IFG via the extreme capsule 
. Recently, right-lateralization of the SLF III was identified, and the degree of SLF II right-lateralization was correlated with performance on tasks involving visuospatial attention 
. However, it remains unknown whether hemispheric differences exist in the strength of connections between specific VAN gray matter regions.
Therefore, the aim of this study was to determine the strength and laterality of the structural connectivity between the TPJ and regions within the VAN and elsewhere that are involved in salience detection, including pain. We used DW-MRI and probabilistic tractography to characterize and compare white matter connectivity profiles of the right TPJ (rTPJ) and left TPJ (lTPJ) to test the hypothesis that the TPJ exhibits stronger connectivity with the insula, IFG, cingulate cortex, thalamus and putamen in the right compared to left hemisphere.