The brain of the tree pangolin (Manis tricuspis). VII. The amygdaloid body

Abstract

Here, we describe the cytoarchitecture and chemoarchitecture of the amygdaloid body of the tree pangolin. Our definition of the amygdaloid body includes the pallial portions of the amygdala, and the centromedial group that is a derivative of the subpallium and part of the extended amygdala. The remainder of the extended amygdala is not described herein. Within the amygdaloid body of the tree pangolin, we identified the basolateral group (composed of the lateral, basal, and accessory basal amygdaloid nuclei), the superficial, or cortical nuclei (the anterior and posterior cortical nuclei, the periamygdaloid cortex, and nuclei of the olfactory tract), the centromedial group (the central amygdaloid nucleus and the medial nuclear cluster), and other amygdaloid nuclei (the anterior amygdaloid area, the amygdalohippocampal area, the intramedullary group, and intercalated islands). The location within and relative to each other within the amygdaloid body and the internal subdivisions of these groups were very similar to that reported in other mammalian species, with no clearly derived features specific to the tree pangolin. The only variation was the lack of an insular appearance of the intercalated islands, which in the tree pangolin were observed as a continuous band of neurons located dorsomedial to the basolateral group similar in appearance to and almost continuous with the intramedullary group. In carnivores, the closest relatives of the pangolins, and laboratory rats, a similar appearance of portions of the intercalated islands has been noted.

The brain of the tree pangolin (Manis tricuspis). IX. The pallial telencephalon

“…Our architectural analysis indicates that there are several cortical regions, each containing multiple, distinct cortical areas (Figures 6 and 8). Within the tree pangolin brain, in addition to the olfactory and limbic cortical regions previously described (Imam et al., 2018a, 2019a, 2022a), we noted putatively as there is no electrophysiological evidence to support these functionally assigned regions, a prefrontal cortical region, a motor cortical region, a somatosensory cortical region, a visual cortical region, an auditory cortical region, a pararhinal cortical region, a cingulate cortical region, and retrosplenial/postsplenial cortical region. The putative assignation of cortical regions and areas is based on comparisons primarily to carnivores, but also more broadly across mammals.…”

“…Our architectural analysis indicates that there are several cortical regions, each containing multiple, distinct cortical areas (Figures 6 and 8). Within the tree pangolin brain, in addition to the olfactory and limbic cortical regions previously described (Imam et al, 2018a(Imam et al, , 2019a(Imam et al, , 2022a, we noted putatively as there is no electrophysiological evidence to support these functionally assigned regions, a prefrontal cortical region, a motor cortical region, a somatosensory…”

“…Here, we provide a detailed cyto‐, myelo‐, and chemoarchitectonic description of the adult derivatives of the portions of the tree pangolin pallial telencephalon that have not been described previously (e.g., Imam et al., 2017; 2018a; 2019a; 2022a, b). These structures include the claustrum and endopiriform nuclei, the white matter and WMICs, as well as the various areas of the cerebral cortex.…”

“…The brain of the tree pangolin has been observed to contain all the structures typically forming the mammalian pallial telencephalon (Imam et al., 2017). In addition, detailed descriptions of the olfactory portions of the pallial telencephalon (Imamet al., 2018a), the hippocampal formation (Imam et al., 2019a), and amygdaloid body (Imam et al., 2022a; Imam et al., 2022b) have been provided previously. Here we continue our detailed anatomical description of the structure of the brain of the tree pangolin (Imam et al., 2017; Imam et al., 2018a; Imam et al., 2018b; Imam et al., 2019a; Imam et al., 2019b; Imam et al., 2019c; Imam et al., 2022a, b) by providing a comprehensive architectonic account of the as yet undescribed structures of the pallial telencephalon.…”

“…In addition, detailed descriptions of the olfactory portions of the pallial telencephalon (Imamet al., 2018a), the hippocampal formation (Imam et al., 2019a), and amygdaloid body (Imam et al., 2022a; Imam et al., 2022b) have been provided previously. Here we continue our detailed anatomical description of the structure of the brain of the tree pangolin (Imam et al., 2017; Imam et al., 2018a; Imam et al., 2018b; Imam et al., 2019a; Imam et al., 2019b; Imam et al., 2019c; Imam et al., 2022a, b) by providing a comprehensive architectonic account of the as yet undescribed structures of the pallial telencephalon. The structures include the claustrum and endopiriform nuclear complex (e.g., Real et al., 2003; Smith et al., 2018; Watson & Puelles, 2017), the white matter and white matter interstitial cells (WMICs, e.g., Bhagwandin et al., 2020; Swiegers et al., 2018), and the cerebral cortex (e.g., Homman‐Ludiye et al., 2010; van Essen & Dierker, 2007; van der Gucht et al., 2007).…”