The Role of LGN Directional Selectivity in Visual Cortical Processing

项目总结 兔和啮齿动物的外侧膝状核(LGN)含有一群神经元，这些神经元 对视觉刺激表现出很强的方向性选择性。尽管这些LGN DS神经元 已知投射到初级视觉皮质(V1)，它们的突触目标，以及它们在合成中的作用 %的V1感受野未知。而在猫和灵长类动物中，LGN神经元很少或根本没有显示 取向和方向选择性，而这些性质被认为主要是在 在兔和啮齿类动物中，这些特性可能部分遗传自LGN DS 神经元。拟议的实验将解决这个问题，旨在了解LGN DS是如何 神经元参与了V1神经元不同感受野的合成。这将是 在完全清醒的兔子身上，使用两套互补的方法完成。首先(目标1)，我们将 确定V1的哪些层接受来自LGN DS神经元的强输入。我们将使用以下工具完成此操作 单轴突棘波触发的电流源密度分析，一种方法，提供了 突触前(轴突)和单突触局部场电位和电流的层状轮廓 由单个丘脑皮质神经元的棘波产生 受体皮质。下一步(目标2)，我们将记录两个LGN DS神经元的棘波序列，以及 不同感受野类别的视网膜定位皮质神经元。我们将确定哪一个 LGN-DS神经元突触接受区内的皮质神经元接受突触输入 (使用细胞外互相关方法)，以及LGN DS的方向偏好如何 神经元与它们的突触目标的偏好有关。方向和取向选择性是 视觉皮层神经元最显著的反应特性之一，这个项目的目的是 了解这些特性是如何出现的。

PROJECT SUMMARY The lateral geniculate nucleus (LGN) of rabbits and rodents contains a population of neurons that show strong directional selectivity (DS) to visual stimulation. Although these LGN DS neurons are known to project to the primary visual cortex (V1), their synaptic targets, and their role in the synthesis of V1 receptive fields are unknown. Whereas in cats and primates, LGN neurons display little or no orientation and directional selectivity and these properties are thought to be largely synthesized within V1, in rabbits and rodents these properties could potentially be inherited, in part, from the LGN DS neurons. The proposed experiments will address this question, aiming to understand how LGN DS neurons contribute to the synthesis of the diverse receptive field seen in V1 neurons. This will be accomplished using two sets of complementary methods, in fully awake rabbits. First (Aim 1), we will determine which layers of V1 receive a strong input from LGN DS neurons. We will do this using single-axon spike-triggered current source-density analysis, a method that provides a view of the laminar profile of the presynaptic (axonal) and monosynaptic local field potentials and currents generated by the spikes of single thalamocortical neurons within the topographically aligned region of recipient cortex. Next (Aim 2), we will record the spike trains of both LGN DS neurons, and retinotopically aligned cortical neurons of different receptive field classes. We will determine which cortical neurons within the synaptic recipient zone of the LGN DS neuron receives synaptic input (using methods of extracellular cross-correlation), and how the directional preferences of the LGN DS neurons relate to the preferences of their synaptic targets. Direction and orientation selectivity are among the most salient response properties of visual cortical neurons and this project is aimed at understanding how these properties emerge.