Neural processing in covert attention

项目摘要 几个世纪以来，魔术师和幻术师都知道，如果他们分散你的目光和注意力，你不太可能 注意他们在做什么。这种无意视盲是我们能力有限的结果 在视觉场景的一切，传统上是在实验室中说明的设置大小的效果，在视觉 搜索：你必须搜索的项目越多，就越难找到你要找的东西， 代价我们最近发现，这种限制似乎并不涉及视觉区域的视觉处理， 而是在视觉信息传递到联合皮层时发生的。我们假设分裂 后顶叶皮层的外侧顶内区（LIP）的正常化在该过程中起关键作用。 我们的假设结合了我们对注意力、分裂正常化和决策的神经生理学知识 从而解释与集合大小变化相关的行为效应。具体来说，我们建议 当寻找一个项目时，LIP的活动代表了视觉区域的证据积累， 项目是在神经元的反应领域，如果活动达到阈值之前的最后期限，动物 表示该项目位于该位置。这种积累受到分裂规范化的影响： 在视觉世界中，整个区域的活动越多，标准化程度越高， 积累率。我们知道，视觉注意力增强了视觉区域的反应，并提出， LIP输入中增益的有效增加有助于克服由于分频而导致的有效增益降低 标准化在这个项目中，我们将测试这一假设使用视觉搜索任务，利用移动点刺激。 具体地说，我们将记录来自MT区（运动处理区）和LIP区的单个神经元， 执行视觉搜索任务，其中阵列中的1、2或4个对象是移动的点图案。如果目标方向 如果存在，那么动物必须看着它，否则，它们必须保持固定。我们将改变信号， 每个补丁中的点的颜色，并且将有三个注意力条件。在空间注意条件下， 动物被空间提示，指示目标将出现在哪个位置（如果它出现的话）。在这部电影里- 根据注意力条件，动物会获得颜色提示，如果目标出现，它将出现在一个补丁中， 和球杆颜色一样的圆点在分散注意条件下，动物没有得到任何提示。我们将模型 基于我们假设的行为（正确率和反应时间）以及MT和LIP中的活性。 然后，我们将直接测试这一假设，通过在额叶眼场的操纵反应， 同时记录来自LIP和MT的行为和神经元数据。我们希望我们的研究结果能揭示 神经机制的基础上，我们有限的能力，处理视觉信息的场景，但也可以 这表明了已经研究了近30年的注意力调节的功能作用。

Project Summary For centuries, magicians and illusionists have known that if they distract your gaze and attention, you are unlikely to notice what they are doing in plain sight. This inattentional blindness is a result of our limited ability to take in everything about the visual scene and is traditionally illustrated in the lab by set-size effects in visual search: the more items you have to search through, the harder it is to find what you are looking for and the longer it takes. We have recently found that this limitation does not appear to involve visual processing in visual areas, but takes place as the visual information is passed up to association cortices. We hypothesized that divisive normalization in the lateral intraparietal area (LIP) of posterior parietal cortex plays a key role in this process. Our hypothesis combines our knowledge of the neurophysiology of attention, divisive normalization and decision making to explain the behavioral effects associated with changes in set-size. Specifically, we have suggested that when looking for an item, activity in LIP represents the accumulation of evidence from visual areas that the item is in the neuron's response field and if the activity reaches a threshold before a deadline, the animal indicates that the item is in that location. This accumulation is affected by divisive normalization: the more items in the visual world, the more activity across the area and the greater the normalization, resulting in lower accumulation rates. We know that visual attention enhances responses in visual areas, and propose that this effective increase in gain in the input to LIP helps override the effective gain decrease due to the divisive normalization. In this project, we will test this hypothesis using a visual search task utilizing moving dot stimuli. Specifically, we will record from single neurons in areas MT (a motion processing area) and LIP while animals perform a visual search task in which the 1, 2 or 4 objects in the array are moving dot patterns. If a target direction is present, then the animals must look at it, otherwise, they must maintain fixation. We will vary the signal and the color of the dots in each patch and will have three attentional conditions. In the spatial attention condition, the animal is spatially cued, indicating which location the target will appear in, if it appears at all. In the feature- based attention condition, the animal is given a color cue and the target, if it appears, will appear in a patch with dots the same color as the cue. In the spread attention condition, the animal is not given any cue. We will model the behavior (both percent correct and reaction times) based on our hypothesis and the activity in MT and LIP. We will then directly test this hypothesis, by pharmacologically manipulating responses in the frontal eye field while recording behavioral and neuronal data from LIP and MT. We expect that our results will shed light on the neuronal mechanisms underlying our limited ability to process visual information in the scene, but could also indicate a functional role for the attentional modulation that has been studied for almost 30 years.