INTERNAL SIGNALS IN THE PARIETAL VISUAL PATHWAY

描述（由申请人提供）：视觉感知依赖于视觉输入。大脑不断产生内部信号，调节对外部视觉刺激的反应。动态的内部信号允许神经网络对相同的刺激做出不同的反应，使生物体能够适应不断变化的任务需求。内部网络动态也支持与视觉工作记忆相关的持续神经活动。在这个建议中，我们研究内部信号的影响，继续我们的重点顶叶皮层。一类重要的内部信号与自我运动有关。我们已经确定了一个强大的抑制顶叶神经元的发射微扫视-但只有在一个任务需要一个短暂的运动检测，可以模仿微扫视的视觉效果。目的1检验的假设，抑制可能是灵活的“门控”的任务要求。目的1还探讨了嘴侧上级丘（一个参与微眼跳产生的区域）在抑制中的潜在作用。目标2测试两种不同的神经元信号，已经报告在顶叶皮层-“分类”和“知觉决策”-实际上是同一件事。大多数知觉决策实验没有测试信号是否可以独立的形式的动物的报告，我们建议，如果知觉决策信号是独立的报告，他们将是无法区分的“分类”信号。我们将检查LIP神经元是否提供通用的视觉分类信号，我们将在同一实验中，在相同的神经元中，头对头地比较“感知决策”和“分类”信号。目的3探讨顶叶皮层持续放电的机制。递归网络模型表明，持续的记忆延迟期活动是递归电路的自然动态。最近的一个递归网络模型做出了几个强大而令人惊讶的预测;例如，如果在不同条件下可以诱发不同水平的持续活动，那么整个神经元群体的活动幅度应该是彼此和自发活动的缩放版本。此外，神经元在持续放电时应该有一个共同的偏好顺序，这是皮层的一种极不寻常的组织。目标3使用目标1和目标2生成的实验数据来测试和改进该模型。我们的实验将提供一个关于大脑内部状态如何促进和影响外部视觉世界感知的机制视角。获得这些过程的基本信息是理解正常和异常大脑处理的重要步骤。 公共卫生相关性：我们的实验将研究大脑的内部状态如何促进和影响外部视觉世界的感知。改变内部状态使大脑能够灵活地适应不断变化的行为需求。获得这些过程的基本信息是理解正常和异常大脑处理的重要步骤。

DESCRIPTION (provided by applicant): Visual perception depends on more than visual input. The brain constantly generates internal signals that modulate responses to external visual stimuli. Dynamic internal signals allow neural networks to respond differently to the same stimulus, enabling organisms to adapt to changing task demands. Internal network dynamics also support persistent neural activity related to visual working memory. In this proposal, we examine the influence of internal signals, continuing our focus on parietal cortex. An important class of internal signals are related to self-movement. We have identified a powerful suppression of the firing of parietal neurons by microsaccades - but only during a task requiring a transient motion-detection that may be mimicked by a microsaccade's visual effect. Aim 1 examines the hypothesis that the suppression may be flexibly "gated" by task demands. Aim 1 also investigates the potential role of the rostral superior colliculus, an area involved in microsaccade generation, in the suppression. Aim 2 tests whether two different neuronal signals that have been reported in parietal cortex -- "categorization" and "perceptual decision" -- are actually the same thing. Most perceptual decision experiments did not test whether the signals could be independent of the form of the animal's report; we propose that if perceptual decision signals were independent of the report, they would be indistinguishable from "categorical" signals. We will examine whether LIP neurons provide generic visual categorical signals, and we will compare "perceptual decision" and "categorical" signals head-to- head, in the same experiment, in the same neurons. Aim 3 examines the mechanisms underlying persistent firing in parietal cortex. Recurrent network models posit that persistent memory-delay period activity is a natural dynamic of recurrent circuits. A recent recurrent network model makes several robust yet surprising predictions; for example, if different levels of persistent activity can be evoked under different conditions, the amplitude of the activities across the neuronal population should be scaled versions of each other and of the spontaneous activity. In addition, there should be a common order of preference among neurons in their persistent firing, a highly unusual organization for cortex. Aim 3 uses the experimental data generated from Aims 1&2 to test and refine this model. Our experiments will provide a mechanistic perspective on how internal states of the brain facilitate and affect the perception of the external visual world. Gaining basic information on these processes is an essential step for understanding normal and abnormal brain processing. PUBLIC HEALTH RELEVANCE: Our experiments will investigate how internal states of the brain facilitate and affect the perception of the external visual world. Changing internal states allows the brain to flexibly adapt to changing behavioral demands. Gaining basic information on these processes is an essential step for understanding normal and abnormal brain processing.