Santiago Lucidia F, Freire Marco Aurelio M, Picanço-Diniz Cristovam W, Franca João G, Pereira Antonio
Laboratory of Investigations in Neurodegeneration and Infection, Institute of Biological Sciences, Federal University of Pará, Belém, Brazil.
Laboratory of Experimental Neuroprotection and Neuroregeneration, Institute of Biological Sciences, Federal University of Pará, Belém, Brazil.
Front Neuroanat. 2019 Jan 14;12:118. doi: 10.3389/fnana.2018.00118. eCollection 2018.
In order to understand how the mammalian sensory cortex has been structured during evolution, it is necessary to compare data from different species across distinct mammalian lineages. Here, we investigated the organization of the secondary somatosensory area (S2) in the agouti (), a medium-sized Amazonian rodent, using microelectrode mapping techniques and neurotracer injections. The topographic map obtained from multiunit electrophysiological recordings were correlated with both cytochrome oxidase (CO) histochemistry and with patterns of corticocortical connections in tangential sections. The electrophysiological mapping of the lateral strip of parietal cortex adjacent to the primary somatosensory area (S1) revealed that S2 displays a mirror-reversed topographical representation of S1, but with a smaller cortical magnification factor. The caudal border of S2 is surrounded by sensory fields which also respond to auditory stimulation. BDA injections into the forelimb representation of S2 revealed a dense homotopic ipsilateral projection to S1, supplemented by a less dense projection to the caudolateral cortex located near the rhinal sulcus (parietal rhinal area) and to a frontal region probably associated with the motor cortex. Our findings were similar to those described in other mammalian species, reinforcing the existence of a common plan of organization for S2 in the mammalian parietal cortex.
为了了解哺乳动物感觉皮层在进化过程中是如何构建的，有必要比较不同哺乳动物谱系中不同物种的数据。在这里，我们使用微电极测绘技术和神经示踪剂注射，研究了刺豚鼠（一种中型亚马逊啮齿动物）的次级体感区（S2）的组织。从多单位电生理记录获得的地形图与细胞色素氧化酶（CO）组织化学以及切线切片中的皮质皮质连接模式相关。对与初级体感区（S1）相邻的顶叶皮质外侧带进行电生理测绘发现，S2呈现出S1的镜像反转地形图，但皮质放大因子较小。S2的尾侧边界被也对听觉刺激有反应的感觉场包围。向S2的前肢代表区注射生物素示踪剂（BDA）显示，有密集的同侧同位投射到S1，此外还有较稀疏的投射到靠近鼻沟的尾外侧皮质（顶叶鼻周区）以及可能与运动皮层相关的额叶区域。我们的发现与其他哺乳动物物种中描述的结果相似，这进一步证明了哺乳动物顶叶皮质中S2存在共同的组织模式。
