Neurobiological Analyses of Plasticity: Learning and Memory

汤普森博士研究的长期目标是了解哺乳动物的大脑如何编码、储存和提取记忆。这已被证明是神经科学和心理学领域中最复杂的问题之一。它也是最重要的。在进化过程中，生物有机体发展出了两种存储信息的方式。一个是我们熟悉的嵌入DNA中的遗传密码；另一项同样重要的能力是在大脑中储存获得的信息和经验的能力。为了理解记忆存储的机制，有必要确定大脑中存储特定类型记忆所需的特定电路。汤普森博士选择了人类和其他哺乳动物共同拥有的一种基本的联想学习形式，即对离散行为反应的经典条件反射，用来处理厌恶事件。这种条件反射的一个例子是学习闭上眼睑，以回应一个音调（条件刺激，或CS），这表明眼睛上出现了一阵空气（无条件刺激，或US）。汤普森博士和他的同事们发现，小脑中非常分散的区域对这种基本的学习方式至关重要。他们还成功地确定了与这种基本形式的联想学习有关的大部分基本大脑回路。Thompson博士和他的同事将使用几种神经生理学方法和行为训练程序来(1)完成对基本听觉CS通路的识别，(2)确定在该通路到达小脑之前是否在该通路中形成记忆痕迹，(3)表征基本US通路和基本条件反应通路中的神经元反应模式，(4)确定记忆痕迹形成的确切位置；(5)开始分析记忆痕迹形成的机制；(6)确定小脑回路是否能调节“认知”行为现象的“阻塞”；(7)探索高级大脑结构（大脑皮层、海马体）如何调节小脑记忆痕迹回路。除了理解记忆储存的基本机制外，汤普森博士的工作还为理解运动技能是如何编码和学习的提供了希望。潜在的实际应用范围从治疗学习障碍到提高熟练的人类表现，再到开发一种全新的方法来解决机器人运动控制问题。

The long-term goal of Dr. Thompson's research is to understand how the mammalian brain codes, stores, and retrieves memories. This has proved to be one of the most complex problems in the fields of neuroscience and psychology. It is also one of the most important. Over the course of evolution, biological organisms have developed two ways of storing information. One is the familiar genetic code embedded in the DNA; the other, no less important, is the ability to store acquired information and experience in the brain. In order to understand the mechanisms of memory storage, it is necessary to identify the specific circuitry in the brain required to store a given type of memory. Dr. Thompson has selected a basic form of associative learning shared equally by humans and other mammals, classical conditioning of discrete behavioral responses learned to deal with aversive events. An example of such conditioning is learning to close the eyelid in response to a tone (conditional stimulus, or CS) that signals the occurrence of a puff of air on the eye (unconditional stimulus, or US). Dr. Thompson and his colleagues have discovered that very discrete regions of the cerebellum are essential for this basic form of learning. They have also succeeded in identifying most of the essential brain circuitry involved in this basic form of associative learning. Dr. Thompson and his colleagues will use several neurophysiological methods and behavioral training procedures to (1) complete the identification of the essential auditory CS pathway, (2) determine whether or not memory traces are formed in this pathway before it reaches the cerebellum, (3) characterize the patterns of neuronal response in the essential US pathway and in the essential conditional- response pathway, (4) determine the exact locations where memory traces are formed, (5) begin analysis of the mechanism of memory-trace formation, (6) determine if the essential cerebellar circuit can mediate the "cognitive" behavioral phenomenon of "blocking," and (7) explore how higher brain structures (cerebral cortex, hippocampus) modulate the essential cerebellar memory-trace circuit. In addition to understanding basic mechanisms of memory storage, Dr. Thompson's work offers the promise of understanding how motor skills are coded and learned. The potential practical applications range from treatment of learning disabilities to enhancement of skilled human performance to the development of an entirely new approach to the problem of control of movement in robotics.