Mécanismes de la plasticité neuronale et de l'encodage des signaux visuels

我们的研究计划集中在神经科学中的两个重要主题：A)神经元可塑性的机制，B)感觉信号的编码过程。成年感觉神经细胞适应变化刺激的能力是神经元的一项重要能力。我们提出了一系列实验，旨在研究麻醉成年猫视皮层适应后皮质可塑性的生理机制。将研究以下特性：方向和空间频率偏好、方向速度选择性。更具体地说，我们将研究抑制在调谐曲线峰位吸引和排斥移动中的作用。几种与谷氨酸受体有关的药物被认为可以促进或防止皮质可塑性。我们将测试局部药物应用对神经元适应后改变其首选刺激的能力的影响。利用本征光学成像，我们将研究复合方位图的修正。具体地说，将比较风车、主方位和斜方位，以提供适应后的详细结构图。我们将研究18区的细胞如何对17区细胞的可塑性做出反应。也就是说，我们将分析从早期大脑皮层继承的适应的影响。同时，我们将以两两成对的方式研究图像结构与反应模式和同步指数之间的关系，检验激发模式和同步与信号处理相关的假设。相异指数(1-r，皮尔逊系数)将把诱发的放电模式和细胞感受野中施加的刺激联系起来(S)。第二个相关性将比较响应于相同图像属性的两个动作电位序列所诱导的同步指数。上述计算将允许为两个区域(17和18)建立两个不同的代表性相异矩阵。这些计算将使我们能够确定哪种属性占主导地位，从而指导在17区和18区建立类别敏感的亚区。然后，我们可以确定在编码图像属性时，激发频率或同步是否更敏感，从而更可靠。

Our research program is centered on two important topics in neuroscience: A) mechanisms of neuronal plasticity, and B) encoding processes of sensory signals. The ability of adult sensory nerve cells to adapt their response to changing stimuli is an important capability of neurons. We propose a series of experiments aimed at studying the physiological mechanisms responsible for cortical plasticity following adaptation in the visual cortex of anesthetized adult cats. The following properties will be investigated: orientation and spatial frequency preferences, direction velocity selectivities. More specifically, we will study the role of inhibition in attractive and repulsive shifts of the peak of the tuning curves. Several drugs linked to glutamate receptors are believed to facilitate or prevent cortical plasticity. We will test the effect of local drug application on the ability of neurons to change their preferred stimulus after adaptation. Using intrinsic optical imaging we will study the modifications of composite orientation maps. Specifically, pinwheels, and cardinal and oblique orientation domains will be compared to provide a detailed structural map after adaptation. We will examine how cells in area 18 react to plasticity in area 17 cells. That is, we will analyze the influence of adaptation inherited from earlier cortical areas. In parallel, we will investigate the relationships between image structures and response patterns and synchronization indexes, in a pairwise fashion, testing the hypothesis that firing patterns and synchronization are related to signal processing. A dissimilarity index (1-r, Pearson coefficient) will correlate evoked firing patterns and stimuli applied within a cell's receptive field(s). A second correlation will compare synchronization indexes induced by two trains of action potentials in response to the same image properties. The above computations will permit establishing two distinct representational dissimilarity matrices for both areas (17 and 18). These computations will allow us to determine which property dominates and hence guide the establishment of category-sensitive subregions in areas 17 and 18. We may then determine if firing rates or synchronization are more sensitive, and thus more reliable, in coding image properties.