Visual Cortical Adaptation

描述(申请人提供)：视觉神经元强烈地受感官历史或适应的影响。我们的长期目标是了解这种体验如何影响大脑皮层的处理和对视觉的贡献。适应效应已经在整个视觉系统中得到了描述，从视网膜到高级视觉皮质。几乎无一例外，这些影响 已经在单个神经元中进行了测量。这是有问题的，因为人们普遍认为，感觉信息是由分布在多个皮质区域的神经元群体编码和处理的。群体编码不能用单个神经元的平均调谐函数来充分描述；它可能受到不同神经元之间的活动协调的强烈影响 细胞。适应是如何影响种群编码的，人们对此知之甚少，这阻碍了我们对经验驱动的皮层环路变化如何影响视觉体验的理解。在这个建议中，我们利用最近在理解种群编码方面的理论工作，来测试适应如何影响分布在猕猴视觉系统多个阶段的神经元种群对刺激方向的编码。在具体目标1中，我们将确定短暂的适应阶段如何影响执行注视任务的清醒猴子的初级视觉皮质(V1)和V4区的神经元调谐、反应变异性和反应相关性。在具体目标2中，我们将把V1和V4中群体反应的变化与动物在精细定向辨别任务中的表现联系起来。我们将测试从测量的种群反应中估计刺激方向的算法，并将这些算法与最好地预测动物在控制和适应状态下的感知决定的算法进行比较。这将揭示动物如何对感官反应进行加权以做出知觉决定，这种加权如何对应于估计取向的理论上的最佳，以及这种加权如何被经验驱动的可塑性改变。在具体目标3中，我们将进行补充实验，更加机械化的重点。我们将使用一种新的记录装置来同时测量麻醉动物V1中的输出种群及其下游靶点的活动。我们将确定适应如何改变这些网络之间的功能耦合，以及耦合如何依赖于经验驱动的单个神经元属性和整体反应的变化。我们的项目将提供第一个全面的观点，即视觉皮质中的群体反应如何受到近期历史的影响，以及群体反应是如何被下游网络解释的，从而产生感知体验。最近开发的工具的结合将使我们能够带来前所未有的力量来解决这些中心和基本问题。我们希望这个项目将有助于我们对种群编码、皮质交流和可塑性的广泛理解。所获得的知识对于开发更有效的设备来解释假肢设备的大脑活动，以及理解皮质区域内和皮质之间的活动在健康和疾病中的协调应该是非常宝贵的。

DESCRIPTION (provided by applicant): Visual neurons are strongly influenced by sensory history or adaptation. Our long-term goal is to understand how such experience influences cortical processing and contributes to vision. Adaptation effects have been described throughout the visual system, from the retina to higher visual cortex. Almost without exception, these effects have been measured in individual neurons. This is problematic, as it is widely believed that sensory information is encoded and processed by neuronal populations distributed across multiple cortical areas. Population coding is not adequately described by the mean tuning functions of individual neurons; it can be strongly influence by the coordination of activity among cells. How adaptation affects population coding is poorly understood, hampering our understanding of how experience driven changes in cortical circuits contribute to visual experience. In this proposal, we make use of recent theoretical work in understanding population coding, to test how adaptation influences the encoding of stimulus orientation by populations of neurons distributed across multiple stages of the macaque visual system. In specific aim 1, we will determine how brief periods of adaptation affect neuronal tuning, response variability and response correlations, in the primary visual cortex (V1) and area V4 of awake monkeys performing a fixation task. In specific aim 2, we will relate changes in population responses in V1 and V4 to the animal's performance on a fine orientation discrimination task. We will test algorithms for estimating stimulus orientation from the measured population responses and we will compare these with algorithms that best predict the animals' perceptual decisions, in both control and adapted states. This will reveal how animals weight the sensory responses to make perceptual decisions, how this weighting corresponds to the theoretically-optimal for estimating orientation, and how that weighting is altered by experience-driven plasticity. In specific aim 3, we will conduct complementary experiments, with a more mechanistic focus. We will use a novel recording arrangement to measure simultaneously the activity of an output population in V1 and its downstream targets in V2 in anesthetized animals. We will determine how adaptation alters the functional coupling between these networks, and how coupling depends on the experience-driven changes in single neuronal properties and ensemble responses. Our project will provide the first comprehensive view of how population responses in visual cortex are affected by recent history, and how population responses are interpreted by downstream networks, to give rise to perceptual experience. The combination of recently-developed tools will allow us to bring unprecedented power to addressing these central and basic issues. We expect this project will contribute broadly to our understanding of population coding, corticocortical communication, and plasticity. The knowledge gained should be invaluable for developing more effective devices for interpreting brain activity for prosthetic devices, and for understanding the coordination of activity within and between cortical areas, in health and disease.