Perceptual And Motor Decisions In The Primate Brain

灵长类动物大脑的知觉和运动决策

• 批准号: 6672799
• 负责人: Kirk G Thompson
• 金额: --
• 依托单位: NATIONAL EYE INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6672799
• 关键词: Macaca; attention; brain electrical activity; neural information processing; neurophysiology; prefrontal lobe /cortex; saccades; sensory discrimination; sensory signal detection; visual fields; visual perception; visual stimulus; visual tracking

My research interest is to understand how perception and action emerge from brain activity. My main approach is to record neural activity in the brains of monkeys performing various visual search and forced-choice discrimination tasks. Most of my research has focused on the frontal eye field (FEF), which is located in the prefrontal cortex, and participates in the transformation of visual information into commands to move the eyes. My recent research can be divided into two related projects, (1) Visual Search, and (2) Signal Detection. The goal of the visual search experiments is to understand how the brain chooses which of many possible visual objects will be used to guide eye movements. The signal detection experiments aim to understand the neural mechanisms of near-threshold perceptual judgments. My working hypothesis is that the FEF functions as a visual salience map that combines visual input and cognitive influences into a topographic map of visual conspicuity, or salience, at every location in the visual scene. The salience map is a prominent feature of many theoretical models of directed spatial attention and saccade target selection. I hypothesize that covert spatial attention and saccades are directed to the spatial location represented by the highest activity in the FEF. My coworkers and I have shown that during a visual search task for an oddball target among distractors, visually responsive FEF neurons specify the target before the saccade that directs gaze to the target. The results from our recent work with monkeys performing various visual search tasks strongly suggests that the target discrimination process in the frontal eye field indexes the outcome of visual processing, not saccade preparation. In Sato et al., 2001, we increased the monkeys' reaction times by making the target similar to the distractor or by occasionally changing the location of an easily discriminated target and requiring the monkey to withhold the saccade to the first location and make a single saccade to the new target location. Saccadic reaction time increased in both task conditions, but only the change in discrimination difficulty increased the amount of time it took for frontal eye field neurons to identify the saccade target. In Murthy et al., 2001, we analyzed those trials on which the target changed locations before the saccade. The activity of frontal eye field visual neurons very reliably identified the change in the target stimulus location regardless of whether or not the saccade was made to that stimulus. Recently we have investigated the effect of prior knowledge on the target discrimination process by manipulating the similarity of the distractors to an unchanging target during visual search. We found that the neural representation of the distractors that were more similar to the target was greater than the neural representation of the distractors that were less similar to the target, even when no target was present. This shows that the neural representation of objects in the frontal eye field is a combination of the physical properties of the image and a top-down knowledge of what is being looked for. An analysis of FEF visual activity on error trials showed that when the representation of the distractor exceeds that of the target, even by a small amount, the saccade is made to that distractor. These studies have extended our understanding about the frontal eye field far beyond its familiar role in controlling eye movements. Taken together, they validate computational models of selective attention by identifying a population of neurons that have all of the characteristics of a theoretical salience map. With this knowledge we can design experiments to investigate the flow of sensory information through the brain as it is transformed into perception and action.

我的研究兴趣是了解大脑活动中的感知和行动如何出现。我的主要方法是记录执行各种视觉搜索和强制选择歧视任务的猴子大脑中的神经活动。我的大多数研究都集中在位于前额叶皮层中的额叶眼场（FEF）上，并参与将视觉信息转换为命令以移动眼睛。我最近的研究可以分为两个相关的项目：（1）视觉搜索和（2）信号检测。视觉搜索实验的目的是了解大脑如何选择许多可能的视觉对象中的哪些来指导眼动。信号检测实验旨在了解近阈值感知判断的神经机制。 我的工作假设是，FEF充当视觉显着性图，将视觉输入和认知影响结合到视觉场景中的每个位置的视觉效果或显着性的地形图中。显着图是许多定向空间注意力和扫视目标选择的许多理论模型的突出特征。我假设秘密的空间注意力和扫视是针对FEF中最高活动的空间位置。我和我的同事表明，在视觉搜索任务中，在干扰器中进行奇数球目标时，视觉响应的FEF神经元在将目光引导到目标的扫视之前指定了目标。我们最近与猴子执行各种视觉搜索任务的工作的结果强烈表明，额眼场中的目标歧视过程索引了视觉处理的结果，而不是扫视的准备。在Sato等人，2001年，我们通过使目标与干扰物相似或偶尔更改易于区分的目标的位置，并要求猴子将扫视固定到第一个位置，并将单个扫视与新的目标位置保持单一的扫视，从而增加了猴子的反应时间。在这两个任务条件下，Saccadic反应时间都会增加，但是只有歧视难度的变化增加了额眼野外神经元确定扫视靶标的时间。在Murthy等人，2001年，我们分析了目标在扫视前改变位置的试验。额眼视野视觉神经元的活性非常可靠地确定了目标刺激位置的变化，而不管是对刺激的刺激是否是对刺激的。最近，我们通过在视觉搜索过程中操纵分心者与不变目标的相似性来研究先验知识对目标歧视过程的影响。我们发现，与目标更相似的干扰因素的神经表示大于与目标的神经表示，即使没有目标也不相似。这表明，额眼场中物体的神经表示是图像的物理特性和对所寻求内容的自上而下的知识的结合。对错误试验中FEF视觉活动的分析表明，当分散因子的表示超过目标的表示时，即使是少量，就会对该干扰物进行扫视。 这些研究扩展了我们对额眼场的理解，远远超出了其在控制眼动运动中熟悉的作用。综上所述，他们通过识别具有理论显着性图的所有特征的神经元人群来验证选择性注意的计算模型。有了这些知识，我们可以设计实验，以研究感觉信息通过大脑转化为感知和动作的流动。