Cortical projection to the human red nucleus: complementary results with probabilistic tractography at 3 T

Introduction In a previous study using streamlined diffusion tensor imaging (DTI) axonal tracking at 1.5 T, we found that the main afferents to the human red nucleus arise from the sensorimotor and prefrontal cortices. However, the spatial resolution of our data was low and our streamlining DTI algorithm was less powerful than the probabilistic tractography algorithm usually used to define connections between low anisotropic cortical or nuclear areas. Therefore, we reassessed and completed our previous results with trajectories computed with a probabilistic algorithm and with a high-field MRI system. Methods Afferents to the red nuclei of five volunteers were studied at 3 T using probabilistic DTI axonal tracking. Results Trajectories were constantly tracked between the red nucleus and the ipsilateral prefrontal, pericentral, temporal and occipital cortices, and the ipsilateral lentiform and contralateral dentate nuclei. We showed that the dentate nucleus was connected to the mammillary tubercle and, through the contralateral ventral thalamus, to the frontal and prefrontal cortices. Conclusion The red nucleus receives extensive projections from the cerebral cortex and has dense subcortical connections to the striopallidal system.