FUNCTIONAL PROPERTIES OF NEURONAL CIRCUITS FOR VISION

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。目的：本研究的长期目标是了解外侧膝状体核（LGN）和视觉皮层之间前馈和反馈通路的功能组织。对于感觉系统，来自丘脑中继细胞的前馈投射为皮层提供关于外部环境的信息。反过来，皮层向丘脑中继细胞发送广泛的反馈。因此，皮层既能处理丘脑提供的信息，又能动态地影响丘脑输入的传递。 拟议的研究涉及三组实验。第一组实验涉及大细胞和小细胞LGN输入在视皮质4C层突触后感受野的构建中发挥什么作用的问题。将从LGN和4C层中的单突触连接的神经元进行记录，以比较突触前和突触后感受野的组织以及评估突触传递的动力学。 第二组实验涉及确定位于视觉皮层第6层的皮质膝状体反馈神经元的生理学。层6中向LGN提供反馈输入的神经元位于该层的上三分之一和下三分之一。上三分之一的神经元专门投射到小细胞膝状体层;下三分之一的神经元主要投射到大细胞层。我们将研究这些神经元的生理特性，以确定它们是否对视觉刺激敏感。如果是这样的话，那么第6层上下区域的神经元似乎应该能够对大细胞流和小细胞流中的活动进行不同的调节。 第三组实验涉及皮质反馈对膝状体活动的功能影响。通过记录膝状体神经元的集合，我们将确定皮质反馈是否选择性地影响LGN大细胞层和小细胞层神经元的活动。如果发现反馈影响LGN活动的时间模式，那么我们将检查第一组实验的数据，以确定这些模式在驱动皮层反应中的功效。

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. Objective: The long-term objectives of this proposal are to understand the functional organization of feedforward and feedback pathways between the lateral geniculate nucleus (LGN) and visual cortex. For sensory systems, feedforward 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 proposed studies involve three sets of experiments. The first set of experiments deals with the issue of what role magnocellular and parvocellular LGN inputs play in the construction of postsynaptic receptive fields in layer 4C of visual cortex. Recordings will be made from monosynaptically connected neurons in the LGN and layer 4C in order to compare the organization of pre- and postsynaptic receptive fields as well as to assess the dynamics of synaptic transmission. The second set of experiments deals with determining the physiology of corticogeniculate feedback neurons located in layer 6 of visual cortex. Neurons in layer 6 that provide feedback input to the LGN are located in the upper third and lower third of the layer. Neurons in the upper third project exclusively to the parvocellular geniculate layers; neurons in the lower third project primarily to the magnocellular layers. We will examine the physiological properties of these neurons to determine whether they are differentially sensitive to visual stimuli. If so, then it seems likely that neurons in the upper and lower regions of layer 6 should be able to differentially modulate activity traveling in the magno- and parvocellular streams. The third set of experiments deals with the functional influence of cortical feedback on geniculate activity. By recording from ensembles of geniculate neurons, we will determine whether cortical feedback selectively influences the activity of neurons in the magno- and parvocellular layers of the LGN. If feedback is found to influence the temporal patterns of LGN activity, then we will examine data from the first set of experiments to determine the efficacy of these patterns in driving cortical responses.