Internal Subdivisions of the Marmoset Claustrum Complex: Identification by Myeloarchitectural Features and High Field Strength Imaging.

Xiuxian Pham,Katrina H Worthy,David K Wright,Nafiseh Atapour,David H Reser,Kirsty J Watkins,Amy Reichelt,Marcello Rosa,Jonathan M.-H Chan

doi:10.3389/fnana.2019.00096

Abstract

There has been a surge of interest in the structure and function of the mammalian claustrum in recent years. However, most anatomical and physiological studies treat the claustrum as a relatively homogenous structure. Relatively little attention has been directed toward possible compartmentalization of the claustrum complex into anatomical subdivisions, and how this compartmentalization is reflected in claustrum connections with other brain structures. In this study, we examined the cyto- and myelo-architecture of the claustrum of the common marmoset (Callithrix jacchus), to determine whether the claustrum contains internal anatomical structures or compartments, which could facilitate studies focused on understanding its role in brain function. NeuN, Nissl, calbindin, parvalbumin, and myelin-stained sections from eight adult marmosets were studied using light microscopy and serial reconstruction to identify potential internal compartments. Ultra high resolution (9.4T) post-mortem magnetic resonance imaging was employed to identify tractographic differences between identified claustrum subcompartments by diffusion-weighted tractography. Our results indicate that the classically defined marmoset claustrum includes at least two major subdivisions, which correspond to the dorsal endopiriform and insular claustrum nuclei, as described in other species, and that the dorsal endopiriform nucleus (DEnD) contains architecturally distinct compartments. Furthermore, the dorsal subdivision of the DEnD is tractographically distinguishable from the insular claustrum with respect to cortical connections.

Highlights

The claustrum is a bilateral subcortical structure located between the insular cortex and basal nuclei of most mammalian species, and characterized by widespread connectivity to the neocortex
The claustrum complex is resolved from surrounding forebrain structures along most of its span, with the exception of the rostral most 200–500 μm, and at its lateral-most extent, where it is closely adjacent to, and possibly contiguous with, the cortical concavity at the fundus of the lateral sulcus
Its long axis was oriented mediolaterally at the rostral edge, changing smoothly to a dorsalventral orientation at approximately the rostral extent of the amygdala in the coronal plane of section. This warping of the claustrum structure can result in confusion of anatomical reference, such that the lateral terminus of the rostral claustrum complex is adjacent to the dorsal edge of the mid-claustrum

Summary

Introduction

The claustrum is a bilateral subcortical structure located between the insular cortex and basal nuclei of most mammalian species, and characterized by widespread connectivity to the neocortex. A number of alternative hypotheses regarding claustrum function have been proposed, including the salience-attention hypothesis (Mathur et al, 2009; Remedios et al, 2014; Smythies et al, 2014; Goll et al, 2015), and the network hypothesis (Patru and Reser, 2015; Reser et al, 2017). The majority of anatomical and hodological work on the claustrum has been performed in rodents, which has produced several of the leading hypotheses surrounding claustrum function (Mathur et al, 2009; Smith et al, 2017; Watson et al, 2017; White et al, 2018). Several as yet unexplained differences in claustrum-cortex connectivity have been reported between rodents and primates (Smith and Alloway, 2010; Reser et al, 2017; Smith et al, 2017)

Methods

Results

Discussion

Conclusion