NEURONAL PROCESSING OF NATURAL IMAGES

在拟议的研究中，我们计划采用一种相对较新的 实验范式--被称为“自由观看”--其中一只猴子自由地 查看一组自然图像，以调查发射模式 同时记录的纹状皮质神经元对的数量 近乎自然发生的条件。我们的目标是 获得三类问题的答案。首先，是 在自由观看期间测量的V1神经元的感受野特性， 与相同细胞的感受场特性一致 用经典技术测量？这个问题的答案将是 帮助我们确定经典测量的接受度 视野属性可以解释初级视觉皮质的行为 在自然条件下。第二，V1神经元的活动在 免费观看与稀疏假设的预测一致 自然图像的编码？在这个框架中，一个高效的代码 自然场景是通过使用 同时处于活动状态的细胞数量最少。免费观看 范型将提供一个机会来测试几个具体的 对这一假设的预测。第三，做到同步录音 V1中的神经元对自然图像特征表现出同步反应 与知觉分组的假说相一致？大号 大量证据表明，皮质神经元参与了 依赖刺激的同步发射。拟议中的实验将 确定是否同步以及对哪些刺激特征做出响应 活动发生在自由观看自然图像的过程中。回答 这些问题，我们将从PARS进行两种类型的测量 清醒的猕猴V1区的单个单位。第一, 当动物执行简单的注视任务时，我们将定量地 使用i)漂移正弦波映射每个单元的感受场属性 (2)反相关分析方法。第二, 当这些动物执行与样本匹配的任务时，它们在视觉上 扫描一组自然图像来识别提示对象，我们将测量 神经元对这些刺激的反应而产生的联合活动。 这些数据将使我们能够解决上面提出的问题，因此 提高我们对初级视皮层行为的理解 自然条件。

In the proposed research, we plan to employ a relatively new experimental paradigm-termed "free viewing"-in which a monkey freely views a collection of natural images, to investigate the firing patterns of pairs of simultaneously recorded neurons in striate cortex under conditions approximating those occurring naturally. Our goal is to obtain answers to three categories of questions. First, are the receptive field properties of V1 neurons, measured during free viewing, consistent with the receptive field properties of the same cells measured using classical techniques? An answer to this question will help us to determine the extent to which classically measured receptive field properties can account for the behavior of primary visual cortex under natural conditions. Second, is the activity of V1 neurons during free viewing consistent with the predictions of a hypothesis for sparse coding of natural images? In this framework, an efficient code for natural scenes is achieved by representing visual images with the smallest number of simultaneously active cells. The free viewing paradigm will provide an opportunity to test several specific predictions of this hypothesis. Third, do simultaneously recorded neurons in V1 exhibit synchronous responses to natural image features that are consistent with a hypothesis for perceptual grouping? A large body of evidence has demonstrated that cortical neurons engage in stimulus dependent synchronous firing. The proposed experiment will determine if, and in response to what stimulus features, synchronous activity occurs during the free viewing of natural images. To answer these questions, we will conduct two types of measurements from pairs of single units in area V1 of awake behaving macaques monkeys. First, while the animals perform a simple fixation task, we will quantitatively map each cell's receptive field properties using i) drifting sinewave gratings, and ii) the methods of reverse correlation analysis. Second, while the animals perform a match-to-sample task, in which they visually scan a set of natural images to identify a cued object, we will measure the joint activity of pairs of neurons in response to these stimuli. These data will allow us to address the questions posed above, and thus improve our understanding of the behavior of primary visual cortex under natural conditions.