Perceptual And Motor Decisions In The Primate Brain

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。为此，我们一直在研究额叶眼场在视觉知觉中的作用。FEF位于前额叶皮质，参与将视觉信息转化为移动眼睛的命令。多条证据表明，发源于前额叶的动眼神经指令调节视觉空间注意。我们通过记录猴子在没有眼球运动的情况下执行隐蔽视觉搜索任务的FEF中与视觉和眼跳相关的神经元来验证这一假设。我们发现，视觉反应神经元，而不是眼跳相关神经元，是FEF中注意信号的来源。通过分析和比较这一认知信号在FEF的输入和输出中的时间进程，我们发现在FEF中视觉场景的空间选择性表征是由非空间选择性输入(REF)产生的。3)。这意味着FEF是调节自上而下聚焦视觉注意的重要信号来源。在裁判中4我们发现，猴子FEF中对目标位置的准确知觉表征并不总是预测猴子对目标位置的准确行为报告。这一发现很重要，因为它表明知觉和运动过程可以在某种程度上独立运行，并对理解在报告知觉决定时公开行为的可靠性有意义。利用一个简单的扩散模型，我们证明了与感知处理无关的噪声是决策中的一个重要因素。 另一项研究(参考文献5)，我们探讨了在缺乏视觉输入的情况下，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。 我们还研究了当我们面对使我们当前的行为不适当的意外事件时，我们如何调整行为的神经基础。1)。我们记录了执行视觉搜索任务的猴子的眼跳指令信号，在视觉搜索任务中，搜索的目标与其中一个分心物意外地改变了位置。因此，一些扫视被错误地引导到最初的目标位置，并经常被无偿的纠正扫视引导到最终的目标位置。我们发现，在错误试验中产生纠正性眼跳的眼跳相关活动在视觉传入信号之前和错误识别信号对错误眼跳执行后的改变的图像做出反应之前就开始了。这些观察结果为错误行为可以被视觉系统或错误监控系统检测到之前的快速纠错机制提供了直接证据。在裁判中2我们比较了人类和非人类灵长类动物在这项任务中的行为，在这项任务中，眼跳目标意外地改变了位置。我们表明，人类和猴子的行为是不可区分的，可以用三个独立的随机过程之间的竞争来建模，从而提供了当图像意外变化时眼跳产生的计算帐户。 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常见作用。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注意力相关障碍是必要的。

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. To this end, we have been investigating the role of the frontal eye field (FEF) in visual perception. The FEF is located in the prefrontal cortex and participates in the transformation of visual information into commands to move the eyes. Multiple lines of evidence suggest that developing oculomotor commands originating from the FEF mediate visual 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. By analyzing and comparing the time course of this cognitive signal in the inputs and the outputs of FEF, we found that a spatially selective representation of the visual scene is generated de novo in FEF from non-spatially selective inputs (ref. 3). This means that FEF is an importante source of signals that mediate top-down focused visual attention. In ref. 4 we show that an accurate perceptual representation of target location in a monkeys' FEF does not always predict an accurate behavioral report of target location by the monkey. This finding is important because it demonstrates that perceptual and motor processes can run somewhat independently and has implications for understanding the reliability of overt behavior in reporting a perceptual decision. Using a simple diffusion model, we show that noise unrelated to perceptual processing is an important factor in decision-making. In another study (ref. 5), 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. We also examined the neural basis of how we adjust our behavior when confronted with unexpected events that render our current actions inappropriate (ref. 1). 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 before 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. In ref. 2 we compared human and non-human primate behavior during this task in which a saccade target unexpectedly changes locations. We show that human and monkey behavior are indistinguishable and can be modeled by a race between three independent stochastic processes, thereby providing a computational account of saccade production when the image changes unexpectedly. 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.