Development and Reorganization of Orientation Representation in the Cat Visual Cortex: Experience-Dependent Synaptic Rewiring in Early Life
Development and Reorganization of Orientation Representation in the Cat Visual Cortex: Experience-Dependent Synaptic Rewiring in Early Life
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DOI：
10.3389/fninf.2020.00041
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发表时间：
2020-08-20
影响因子：
3.5
通讯作者：
Ribot, Jerome
中科院分区：
文献类型：
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作者：
Tanaka, Shigeru;Miyashita, Masanobu;Ribot, Jerome
迄今为止，基于某些类型的Hebbian突触学习，已经提出了许多数学模型来解释定向图的活动依赖性发展以及神经元定向选择性。这些模型成功地再现了类似方位地图的空间模式。然而，我们仍然有一些问题：(1)在生命早期形成有序定向图的过程中，视觉皮层的突触重新布线是如何发生的？(2)视觉经验如何促进视觉皮质神经元的定向选择性成熟和定向图谱的重组？(3)取向可塑性的敏感期如何结束？在这项研究中，我们通过动物实验和数学模型来了解突触重新布线的机制，以了解经验依赖的方向图的形成和重组。首先，我们通过安装圆柱透镜的护目镜，从猫在单方向暴露下饲养的17区固有信号光学成像中可视化方向图。实验表明，代表经验取向的皮质区域的扩张程度取决于单一取向暴露开始的年龄。得到了取向塑性的敏感期曲线。接下来，我们在假设重新布线是由同一树突棘上瞬态突触接触之间的竞争性相互作用引起的基础上，对先前提出的丘脑-皮质输入的活动依赖自组织的数学模型进行了改进。尽管已经报道了多种分子参与这种相互作用，但我们试图建立一个数学模型来描述以脑源性神经营养因子（BDNF）及其相关分子为重点的突触重新布线。基于改进的模型进行计算机模拟，我们成功地再现了在单一方向暴露和正常视觉体验下饲养的小猫重组的方向图。我们还重现了实验得到的取向塑性敏感周期曲线。实验观察和理论重现之间的良好一致性表明，bdnf诱导的来自同一脊柱不同轴突的突触接触之间的竞争性相互作用是经验依赖性取向选择和取向图形成和重组的重要因素。
To date, numerous mathematical models have been proposed on the basis of some types of Hebbian synaptic learning to account for the activity-dependent development of orientation maps as well as neuronal orientation selectivity. These models successfully reproduced orientation map-like spatial patterns. Nevertheless, we still have questions: (1) How does synaptic rewiring occur in the visual cortex during the formation of orderly orientation maps in early life? (2) How does visual experience contribute to the maturation of orientation selectivity of visual cortical neurons and reorganize orientation maps? (3) How does the sensitive period for orientation plasticity end? In this study, we performed animal experiments and mathematical modeling to understand the mechanisms underlying synaptic rewiring for experience-dependent formation and reorganization of orientation maps. At first, we visualized orientation maps from the intrinsic signal optical imaging in area 17 of kittens reared under single-orientation exposure through cylindrical-lens-fitted goggles. The experiments revealed that the degree of expansion of cortical domains representing the experienced orientation depends on the age at which the single-orientation exposure starts. As a result, we obtained the sensitive period profile for orientation plasticity. Next, we refined our previously proposed mathematical model for the activity-dependent self-organization of thalamo-cortical inputs on the assumption that rewiring is caused by the competitive interactions among transient synaptic contacts on the same dendritic spine. Although various kinds of molecules have been reported to be involved in such interactions, we attempt to build a mathematical model to describe synaptic rewiring focusing on brain-derived neurotrophic factor (BDNF) and its related molecules. Performing computer simulations based on the refined model, we successfully reproduced orientation maps reorganized in kittens reared under single-orientation exposure as well as normal visual experience. We also reproduced the experimentally obtained sensitive period profile for orientation plasticity. The excellent agreement between experimental observations and theoretical reproductions suggests that the BDNF-induced competitive interaction among synaptic contacts from different axons on the same spine is an important factor for the experience-dependent formation and reorganization of orientation selectivity and orientation maps.