Neural Mechanisms of Optimal Multisensory Integration

描述（申请人提供）：多感觉整合是许多认知现象的核心。它提供了一种生存优势，因为它允许大脑将来自不同感觉模式的独立估计组合成一个单一的估计，比任何单独的单一模式都更准确。进步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。如果感官模态#1声称环境是“X”，而感官模态#2声称环境是“Y”，那么如何才能最好地结合这些估计来指导行为？行为学研究的一个重要发现是，多感觉整合是贝叶斯最优的，也就是说，在整合时考虑到不同感觉模式的可靠性。可靠（信息丰富）的感官输入得到更大的权重，而信息较少的感官输入得到更少的权重。本研究的目的是揭示最佳视觉-触觉整合的神经机制。我们的中心假设采用了一个简单模型的形式，在这个模型中，从单感觉到多感觉的大脑区域的连接强度是由每种模式的刺激的可靠性来调节的。一个不可靠的刺激会导致弱连接，降低该模式在整合区域的有效性，而一个可靠的刺激会导致强连接，提高驱动行为的能力。为了测试我们的模型，我们提出了四个具体的目标，将检查两种不同的范式：触摸传递到手上，既能看到又能感觉到；以及既能看见又能听见的言语。在第一个目标中，我们将使用血氧水平依赖功能磁共振成像（BOLD fMRI）来确定涉及这两种刺激的大脑区域。我们将测试顶叶内沟（IPS）会对视觉和触觉触摸做出反应，而颞上沟（STS）会对听觉和视觉语言做出反应的假设。在第二个目标中，我们将证明神经连接强度与刺激可靠性成正比。我们将测试单感觉和多感觉区域之间的有效连接将与该模式中呈现的刺激的可靠性成正比的假设。在第三个目标中，我们将使用多体素模式分析（MVPA）证明多感觉大脑活动与行为之间的相关性。在第四个目标中，我们将揭示大脑活动与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），我们将验证多感觉区域的经颅磁刺激会消除多感觉刺激的行为优势的假设，以及单感觉区域的经颅磁刺激会损害行为表现的假设，该假设与该模式下刺激的可靠性成正比。

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.