The Neurophysiology of Visual Search: Oculomotor and Visual Mechanisms

视觉搜索是动物的一种基本行为，必须寻找食物或繁殖。在……下面 通常情况下，人类和非人类灵长类动物使用眼球运动来探索他们的视觉世界，并且 人类视觉搜索的效率与这些眼球运动的数量和准确性有关。 视觉搜索的基本过程包括纯视觉处理、视觉注意的产生和 通常，眼球运动的产生。由视觉、注意力和动眼区域组成的大脑网络是 参与视觉搜索，但对灵长类大脑的神经过程知之甚少 完成这一关键过程。这个项目的目标是了解大脑的机制 通过研究网络中3个节点的活动进行视觉搜索，即外侧顶内区(LIP)、额叶 视场(FEF)和纹前视区V4。 我们最近发现，在视觉搜索过程中，嘴唇上的神经元表现出3种不同的信号 在我们研究过的几乎每一个神经元的活动中都能辨别出它们：1)自下而上的视觉信号 描述对象在其响应域中的突然出现，但不包含有关 即将到来的眼跳的方向或接受野中刺激的性质(例如，无论是 搜索目标或分心物)；2)预测即将到来的目标和反应时间的扫视信号 眼动；以及3)描述对象在其响应场中的性质的认知信号 无论眼球运动的方向如何。这些信号以一种可预测的方式相加，以创建 大脑在视觉搜索中使用的显著图。LIP连接到两个动眼区域，它可以 发送和接收对产生眼球运动有用的信息，并发送和接收到视觉区域， 同样的信息也可以用来指定视觉注意的轨迹。 V4和FEF项目到LIP，并且可能对4有不同的贡献。在这些实验中，我们将 研究视觉搜索中所有三个区域的活动，并研究每个区域对哪些类型的信息有贡献 另外两个。我们将训练恒河猴进行两项视觉搜索任务，其中一项是自由的 移动他们的眼睛，其中一个必须保持他们的眼睛不动，盯着一个中心点。神经活动将是 在猴子执行任务时录制。该项目的目标是首先研究 神经元LIP、V4和FEF，比较自由观看和注视任务中的活动以及它们在 简单的视觉引导延迟扫视任务..二是研究电刺激对大鼠的影响。 每个区域的表现就是猴子在搜索任务中的表现。三是研究瞬变效应。 每个区域的失活对任务的执行和其余区域的神经元活动都有影响。 这些实验将提供关于大脑如何在视觉过程中决定看哪里的洞察力 搜索，以及它如何将视觉信息转换为运动。项目叙事 有顶叶和额叶损害的人类患者视觉搜索功能受损。 回答这些具体目标中提出的问题将导致更大的 理解大脑皮层如何对视觉搜索的基本过程进行排序。 这反过来将导致对视觉和动眼运动缺陷的洞察 对额叶和顶叶皮质损害的人类具有破坏性，并将有助于 设计诊断、预测和康复策略。

Visual search is a basic behavior in animals that must forage for sustenance or reproduction. Under ordinary circumstances humans and non-human primates explore their visual world using eye movements, and the efficiency of visual search in humans is related to the number of and accuracy of those eye movements. The processes underlying visual search involve pure visual processing, the generation of visual attention, and ordinarily, the generation of eye movements. A brain network of visual, attentional, and oculomotor areas is involved in visual search, but little is known about the neural processes by which the primate brain accomplishes this critical process. The goal of this project is to understand the brain mechanisms underlying visual search by studying the activity of 3 nodes in the network, the lateral intraparietal area (LIP), the frontal eye field (FEF) and prestriate visual area V4. We have recently discovered that neurons in the LIP exhibit 3 different signals during visual search which are discernable in the activity of almost every neuron we have studied: 1) a bottom-up visual signal describing the abrupt appearance of an object in its response field but bearing no information about the direction of the impending saccade or the nature of the stimulus in the receptive field (e.g. whether it is the search target or a distractor); 2) a saccadic signal which predicts the goal and reaction time of an impending eye movement; and 3) a cognitive signal which describes the nature of the object in its response field regardless of the direction of the impending eye movement. These signals sum in a predictable way to create a salience map used by the brain in visual search. LIP is connected both to oculomotor areas, to which it can send and receive information useful for the generation of eye movements, and to visual areas, to which the same information can be used to specify the locus of visual attention. V4 and the FEF project to LIP, and presumably contribute differently to 4. In these experiments we will study the activity of all 3 areas in visual search, and study what types of information each area contributes to the other two. We will train Rhesus monkeys on two visual search tasks, one in which they which they are free to move their eyes, and one in which must hold their eyes still, fixating a central point. Neural activity will be recorded while the monkeys perform the tasks.. The aims of the project are first to study the activity of neurons LIP, V4, and FEF, comparing activity in the free-viewing and fixation tasks as well as their activity in a simple visually guided delayed-saccade task.. The second is to study the effects of electrical stimulation in each area on the performance of the monkeys in the search tasks. The third is to study the effects of transient inactivation of each area on the performance of the tasks and the activity of neurons in the remaining areas. These experiments will provide insight into how the brain makes decisions about where to look during visual search, and how it transforms visual information into movement. Project Narrative Visual search is impaired in human patients with parietal and frontal lesions. Answering the questions posed in these specific aims will lead to a greater understanding of how the cerebral cortex orders the processes underlying visual search. This in turn will lead to insight into the visual and oculomotor deficits that are so devastating in humans with lesions of frontal and parietal cortex, and will aid the designing of diagnostic, prognostic, and rehabilitative strategies.