Neural Mechanisms of Optimal Multisensory Integration

描述（由申请人提供）：多感觉整合是许多认知现象的核心。它提供了一个生存优势，因为它允许大脑将来自不同感觉模态的独立估计值联合收割机组合成一个单一的估计值，这个估计值比孤立的任何单一模态都更准确。进展的一个关键障碍是我们缺乏关于大脑如何结合不同模式的知识。如果感觉模态#1声称环境是“X”，而感觉模态#2声称环境是“Y”，那么如何最好地组合估计以指导行为？行为研究中的一个重要发现是，多感觉整合是贝叶斯最优的-也就是说，在整合它们时考虑了不同感觉方式的可靠性。可靠的感官输入（更多信息）接收更大的权重，而信息较少的感官输入接收更少的权重。这项建议的目标是揭示最佳视觉触觉整合的神经机制。我们的中心假设采用了一个简单的模型，在这个模型中，从单感觉到多感觉的大脑区域的连接强度受到每种模式中刺激的可靠性的调制。不可靠的刺激导致弱连接，降低整合区域中该模态的有效性，而可靠的刺激导致强连接和增强驱动行为的能力。为了测试我们的模型，我们提出了四个具体的目标，将检查两个不同的范式：一个触摸传递到的手，既看到和感觉到的;和讲话，既看到和听到的。在第一个目标中，我们将使用血氧水平依赖性功能磁共振成像（BOLD fMRI）来确定这两种刺激所涉及的脑区。我们将测试的假设，即顶内沟（IPS）将响应视觉和触觉触摸和上级颞沟（STS）将响应听觉和视觉语言。在第二个目标中，我们将表明，神经连接的强度是成正比的刺激的可靠性。我们将检验这一假设，即单感觉区和多感觉区之间的有效连接将与该模式中呈现的刺激的可靠性成比例。在第三个目标中，我们将使用多体素模式分析（MVPA）证明多感觉脑活动和行为之间的相关性。在第四个目标中，我们将揭示大脑活动和行为多感觉整合之间的因果关系。使用fMRI引导的经颅磁刺激（TMS），我们将测试的假设，即多感觉区的TMS将消除多感觉刺激的行为优势和假设，即单感觉区的TMS将损害行为表现成比例的刺激的可靠性，在该模式。 公共卫生相关性：多感觉整合是许多认知现象的核心。我们将使用功能性磁共振成像（fMRI）和经颅磁刺激（TMS）在正常人受试者中研究多感觉整合过程中大脑的组织和运作。

DESCRIPTION (provided by applicant): Multisensory integration is at the core of many cognitive phenomena. It provides a survival advantage because it allows the brain to combine the independent estimates available from different sensory modalities into a single estimate that is more accurate than any single modality in isolation. A key obstacle to progress is our lack of knowledge about how the brain combines different modalities. If sensory modality #1 claims that the environment is "X" while sensory modality #2 claims that the environment is "Y", how can the estimates best be combined to guide behavior? An important finding in behavioral studies is that multisensory integration is Bayes-optimal-that is, the reliability of different sensory modalities are taken into account when integrating them. Sensory inputs that are reliable (more informative) receive greater weights, while sensory inputs that are less informative receive less weight. The goal of this proposal is to uncover the neural mechanisms for optimal visual-tactile integration. Our central hypothesis takes the form of a simple model in which the strengths of connections from unisensory to multisensory brain areas are modulated by the reliability of the stimulus in each modality. An unreliable stimulus results in a weak connection, decreasing the effectiveness of that modality in the integration area, while a reliable stimulus results in a strong connection and increased ability to drive behavior. To test our model, we propose four specific aims that will examine two distinct paradigms: a touch delivered to the hand that is both seen and felt; and speech that is both seen and heard. In the first aim, we will determine the brain areas involved in these two types of stimuli using blood oxygen-level dependent functional magnetic resonance imaging (BOLD fMRI). We will test the hypothesis that the intraparietal sulcus (IPS) will respond to visual and tactile touch and that the superior temporal sulcus (STS) will respond to auditory and visual speech. In the second aim, we will show that neural connection strengths are proportional to stimulus reliability. We will test the hypothesis that the effective connectivity between unisensory and multisensory areas will be proportional to the reliability of the stimulus presented in that modality. In the third aim, we will demonstrate a correlation between multisensory brain activity and behavior using multi-voxel pattern analysis (MVPA). In the fourth aim, we will reveal a causal link between brain activity and behavioral multisensory integration. Using fMRI-guided transcranial magnetic stimulation (TMS), we will test the hypothesis that TMS of multisensory areas will eliminate the behavioral advantage of multisensory stimuli and the hypothesis that TMS of unisensory areas will impair behavioral performance proportional to the reliability of the stimulus in that modality. PUBLIC HEALTH RELEVANCE: Multisensory integration is at the core of many cognitive phenomena. We will use functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) in normal human subjects to study the organization and operation of the brain during multisensory integration.