The Mechanisms of Perceptual Learning

描述(申请人提供)：知觉学习(PL)被定义为视觉特征由于训练或接触该特征而提高的表现，并被认为是感觉/知觉加工中的可塑性的表现。虽然我们正在进行的项目(R01EY015980)已经揭示了外部因素如何影响PL，但当前的提议将解决一个更基本但尚未回答的问题：神经机制如何与PL的相关性发生变化？研究发现，有几个因素从根本上影响了PL的作用机理。首先，由于检测任务和辨别任务的训练(任务相关学习)或暴露于随时间呈现的任务无关特征(任务无关学习)而形成PL。不同的训练方法会以不同的方式影响PL的作用机制。第二，随着学习的进行，PL的神经加工似乎发生了很大的变化。第三，对受试者的任务执行情况的外部反馈可以促进任务执行，或者在某些情况下对任务执行是必要的。然而，这三个因素是如何影响PL的神经机制的，目前尚不清楚。我们将通过系统地检查在大脑视觉处理的多个区域中获得的训练特征的调谐函数的变化来解决这个问题。为此，我们将测量被认为反映神经活动的血氧水平依赖(BOLD)信号。具体地说，大胆的反应调谐功能变化将在视觉处理的多个领域与PL相关联地进行测量。我们将首先研究不同的训练方法如何发生大胆的活动变化，如检测任务的训练、辨别任务的训练和任务无关特征的暴露，并解决不同训练方法引起的神经变化如何相互关联的问题。其次，我们将考察在学习的过程中如何发生大胆的活动变化。注意，粗体响应调谐函数的改变可以被描述为对某些特征值的响应增加和/或对其他值的减少。我们将研究在学习过程中调谐函数中相对大胆反应的增加和减少是如何发生的，并测试大胆信号的增加和减少是否来自相同的机制。第三，我们将研究外部反馈是否以及如何影响反映在视觉处理的多个区域的大胆反应调节功能的变化。如果反馈影响了大胆的反应调节功能，我们将进一步研究它在反应调节功能中是只促进反应增加，还是只促进反应减少，还是两者兼而有之。总体而言，虽然这三个基本因素引起的神经变化似乎有很大的不同，但对当前建议的三个目标的系统研究可能澄清，在理论上是否可以将这些变化视为导致反应增加的兴奋性输入和引起反应减少的抑制信号在PL时间过程中组合的结果。公共卫生相关性拟议的研究具有临床应用的潜力，因为它促进了科学知识，从而改善了对大脑疾病和损伤的诊断和康复治疗，特别是与感觉功能有关的疾病和损伤。

DESCRIPTION (provided by applicant): Perceptual learning (PL) is defined as performance increase of a visual feature as a result of training or exposure to the feature and is regarded as a manifestation of plasticity in sensory/perceptual processing. While our on-going project (R01EY015980) has revealed how external factors gate PL, the current proposal will address a more fundamental but unanswered question; how do neural mechanisms change in correlation with PL? It has been found that several factors fundamentally influence the mechanism of PL. First, PL is formed as a result of training of a detection task and a discrimination task (task-relevant learning) or exposure to a task- irrelevant feature presented over time (task-irrelevant learning). Different training methods could influence the mechanisms of PL in different ways. Second, the neural processing of PL seems to greatly change as learning proceeds. Third, external feedback to subjects as to their performance of a task can facilitate PL or in some cases is necessary for PL. Nevertheless, it has yet to be clarified how these 3 factors influence the neural mechanisms of PL. We will address this question by systematically examining changes of tuning functions of a trained feature that are obtained in multiple areas of visual processing in the brain. For this purpose, we will measure blood oxygen level dependent (BOLD) signals that are regarded as reflecting neural activity. Specifically, BOLD response tuning function changes will be measured in multiple areas of visual processing in correlation with PL. We will first examine how BOLD activity changes occur by the different training methods such as training of a detection task, training of a discrimination task and exposure to a task-irrelevant feature and address the question concerning how neural changes resulting from different training methods are related to each other. Second, we will examine how BOLD activity changes occur during the time course of learning. Note that BOLD response tuning function changes can be characterized as response increases for some feature values and/or decreases for other values. We will examine how relative BOLD response increases and decreases occur in tuning functions during the time course of learning and also test whether BOLD signal increases and decreases originate from the same mechanism. Third, we will examine whether and how external feedback influences BOLD response tuning function changes reflected in multiple areas of visual processing. If feedback influences BOLD response tuning functions, we will further investigate whether it facilitates response increase only, response decrease only, or both, in response tuning functions. Overall, while the neural changes by the 3 fundamental factors appear to be highly different, the systematic investigation in 3 aims of the current proposal may clarify whether it is theoretically possible to view these changes as a result of combinations of excitatory inputs that cause response increases and inhibitory signals that cause response decreases over the time course of PL. PUBLIC HEALTH RELEVANCE The proposed research has potential for clinical applications by contributing to scientific knowledge leading to improved diagnosis of, and rehabilitative therapies for, brain disorders and lesions, in particular those related to sensory function.