Multisensory Development: Cortical-Midbrain Interactions

项目摘要 感觉加工中的无知的一个主要问题是大脑如何发展其非凡的能力来使用它的 感官协同，这是正常知觉的关键要求。然而，我们知道，获得这一点 能力是一个漫长的后天过程，是一种协同使用视觉和听觉信息的能力 必须要学会。这一过程最好的理解是通过检测和定位行为来调节的 上丘(SC)是一种中脑结构，具有丰富的多感觉神经元。经过广泛的 视觉-听觉体验，动物表现出增强的视觉-听觉检测和定位行为。他们的 多感觉SC神经元表现出类似的变化--现在整合它们不同的感觉输入以增强 他们的反应和启动事件的生理突显。大脑已经来治疗这些交叉- 将情态刺激作为一个连贯的整体，而不是作为一组相互竞争或无关的线索。这些变化是 在黑暗中饲养或有掩蔽噪音的动物中看不到，化学损伤优先消除 SC多感觉神经元消除了增强的多感觉检测和定向行为 扰乱了对它们各自成分线索的反应。有趣的是，这种综合能力和它的 在检测和定位外部事件方面的性能优势可以在黑暗环境和噪声环境中获得。 通过在以后的生活中给予动物适当的经验来饲养动物。但是，这一概念和实际用途 由于对其收购和运营背后的因素缺乏了解，信息受到限制。 我们认为，这种供应链能力的获得并不依赖于在 人们普遍认为是感官形式。相反，它涉及一种复杂得多的统计学习形式 其中对来自同一事件的任何一组跨模式输入的概率进行编码。这 然后，电路使用信息来确定它稍后将如何响应此类事件。但要想有效 在这方面，这些跨模式输入必须通过来自关联的单一感觉投影来访问SC 大脑皮层(并被SC固有的偏见过滤)。我们假设这一自然过程是可以复制的 在缺乏外部刺激的情况下，通过诱导这些汇聚的皮质-SC传入的协变激活来人为地 暗示，并且没有任何强化意外或通常与公开的认知因素相关的认知因素 行为。最后，我们假设nmda受体为编码这一基因提供了关键的机制基础。 通过启动类似Hebbian的学习算法来体验。最终的结果是一个多感官系统， 对特定的跨模式刺激配置极其敏感，这些配置被学习为属于 同样的事件。这让他们优先使用神经机器，这将进一步增强他们的 生理突显及其诱导SC中介行为的能力，确保系统适应 它形成的环境，以及它可能被使用的环境。

Project Summary A major issue of ignorance in sensory processing is how the brain develops its remarkable ability to use its senses synergistically, a critical requirement for normal perception. We do know however, that acquiring this capability is a protracted postnatal process, and the ability to use visual and auditory information cooperatively must be learned. This process is best understood in terms of the detection and orientation behaviors mediated by the superior colliculus (SC), a midbrain structure well-endowed with multisensory neurons. After extensive visual-auditory experience, animals show enhanced visual-auditory detection and localization behaviors. Their multisensory SC neurons show similar changes – now integrating their different sensory inputs to enhance their response and the physiological salience of the initiating events. The brain has come to treat these cross- modal stimuli as a coherent whole rather than as a set of competitive or unrelated cues. These changes are not seen in animals reared in darkness or with masking noise, and chemical lesions preferentially eliminating SC multisensory neurons eliminate the enhanced multisensory detection and orientation behaviors without disrupting responses to their individual component cues. Interestingly, this integrative capacity and its performance benefits in detecting and orienting to external events can be acquired in dark-reared and noise- reared animals by giving them appropriate experience later in life. But, the conceptual and practical use of this information is limited by a poor understanding of the factors underlying its acquisition and operation. We suggest the acquisition of this SC capacity does not depend on forming generic associations between the sensory modalities as is widely believed. Rather, it involves a far more sophisticated form of statistical learning in which the probability that any set of cross-modal inputs derive from the same event is encoded. This information is then used by the circuit to determine how it will later respond to such events. But to be effective in this regard, those cross-modal inputs must access the SC through unisensory projections from association cortex (and be filtered by the SC’s inherent biases). We posit that this natural process can be reproduced artificially by inducing covariant activation of these converging cortico-SC afferents - in the absence of external cues, and without any of the reinforcement contingencies or cognitive factors normally associated with overt behavior. Finally, we hypothesize that NMDA receptors provide the crucial mechanistic basis for encoding this experience by initiating Hebbian-like learning algorithms. The end result is a multisensory system that is extremely sensitive to the particular cross-modal stimulus configurations that were learned to belong to the same events. This gives them preferential access to the neural machinery that will still further enhance their physiological salience and their ability to elicit SC-mediated behavior, ensuring that the system is adapted to the environment in which it was formed, and in which it will likely be used.