The Mechanisms of Perceptual Learning

描述（由申请人提供）：知觉学习（Perceptual learning， PL）被定义为由于训练或接触视觉特征而导致的视觉特征的表现提高，被认为是感觉/知觉加工可塑性的表现。虽然我们正在进行的项目（R01EY015980）揭示了外部因素如何影响PL，但当前的提案将解决一个更基本但未解决的问题；与PL相关的神经机制是如何变化的？研究发现，有几个因素从根本上影响学习记忆的形成机制。首先，学习记忆的形成是由于检测任务和辨别任务（任务相关学习）的训练，或者长期暴露于任务无关特征（任务无关学习）。不同的训练方法会以不同的方式影响PL的机制。其次，随着学习的进行，PL的神经处理似乎发生了很大的变化。第三，对受试者的任务表现的外部反馈可以促进PL，或者在某些情况下是PL所必需的。然而，尚不清楚这3个因素如何影响PL的神经机制。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功能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。具体而言，将在与PL相关的视觉处理的多个领域测量BOLD响应调谐函数的变化。我们将首先检查不同的训练方法（如检测任务的训练、区分任务的训练和暴露于任务无关的特征）如何发生BOLD活动变化，并解决有关不同训练方法导致的神经变化如何相互关联的问题。其次，我们将研究在学习的时间过程中，BOLD活动是如何发生变化的。请注意，BOLD响应调优函数的变化可以表征为某些特征值的响应增加和/或其他值的响应减少。我们将研究在学习的时间过程中，调谐函数的相对BOLD响应是如何增加和减少的，并测试BOLD信号的增加和减少是否源于相同的机制。第三，我们将研究外部反馈是否以及如何影响反映在视觉加工多个领域的BOLD响应调谐功能变化。如果反馈影响了BOLD响应调优函数，我们将进一步研究它在响应调优函数中是只促进响应增加、只促进响应减少，还是两者兼而有之。总的来说，虽然这三种基本因素引起的神经变化似乎非常不同，当前提案的3个目标的系统调查可能会澄清在理论上是否可能将这些变化视为导致反应增加的兴奋输入和导致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潜力，有助于提高科学知识，从而改善诊断和康复治疗，大脑紊乱和损伤，尤指与感觉功能有关的

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.