Motor and higher‐order functions topography of the human dentate nuclei identified with tractography and clustering methods

Abstract

Deep gray matter nuclei are the synaptic relays, responsible to route signals between specific brain areas. Dentate nuclei (DNs) represent the main output channel of the cerebellum and yet are often unexplored especially in humans. We developed a multimodal MRI approach to identify DNs topography on the basis of their connectivity as well as their microstructural features. Based on results, we defined DN parcellations deputed to motor and to higher‐order functions in humans in vivo. Whole‐brain probabilistic tractography was performed on 25 healthy subjects from the Human Connectome Project to infer DN parcellations based on their connectivity with either the cerebral or the cerebellar cortex, in turn. A third DN atlas was created inputting microstructural diffusion‐derived metrics in an unsupervised fuzzy c‐means classification algorithm. All analyses were performed in native space, with probability atlas maps generated in standard space. Cerebellar lobule‐specific connectivity identified one motor parcellation, accounting for about 30% of the DN volume, and two non‐motor parcellations, one cognitive and one sensory, which occupied the remaining volume. The other two approaches provided overlapping results in terms of geometrical distribution with those identified with cerebellar lobule‐specific connectivity, although with some differences in volumes. A gender effect was observed with respect to motor areas and higher‐order function representations. This is the first study that indicates that more than half of the DN volumes is involved in non‐motor functions and that connectivity‐based and microstructure‐based atlases provide complementary information. These results represent a step‐ahead for the interpretation of pathological conditions involving cerebro‐cerebellar circuits.

The CCAS-scale in hereditary ataxias: helpful on the group level, particularly in SCA3, but limited in individual patients

“…Second, the dentate nuclei are strongly affected in SCA3. Cerebellar nuclei are the main output structures of the cerebellum, and similar to the cerebellar cortex there is compartmentalization of the dentate nuclei in motor and cognitive areas [ 48 , 49 ]. Patients with focal lesions of the dentate nuclei performed worse on cognitive testing than patients with cerebellar lesions sparing the dentate nuclei [ 25 ].…”

The Cerebellar Involvement in Autism Spectrum Disorders: From the Social Brain to Mouse Models

“…The DCN send direct projections to the ventrolateral (VL) and the intralaminar thalamic nuclei, particularly the dorsomedial (MD) nucleus [ 125 ]. The VL nucleus, classically known as an integrative center for sensorimotor transformations, targets the primary motor cortex (M1) [ 42 , 126 , 127 ], whereas the MD nucleus, like other intralaminar nuclei, has widespread cortical projections including the mPFC ( Figure 3 A) and the superior temporal sulcus [ 128 , 129 , 130 , 131 , 132 ]. Past anatomical studies demonstrated that the cerebellum is interconnected with parts of the limbic system, including the hippocampus, amygdala, and cingulate cortex ( Figure 3 B) [ 133 , 134 ].…”

Automated facial–vestibulocochlear nerve complex identification based on data‐driven tractography clustering

“…Second, as the FVN is under tumor compression, probabilistic tractography is somewhat superior to deterministic tractography for high curvature fiber tracts in the cerebellum. 62 Recent studies 61,63 have demonstrated the advantages of probabilistic tractography in crossing fibers in the cerebellum. Third, similar to the automatic identification pipeline in this study, a cerebellum tractography atlas can be created to automatically identify subject-specific fiber tracts in the cerebellum.…”

“…First, similar to small‐scale FVN, identifying highly extruded fiber tracts in the cerebellum requires high‐resolution dMRI data. Furthermore, multicompartment diffusion models based on multishell data 61 are recommended to ensure the accuracy of fiber orientation estimation. Second, as the FVN is under tumor compression, probabilistic tractography is somewhat superior to deterministic tractography for high curvature fiber tracts in the cerebellum 62 .…”