Perceptual And Motor Decisions In The Primate Brain

我的研究兴趣是了解主观感知和自愿运动动作是如何从大脑活动中产生的。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场（FEF）上，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。该项目的目标是了解我们如何做出感知决策，选择在哪里直接注视，并了解定向视觉注意的神经基础。 认知神经科学的一个突出问题是，我们如何能够在不移动眼睛的情况下将视觉注意力集中在特定的物体和位置上。多线的证据表明，发展中的眼命令源于FEF介导的空间注意。我们测试了这一假设，记录从视觉和扫视相关的神经元在FEF猴子执行隐蔽的视觉搜索任务，没有眼球运动。我们发现视觉反应神经元，而不是扫视相关神经元，是FEF中注意信号的来源（参考文献1）。在另一项研究中，我们探讨了在没有视觉输入的情况下，认知过程如何控制空间注意力的问题。我们记录了额叶眼场活动的猴子训练执行一个困难的歧视任务，其中猴子出席的位置的视觉刺激，以区分之前，他们实际上出现。我们发现，大多数FEF神经元表现出升高的活动时，一个线索通知猴子，刺激会出现。FEF中的这种预期注意相关活动在没有任何视觉刺激的情况下发生，并且与运动过程无关（参考文献2）。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和眼跳命令信号是独立的。因此，FEF除了在眼跳产生中的作用外，还可能在控制视觉空间注意中发挥重要作用。 我们还研究了当我们面对使我们当前的行为变得不合适的意外事件时，我们如何调整我们的行为的神经基础（参考文献3）。我们记录扫视命令信号的FEF的猴子执行视觉搜索任务，在搜索的目标出乎意料地改变位置的干扰之一。因此，一些扫视被错误地指向原始目标位置，并且随后频繁地被指向最终目标位置的未奖励的校正扫视。我们发现，眼跳相关的活动产生纠正眼跳错误试验开始之前，视觉传入信号和错误识别信号可以响应于执行错误眼跳后的变化的图像。这些观察结果提供了一个快速纠错机制的直接证据之前，错误的行为可以检测到的视觉系统或错误监控系统。 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 subjective perception and voluntary motor actions 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. The goal this project is to understand how we make perceptual decisions, choose where to direct gaze and to understand the neural basis of directed visual attention. One of the outstanding questions of cognitive neuroscience is how we are able to focus visual attention on specific objects and locations without moving our eyes. Multiple lines of evidence suggest that developing oculomotor commands originating from the FEF mediate spatial attention. We tested this hypothesis by recording from visual and saccade related neurons in the FEF of monkeys performing covert visual search tasks without eye movements. We found that the visually responsive neurons, and not the saccade-related neurons, are the source of attention signals in FEF (ref. 1). In another study, 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 (ref. 2). 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. We also examined the neural basis of how we adjust our behavior when confronted with unexpected events that render our current actions inappropriate (ref. 3). We recorded saccade command signals in the FEF of monkeys performing a visual search task in which the target of a search unexpectedly changed position with one of the distractors. Consequently, some saccades were directed in error to the original target location and were followed frequently by unrewarded corrective saccades to the final target location. We found that saccade-related activity producing corrective saccades on error trials begins before visual afferent signals and error recognition signals could respond to the changed image following the execution of the error saccade. These observations provide direct evidence for a rapid error correction mechanism before an errant behavior can be detected by the visual system or by the error monitoring system. 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.