Mapping the structural connectivity between the periaqueductal gray and the cerebellum in humans

Abstract

The periaqueductal gray is a mesencephalic structure involved in modulation of responses to stressful stimuli. Structural connections between the periaqueductal gray and the cerebellum have been described in animals and in a few diffusion tensor imaging studies. Nevertheless, these periaqueductal gray–cerebellum connectivity patterns have yet to be fully investigated in humans. The objective of this study was to qualitatively and quantitatively characterize such pathways using high-resolution, multi-shell data of 100 healthy subjects from the open-access Human Connectome Project repository combined with constrained spherical deconvolution probabilistic tractography. Our analysis revealed robust connectivity density profiles between the periaqueductal gray and cerebellar nuclei, especially with the fastigial nucleus, followed by the interposed and dentate nuclei. High-connectivity densities have been observed between vermal (Vermis IX, Vermis VIIIa, Vermis VIIIb, Vermis VI, Vermis X) and hemispheric cerebellar regions (Lobule IX). Our in vivo study provides for the first time insights on the organization of periaqueductal gray–cerebellar pathways thus opening new perspectives on cognitive, visceral and motor responses to threatening stimuli in humans.

Structural Connectivity-Based Parcellation of the Dopaminergic Midbrain in Healthy Subjects and Schizophrenic Patients

“…The above described connectivity patterns partially reflect the functional organization of dopaminergic striatal circuitry described in primate models [ 19 , 21 , 22 , 23 , 73 ], although a clearly-described ventro-dorsal organization pattern could not be identified. While this could be in part conditioned by all the intrinsic limitations of tractography, that is not able to identify neuronal terminations at the synaptic level [ 74 , 75 ], the good agreement with animal findings support the hypothesis of a tripartite SNc/VTA subdivision in the human brain. These distinct topographical regions may play a crucial role in integrating different aspects of behavioral response to salient stimuli, from salience detection to finalized motor responses, incentive learning and habit formation [ 20 ].…”

Spatially coherent and topographically organized pathways of the human globus pallidus

“…Finally, the choice of a hard‐segmentation approach could represent an inherent limitation since it attributes voxels to the clusters exhibiting higher connectivity density (Behrens et al, 2003). Although widely used in literature (Cacciola, Milardi, Basile, et al, 2019; Cacciola, Milardi, Basile, et al, 2019; Middlebrooks, Tuna, Almeida, et al, 2018; Middlebrooks, Tuna, Grewal, et al, 2018), the use of such approach may introduce a bias selecting only the most connected voxels as part of each connectivity map therefore imposing a stricter parcellation in respect to the anatomical reality. This is particularly true when brain structures are thought to be composed of partially overlapping functional territories rather than well‐delineated subdivisions (Alkemade, Schnitzler, & Forstmann, 2015; Lambert et al, 2015; Plantinga et al, 2018).…”

Endoscopic Endonasal Resection of a Schwannoma of the Anterior Cranial Fossa

“…Althought MRI or CT are particularly useful for the scanning and detection of abnormalities in soft tissue 4,5 , there are no specific findings to differentiate Schwannomas from other types of contrast-enhancing formations. So, a preoperative biopsy has been performed to identify the nature of the mass.…”