The cortico-rubral and cerebello-rubral pathways are topographically organized within the human red nucleus

Alberto Cacciola,Gianpaolo Antonio Basile,Giuseppina Rizzo,Alessia Bramanti,Gaetana Chillemi,Fabio Trimarchi,Giuseppe Paladina,Giuseppe Anastasi,Alessandro Calamuneri,Demetrio Milardi,Salvatore Bertino,Federica Impellizzeri

doi:10.1038/s41598-019-48164-7

Alberto Cacciola, Gianpaolo Antonio Basile + Show 10 more

Open Access

https://doi.org/10.1038/s41598-019-48164-7

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Abstract

The Red Nucleus (RN) is a large nucleus located in the ventral midbrain: it is subdivided into a small caudal magnocellular part (mRN) and a large rostral parvocellular part (pRN). These distinct structural regions are part of functionally different networks and show distinctive connectivity features: the mRN is connected to the interposed nucleus, whilst the pRN is mainly connected to dentate nucleus, cortex and inferior olivary complex. Despite functional neuroimaging studies suggest RN involvement in complex motor and higher order functions, the pRN and mRN cannot be distinguished using conventional MRI. Herein, we employ high-quality structural and diffusion MRI data of 100 individuals from the Human Connectome Project repository and constrained spherical deconvolution tractography to perform connectivity-based segmentation of the human RN. In particular, we tracked connections of RN with the inferior olivary complex, the interposed nucleus, the dentate nucleus and the cerebral cortex. We found that the RN can be subdivided according to its connectivity into two clusters: a large ventrolateral one, mainly connected with the cerebral cortex and the inferior olivary complex, and a smaller dorsomedial one, mainly connected with the interposed nucleus. This structural topography strongly reflects the connectivity patterns of pRN and mRN respectively. Structural connectivity-based segmentation could represent a useful tool for the identification of distinct subregions of the human red nucleus on 3T MRI thus allowing a better evaluation of this subcortical structure in healthy and pathological conditions.

Highlights

The red nucleus (RN) is a large neuronal structure located in the most rostral part of ventral midbrain
For quantitative volume analysis and anatomical description, we considered the 75%-thresholded Maximum Probability Map (MPM), which allows an optimal distinction of boundaries between clusters
By using connectivity-based segmentation we demonstrated that the human Red Nucleus (RN) is topographically organized according to its structural connectivity into two spatially distinguished clusters: a larger ventral one, mainly connected with the cerebral cortex and the inferior olivary complex, and a smaller dorsal one, mostly connected with the interposed nucleus

Summary

Introduction

The red nucleus (RN) is a large neuronal structure located in the most rostral part of ventral midbrain. The pRN receives afferents from the dentate nucleus[7,8] and different regions of the cerebral cortex[3,9,10] with the ipsilateral inferior olivary complex as main efference[11,12,13]. This different organization of connections likely reflects different functional roles. Since mRN and pRN are not distinguishable on conventional structural MRI scans, making inferences about which subregions of the RN were involved in the aforementioned studies is challenging

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