How do spatial and angular resolution affect brain connectivity maps from diffusion MRI?

Diffusion tensor imaging (DTI) is sensitive to the directionally-constrained flow of water, which diffuses preferentially along axons. Tractography programs may be used to infer matrices of connectivity (anatomical networks) between pairs of brain regions. Little is known about how these computed connectivity measures depend on the scans´ spatial and angular resolutions. To determine this, we scanned 8 young adults with DTI at 2.5 and 3mm resolutions, and an additional subject at 4 resolutions between 2-4 mm. We computed 70×70 connectivity matrices, using whole-brain tractography to measure fiber density between all pairs of 70 cortical and subcortical regions. Spatial and angular resolution affected the computed connectivity for narrower tracts (internal capsule and cerebellum), but also for the corticospinal tract. Data resolution affected the apparent role of some key structures in cortical anatomic networks. Care is needed when comparing network data across studies, and interpreting apparent disagreements among findings.