Perceptual And Motor Decisions In The Primate Brain

在感知和行动单元中，我们研究视觉输入如何转化为感知和行为。我们的大部分研究都集中在额叶眼区(FEF)，这是前额叶皮质中将视觉信息转换为眼动指令的区域。我们已经证明，FEF将视觉输入与认知知识相结合，形成了视觉空间的优先地图，该地图识别视觉场景中最重要的对象的位置，以指导凝视。在过去的一年里，我们扩展了这一发现，以表明FEF预测未来重要视觉刺激将出现的位置(参考文献1)。在一项合作研究中，我们调查了视觉运动系统对视觉场景的突然变化的反应，这些变化需要眼跳规划的动态变化(参考文献2)。此外，我们最近提交了3篇论文(目前正在审查中)，描述了我们的研究结果，即额叶皮质的空间选择性信号如何增强视觉处理，导致在颞叶下部皮质进行物体识别和复杂的物体表征。 在裁判中1我们讨论了在没有视觉输入的情况下，认知过程如何控制空间注意的问题。我们记录了猴子的前额眼场活动，这些猴子被训练来执行一项困难的辨别任务，在视觉刺激实际出现之前，猴子会注意到要辨别的位置。我们发现，当一个提示通知猴子将出现刺激时，大多数FEF神经元表现出升高的活动。FEF的这种与注意力相关的预期活动在没有任何视觉刺激的情况下发生，也与运动过程无关。总之，这些研究表明，刺激驱动和认知驱动的空间注意信号存在于FEF中，并且独立于眼跳命令信号。因此，除了在眼跳产生中起着众所周知的作用外，FEF可能还在控制视觉空间注意方面起着重要作用。 在裁判中2.我们研究了视觉搜索与经典双步眼跳任务相结合的搜索步长任务下，猕猴前额叶视觉选择和眼跳准备的动态变化。奖励是因为对一名有色人种单身汉进行了一次扫视。在随机试验中，目标和一个分心物体在扫视之前交换了位置，猴子因将目光转移到新的单身位置而获得奖励。对目标步骤的神经反应的计时分析表明，视觉反应神经元和运动相关神经元的调制发生得足够早，足以将注意力和扫视准备从旧的目标位置转移到新的目标位置。这些发现表明，前部眼场中的视觉活动发出定向目标位置的信号，而与运动相关的活动则实例化扫视准备。 这些研究扩大了我们对视觉处理的理解。我们已经证明，额叶眼场提供自上而下的认知衍生信号，调节正在进行的视觉处理。我们还发现，在前视视野中有两个独立和分离的认知过程，即视觉选择和眼跳准备。这两个过程对于正常的视觉和与世界的互动都至关重要。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。这项工作帮助我们了解大脑如何集中注意力做出知觉决定和指导行为的机制，这对于能够理解和治疗人类的眼球运动和注意力相关障碍是必要的。

In the Unit on Perception and Action we investigate how visual inputs are transformed into perception and behavior. Most of our research has been focused on the frontal eye field (FEF), an area in the prefrontal cortex that converts visual information into eye movement commands. We have shown that FEF combines visual inputs with cognitive knowledge to form a priority map of visual space that identifies the location of the most important objects in the visual scene to guide gaze. During the past year we have extended this finding to show that FEF anticipates future locations in which important visual stimuli will appear (Ref 1). In a collaborative study, we investigated how the visuomotor system reacts to sudden changes in the visual scene that require a dynamic change in saccade planning (Ref 2). In addition, we have recently submitted 3 papers (currently under review) that describe results from our investigations on how spatially selective signals in the frontal cortex enhance visual processing leading to object recognition and complex object representations in the inferior temporal cortex. In ref. 1 we addressed the question of how cognitive processes control spatial attention in the absence of visual input. We recorded frontal eye field activity in monkeys trained to perform a difficult discrimination task in which the monkeys attended the locations of the visual stimuli to be discriminated before they actually appeared. We found that most FEF neurons exhibited elevated activity when a cue informed the monkey that a stimulus would appear. This anticipatory attention-related activity in FEF occurred without any visual stimulation and was not related to motor processes. Together, these studies demonstrate that stimulus-driven and cognitively-driven spatial attention signals are present in FEF and are independent of saccade command signals. Therefore, FEF probably serves an important role in controlling visual spatial attention in addition to its well known role in saccade production. In ref. 2 we investigated the dynamics of visual selection and saccade preparation in the FEF of monkeys performing a search-step task combining the classic double-step saccade task with visual search. Reward was earned for producing a saccade to a color singleton. On random trials the target and one distractor swapped locations before the saccade and monkeys were rewarded for shifting gaze to the new singleton location. Chronometric analyses of the neural responses to the target step revealed that the modulation of visually responsive neurons and movement-related neurons occurred early enough to shift attention and saccade preparation from the old to the new target location. These findings indicate that visual activity in the frontal eye field signals the location of targets for orienting, whereas movement-related activity instantiates saccade preparation. These studies have extended our understanding of visual processing. We have shown that the frontal eye field provides top-down cognitively-derived signals that modulate ongoing visual processing. We also have identified two separate and dissociable cognitive processes within the frontal eye field, visual selection and saccade preparation. Both of these processes are crucial for normal vision and for interacting with the world. 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 eye movement and attention-related disorders in humans.