Neural Mechanisms of Optimal Multisensory Integration

描述(申请人提供)：多感官整合是许多认知现象的核心。它提供了生存优势，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比任何单独的单一模式更准确的估计。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。如果感觉通道#1声称环境是“X”，而感觉通道#2声称环境是“Y”，那么如何最好地结合这些估计来指导行为？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，当整合它们时，不同感觉模式的可靠性被考虑在内。可靠(信息量较大)的感觉输入获得的权重较大，而信息量较少的感觉输入获得的权重较小。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模型的形式，在这个模型中，从单一感觉到多感觉大脑区域的连接强度受到每种模式中刺激的可靠性的调节。不可靠的刺激导致弱连接，降低了整合区域中该通道的有效性，而可靠的刺激导致强大的连接和增强的驱动行为的能力。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例：传递到手的触摸，既能看到也能感觉到；以及语言既能看到又能听到。在第一个目标中，我们将使用血氧水平依赖的功能磁共振成像(BOLD FMRI)来确定这两种刺激涉及的大脑区域。我们将检验这样一种假设，即顶内沟(IPS)将对视觉和触觉触摸做出反应，而颞上沟(STS)将对听觉和视觉语音做出反应。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。我们将检验这一假设，即单感觉和多感觉区域之间的有效连接将与该通道中呈现的刺激的可靠性成正比。在第三个目标中，我们将使用多体素模式分析(MVPA)来证明多感官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和行为多感官整合之间的因果联系。使用fMRI引导的经颅磁刺激(TMS)，我们将检验多感官区域的TMS将消除多感觉刺激的行为优势的假设，以及单感觉区域的TMS将损害行为绩效的假设，该假设与该通道中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.