Midbrain Mechanisms of Sensory-Guided Oculomotor Choice

描述(由申请人提供)：本项目的目标是调查上丘(SC)对选择行为的知觉和运动贡献；具体地说， 我们建议在一项紧迫的决策任务的背景下这样做，这项任务使我们能够以前所未有的巨大效率将知觉和运动表现分开。神经学家对选择行为进行了深入的研究，在许多任务中，做出了知觉判断，然后是运动报告。虽然非常成功，但这种方法也有局限性。最值得注意的是，注意力、预期、动机或任务难度等各种隐蔽因素可以相互交换，造成不能通过标准的心理物理指标，即反应时间和选择准确度来解决的模糊性。因此，关于选择时机的根本问题仍然知之甚少。与执行运动动作来报告相比，做出感性判断需要多长时间？在什么时间点上，受试者会致力于某一特定选项？当成功率增加时，是因为刺激的处理效率更高，还是速度更快，还是因为有更多的时间用于分析？该项目中的PI最近开发了一项紧急选择任务，通过该任务，这些问题及其潜在的神经机制可以直接、明确的方式进行检查。它产生了一种新的心理物理测量，即测速曲线，它表征了受试者在一段时间内独立于运动执行的知觉表现。PI还构建了一个计算模型，将神经元反应与受试者的行为联系起来，并进行了大量的量化 细节。在拟议的实验中，将记录训练过的猴子的SC中的神经元活动 来完成这项新颖的跳跃选择任务。将解决两个问题。首先，SC参与知觉处理，这与SC在扫视执行中牢固确立的角色形成对比，仍然没有得到很好的描述。测速曲线的独特性质将被用来确定知觉信息何时通知SC活动，以及这与任务执行期间受试者感知的时间演变(目标1)如何相关。此外，阈值以下微刺激电流将通过不同的空间和时间配置注入SC，以确定人工诱发活动如何影响知觉和运动表现(AIM2)。第二个问题是，当选择行为由多感官刺激驱动时，选择行为如何改变；也就是说，由视觉和听觉提示的同时呈现。这个 众所周知，SC对这些刺激组合的反应最有效，但它们在选择行为中的影响尚未被评估。这项任务的多感官变量将被用来确定多感官整合是否改变了知觉判断或眼跳运动计划的速度(目标3)。这项工作将提供关于知觉信息如何动态转化为运动输出的关键见解，将表征神经元水平上的多感觉整合如何导致行为表现的增强，并将确定SC如何参与这些过程。

DESCRIPTION (provided by applicant): The goal of this project is to investigate the perceptual andmotor contributions of the superior colliculus (SC) to choice behavior; specifically, we propose to do this in the context of an urgent decision-making task that allows us to dissociate perceptual and motor performance with great, unprecedented effectiveness. Neuroscientists have intensely studied choice behavior with numerous tasks in which a perceptual judgement is made and is followed by a motor report. While highly successful, this approach has limitations. Most notably, various covert factors such as attention, anticipation, motivation or task difficulty can be traded against each other, creating ambiguities that cannot be resolved via standard psychophysical metrics, i.e., reaction time and choice accuracy. Thus, fundamental questions about the timing of choices remain poorly understood. How long does it take to make a perceptual judgement versus executing a motor action to report it? At what point in time is a subject committed to a particular option? When the success rate increases, is it because stimuli are processed more efficiently, or faster, or because more time is dedicated to their analysis? The PIs in this project recently developed an urgent-choice task with which these questions - and the underlying neural mechanisms - can be examined in a direct, unambiguous way. It produces a new psychophysical measure, the tachometric curve, which characterizes a subject's perceptual performance over time independently of motor execution. The PIs have also constructed a computational model that relates neuronal responses to the subjects' behavior with great quantitative detail. In the proposed experiments, neuronal activity in the SC will be recorded from monkeys trained to performthis novel saccadic-choice task. Two problems will be addressed. First, the participation of the SC in perceptual processing, which in contrast to the SC's firmly established role in saccade execution, remains less well characterized. The unique properties of the tachometric curve will be exploited to determine when perceptual information informs the SC activity, and how this correlates with the temporal evolution of the subject's percept during task performance (Aim 1). In addition, subthreshold microstimulation current will be injected into the SC using various spatial and temporal configurations to determine how the artificially evoked activity impacts perceptual and motor performance (Aim2). The second problemis how choice behavior changes when it is driven by multisensory stimuli; that is, by the simultaneous presentation of visual and auditory cues. The SC is known to respond most effectively to such stimulus combinations, but their impact during choice behavior has not been assessed. A multisensory variant of the task will be used to determine whether multisensory integration alters the speed of the perceptual judgements or of the saccadic motor plans (Aim 3). This work will provide critical insight about how perceptual information is dynamically translated into motor output, will characterize how multisensory integration at the neuronal level leads to enhanced behavioral performance, and will determine how the SC participates in these processes..