Perceptual And Motor Decisions In The Primate Brain

我的研究兴趣是了解感知和行动如何从大脑活动中产生。我的主要方法是记录猴子在执行各种视觉搜索和强迫选择辨别任务时大脑中的神经活动。我的大部分研究都集中在额叶眼区，它位于前额叶皮层，参与将视觉信息转化为移动眼睛的命令。我最近的研究可以分为两个相关的项目，（1）视觉搜索，（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一个将用于引导注意力和眼球运动。信号检测实验旨在了解近阈值知觉判断的神经机制。 我的工作假设是，额叶眼场的功能是作为一个视觉显着地图，结合视觉输入和主题的知识到地形图的视觉显着性，或显着性，在视觉场景中的每一个位置。显著图是定向空间注意和眼跳目标选择的许多理论模型的显著特征。我假设，内隐空间注意和眼跳是针对空间位置所代表的最高活动在额叶眼场。我和我的同事已经证明，在视觉搜索任务中，在干扰物中寻找一个奇怪的目标时，视觉响应的额叶眼野神经元在将目光引导到目标的扫视之前指定目标。我们最近的工作与猴子执行各种视觉搜索任务的结果强烈表明，在额眼场的目标识别过程索引的视觉处理的结果，而不是眼跳准备。Schall等人（2003年）综述了额眼场在视觉处理和扫视产生中的作用。在Thompson（2003）中，我回顾了在额眼场观察到的视觉选择过程与眼跳产生无关的证据，并提出了一些新的证据支持额眼场参与分配内隐注意的观点。在猴子使用手动响应执行视觉搜索任务时，即使没有眼球运动，额叶眼野神经元也能在干扰物中识别视觉目标的位置。在Sato et al.（2003）中，我们通过操纵视觉搜索过程中干扰项与不变目标的相似性，研究了先验知识对目标识别过程的影响。我们发现，与目标更相似的干扰物的神经表征大于与目标不太相似的干扰物的神经表征，即使没有目标存在。这表明，在前眼区对物体的神经表征是图像的物理属性和正在寻找的知识的结合。 这些研究扩展了我们对额叶眼场的理解，远远超出了它在控制眼球运动中的熟悉作用。有了这些知识，我们可以设计实验来研究感觉信息在大脑中的流动，因为它被转化为感知和行动。这项工作有助于我们了解大脑如何集中注意力以做出感知决策和指导行为的机制，这对于理解和治疗人类的注意力相关疾病是必要的。

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, 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 attention and eye movements. The signal detection experiments aim to understand the neural mechanisms of near-threshold perceptual judgments. My working hypothesis is that the frontal eye field functions as a visual salience map that combines visual input and the subject's knowledge 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 frontal eye field. My coworkers and I have shown that during a visual search task for an oddball target among distractors, visually responsive frontal eye field 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. The role of the frontal eye field in visual processing and saccade generation is reviewed in Schall et al. (2003). In Thompson (2003), I review the evidence that the visual selection process observed in the frontal eye field is dissociated from saccade generation and present some new evidence that supports the view that the frontal eye field is involved in allocating covert attention. In monkeys performing a visual search task using a manual response, frontal eye field neurons identify the location of a visual target among distractors even though no eye movements were made. In Sato et al. (2003), we 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 knowledge of what is being looked for. These studies have extended our understanding about the frontal eye field far beyond its familiar role in controlling eye movements. 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. This work helps us understand the mechanisms of how the brain focuses attention to make perceptual decisions and guide behavior, which is necessary to be able to understand and treat attention-related disorders in humans.