CRCNS:Investigating perceptual processing speed and its impact on choice behavior

描述（由申请人提供）：选择行为的神经生物学已经通过实验室任务进行了深入研究，其中受试者做出感知判断并用运动动作指示结果。因此，结合心理物理学和神经生理学实验的特点知觉决策能力作为信号质量，强度和主观价值的函数，并揭示了许多潜在的神经回路及其特定的作用。然而，时间的基本问题更难解决：做出一个知觉判断需要多长时间，而执行一个运动动作来报告这个判断需要多长时间？受试者在什么时候会做出特定的选择，又是什么神经机制决定了这一点？这些问题与许多需要快速选择的现实情况有关;例如，当驾驶员看到交通灯时，必须根据灯的颜色快速决定是踩刹车还是加速器。但是，进行精确的计时测量是复杂的，因为它们受到许多感官和运动因素的影响，如准备，动机，任务难度和速度-准确性权衡。因此，目前关于知觉决策的时间动态的知识是相当粗糙的。该项目中的PI最近开发了一项任务，消除了这些混淆，并产生了一种新的心理物理测量方法，即转速曲线，它隔离了受试者的感知处理能力，并以前所未有的时间分辨率对其进行量化。他们还构建了一个计算模型，可以非常详细地再现受试者的行为。新的范式和模型将被用来共同研究知觉判断的时间及其神经基础。具体的模型预测将通过单神经元记录和微刺激测试在各种条件下训练执行任务的猴子的额叶眼区（FEF）内。有三个具体目标。目标1：为了检验这一假设，即感知处理速度的变化表现为转速曲线的斜率变化（心理学上）和与扫视选择相关的眼球活动的加速（神经学上）。根据该模型，与扫视选择相关的转速曲线和眼球活动应该以特定的方式取决于感知难度。为了测量这种依赖性，受试者将执行3个版本的相同的选择任务，这将根据不同的刺激特征来区分知觉难度。目标二：为了检验这一假设，即当知觉处理速度保持恒定时，即使心理物理性能的其他测量值发生变化，转速曲线的斜率和眼动活动的加速度也将保持恒定。因此，这些实验是对目标1的补充。受试者将执行选择任务的4个变体，其中感知难度将是固定的，但与两种可能的运动反应相关的可能性和奖励将有所不同。受试者的表现水平、反应时间和选择比例预计会在4种条件下发生急剧变化，但感知处理速度的测量相关性不应发生变化。目标3：为了验证这一假设，即在FEF激活水平的整体增加改变了时间和准确性的主题的选择，但不是观察到的知觉处理速度。阈下微刺激电流将在任务执行期间的不同时间点注入FEF。问题是，诱发的活动是否被解释为纯粹的运动信号，或者它是否对受试者的感知处理能力有直接影响。智力优点：拟议中的实验跟踪受试者的感知表现如何及时展开，并为研究如何做出选择开辟了一条全新的途径。这将有可能（1）确定各种认知因素如注意力、动机、运动准备和知觉处理速度对受试者测量的心理物理表现的具体贡献，（2）研究在选择任务期间神经元活动如何与这些因素中的每一个相关，以及（3）揭示这种神经元活动的时间过程如何与受试者的选择准确性的时间过程相关。影响：（1）教学。这项研究的结果将纳入初级研究所教授的课程。(2)教育未成年人在神经科学的本科生将在PI的实验室主持研究学术信贷。一名研究生和一名博士后将发展电生理学和计算技能。(3)科学的理解。预计将广泛讨论和传播这些结果。(4)加强研究基础设施。将购置尖端设备用于本项目和未来项目。(5)对社会有益。这种新颖的任务设计有可能适用于人类受试者，并成为一种强大的诊断工具，用于阐明特定的神经回路或大脑“模块”如何受到给定精神障碍的损害。

DESCRIPTION (provided by applicant): The neurobiology of choice behavior has been intensely studied with laboratory tasks in which a subject makes a perceptual judgement and indicates the result with a motor action. Combined psychophysical and neurophysiological experiments have thus characterized perceptual decision-making capacity as a function of signal quality, strength, and subjective value, and have revealed many of the underlying neural circuits and their specific roles. However, the fundamental question of timing has been much harder to tackle: how long does it take to make a perceptual judgment, versus executing a motor action to report that judgment? At what point in time is a subject committed to a particular choice, and what neural mechanisms determine that? These issues are relevant to many real-life situations that require quick choices; for instance, when a driver sees a traffic light and must rapidly decide whether to step on the brake or the accelerator, depending on the light's color. But making accurate timing measurements is complicated because they are affected by numerous sensory and motor factors, such as readiness, motivation, task difficulty and speed-accuracy trade-offs. Consequently, current knowledge about the temporal dynamics of perceptual decision-making is rather crude. The PIs in this project recently developed a task that eliminates these confounds and produces a new psychophysical measure, the tachometric curve, which isolates a subject's perceptual processing capacity and quantifies it with unprecedented temporal resolution. They have also constructed a computational model that reproduces the subjects' behavior with great detail. The new paradigm and the model will be used jointly to investigate the timing of perceptual judgments and its neural basis. Specific model predictions will be tested via single-neuron recording and microstimulation within the Frontal Eye Field (FEF) of monkeys trained to perform the task under a variety of conditions. There are three specific aims. Aim 1: To test the hypothesis that changes in perceptual processing speed are manifested as changes in the slope of the tachometric curve (psychophysically) and in the acceleration of the oculomotor activity associated with a saccadic choice (neurally). According to the model, the tachometric curve and the oculomotor activity associated with saccadic choices should depend in specific ways on perceptual difficulty. To measure this dependency, subjects will perform 3 versions of the same choice task that will vary in perceptual difficulty according to different stimulus features to be discriminated. Aim 2: To test the hypothesis that when perceptual processing speed remains constant, both the slope of the tachometric curve and the acceleration of the oculomotor activity will stay constant as well, even if other measures of psychophysical performance do change. These experiments are thus complementary to those of Aim 1. Subjects will perform 4 variants of the choice task in which perceptual difficulty will be fixed but the likelihoods and rewards associated with the two possible motor responses will vary. The subject's performance level, reaction times and proportions of choices are expected to change drastically across the 4 conditions, but the measured correlates of perceptual processing speed should not. Aim 3: To test the hypothesis that an overall increase in the level of activation in FEF alters the timing and accuracy of a subject's choices, but not the observed perceptual processing speed. Subthreshold microstimulation current will be injected into the FEF at different points in time during task performance. The question is whether the evoked activity is interpreted as a purely motor signal or if it has a direct impact on the subject's perceptual processing capacity. Intellectual merit: The proposed experiments track how a subject's perceptual performance unfolds in time, and open up an entirely new avenue for investigating how choices are made. It will be possible (1) to determine the specific contributions of various cognitive factors such as attention, motivation, motor preparation, and perceptual processing speed to a subject's measured psychophysical performance, (2) to investigate how neuronal activity is related to each of these factors during a choice task, and (3) to reveal how the time course of this neuronal activity correlates with the time course of a subject's choice accuracy. Broader impacts: (1) Teaching. The results of this study will be incorporated into courses taught by the PIs. (2) Education. Undergraduate students with a minor in neuroscience will be hosted for research academic credit in the PIs' laboratories. A graduate student and a postdoctoral fellow will develop combined electrophysiological and computational skills. (3) Scientific understanding. The results are expected to be widely discussed and disseminated. (4) Enhancement of infrastructure for research. Cutting-edge equipment will be acquired for use in this and future projects. (5) Benefits to society. The novel task design has the potential to be adapted to human subjects and become a powerful diagnostic tool for elucidating how specific neural circuits or brain 'modules' are compromised by a given mental disorder.