Tackling the gyral bias and bottleneck problems with hybrid diffusion-microscopy tractography in the BigMac dataset

We present data fusion combining precisely co-registered dMRI and microscopy to reconstruct 3D fibre orientation with micron-scale spatial resolution. We then perform hybrid dMRI-microscopy tractography to investigate two known challenges in tractography: the gyral bias and bottleneck problems. Our results using hybrid tractography suggest that the gyral bias can be overcome by increased spatial resolution, and that microstructure-informed fibre orientations can overcome the bottleneck problem, irrespective of spatial resolution. These observations can be used to inform tractography analyses in vivo. This approach builds on the complementary strengths of microscopy (high spatial resolution) and dMRI (3D whole-brain coverage).