Multisensory Development: Cortical-Midbrain Interactions

项目摘要 在感觉处理中，无知的一个主要问题是大脑如何发展其非凡的能力， 感觉协同，正常感知的关键要求。但我们知道，获得这个 能力是一个长期的出生后的过程，以及合作使用视觉和听觉信息的能力 必须学习。这一过程最好理解为检测和定向行为介导的 由上级丘（SC），一个中脑结构，以及赋予多感觉神经元。经过广泛 在视觉-听觉体验方面，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神经元显示出类似的变化-现在整合了它们不同的感觉输入， 他们的反应和起始事件的生理显著性。大脑已经开始处理这些交叉- 模态刺激作为一个连贯的整体，而不是作为一组竞争或不相关的线索。这些变化是 在黑暗中饲养或有掩蔽噪声的动物中未见，化学损伤优先消除 SC多感觉神经元消除增强的多感觉检测和定向行为， 扰乱了对个体线索的反应。有趣的是，这种综合能力及其 在检测和定向外部事件方面的性能益处可以在黑暗饲养和噪声中获得， 通过在以后的生活中给它们适当的经验来饲养动物。但是，这个概念的概念和实际应用 由于对信息获取和运作的基本因素缺乏了解，信息受到限制。 我们认为，这种SC能力的获得并不依赖于在 正如人们普遍认为的那样。相反，它涉及到一种更为复杂的统计学习形式 其中对任何一组跨模态输入从同一事件导出的概率进行编码。这 然后，电路使用该信息来确定它以后将如何响应这些事件。但为了有效 在这一点上，这些跨模态输入必须通过联合体的统一预测进入供应链 皮质（并通过SC的固有偏见进行过滤）。我们假设这个自然过程可以复制 通过诱导这些会聚的皮质-SC传入的协变激活-在没有外部刺激的情况下， 线索，而没有任何强化偶然性或认知因素通常与显性 行为最后，我们假设NMDA受体提供了编码这一过程的关键机制基础。 通过启动类似于赫布的学习算法来获得经验。最终的结果是一个多感官系统， 对特定的跨模态刺激配置非常敏感，这些刺激配置被认为是属于 同样的事件。这使他们能够优先进入神经机制，这将进一步增强他们的能力。 生理显著性及其引发SC介导行为的能力，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.