Cytoarchitecture and myeloarchitecture of the entorhinal cortex of the common marmoset monkey (Callithrix jacchus)

Abstract

The entorhinal cortex (EC) is associated with impaired cognitive function such as in the case of Alzheimer's disease, Parkinson's disease and Huntington's disease. The present study provides a detailed analysis of the cytoarchitectural and myeloarchitectural organization of the EC in the common marmoset Callithrix jacchus. Data were collected using Nissl and fiber stained preparations, supplemented with acetylcholinesterase and parvalbumin immunohistochemistry. The EC layers and subfields in the marmoset seem to be architectonically similar to those that have been proposed in nonhuman primates and humans to date; however, slight differences could be revealed using the present techniques. Throughout its rostrocaudal length, the entorhinal cortex presents a clear six‐layered pattern. The entorhinal cortex is divided into six fields, named mainly in accordance to their rostrocaudal and mediolateral positions. At rostral levels, the neurons tend to be organized in patches that are surrounded by large, thick, radially oriented bundles of fibers, and the deep layers are poorly developed. At caudal levels, the divisions are more laminated in appearance. AChE staining at the borders of adjacent fields are consistent with the changes in layering revealed in Nissl‐stained sections, of which the lateral regions of the EC display denser AChE staining than that of the medial banks. PV immunoreactivity was found in the labeled somata, dendrites, and axons in all layers and subdivisions. Additionally, we distinguished three subtypes of PV‐immunoreactive neurons: multipolar, bipolar and spherical‐shaped neurons, based on the shape of the somata and the disposition of the dendrites.

Histology-based average template of the marmoset cortex with probabilistic localization of cytoarchitectural areas

“…4A, A+7.4). These characteristics correspond to well-described cytoarchitectural features of these areas in the marmoset (Burman et al, 2008(Burman et al, , 2011(Burman et al, , 2014b; Góis Morais et al, 2019).…”

The hippocampal formation of two carnivore species: The feliform banded mongoose and the caniform domestic ferret

“…The subicular complex shares borders with the CA1 field, and is typically divided into four parts, the subiculum (dorsal and ventral parts), the presubiculum, parasubiculum, and transitional subicular cortex (the transitional subicular cortex being located at the caudal lateral pole of the hippocampal curvature, see Paxinos & Watson, 2009; however, in earlier versions of rat atlases the transitional subicular cortex is labeled only as subiculum, e.g., Paxinos, Carrive, Wang, & Wang, 1999). The entorhinal cortex, the gateway between the remainder of the brain and the hippocampal formation, lies laterally adjacent to the parasubiculum, and while typically composed of medial and lateral cortical areas (e.g., Witter, Doan, Jacobsen, Nilssen, & Ohara, 2017), some studies have indicated that the entorhinal cortex may be comprised of several distinct cortical areas (e.g., de Góis Morais et al, 2019; Insausti & Amaral, 2008; Schultz & Engelhardt, 2014).…”

Hippocampal Connectivity of the Presubiculum in the Common Marmoset (Callithrix jacchus)

“…Although a previous study subdivided marmoset EC into six fields ( de Góis Morais et al, 2020 ), the boundary between such subsegments of EC was not identified by Nissl staining alone. Thus, in the present study, EC was defined as a cortical region that was identified by a distinct layer II that was composed of densely stained, large-sized cells ( Figure 1A ), and we did not parcellate EC into medial (MEC) and lateral (LEC) parts.…”