Neural pathways underlying human 3D motion perception

我们用眼睛和大脑在周围的环境中自信地移动，而不会撞到东西，识别物体是危险的还是吸引人的，并分析面部表情的微妙变化。视觉是一个非常复杂的过程，它使用了大量的大脑资源，需要在能量效率、速度和准确性之间不断权衡。这是如何实现的呢？回答这个问题的线索来自基础生物学。从解剖学上讲，视觉系统中有多条通路，不同视觉区域的神经元和通路对某些类型的视觉信息（如颜色或运动）表现出不同的敏感，这一点令人震惊。很明显，一些大脑视觉区域和通路在不同的时间和不同的功能进化。将不同的路径用于不同的功能可以降低处理问题的复杂性——允许大脑并行计算独立的属性。在这里，我们感兴趣的是一组特定的通路，它们似乎表现出这种类型的强烈独立性：那些与三维空间运动感知有关的通路。虽然运动对于背侧通路的“位置”功能至关重要，但很少有人关注运动的双目信息是如何处理的，也很少有人关注是什么通路进行处理的。在这个项目中，我们探讨了关于运动深度（MID）的双目视觉信息是如何被几种不同的视觉通路处理和携带的。已经提出了两种计算过程来使用双目信息进行MID，并且有证据表明它们中的每一种都对人类视觉有用。这些信号是通过大脑中不同的基本途径处理的吗？为什么问这个问题很有趣？(1)因为这两种途径都没有被完全理解：以两种方式处理MID所涉及的计算的位置和性质尚未被确定。更有趣的是，虽然一条途径已经被研究得很多，但另一条途径几乎没有被探索过，从进化的角度来看，人们对它知之甚少，而且可能很古老。(2)这两种途径可能具有不同的功能，我们提出了一系列的研究来具体探索这些功能。我们的项目范围非常广泛，我们在解剖水平上探索假定通路的本质，使用功能磁共振成像（fMRI）来定位功能，并使用源成像脑电图（EEG）来了解视觉处理的时间动态。我们将使用心理物理行为研究来研究MID感知过程中发生的计算过程，使用正常人群来探索正常功能，以及我们所知道的使用特定途径损害MID处理的临床受试者组（斜视弱视）。此外，我们将使用经颅磁刺激（TMS）来降低特定视觉区域的信息，以测试fMRI和EEG识别的中响应区域的因果关系。最后，我们还将采用眼动追踪方法来了解MID信息的具体来源。使用所有这些技术将使我们能够全面了解MID的潜在过程。为了实现这一目标，我们需要三个机构的专业知识，我们将需要主持两个RA，一个具有视觉行为和眼动追踪技能，另一个具有成像证书。在这个项目中提出的工作主要是核心视觉神经科学。然而，它对人类健康有影响。我们的一项技术将利用斜视（斜视性弱视）患者无法使用MID信息的核心来源，即双目视差这一事实。有迹象表明，该小组可能会使用其他来源的MID。我们小组将是第一个全面探讨这个问题的小组。

We use our eyes and brain to move confidently within our surroundings without bumping into things, identifying objects as dangerous or attractive and parsing subtle changes in facial expression. Vision is a hugely complex process that uses much of the brain's resources and involves a constant trade-off between energetic efficiency, speed and accuracy. How is this achieved? Clues to answer this question come from fundamental biology. Anatomically, it is striking that there are multiple pathways in the visual system and neurons in different visual areas and pathways appear differentially sensitive to certain types of visual information, such as colour or motion. It is clear that some visual brain areas and pathways have evolved at different times and for different functions. Dedicating different pathways to different functions can be a way of reducing the complexity of the processing problem - allowing the brain to compute independent properties in parallel. Here, we are interested in a specific set of pathways that seem to show strong independence of this type: those involved in the perception of motion in three dimensional space.Whilst motion is known to be critical for the 'where' functions of the dorsal pathway, very little attention has been placed on how binocular information for motion is processed, nor what pathways carry out that processing. In this project we explore how binocular visual information about motion-in-depth (MID) is processed and carried by several different visual pathways. Two computational processes have been proposed for using binocular information for MID, and there is evidence for each of them being useful for human vision. Are these signals processed along different fundamental pathways in the brain? Why is it interesting to ask this question? (1) Because neither pathway is fully understood: the sites and natures of the computations involved in processing MID in two ways have not been identified. Even more intriguingly, while one pathway, has been much studied, the other is barely explored, very poorly understood and potentially ancient, in an evolutionary sense. (2) The two pathways might perform different functions, and we propose a series of studies to specifically explore what those functions might be.Our project has very broad scope, we explore the nature of the putative pathways at the anatomical level, using functional magnetic resonance imaging (fMRI) to localize function, and source-imaged electroencephalography (EEG), which can be used to understand the temporal dynamics of visual processing. We will use psychophysical behavioural studies to study what computational processes take place during MID perception, using both a normal population to explore normal function, and a clinical group of subjects (strabismic amblyopes) that we know have compromised MID processing using one specific pathway. Additionally using Transcranial Magnetic Stimulation (TMS) to degrade information in a particular visual area we will test the causal relevance of MID-responsive regions identified with fMRI and EEG. Finally, we will also employ eye-tracking methods to understand what specific sources of MID information are useful for. Using all these techniques will allow us to get a full picture of the processes underlying MID. To achieve this we require the expertise of three institutions, and we will need to host two RA's, one with visual behavioural and eye tracking skills, the other with imaging credentials.The work proposed in this project is primarily core visual neuroscience. However, it has implications for human health. One of our techniques will exploit the fact that a person with a squint (strabismic amblyopes) is unable to use a core source of MID information, namely binocular disparity. There are hints that this group may be able to use other sources of MID. Our group will be the first to explore this issue comprehensively.