FUNCTIONAL PROPERTIES OF NEURONAL CIRCUITS FOR VISION

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 对于感觉系统，丘脑中继细胞的前馈投射为大脑皮层提供有关外部环境的信息。反过来，大脑皮层向丘脑的中继细胞发送广泛的反馈。因此，大脑皮层既能处理丘脑提供的信息，又能动态影响丘脑输入信息的传递。本方案中提出的实验的主要目标是确定皮质膝状体反馈投射的功能组织及其对视觉加工的影响。这项拟议的研究涉及四组实验。第一个主要的系列实验(具体目标1)将检验这样一个假设，即皮质膝状体通路包含生理上不同的神经元群体，这些神经元选择性地支配LGN的大细胞层和小细胞层。剩下的实验将研究皮质膝状体投射在视觉处理中的功能作用。总体而言，已提出的皮质膝状体功能的作用可分为两大类：(1)皮质丘脑通路用于增强丘脑神经元的感受野特性；(2)皮质丘脑通路用于增强感觉信息从外周到皮质的传递。因此，第二系列实验(具体目标2)将检验这样一种假设，即皮质膝状体反馈通过抑制经典外感受野而使LGN感受野锐化。第三系列实验(具体目标3)将检验皮质膝状体反馈调节LGN反应的非空间方面的假设。最后，第四系列实验(特定目标4)将比较定向注意对皮质膝状体神经元和LGN神经元的影响，以验证注意和皮质膝状体通路影响LGN对视觉刺激反应获得的假说。鉴于皮质丘脑通路在调节丘脑皮质网络兴奋性方面的核心重要性，我们必须了解皮质丘脑通路的功能特性，因为该通路的紊乱可能是影响视力和视觉处理的几种疾病的基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. For sensory systems, feed forward projections from thalamic relay cells provide the cortex with information about the external environment. The cortex, in turn, sends extensive feedback to thalamic relay cells. The cortex thus functions both to process information supplied by the thalamus as well as to influence dynamically the transmission of thalamic input. The primary goal of the experiments presented in this proposal is to determine the functional organization of corticogeniculate feedback projections and their influence on visual processing. The proposed study involves four sets of experiments. The first major series of experiments (Specific Aim 1) will test the hypothesis that the corticogeniculate pathway contains physiologically distinct populations of neurons that selectively innervate the magnocellular and parvocellular layers of the LGN. The remaining experiments will examine the functional role of corticogeniculate projections during visual processing. In general, proposed roles for corticogeniculate function fall into two broad categories: (1) the corticothalamic pathway serves to sharpen the receptive field properties of thalamic neurons, and (2) the corticothalamic pathway serves to enhance the transmission of sensory information from periphery to cortex. The second series of experiments (Specific Aim 2) will therefore test the hypothesis that corticogeniculate feedback sharpens LGN receptive fields by suppression from the extraclassical receptive field. The third series of experiments (Specific Aim 3) will test the hypothesis that corticogeniculate feedback adjusts non-spatial aspect of LGN responses. Finally, the fourth series of experiments (Specific Aim 4) will compare the effects of directed attention on corticogeniculate neurons and LGN neurons in order to test the hypothesis that attention and the corticogeniculate pathway influence the gain of LGN responses to visual stimuli. Given the central importance of corticothalamic pathways for governing the excitability of thalamocortical networks, it is important that we understand the functional properties of the corticothalamic pathway, as disorders of the pathway likely underlie several illnesses affecting vision and visual processing.