Department of Animal Anatomy and Physiology, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland.
Department of Human Physiology and Pathophysiology, School of Medicine, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland.
J Anat. 2022 Mar;240(3):489-502. doi: 10.1111/joa.13571. Epub 2021 Oct 14.
The amygdala primarily evolved as a danger detector that regulates emotional behaviours and learning. However, it is also engaged in stress responses as well as olfactory/pheromonal and reproductive functions. All of these functions are processed by a set of nuclei which are derived from different telencephalic sources (pallial and subpallial) and have a unique cellular structure and specific connections. It is unclear how these individual anatomical and functional units evolved to fit the amygdala to the specific needs of various mammals. Thus, this study provides quantitative data regarding volumes, neuron density and neuron numbers in the main amygdala nuclei of the common shrew, guinea pig, rabbit, fox and pig - species from across the mammalian phylogeny which differ in brain complexity and ecology. The results show that the volume of the amygdala and its individual nuclei scale with negative allometry relative to brain mass (an allometric coefficient below one). However, in relation to the whole amygdala volume, volumes and volumetric percentages of the lateral (LA) and basomedial (BM) nuclei scale with positive allometry, for the medial (ME) and lateral olfactory tract (NLOT) nuclei these parameters scale with negative allometry while the values of these parameters for the basolateral (BL), central (CE) and cortical (CO) nuclei scale with isometry. Moreover, density of neurons scales with strong negative allometry relative to both brain mass and amygdala volume with values of allometric coefficient below zero across studied species. This value for BL is significantly lower than that for the whole amygdala, for ME it is significantly higher while values for NLOT, CE, CO, LA and BM are quite similar to the value for whole amygdala. Finally, neuron numbers in the whole amygdala and its individual nuclei scale with negative allometry in relation to brain mass. However, in relation to the number of neurons in the whole amygdala, neuron numbers and percentages of neurons for LA and BM scale with positive allometry, for BL and NLOT they scale with negative allometry while the values of these parameters for CE, CO and ME scale with isometry. In conclusion, all of these results indicate that each of the nuclei studied displays a different and unique pattern of evolution in relation to brain mass or the whole amygdala volume. These patterns do not match with the various classical concepts of amygdala parcellation; however, in some way, they reflect diversity revealed by the expression of homeobox genes in various embryological studies.
杏仁核主要作为危险探测器进化，调节情绪行为和学习。然而，它也参与应激反应以及嗅觉/信息素和生殖功能。所有这些功能都是由一组核团处理的，这些核团来自不同的端脑来源（皮层和皮层下），具有独特的细胞结构和特定的连接。目前尚不清楚这些单独的解剖和功能单位是如何进化的，以适应各种哺乳动物的特定需求。因此，本研究提供了关于常见鼩鼱、豚鼠、兔、狐和猪的主要杏仁核核团的体积、神经元密度和神经元数量的定量数据，这些物种来自哺乳动物系统发育的不同分支，其脑复杂性和生态不同。结果表明，杏仁核及其各个核团的体积与脑质量呈负异速生长（异速生长系数小于 1）。然而，就整个杏仁核体积而言，外侧核（LA）和基底内侧核（BM）的体积和体积百分比与正异速生长相关，对于内侧核（ME）和外侧嗅束核（NLOT），这些参数与负异速生长相关，而这些参数对于基底外侧核（BL）、中央核（CE）和皮质核（CO），则与等速生长相关。此外，神经元密度与脑质量和杏仁核体积呈强烈负异速生长，在研究的所有物种中，异速生长系数的值都小于零。对于 BL，该值显著低于整个杏仁核的值，对于 ME，则显著高于整个杏仁核的值，而对于 NLOT、CE、CO、LA 和 BM，该值与整个杏仁核的值相当。最后，整个杏仁核及其各个核团的神经元数量与脑质量呈负异速生长相关。然而，就整个杏仁核的神经元数量而言，LA 和 BM 的神经元数量和百分比与正异速生长相关，对于 BL 和 NLOT，则与负异速生长相关，而这些参数对于 CE、CO 和 ME，则与等速生长相关。总之，所有这些结果表明，在所研究的每个核团中，与脑质量或整个杏仁核体积相关的进化模式都不同且独特。这些模式与各种经典的杏仁核分区概念不匹配；然而，在某种程度上，它们反映了各种胚胎发育研究中同源盒基因表达所揭示的多样性。
