Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah, USA.
DENLABS, Draper, Utah, USA.
Brain Behav Evol. 2023;98(4):183-193. doi: 10.1159/000530316. Epub 2023 Mar 27.
Local circuit neurons are present in the thalamus of all vertebrates where they are considered inhibitory. They play an important role in computation and influence the transmission of information from the thalamus to the telencephalon. In mammals, the percentage of local circuit neurons in the dorsal lateral geniculate nucleus remains relatively constant across a variety of species. In contrast, the numbers of local circuit neurons in the ventral division of the medial geniculate body in mammals vary significantly depending on the species examined. To explain these observations, the numbers of local circuit neurons were investigated by reviewing the literature on this subject in these two nuclei in mammals and their respective homologs in sauropsids and by providing additional data on a crocodilian. Local circuit neurons are present in the dorsal geniculate nucleus of sauropsids just as is the case for this nucleus in mammals. However, sauropsids lack local circuits neurons in the auditory thalamic nuclei homologous to the ventral division of the medial geniculate body. A cladistic analysis of these results suggests that differences in the numbers of local circuit neurons in the dorsal lateral geniculate nucleus of amniotes reflect an elaboration of these local circuit neurons as a result of evolution from a common ancestor. In contrast, the numbers of local circuit neurons in the ventral division of the medial geniculate body changed independently in several mammalian lineages.
局部回路神经元存在于所有脊椎动物的丘脑内，被认为是抑制性的。它们在计算中起着重要作用，并影响从丘脑到端脑的信息传递。在哺乳动物中，背外侧膝状体核中的局部回路神经元的百分比在各种物种中相对恒定。相比之下，哺乳动物中内侧膝状体腹侧部分的局部回路神经元的数量根据所检查的物种而有很大差异。为了解释这些观察结果，通过回顾哺乳动物这两个核以及它们在蜥形类动物中的同源核中关于这个主题的文献，以及提供关于鳄鱼的数据，研究了局部回路神经元的数量。局部回路神经元存在于蜥形类动物的背侧膝状体内，就像哺乳动物中的这个核一样。然而，蜥形类动物缺乏与内侧膝状体腹侧部分同源的听觉丘脑核中的局部回路神经元。对这些结果的系统发育分析表明，羊膜动物背外侧膝状体核中局部回路神经元数量的差异反映了这些局部回路神经元的进化，是从共同祖先演变而来的。相比之下，内侧膝状体腹侧部分的局部回路神经元的数量在几个哺乳动物谱系中独立发生了变化。
