Dynamic regulation of receptive fields and maps in the adult sensory cortex.
Dynamic regulation of receptive fields and maps in the adult sensory cortex.
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DOI：
10.1146/annurev.ne.18.030195.001021
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发表时间：
1995
影响因子：
13.9
通讯作者：
N. Weinberger
中科院分区：
文献类型：
--
作者：
N. Weinberger
神经科学中一个主流观点认为，与神经系统发育过程中广泛且普遍存在的可塑性不同，成年人的感觉系统是稳定的。这种感觉不变性的理论基础包括麻醉动物中感觉神经元通常精确且稳定的反应，以及感觉皮层可塑性在发育关键期之后的降低。神经科学家的主观经验也支持这一观点。对外部世界的感知似乎是清晰、即时且毫不费力的。对大多数研究者来说，这意味着感觉系统一旦发育成熟，就必须保持稳定，以便提供有关环境的准确信息。然而，大量迅速增长的文献证明，在多种情况下（学习、感觉刺激和感觉传入神经阻滞），感受野（RF）会在很大程度上发生短期和长期的改变，以及表征图谱会发生重组。本章回顾了有关成人大脑初级听觉、躯体感觉和视觉皮层中感受野和图谱动态调节的当代研究成果。与以往主要局限于感觉生理学视角的综述不同，本文还强调了行为方面的考量。这似乎是恰当的，如果不是必须的话，因为行为通常是动态且具有适应性的，而感觉皮层因其进化发展以及在高级功能中的作用而引人注目。由于篇幅所限，本文的涵盖内容具有高度选择性。无法对文献进行详细分析，对感觉传入神经阻滞影响的讨论不得不局限于对主要影响及其与感觉刺激和学习可能相关性的简要总结；幸运的是，传入神经阻滞的影响已有详细综述（Kaas，1991）。在有关感觉刺激和学习的文献中，仅限于标准学习范式的研究未被纳入，而是倾向于对感受野和表征图谱的研究。这些限制不应过度影响本综述，因为其主要目的是概念性的。具体而言，目标是提供一个框架，有助于思考当前和未来有关成感觉皮层可塑性和重组的研究。这个框架基于一个在神经科学中尚未得到广泛认可的经验法则。可总结如下：有行为（即清醒）的动物能够持续获取并保留关于（a）单个感觉刺激、（b）各种感觉刺激之间的关系以及（c）自身行为及其感觉后果之间关系的信息。这一法则的一个含义是，要充分理解成人大脑中的感觉皮层如何服务于感知和行为，还需要对学习在感觉皮层中的作用有充分的解释。从理论上讲，这种作用可能为零。但事实上并非如此，明确的学习实验结果以及其他可合理视为涉及学习的研究都证明了这一点。学习在去神经支配诱导的可塑性和重组中的作用目前在很大程度上是推测性的，但不能被忽视。接下来依次讨论以下主题：感觉生理学与学习之间的关系、与成人大脑皮层可塑性特别相关的基本学习形式、方法学考量、学习和感觉皮层中的主要问题和新兴原则、来自学习文献的这些原则的实例、对感觉传入神经阻滞影响的简要评论以及结论。
A dominant belief in neuroscience is that sensory systems in the adult are stable, in contrast to the extensive and pervasive plasticity that characterizes development of the nervous system. Empirical bases for this dogma of sensory immutability include the usually precise and stable responses of sensory neurons in anesthetized animals and the reduction of sensory cortical plasticity beyond critical periods of development. The subjective experience of neuro-scientists also supports the dogma. Perception of the outside world appears to be clear, immediate and effortless. To most workers, this implies that the sensory systems, once having developed, must be stable in order to provide accurate information about the environment. However, a rapidly growing literature attests to a very large degree of short- and long-term modification of receptive fields (RF) and reorganization of representational maps under variety of circumstances: learning, sensory stimulation, and sensory deafferentation. This chapter reviews contemporary findings concerning the dynamic regulation of receptive fields and maps in the primary auditory, somatosensory, and visual cortices of the adult brain. In contrast to previous reviews that have been confined largely to the perspective of sensory physiology, this article also emphasizes behavioral considerations. This seems to be appropriate, if not mandatory, because behavior is normally dynamic and adaptive, and sensory cortex is notable for its evolutionary development and implication in higher functions. The present coverage is highly selective, necessitated by severe constraints of space. Detailed analyses of publications were not possible and coverage of the effects of sensory deafferentation had to be limited to a scant summary of major effects and their possible relevance to sensory stimulation and learning; fortunately the effects of deafferentation have been reviewed in detail (Kaas 1991). Within the literature on sensory stimulation and learning, studies limited to standard learning paradigms were not included, in favor of studies of receptive fields and representational maps. These limitations should not unduly compromise this review because its intention is mainly conceptual. Specifically, the goal is to provide a framework that will be useful for thinking about both current and future research on adult sensory cortical plasticity and reorganization. This framework is based on an empirical law that is not yet widely appreciated in neuroscience. It may be summarized as follows: Behaving (i.e. waking) animals can continually acquire and retain information about (a) individual sensory stimuli, (b) relationships between various sensory stimuli, and (c) relationships between their own behavior and its sensory consequences. An implication of this law is that the attainment of an adequate understanding of how sensory cortex in the adult subserves perception and behavior also requires achieving an adequate account of the role of learning in sensory cortex. In theory, this role could have been nil. In fact it is not, as attested by the results of explicit learning experiments and other studies that can reasonably be considered to involve learning. The role of learning in denervation-induced plasticity and reorganization is currently largely conjectural but cannot be discounted. The following topics are discussed in turn: the relationship between sensory physiology and learning, basic forms of learning that are particularly relevant to adult cortical plasticity, methodological considerations, major issues and emerging principles in learning and sensory cortex, examples of these principles from the literature on learning, brief comments on the effects of sensory deafferentation, and conclusions.